ENGINE & RELATED EQUIPMENT
CHOICES
CONVERSION
CONICAL
MOUNT TORQUE
CARBURETOR
MOUNTING
INSTRUMENTATION
SENSORS
FUEL SYSTEM
PRIMER SYSTEM
ENGINE STAND
OIL SUMP (Tank)
OIL COOLER
OIL HOSES
EXHAUST
CARB AIR/HEAT
CABIN HEAT
Before even talking about engines, the reader should be aware that it is not necessary to purchase an engine at the same time as a kit. This is an expensive purchase and can easily be delayed while the builder shops around or just waits until the appropriate phase of construction. One should be aware that lead times can often be up to four months and the engine will be required to build the shroud and mount the transmission. Although the type of engine mount is critical when ordering the kit, there are only three engine conversion kit components plus the fan/clutch drum and the exhaust system that may differ according to engine choice. A purchaser may wish to consider discussing delayed shipment of these four [or five] parts from CHR.
One of the interesting things about amateur-built (i.e. experimental) craft is that the builder has a lot of freedom in their choice of powerplant and is free to choose from brand new certified engines through to performing an overhaul of a used engine themselves. While a builder may want to try a turbine, one of the new diesels or even their 300HP Belchfire 400 in a Safari, I would highly recommend against this, especially until the craft has considerable time on it. There are two main reasons for this:
Before delving into the engine choice, a person not familiar with aircraft engines faces a myriad of terms that must be deciphered and filtered. I definitely do not consider myself an engine expert, but I did have to gather some layman's knowledge before making my engine choices; for specific details, the reader should consult a reliable engine assembler. While not exhaustive, the following terms will start the new reader down the path to understanding:
Certified: An aircraft certified engine may be bought new or as an overhauled engine where the work has been performed by a licensed AME (A&P). While this is mandatory for certified aircraft, it should be noted that once the dry sump conversion for use in the Safari has been performed the engine is no longer considered certified. An engine that has a legitimate field overhaul in the US may not be eligible as certified within Canada, although if the same overhaul was performed at a FAA approved facility it would be acceptable.
Engine mount: There are two main kinds of mounts used by Lycoming engines; conical and dynafocal (types I and II). The conical mount uses cone shaped rubber bushings that are flat along the back (i.e. parallel to an aircraft's firewall) and the mounting bolts are parallel to the crankshaft. The dynafocal mounts are angled (type I = 30°, type II = 18°) towards the center of the engine and use a multipart bushing sandwich which are both much more expensive and harder to align/install properly when building an engine mount. The preferred Safari mount is the conical style, although a dynafocal mount may be built or ordered. While the dynafocal mount is supposed to significantly reduce vibration, one should also remember that in the Safari the normal front of the engine has limited excursion due to the clutch drum riding on the shoes within the rigidly mounted transmission.
Conical Bushings & Washers
Accessory Housing: This is the cast casing on the rear of the engine that both covers the gear train and provides the mounting pads for the magnetos, fuel pump, vacuum pump, governor pump, etc.
Carburetor vs. Fuel Injection: This was a difficult question for me. The carburetor retains a keep-it-simple philosophy and a gravity-fed fuel delivery system, but has a downside that it may be prone to icing conditions with consequential loss of power. The injection system removes the icing issue, but is considerably more expensive and requires a pressurized fuel system. In the end, I went with the carburetor and figured that I could always convert to injection at a later date if I figured it was worthwhile.
Update: As of Nov. 1/07 this may no longer be an issue. Most
of our carbs are built by Precision Airmotive and they have
clearly stated that all shipments of carburetors and replacement
parts are on hold. Seems they can't get product liability
insurance and are electing to close down that part of their
business.
Update2: Looks like I might have been a bit premature with the
above statements. It now looks like Aero Accessories is
trying to purchase the carburetor line and planning on
manufacturing and supporting them.
Just when I think I've got these terms and options figured out, I learn about new developments. I was looking at the Precision Airmotive website to get some more information on the MSA carbs and RSA injection systems and discovered two new and interesting products that I hadn't heard of before. The first is the "Silver Hawk EX" fuel injection system for experimental use only and the second is "Eagle EMS" engine management system which is a combined fuel injection and electronic ignition system. I'll let the reader pursue these further if they're interested, but both of these appear to be very interesting developments.
There is also a FADEC (Full Authority Digital Engine Control) system available from Aerosance which basically combines electronic fuel injection and electronic ignition. It is interesting to note in their availability section that they indicate there is a Safari / Baby Belle flying with one of these systems, but I have no knowledge who the owner is. While this appears to be a very interesting system, it does add complexity while forcing an electrical dependancy and is quite expensive (over $7,000 US at the time of this writing).
For those that like to tinker and/or design their own systems, there is also a lot of good parts and information for fuel injection systems available from Racetech Inc. (SDS or Simple Digital Systems).
Fixed Pitch/Constant Speed: These terms are applicable to aircraft propellers where the propeller may be either fixed pitch (i.e. a carved wooden prop) or constant speed (i.e. variable pitch). In summary, the Safari requires a fixed pitch crankshaft since the blade pitch is controlled by mechanical linkages and there is no need for a fixed-wing style governor. However, just to complicate things there are also hollow cranks and solid cranks. Normally the hollow crank is used with a constant speed prop but it can be plugged so it can be used with a fixed pitch prop. The hollow crank is the preferred unit for use in the Safari as it is considerably lighter.
Magnetos: Impulse coupled, non-impulse, retard breaker, shower of sparks, LASARŪ, FADEC, Lightspeed, CDI, dual, left vs. right, etc. etc. There are a lot of adjectives that I found pretty confusing at first ... well perhaps even now. Most of these are in some way associated with the fact that the classic magneto has a fixed advance (i.e. 20° or 25°) that makes the engine hard to start and run rough at idle. I believe most builders would be seriously looking at impulse coupled (essentially a spring to retard timing at low speed and provide a "snap" for higher voltage), LASARŪ (electronic ignition with direct drive or impulse coupled fallback) or the Lightspeed units ( a widely used non-certified electronic ignition that replaces either one or both magnetos). I've also recently become aware of new E-Mag and P-Mag units from E-MAG Ignitions. I don't have any other information than what's available on their website, but they definately sound interesting. Another electronic ignition system is being offered by Electroair and is reported to be quite reliable ... for those that have been around homebuilts for a while, this is the system originally developed by Jeff Rose and I'm led to believe they use a lot of parts from Electromotive, Inc. Yet another player has entered the market ... the G3I ignition module is basically an interface box that uses slightly modified magnetos and an MSD module to create electronic ignition with magneto backup. I have no further information than the website but it appears to be an interesting alternative.
- If one is using standard mags, they may want to consider
having an extra set of points installed while the engine is being
prepared. This would make it very easy to install an R22 governor
or tach in the future.
- For those that want to know the basics of a magneto and how
they're assembled, there's a great demo here.
- If one is using dual electronic ignition such as Lightspeed
units then I'd HIGHLY recommend that
they carefully review their electrical systems for single points
of failure and consider alternate backup power sources ... loss
of electrical power to these units will result in an engine
failure.
Update: There has been a lot of talk on the Van's forum about problems with the E/P-Mag. The gist of it seems to be that there might be software glitches and there has been forced landings ... no one seems to have a lot of snag-free time on these units yet. Also, the stock electrical connectors leave a bit to be desired ... one may want to use ferrules such as available in the Eclipse 300-016 crimper set (about $15). To be fair, there has also been discussions by people who have been having problems with LASARŪ mags.
Alternators: Unlike automobiles, aircraft engines normally use an externally regulated alternator that is usually not delivered with the engine. These are availabe in "boss mount" (newer cases with a flat pad containing pre-tapped holes for the bracket) or "case mount" (uses three of the case half bolts to mount the bracket). I ended up getting a lightweight internally regulated alternator, but I am also making some electrical solenoid board changes to compensate for some of it's potential shortcomings. The alternator that I chose appears to no longer be available, but I recently found a link to Plane-Power who offer an internally regulated alternator that has some extra features to prevent an over-voltage situation and was recently selected by Superior Air Parts for use on it's Vantage engine. The Safari kit comes with an unmarked external regulator, but if I were to go with an externally regulated alternator, I would probably choose a B&C alternator and their regulator. While these are expensive, they have an excellent reputation for high quality.
Oil Pressure Screen / Full Flow Oil
Filter: Essentially there are two main ways of
filtering the oil and providing a mount for the vernatherm. The
oil pressure screen is essentially that (i.e. a metal screen)
whereas the true oil filter is more similar to the kind of
replaceable filters we're used to for cars. As a variation, the
oil filter may be either attached to the rear of the engine
accessory housing (straight or at 90°) or remotely via hoses and
adapters. One thing to note is that pressure screens have a 25
hour oil change recommendation whereas its 50 hours for a full
flow filter. I've got the attached filter, but it looks like the
actual filter may have to be removed during engine installation
due to the extra length; it should fit fine after engine
installation.
Update: The filter removal during engine installation has been
confirmed as a requirement ... not a big deal. This is with the
type of adapter where the filter goes straight out from accessory
housing; it would be tight, but the 90° adapter MIGHT allow the
filter to remain attached or possibly could require the removal
of the filter. However, the filter on a 90° adapter would create
for messier oil changes ... the straight style is much more
preferable for the Safari.
Vernatherm: A fancy name (and an expensive price tag) for a thermostatic valve in the oil system that diverts oil through the oil cooler once the oil has reached a preset temperature.
With[out] accessories: This is a term to watch out for especially when purchasing a used or overhauled engine. Although I've seen it used in many different ways, essentially it refers to whether or not the engine comes with accessories such as magnetos, starter and alternator. What may look like a great deal could come without these items which can cost thousands of dollars to replace.
Piston cooling and cam oiling nozzles: These do not seem to be well documented and are primarily used on turbo engines. After talking about this with my engine assembler, we chose not to include them as he felt there were more negatives than positives for this application. If I was building another engine, I would definitely rethink the option of adding cam oiling nozzles and would probably do so. I've also heard the cam oiling nozzles referred to as a "Ney Nozzle".
Turbo: Although the
basic concept is the same, there are two different styles; turbo-charging
which actually boosts above sea-level pressure and turbo-normalizing
which attempts to retain sea-level pressure at higher elevations/altitudes.
Some of the CHR factory literature talked about using a turbo,
but it appears this is no longer recommended. I briefly
considered turbo-normalizing, but this would add extra
complexity, weight and the need for a custom mounting and exhaust
system.
Update: I am now aware of a Safari builder who has recently added
a turbocharger to his machine and at this time he has about 70
hours on it. He's extremely pleased with it's performance and has
written an article in the Sept. 2006
issue of Experimental Helo
about the implementation.
Supercharger: Although these are not nearly as common as turbochargers, there are some units available for aviation engines. Most of these are centrifugal-style internal compression superchargers which compress the air inside of the unit before discharging it. It would appear that there are benefits over turbochargers such as cooler air delivery and the ability to be belt driven. One company that has been doing work on these for the experimental market is Aero Supercharger Solutions.
Compression Ratio: It appears that the normal compression nowadays is 8.5:1 and this will allow the use of mogas if certain other factors are allowed for. By going to 9:1, one has to use 100LL but there is also a 5 HP gain from most of the charts I've seen. I believe there is also something like a 9.2:1 option. Compression ratios up to 10:1 are readily available but I wonder if these higher ratios start to effect long-term reliability.
Angle Valve vs. Straight Valve: This refers to the geometry of the valves in the cylinder head. Most engines use the straight valve style, but there are angle valve models that add about 20 HP. However, I believe this HP gain is also in conjunction with the use of an increased compression ratio.
Preservation: In order to prevent internal rusting of an engine when it is not being used it is necessary to take special steps such as first running it with preservative oil and then trying to keep the internal areas oil coated and moisture free. This is especially true for a new engine and if one is not familiar with the process they should consult a good reference or someone with experience. I was surprised to notice one of my dehydrator plugs change slightly after a very light rain even though the ambient RH had been in the teens for the week before; the silica immediately changed to bright blue as soon as it was placed in an oven.
Dehydrator Plugs: These are clear plastic "spark plugs" that have a fine mesh at the bottom and contain silica which is used to absorb moisture. Since the plugs are clear, you can see when the silica has absorbed moisture; when dry it's a bright blue and as it absorbs moisture it changes to an almost clear and then pink colour. There are some o-rings and an extra threading in them that allow these plugs to be dis-assembled and the silica removed. The silica can then be baked at ~200° F for a short time (15 - 30 minutes) to rejuvenate it. I put the silica in disposable tin foil muffin forms (I'm not a baker so I can't remember the proper term) and then use an old toaster oven.
Preheat: There are several third-party options available to preheat the engine in very cold weather. Due to the design of the shroud, I don't believe that the forced air method is viable. That leaves either the Tanis or Reiff electric heaters. Since the Safari kit is supplied with a quad CHT gauge and probes, the Tanis heaters would require their expensive combination heater probes whereas the Reiff bands should be able to be directly attached (perhaps with a small change for clearance in some of the baffling). Personally, if I was going to install one of these units I would probably choose the Reiff system with an extra pad for the oil tank. When flying R22s in -20°C weather, we would roll them out of the hangar (well above freezing) and start them immediately before they could cold soak. Between flights they were fine for about an hour and we never had any problems.
Break-in: Although there are many factors to consider when first running the engine, one should be conscious of the proper break-in procedure and type of oil that is to be used. There is an initial quick run to check for oil leaks followed by various increasing length runs and then the engine is run at relatively high power (75% +) to seat the rings. This procedure is well described in various manufacturer's bulletins such as Lycoming's SI1427B. If the engine has been purchased or rebuilt by an engine assembler, they will normally perform the initial runs in a test stand to verify it's operation. Since a helicopter's first flight regime is a hover, this is usually a high power attitude that can be used to further break-in the engine and/or transmission. At the time I ordered my engine I was somewhat concerned about initial testing of both a new helicopter and a new engine ... due to my altitude, on hot days a helicopter can be pulling a lot of power in a hover. I chose to have my engine assembler run my engine for an additional three hours on their test stand where they could carefully monitor it.
Pre-Oiler: If an engine has been sitting a long time, such as during construction, the oil will run down from it's various galleries and any surface film will become extremely thin. Preservative oil will help prevent this as it is extremely tenatious in it's ability to cling to various surfaces. Since the worst wear condition will be right at startup, the best solution is to use a pre-oiler before startup. This is an external device which essentially acts like the oil pump to circulate the oil under pressure. I've heard of two ways of doing this: a fancy electrical pre-oiler which can optionally be permanently installed and a cheap homebuilder's solution. The homebuilder's solution is to partially fill a sealable pressureable container with oil, connect the outlet of the container to the engine's oil supply line and then use an air hose to apply pressure to the container thus forcing the oil into the engine. Lycoming details a different procedure in Service instruction SI-1241C whereby they use the engine's starter with the spark plugs removed.
One of the things I did just before starting my engine was to remove a quart of oil from the oil tank and put it into the oil cooler return line. My thinking was that gravity would help to distribute a bit of it to various parts of the engine internals.
Tip: When my engine was preserved, it had dehydrator plugs installed in the top spark plug holes and yellow plastic screw-in plugs in the lower holes. I don't know if it was due to over-tightening, age, temperature changes etc., but it turns out that all four of the plastic plugs were cracked and were NOT creating an effective seal. I wasn't about to install new spark plugs yet so I talked to a local maintenance facility and they found four old unserviceable plugs that had been replaced. These were installed opposite the dehydrator plugs and now create an effective seal.
One of the first questions that may be asked is why the different options for a 320 at 150/160HP and a 360 at 180HP if the running gear is designed for 160HP? The simple answer is density altitude which essentially relates to the horsepower available at a given temperature, pressure altitude and relative humidity. Even though one may have a 180HP engine, on a standard day it will only produce a maximum of approximately 160HP at ~4000' MSL and even less at higher altitudes. By having a choice, those who plan to operate at higher elevations can use the larger engine to get approximately the same power as those at sea level get with the smaller engine. Note that the factory recommends a redline of 26" MP when using a 180HP engine; from my engine graphs this translates to just under 160HP at 2750 RPM.
Although there are many different engines that may be adapted for the Safari, the most common ones I have heard about are:
My base elevation is ~4,000' MSL so the choice of a 360 was obvious. Since I did not have either the tools or experience with aircraft engines, I also decided to go with a new engine as one less headache and thing to worry about. As to choice ... I ended up with a Superior Air Parts XP-360 engine which was considerably cheaper than the Lycoming alternatives that I looked at. Since Superior's engine assembly facility was not yet completed when I ordered my engine, it was actually assembled by Aero Sport Power who I can highly recommend. Superior is now advertising and XP-320 engine, but in my opinion the $400 and extra four pounds for an XP-360 is an extremely cheap investment for an additional 20 HP ... one can always limit the MP (i.e. HP) but it's hard to add it during a hot and/or high flight. For those that really want extra HP, they could investigate the O-390 or XP-400 engines but they would need to look carefully at the slightly higher weight and CofG issues. Another relatively new option is an O-375 from Aero Sport Power. This is basically a stroked O-360 which increases the displacement and horsepower with very little weight gain. While the O-390 and XP-400 will probably require shroud changes, the O-375 should have the exact external dimensions as an O-360.
If I were re-ordering my engine today, I would seriously investigate the XP-360-Plus engine. The big difference is the use of roller lifters vs. flat tappet lifters and a different camshaft profile. One of the big concerns with aircraft engines seems to be camshaft rust and spalling, especially for engines that aren't operated every couple of weeks. During startup, there is little or no oil pressure which means that the valve train is subjected to it's greatest wear, especially the lifters/camshaft which are essentially just rubbing together. I think the roller tappets may be a good solution to this issue and are a well-proven technology in the automotive world.
As for options ... the actual engine I chose was a model A3A2, which was a carbureted, fixed pitch, conical mount version. N.B. Since the time I ordered my engine, Superior has added a lot more model numbers; the referenced model should be carefully checked before accepting it as gospel since I believe certain accessories are now incorporated into various model numbers. It would appear that the engine I received is now a model A3B2 with the difference being the "B" implies LASARŪ mags and PA carb instead of just Unison mags. Since fixed timing goes against my basic engine beliefs, I also chose to use LASARŪ mags. When ordering LASARŪ mags, there are a couple of options one has to select and for the XP-360, I chose/received:
Before ordering a LASARŪ system, one should investigate what is referred to as the "Bush Kit". I've had a lot of trouble trying to find documentation as Unison's literature (including the LASARŪ brochures and Service Letters) seem to be outdated, but in the 2003 Price List (L-1525-D) it shows a part # "4755 - LASAR Bush Magneto" which is one of the few references. Its my understanding that this option removes the one drawback of the LASARŪ system where it requires a minimum of 7 Volts for starting, thus allowing for hand propping or low-voltage starts in backup mode using normal impulse coupling. Even the CHR website which warns of the potential low-voltage problem, fails to mention this seemingly simple solution.
As with a lot of things, I tried to get a clarification on the Bush Kit at Sun-N-Fun and now I'm even more confused. To Unison's credit, they were EXTREMELY busy in their booth and I do have an email contact to get this clarified ... I'll update this when I have the details. In the event that I need/want to upgrade my mags, they seemed more than willing to work with me to obtain the required upgrade parts. The confusion comes about due to their description of the Bush Kit as basically just adding an impulse coupling to one (two?) of the mags. However, my 4771/4775 mags are already listed as impulse coupled in the literature whereas the 4776/4770 mags are listed as direct drive. The 4755 mag is not listed in most of the literature.
One issue that has recently come to light relates to the use of lightweight starters (especially the permanent magnet types), electronic ignitions and kickback. It would appear that some of these ignition systems can cause kickback during starting that leads to starter failures. There's some more information available here and I am aware of at least one Safari owner who has experienced this kind of failure. I intend to initially install the capacitor solution described in the previous link. It will be relatively easy to mount and wire this initially and if I decide to later bypass it, it will be a very simple wiring change.
My engine came with a Magnaflite starter and I'm not impressed with it when used in conjunction with an Odyssey PC680 battery. This starter takes a LOT of "juice" during the initial part of the cranking and unless the battery is fully charged it won't even get the engine over the first compression stroke. The engine seems to start relatively easily but it often requires a boost. I've now done a bunch of reading and it appears that this is a problem with several of the permanent magnet starters. The bottom line is that this combination is unuseable for me in an operational craft ... I'll definitely be changing it. At this point, there appears to be three viable alternatives: Lamar, B&C Specialty and the Sky-Tech HT or HTI.
For now, I am using a lightweight internally regulated alternator from Niagara Air Parts. I've added some extra electrical goodies to provide redundant external over voltage protection since the one problem with an internally regulated alternator is that it is possible for them fail in such a way that there is no voltage regulation which will definately play havoc with avionics etc. It would now appear that Niagara is aware of this problem and has created a description and prevention option as described here. This appears to be a more expensive alternative to the method that I chose and that is shown in my electrical diagrams. If I were to re-purchase an alternator, I would now probably go with the Plane-Power unit for it's simplicity and ease of installation ... the only potential downside is that their smallest unit is rated at 60 amps and I really only need a 40 amp model.
Note the bracket at the bottom of the photo is for a "boss
mount"
The XP-360 is approved for using 91+ octane unleaded auto fuel, although there are some exclusions for ethanol/gasohol and cautions about ignition timing and the use of 100LL for break-in. If a builder were considering this, they should also take careful note of the warnings about vapor lock and 90° fuel line fittings. It would appear that one would need to change the various supplied AN842 90° hose elbows to the style that have a smooth radius and also to change the fittings in the fuel selector valve and modify it such that "ON" is in the straight across leg rather than the 90° leg. Also, before using auto fuel one should note the following in SL-1-96 "The LASARŪ ignition system is approved for use on engines operating with a minimum fuel grade of 100 octane. Operation of LASARŪ equipped engines using a minimum fuel grade of less than 100 octane has not been validated."
I don't have a simple way to measure my final engine weight, but to satisfy my curiosity I am trying to get a rough estimate by taking the claimed dry weight with accessories (287 pounds +/- 2%) subtracting the weight of the removed parts (~ 19 lbs.) and then adding in the weight of the conversion parts (plate plus accessory conversion = 2 lbs, induction ~= 4.5 lbs). Thus it would appear that my basic engine weight is ~ 274.5 pounds, not allowing for the LASARŪ controller and extra wiring (~ 2.5 lbs), the alternator and the sump tank/hoses that all Safaris have. One interesting note is that the XP-320 which is due to be released later this year is only listed as about four pounds lighter than the XP-360! There has also been an XP-400 announced that would appear to only be about 12 pounds heavier.
Miscellaneous
I have been talking to one builder who was concerned about a stiff butterfly valve on his carburetor. He was trying to remove friction from the entire throttle linkage and this seemed to be a persistant area. He talked to others that had experience with this and was told that it is not due to the butterfly valve but rather an internal pump that is moved by the linkage. Supposedly it also gets looser with use. Without fuel in the bowl, my linakge seems relatively smooth and easy to move.
One of the potential problems with the vertically mounted engine is that the magnetos are now hanging under the engine rather than positioned horizontally from the back. I'm aware of several people who have expressed concern about oil getting past the seals on the magneto driveshaft but I haven't heard of anyone actually having this problem. I'm also aware of one builder who had water from a rainfall collect in the distributor cap with the obvious result of a dead mag due to electrical shorting. After drying everything out, his solution was to apply some RTV around the seal where the cap attaches to the magneto housing. A narrow strip of blade tape on the join line might work on some mags as might a coating of DC-4 during assembly.
If one ever has to replace an alternator belt, it requires that the entire drive system (blades and transmission) be removed first. What should be a relatively simple task becomes a major project. Robinson actually mounts a spare belt around the snout of the engine so that this would be a very simple task. Unfortunately, the Safari shroud makes this much more difficult and I abandoned this idea during final assembly as I was installing the various pieces ... I would of had to make changes to the shroud that I wasn't willing to do..
If a builder is having an engine assembler perform an overhaul or build of the engine, they should get them to add a couple of longer bolts holding the two case halves together along the top at the indicated positions (or even at all top locations). These will eventually be used to hold the shroud divider and will require enough room for a .032" baffle and another washer and nut. In my case, they used 1.75" bolts instead of the normal 1.5" ones (oops - the lift-ring bolt is now 2" but could stand to be even longer since the ring is 2 * 3/16") and this leaves enough room for the baffle, washer and an AN363-420 metal locking nut. Note that the indicated locations are for the factory delivered shroud divider but a builder may choose to fabricate their divider differently. I choose to re-make the shroud divider and used the bolts on either side of the lift ring but not the one actually on it so that I can leave the lift ring in place and not have to deal with a "bump" around it. This approach will add an ounce or two but means there's one less thing to lose/find if I ever need the lift ring in the future.
Although the conversion from a wet sump horizontal layout to a dry sump vertical layout appears daunting and involves modifying a VERY expensive engine, the actual task is quite straight forward and goes quickly. The following is my experience with a new XP-360, although different engines may have subtle differences. If one has a crated engine, it is probably easiest to do the first six items while the engine is horizontal on the pallet, then put the engine on the stand for the remaining items. Note that if one is immediately going to proceed to building the shroud then it is easiest to install the two lower end pieces of the shroud before placing the engine on the stand since these pieces encircle the conical bushings. In my conversion, mounting these shroud pieces required the drilling of one additional holddown bolt hole in the case ... OUCH. This took a little courage and triple checking. I also chose to have the bare aluminum parts for the engine conversion anodized before installation.
Remove and plug the oil drain lines
from the cylinder heads to the case just above the sump.
I had difficulty with a couple of the 45° AN fittings
due to the lubricant/sealant used, but eventually got
them out. Note that only 7 plugs are used and the return
hole in the case for the #1 cylinder is actually a hose
nipple which will be used as a pressure vent to the new
sump tank. I drilled a safety wire hole in the hose
nipple's shoulder so it could be safety wired to the
adjacent plug. I debated how to safety wire the head
plugs; I have seen "teardrop" shaped washers
with a bolt hole plus a safety wire hole, but I couldn't
find them in any of my catalogs. I ended up getting four
NAS513-4 washers from Wicks and
knocking off the locking tang. These washers were then
placed under the bolts of the closest intake pipe and
provide a lock wire hole for the plugs in the head drain-down
holes.
Remove the actual sump and possibly
plug some internal passages. This involves first removing
the intake tubes and then the actual sump. Note that this
can be a messy job if there's any residual oil in the
sump; the preservative oil in my engine was like working
with a mixture of pure STP and transmission fluid. The
manual talks about capping off various internal fittings,
but these were not locatable on my engine; obviously
there are variances in different engines and accessory
cases.
Close in the sump opening with the
supplied sump plate. While I found the fit and the pre-cut
holes in my cover were close, they definitely needed some
opening up for alignment. I first drilled all the holes
to 17/64" in order to ensure clearance and then I
ovalled/cleaned up any holes that still did not align
properly. The fitting for the oil pickup needs to be
canted; unfortunately no specific alignment angle is
given and an educated guess must be made until the engine
and oil tank are actually installed. Note the comments
below about oil hoses and also
the next point where two of the bolts are used to hold
the intake manifold in place.
In order to clear the carburetor, the oil pickup fitting
needs to be tapped quite far to allow the fitting to seat
as deeply as possible and this should be done with the
actual fitting that will be used. I am aware that at
least one builder chose to weld the fitting in place in
order to get a good fit and maximum clearance. In hindsight, I wish I'd welded
my fitting in place after first machining the NPT side of
it so that it is almost flush with the plate ... the
extra 3/8"+ would give more clearance for the carb
air SCEET tube. The only difficult part would be to
determine how much of an angle to rotate the fitting
towards the oil tank.
Here's the angle I ended up with but it could
stand to be rotated even a bit more
Install intake manifold and tubes. I have
some concerns about the supplied "spider". The
original sump had a 2.35" ID bore at the carburetor
mount while the supplied manifold has an ~2" bore
thus creating a lip along the air/fuel mixture path; some
of this difference can be taken out by judicious use of a
die grinder creating a more tapered path. The die grinder
was also used to contour the sharp internal shoulders.
It's my understanding that for efficiency the volume of
an intake manifold should be about the swept volume of
one cylinder; using this criterion the supplied manifold
is way too small. I will use
the supplied manifold initially, but plan on later
creating and testing a larger volume version.
While 4130 tube is provided to insert into the intake
runners to prevent hose collapse, I used some 1.75"
x .035 wall stainless since these tubes are fully within
a "rubber" hose and not easily inspected for
corrosion. I have since talked to another builder who I
believe had a much better idea. He went to the local
hydraulic supplier and obtained some 1.75" ID hose
that was externally wire wound (i.e. smooth inner bore)
and was UV, fuel and oil resistant. Basically very simple
and a good way to allow for the flange mis-alignment.
There is about a 3/4" discrepency in the plane of
the stock flanged intake pipes and the supplied "spider".
If one were welding up their own manifold, they may want
to angle the tubes that go to cylinders slightly in the
direction of the crankcase. I have seen pictures of
several ships that have custom intake pipes (I assume
extensions welded onto the stock ones) and I thought
about a couple of other options such as trying to heat /
bend the stock pipes or cutting them part way through the
bend such that there's only one bend instead of an "S".
In the end, I just used the stock pipes with the hose /
tube extenders and allowed the hose to take up the two
angles. I figure that if I later upgrade the intake
manifold then I'll worry about smoothing the flow with
custom pipes at that time.
Since the above photo, the spider has been slighty
rotated counter-clockwise.
Update: I have seen a CHR-supplied intake where the
runners were extended to just about where they meet the
stock intake pipes. This was done with an additional
piece of welded pipe to account for the angle and results
in only requiring the short hose couplers as used on a
stock engine. I'm not sure if this is a change for all
new kits.
As supplied there was about a 3/32" rocker across
the carburetor mounting flange which is much more than
the gasket thickness and since it's across the welded
area I thought it was too much to just torque the
carburetor bolts a little more. I have taken a little of
the rockered material off and have chosen to build up a
flat surface on the flange with JB Weld. The first photo
isn't quite at the correct angle to show the full rocker
and the second one shows the JB Weld setting up. The
yellow tape acts as a mold release as does a piece of
plastic located on the flat plate under the flange.
One also needs to fabricate an adapter that goes from the
carburetor intake flange to a 3" OD for SCEET tubing
(more information later on in the Carb Air/Heat section). The
spun flanges supplied in the kit could work as a start
but they are made of very soft aluminum and don't span
the full gap to the bolt holes. The ideal solution would
be an adapter that is milled to the exact shape required
and has a somewhat beefier flange. Perhaps one is
available, but offhand I don't know a supplier.
I was wondering how to protect these valve covers from corrosion. Since they are of cast aluminum they would not turn out very well if anodized. I then considered having them plated ... chrome has potential problems if the the plater is not very familiar or experienced with working on aluminum but I did consider nickel plating (possibly electroless). In the end, I decided to just alodine them and then prime and paint them on the outside. Regardless of finishing choice, first they had to be flat sanded to remove the heavy scratch marks from the sanding they'd received during production. They were then painted black and a low gloss clear coat was added. After that, they were again wet sanded on a flat surface to add some detail and highlight.
Pair on the left ready for installation, pair on the right before
sanding
As part of the XP-360 conversion process, I opted to replace the following gaskets:
I have to compliment Aero Sport Power. The extra gaskets in the left picture below were ordered at the same time we were arranging for engine delivery and they consciously chose not to charge for them! This gesture just reinforced my positive opinion of them since they had also explained to me how I could lower the total cost by ordering direct through Superior rather than through them. It was extremely refreshing to deal with an aviation-related company that was trying to save me money ... on the other hand, I can think of one supplier in OK that I'll *NEVER* deal with after hearing their prices and policies face-to-face.
Note that the in the standard design, the valve covers must be
removed in order to remove the side panels of the shroud. I chose
to go with re-useable REAL
silicone gaskets for the valve covers instead of the standard
cork gaskets. Since I was replacing the valve covers with the
cast ones, I also chose to keep the non-modified stamped covers
for use during construction. By using unmodified covers it is
possible to remove the shroud sides without having to repeatedly
remove the valve covers for clearance. If I were just using the
supplied covers, I would delay their modification until after
final assembly to allow for the various shroud installation and
removal sequences.
N.B. The REAL gaskets specify a 25 in-lb torque for the valve
cover bolts. However, the standard valve cover has a ridge on the
inside lip to improve the seal whereas the cast covers are just
flat. I ended up applying 40 in-lb to these bolts but may
actually increase this a bit more if there is any sign of leaking
or loosening.
Tip: When installing the hose between the valve covers (and
afterwards) it is much easier to install / remove the valve
covers as a joined pair as there is very little free hose between
the two of them that will flex.
Tip: I talked to one owner who had a problem with water somehow getting into the magneto cap where the leads attach. Since the Safari's engine is mounted vertically, any water that gets into this area is trapped with no way to escape. His solution was to remove the caps and run a fine bead of RTV around the edge before re-assembling them. I would assume that something like DC-4 or a strip of blade tape could also be used for this.
Tip 2: I tried to install my ignition leads based on the Superior wiring diagram and it proved to be pretty confusing since the leads all appeared to be the wrong lengths. I finally woke up and realized that each of the nuts that go on the plugs is stamped with their location (T1, B1 ... T4, B4). DUH !!!
There are two common ways that I've seen for routing the rear (i.e. engine bottom) plug wires on the Safari: via clamps attached to the intake runners or via clamps attached to the rear vertical edge of the shroud. I chose to attach the them to the intake runners which hides them out of the way ... the downside is that one has to be very careful of their clearance to the exhaust runners. Mounting them to the shroud gives a direct and clean installation but I basically chose not to do this simply for added protection and I don't like the looks of the wires on the shroud.
Left-over Parts
Since I started with a new engine, there are several valuable parts that will be surplus to my needs and should be saleable:
When installing the engine, the Safari instruction manual says to "... install the rubber mounts, bolts, washers and the nuts. Tighten the nuts down until 1-1/2 threads show above the nut." I find this somewhat disturbing for several reasons:
I was looking for a way to provide a consistent and reliable method to torque these bolts in place. The more I looked for reliable documentation on conical mounts, the more it seemed that there was inconsistent data out there. For example:
The best source of information I found was on the Super Cub's forum where this issue was debated. There seemed to be a consensus that 1.840" might not be enough compression and that 40 inch-pounds was about right (although there was some dissention that 60-80 might be better). I tried the 40 value and it seemed a little low although there was some bulge. I then tried 60 inch-pounds and this produced both a bulge and the measured distance was approximately 1.840" (hard to measure really accurately). This became my starting point before adjusting the nuts for engine to transmission alignment.
I subsequently talked to a very experienced retired mechanic whose retirement consists of rebuilding Super Cubs on a regular basis (I wish I could complete things as fast as he does). His method is to tighten the nuts until they're first snug and then another 1-1/2 turns ... again a hard to replicate procedure. His philosophy is that if there is too much bulge then there is no flex and vibration isolation.
One of the problems with conical bushings is that the rubber tends to "grab" the bolts and make for either incomplete seating or at the very least a deception. Any torque readings must be made at the nut and not the bolt head. I chose to mount all my bolts with the nuts down which allows for relatively easy access and adjustment. Note that the bolt near cylinder #4 should be placed downwards; otherwise the nut may/will interfere with the pushrod tube. Before measuring the torque, I purposely over-torqued the bushings to fully seat them and then backed the nut off. They were then re-torqued to the value I wanted.
At first thought, this should be a very simple task: bolt on the SCEET tube adapter to the bottom of the carb, use the four supplied AN5 bolts to mount the carb to the intake manifold, attach the fuel fitting, bolt on the mixture adjustment plate, re-orient the throttle arm and fabricate a linkage rod. Sounds quick and simple but it took me a lot longer than planned.
First I mounted the SCEET tube adapter to the bottom of the carb using drilled head 1/4-20 x 5/8" bolts which were then safety wired together. Since drilled head 1/4-20 bolts are not that common, lock washers and regular bolts would probably also work.
When trial fitting the carb to the intake manifold, it was
obvious that the wrong bolts had been supplied in my kit and that
it was going to be very difficult to get the rear bolts tightened
and cotter pinned. My kit came with two AN5-11 bolts and two AN5H-11A
bolts. These were very marginal in length, even when using thin
washers and I opted to replace them with AN5-12 bolts. Because of
the carb's contours and the fact that CHR chose to fabricate my
intake manifold 3/8" closer to the sump plate than the plans
show, it makes the two nuts closest to the sump very
difficult to access ... I might end up having to go to self
locking nuts.
Update: I was able to get the castellated nuts and cotter pins in
place but it was a real bear. One of the things that would
probably make this job a lot easier is to mount the carburetor
before installing the intake runners to the manifold.
During the trial fitting, I looked at the fuel line routing and the CHR supplied 90° fitting. One of the things I'm consious of is that if auto gas may be used then one wants to avoid sharp bends in the lines. Although a straight fitting could have been used, I split the difference and used a 45° fitting. Note that anything other than a straight fitting cannot be installed once the carb is bolted to the manifold due to frame interference as the fitting is being threaded in and must be installed before the carb is mounted.
The supplied mixture plate was designed for an MA4 carb (i.e. O-320) rather than the MA4-5 carb that comes on most O-360's. Because of the MA4-5's mixture arm shape, there is a lot of rotational play around the bolt and the plate is only being held in position by the bolt's tension. Perhaps star lock washers on either side would prevent most of this, but I'm not sure of the long term effectiveness. I tried adding a small clamping plate to stop this movement and while it did stop some of the movement, it wasn't completely effective. I finally coated the arm with PVA and then applied JB-Weld to build a fully conforming bed that locks the arm in position before the bolt is tightenend. I also did not require the bolt spacer that came with this assembly.
The next task was to drill the throttle arm per CHR's
instructions ... ooops, the MA4-5 arm is different than the MA4's
and there is only one hole near the end. After playing around
with this for a while, I figured that there really did need to be
a change in the arm's length and ended up using 1-1/4"
between the pivot center and the new linkage hole ... time will
tell if this was a good guess since the plans do not give a
dimension. Also note that the Rigging Manual shows the linkage
bolt with the nut towards the carb side ... that may work on an
MA4 carb but with the MA4-5 this will probably interfere with the
idle stop and the bolt will need to be oriented with the head
towards the carb body. Certainly this was required in my case.
Update: I certainly wouldn't go any less than the 1-1/4"
distance. With everything installed, the amount of throttle stick
rotation is as small as I'd like and it will probably be somewhat
sensitive. Perhaps the original hole in the arm might be fine but
remember that it will also have an impact on the correlator and a
large washer may have interference on the sump plate. For
reference, my throttle stick rotates 48° using this new hole in
the carb arm but that is before the idle speed has been adjusted
which will probably reduce the range somewhat.
Update 2: I have now seen a CHR-modified MA4-5 throttle arm and
it appears they drilled the hole at approximately 1-3/8"
which would give a bit more rotation than I have. At something
like $50 for a new arm, I'm not going to change mine for now.
The Rigging Manual gives a rough angular measurement for the arm's position. I found that a better method was to check it with the carb mounted to the manifold ... I tried to orient it as far counter-clockwise as I could such that it did not hit the intake runner at full travel. I would have preferred to have it rotated even more for improved linearity, but that would cause interference.
N.B. I would recommend that the length of the rod that goes to
the throttle arm on the torque tube coming from the cabin be
double checked before it is fabricated. The plans indicate 10-1/4"
but mine ended up being 11-1/2". Do not try to cobble the
short rod where the longer one is required ... I've seen the
results on another craft and it leads to a lot
of subtle problems! One thing I noted is that the rod ends and
bolts are relatively heavy and all this weight is on the same
side of the torque tube as the rod ends inside the cabin. I'm
sure that lighter 3/16" rod ends would work equally as well
on this linkage but I haven't made or tested this change ... yet.
Tidbit: It would appear that the throttle arm would work just
fine if it was mounted towards the rear of the craft rather than
towards the front. In fact this would give a straighter run for
the linkage and probably better linearity. However, this change
reverses the direction and should only be made with other changes
that compensate for it. These other changes could be used to try
balance the weight of all the rod ends which are currently on
only one side of the linkage.
The final aspect of the the carb installation is to attach the
SCEET tube from the carb heat valve. This is definitely going to
cause me trouble due to interference with the oil pickup fitting
that prevents a straight vertical run. The choice is to hope that
the wire in the SCEET tube will hold a "dent" and I
won't have any rubbing wear on the tubing or to fabricate a new
adapter plate. The manifold I received was fabricated such that
it sits 3/8" closer to the sump plate (and oil fitting) than
shown in the plans ... this makes the SCEET tube routing much
more difficult. The Catch-22 is that if the carb is mounted
further from the sump then there may be frame interference on the
fuel fitting ... perhaps a small rotational change to the
manifold would prevent this. In hindsight, there are two
undocumented changes that could also have helped reduce this
interference:
1) The SCEET tube adapter plate could have been fabricated such
that the SCEET flange is not centered on the carb intake ... even
1/8"+ rearwards offset would help.
2) The oil pickup fitting could have been been machined for
minimal clearance to the sump plate and then welded into position.
This could provide 3/8"+ of extra clearance.
Bad flash shadow on the oil pickup fitting but one can
just see the edge of the blue fitting.
The other issue that is not obvious in the above picture is the routing of the SCEET tubing around the throttle linkage. It looks like I can't go direct to the air selector box on the right side and will have to go forward and around the various frame members. Perhaps it would have been easier to mount the box on the left side and try clear the various oil lines.
The more I looked at the issue shown in the above photo, the more I was unhappy with the interference between the SCEET tube and the oil pickup fitting. I finally decided to build an offset flange. While this got rid of the interference issue, it still makes for a round about routing of the SCEET tube to the air selector box.
Extra "stuff" in the way but you can see the new
clearance to / around the oil pickup fitting
I have now seen how CHR installed the SCEET tube on an O-360. The first difference was that they welded the oil fitting to the sump plate using the minimal clearance possible. The carb was mounted about 1/4" further from the sump plate than mine (which causes a potential inteference between the fuel fitting and the frame). Even with these changes, the SCEET tube is rubbing on the oil fitting and is somewhat "dented".
It should be noted that the above pictures and discussion are about an MA4-5 carburetor on an O-360. I believe that the MA4 carb as used on O-320's and O-360-J2A's is actually shorter in height. As a reference, my MA4-5 carb is approximately 6-3/8" between mounting surfaces.
If one is using the instrumentation kit as supplied by CHR there are several sensors that need to be mounted to the engine and then wired into their corresponding gauge:
As part of my fuel tank preparation for paint, I performed a pressure test on them. Three of the tank holes were covered with a combination of vacuum bag sealant tape and polyethylene while a latex glove was placed over and sealed to the trap. Shop air was added through a hole in the glove (subsequently sealed) until the glove became about 1-1/2 feet in diameter and ideally it should remain inflated overnight. Using both soapy water and a dunk tank, on the one tank I found a minute pinhole leak in a weld that was then welded shut before further finishing and on the other tank I found five pinholes. Although these holes are extremely small and would probably have been sealed by the finish, I do not consider that to be a good practice as eventually the seal could be broken and it would start to drip fuel. Note that these holes were found with extremely low pressure and I would highly encourage ALL builders to perform this kind of pressure test before considering their tanks ready for paint, powder coating, etc.
Update: Another "glove" test was done and they still
wouldn't stay inflated overnight. As
a result, I decided to try re-testing the tanks at 5 psi to try
find all sources of the leaks. Low and
behold I found 2 more holes in one tank and eight more holes in
the other tank. What with sixteen pinholes, I find it hard to
call these "aviation grade" fuel tanks.
Note that 5 psi is probably a bit higher than required. I've
found other aviation references to 3.5 psi and Robinson uses 1
psi for their pressure test. Obviously the higher the pressure
the easier that small leaks might be found, but I make no claims
about how much pressure the tanks will take before distorting.
Update 2: It's my understanding that CHR has changed their
welding technique and now pressure tests these tanks after
they've been manufactured. I don't know when this procedure
started and based on my experience, I'd still want to do a double
check of any tank before painting it.
I had an AME (A&P) recommend that I use sloshing compound in the tanks. I did consider this but it was my choice of last resort ... besides having to select an appropriate compound and apply it, there is also a concern about the lifespan of the treatment and whether it starts peeling at some time in the future.
The ends of my fuel tanks had a lot of fine ridging from the spinning process. In order to get a good finish on the tanks, I chose to remove most of the ridging before further finishing ... 220 grit paper in an orbital sander at low speed made this a relatively quick and easy procedure.
While tapping the top of the tanks for the fuel level sender
bolts, I discovered that the Westach drilling guide is not to
scale and the supplied gasket is not accurate enough to be used
as a drilling guide. I first cut the probes to length so they
could be inserted into the tanks and then used the gasket to mark
two holes which were double checked against the probe head before
drilling and tapping them for the #10-32 bolts. With the probe
held in place by the two bolts, a #3 drill was used in the
remaining three holes to mark their center. It worked out for me
that all of my probe bolts fit fine without any need for
modification. Note that the supplied bolts have no secondary
locking mechanism and the probe kit doesn't even include washers;
I will be replacing the bolts with AN3H-10A and AN960-10L washers
so they can be properly safety wired per normal aviation practice.
Update: I've seen a newer kit that used the same probes and what
appeared to be the same style of bolts but they were drilled for
safety wire (probably .020 only). Looks like Westach might
finally be learning a bit about aircraft requirements.
N.B. One should try be as careful as possible to avoid getting any drill / tap chips into the tanks from this task as they are very difficult to remove and will tend to cut the o-rings in the drain valves. I drilled part-way through the material and then turned the tanks upside down while finish drilling the holes from below. The tapping operation was done with a lot of cutting oil and the tanks inverted. I also placed a small piece of duct tape on the inside of each hole to further try catch any debris.
The fuel probes supplied with the Instrument Kit are Westach
395-5S-1LL which have adjustments for empty, full and a low level
alarm. However, due to the round tanks, fuel quantity is not
linear which means that the indicated level will drop much more
quickly near the top and bottom of the ranges. The solution is to
install some kind of device that allows more calibration points
and then interpolates the quantity. If anyone has used the Princeton
5 Set Point probes, I would be interested in hearing their
feedback as very little information is available on the web. It
appears that while one may gain linearity with these probes, I
don't see any reference to an alarm level. Also note that the
supplied probes have their adjustment pots on the top and are
exposed to the elements. Once the levels have been calibrated, I
would recommend putting some kind of environmental seal over
these. One has to be very careful
when doing this as these adjustments are extremely
sensitive ... I have no idea why they didn't design them to be
less sensitive or go to 10-turn pots.
Trivia: I have reason to believe that the supplied probes are
made for Westach by Centroid
Products. Even more interesting is that Centroid appears to
have some new style of probes that can be pre-calibrated, even
for irregular-shaped tanks.
I chose to calibrate the fuel probes before I had done my weight and balance plus fuel flow test. That meant that I really didn't want to fill the tanks in order to set the full mark. I made up a 1" capped tube that was long enough to insert the probes into and then filled it with 100LL. The probes were then calibrated for their empty point, followed by inserting them into the tube with 100LL to set their full point. This worked extremely well and only required a couple of cups of 100LL. The alarm points will be set during the first actual filling of the tanks.
The filler neck plates on my tanks had some heat warping from the welding process but were useable. I had planned on installing the filler necks using a liberal application of sealant but changed plans when I wanted to pressure test the tanks before paint and was worried about any silicone residue. After checking the specifications, I installed the filler necks with a thin coat of J-B Weld which is reported as fuel resistant and capable of withstanding 500° F (note that power coating is normally in the 350 to 400° F range).
Both of the holes on the bottom of my tanks were pre-tapped (1/8 NPT and 3/8 NPT) but basically they had been started and were not very deep at all. I chose to re-tap these holes considerably deeper. This has to be done carefully against the actual fuel drains and finger strainers in order to not over-do the tapping. Remember to try keep all chips out of the tank (tapping from below, lots of fluid, blowing the chips out via a different hole, etc.).
Just before final installation of the tanks, they should be sloshed with some kind of solvent to try remove any contaminants and chips that they may contain. I have talked with a couple of builders who did this but still had some problems with chips that showed on the screens and as cut o-rings on the drain valves. If the valves start to leak very early in the testing cycle, these o-rings should be inspected and possibly replaced. If they need to be replaced, then one should also check the screen in the gascolator and possibly the carburetor. Perhaps one might consider temporarily using disposible automotive fuel filters during the very early testing ... it won't save the o-rings but might stop contamination further downstream.
I tried the solvent sloshing using acetone and was quite surprised by what I found, especially since there did not initially appear to be any chips visible inside the tank. I had been very careful both when drilling / tapping the fuel probes and also the NPT holes. The first drain of the solvent showed a lot of very fine particles and a few larger ones. However, when I used a flashlight to inspect the tanks it was obvious that there were still some larger chips inside the tank. I wrapped a pad of solvent-soaked shop towel on the end of a rod using safety wire and could use this to capture as many chips as I could see plus also use it as a mop-like function inside the tank. There was an amazing amount of metal recovered which prompted me to repeat the entire process a second time. Although there was not nearly as much metal recovered, I was again surprised at how much remained. I'm thinking that during the first engine oil change it will also be appropriate to open the gascolator and check both the bowl and the screen in it.
Tank mop ... slow but very effective
The second tank produced an equally surprising number of chips. Interestingly, several of them were long (~1") and straight ... not like drill or tap chips. I'm thinking they might be the result of fabrication such as edges that hadn't been deburred prior to welding. Since the drain sump is at the lowest point in the tank, I assume any remaining chips will eventually collect there. I'll probably pre-order a Curtis valve or two (~$10 each and they don't supply separate O-rings) then change them either at the first oil change or when the valves start leaking due to cut O-rings. It also points out that it would be appropriate to check the finger strainers at that time.
Update: Now that I've run some fuel through the tanks to do the fuel flow, more chips have managed to show up in the sumps where the Curtis valves are. Both valves got small chips under the O-rings which caused them to leak. The valves were removed and about five fill / empty cycles via the valve sump with about 1/4 gallon of fuel finally got a clear result. I'm thinking that these chips probably get trapped against the bent edges of the baffles and one can't see them through the fill hole and probe hole. For now I intend to use the valves as little as possible while doing engine testing and initial tracking and balancing. It really won't be catastrophic if there's a bit of water in the tanks and it will give more time for chips to settle to the bottom of these sumps due to vibration. The real solution would be for the factory to pre-drill and tap all the holes before welding the tanks closed.
As mentioned in the Frame section, I do not like the way the ends of the tank brackets are formed as shown in the construction manual; essentially they're just bent tangs with a hole drilled in them for a bolt. In fact, I am aware of at least one ship where a tang broke off and another ship that had a bolt break. I believe that welded triangular gussets will add significantly to the strength and reliability of the tangs but a better solution is to use T-bolt straps. Another builder has received a price quote from Clampco for custom T-bolt straps that should be appropriate (C511-M-100-1422-S2) ... unfortunately this quote was very high which I assume was due in large part to the setup charges. I checked with a couple of the local truck supplier to see if they made custom straps and it appears that most of the truckers order their straps directly from the truck dealers. It sure would be nice if CHR were to arrange for the bulk purchase of these rather than every builder having to track them down and then pay a setup premium.
Plans vs. gussets on tangs
For my own reference: When mounted on the saddles (including the 1/16" rubber pad), the circumferance of my tank/saddle combination was 43-7/8" or a calculated diameter of ~13.97". This was without the use of the 1/16" rubber channel for the straps; logically they should add another 1/8" for a total circumferance of ~44.27" or a diameter of ~14.09", but it appears that it's more like 44-3/4"+ ( ~14.25" diameter) from actual measurement.
Update: As I suspected, the high cost of Clampco custom straps is largely due to the initial setup / order charge. The cost difference between 4 and 12 straps was negligible (~$25) but the next price break wasn't until quantity 25. I ordered twelve of them and will make the extras available to other builders once I've verified their suitability. I decided upon part number C510-N-100-1425-S2 which have a .040" x 1" band and based on their engineering data these should each have a 4400 pound (1996 Kg.) yield strength. Their specification of size in 1/16" diameter increments is somewhat awkward and I had to decide between 14.1875" and 14.25" ... I went with the slightly larger one since the adjustment range (14.03" - 14.34") seemed fine for what is required.
Theoretical calculations are a good start but in the end it all comes down to an actual trial-and-error fit. In my case, I was disappointed as the straps I ordered are basically too long. I'm not going to go into a lot of analysis, but I think a lot of this is because of rubber compression from the flexible and effective bands. When the clamps are tightened to the point where they are getting into their final torque range they're pretty well bottoming out and there is about 1-3/8" of threads past the nut. I'm thinking that a 14" diameter would have been a much better choice. Although my welder feels confident to cut out a small section (probably on a 30° angle) and weld the band back together, I'm first going to try replacing the thin rubber anti-chafe molding with 1/8" silicone baffle material ... hopefully this will solve the problem (update: the baffle material works well and solves the problem). Another builder went with C511N-100-1409-S4 straps which are slightly shorter in length, thicker material and have a longer T-bolt. They worked perfectly with the CHR-supplied molding and he probably also has a few extras available ... if someone is interested, they can contact me for details.
C510-N-100-1425-S2 (top) versus C511N-100-1409-S4 (bottom)
The next issue with these straps was how to mount the tank
brace. I plan on using the Kiwi-style X brace and wanted to mount
the cross tube at the top of the tanks ... I'm also mounting the
actual T-bolt under the saddle such that it provides equal
pulling forces to both sides of the tank above it. I basically
needed a vertical tab to which which I could mount a bolt to
capture the cross tube. After discussing this with my welder, he
didn't feel comfortable directly welding the tab to the main T-bolt
strap since he's seen many cases of stainless welds cracking
which could lead to a fractured strap. Instead, I cut 3"
pieces out of the CHR-supplied strap material and these were edge
welded to the T-bolt strap. A 1-3/8" wide tab was then
welded to this doubler. Note that the doubler was first double
checked that it's contour matched the tanks and the bottom of the
tab is slightly concave. At this point I can't say how it will
hold up to extended use, but this is method that I'll be trying.
Update: This welding / cracking issue with stainless straps is
very real. I am aware of another builder who had tabs welded
directly to his straps and had one of them fracture. I don't have
the background to make a recommendation other than to say that if
the user doesn't have the background to understand the relevant
factors then they should consult with someone who does.
It's hard to get a good indoor picture of stainless ... the tab will be trimmed once the hole is drilled and the brace fitted
I've talked to another builder who has had a 1/4" bolt break on the CHR-style combined hold-down and cross-brace. His recommendation was to go with separate straps for the hold-down function and for the cross-brace attachment. He also found that the thick CHR-supplied bands (0.070" [or .075" ?] x 1") were too stiff to conform to any irregularities in the tanks. After a bit of flying, the vibration helps to seat the bands better and distribute their clamping force which then requires the bolts to be re-torqued. Perhaps a bolt on each side of the straps would help to equalize the clamping pressure and eliminate the need for some of the cross-bracing. The other alternative would be to place the bolt on the top or preferably on the bottom which should provide equal down-force to try snug the tank into the saddle. The issue then becomes how to attach a cross-brace. Once the bolts have been snugged up, they should be repeatedly checked over the next couple of days. I used a torque wrench on mine and found that they needed additional tightening as the "rubber" took on it's set ... mostly over the first couple of hours after installation. I'll also be double checking these bolts after a few hours of flight where the vibrations may also seat the tanks further.
There has been a lot of debate about the 2/rev issue and why it varies with fuel levels. Certainly if the tanks are not securely mounted then they will vibrate or resonate differently as the fuel level changes which will then make balancing extremely difficult. I have heard how some builders are using a spring resonator between the two fuel tanks to try dampen and/or cancel these effects. It would appear that the Kiwi ships are now using a much more solid "X" brace to try eliminate all movement of the tanks and that appears to be a logical starting point to me. If something is inducing a vibration, it's always best to try eliminate it at the source rather than applying various band-aids to try mask the symptoms. It certainly would be helpful if CHR did some R&D to find and eliminate the true source rather each and every builder having to experiment with what works best on their unique craft.
I also went with the X brace. Since I'm tired of painting, I got lazy and used 1/2" x .065 stainless tubing for this. I briefly considered whether to add adjustable rod ends to the braces and finally decided that it was easiest and fastest to just use flattened ends, carefully drilled holes and a fixed adjustment. If I later decide to experiment with the bracing then I can design and fabricate a new system. I actually broke my vice trying to flatten the ends of the tubing! I then got smart and used my welder's hydraulic press to do them ... it's a 12 ton model and could just flatten the ends enough.
I am aware that several builders have opted to change the fuel lines from the supplied MIL-H-6000 hose to braided hoses which are more robust, especially if covered with firesleeve. Also, the teflon version of these braided hoses have an unlimited shelf and service life. If making this change, there is the option of using either an AN822 elbow (flared tube, pipe thread, 90°) to the tank and using hoses with straight ends or using straight AN816 nipple (flared tube, pipe thread) and using hoses with a 90° fitting on them. If I go this route, I will be using hoses with the 90° fitting since they have a smooth radius versus the sharp corner in the AN822 fittings. While I may never use auto gas, the sharp corners can contribute to vapour lock. Initially I will be using the MIL-H-6000 hose since all the parts are on hand and will defer the decision about braided hoses till after the machine is running.
For those that are familiar with the process, it should be possible to change many of the fuel lines from flexible to hard lines. Specificaly, the lines from the tanks to the fuel shutoff valve and from the valve to the gascolator all mount to pieces that are quite rigid and there are lots of places to attach appropriate supports to the frame. The line from the gascolator to the carburetor should remain as a flexible line to allow for any engine movement on the conical bushings.
I am aware that another builder felt that his fuel shutoff valve was too close to the firewall and had to fabricate a spacer for it. Although there is not a lot of clearance for the hoses, I felt that mine was okay without the use of spacers (thin wedge-shaped spacers are a pain to fabricate). I also chose to safety wire the plug on the capped end of the valve ... something I've seen omitted on many ships.
The gascolator is pretty straight forward but there is one thing that may not be obvious ... the knurled knob on the bottom which is used to remove the bowl has a hole for a safety wire.
I would have preferred to have had the valve on the rearwards side of the bowl but found it was better in my installation to have the valve on the forward side. This allowed for more clearance around the cabin heat SCEET tube when checking the gascolator fuel for water / contaminants. I used the CHR technique of two adel clamps to hold the gascolator to the two tabs that were pre-welded to the frame. The best configuration I found was to put the clamps so their loops were on the downwards side and the clamps were bolted on the bottom side of the tabs.
The tanks are listed as having a 106 liter capacity. On my first fill up with only the unuseable fuel in the system, I only got 102 liters from the fuel truck. Something for me to watch and update ... a gallon is a gallon which is about 7 minutes of time. It would also slightly alter my weight and balance sheets for the full fuel calculations.
I wrestled with this one for awhile. Because I was getting LASARŪ mags that make starting somewhat easier, this becomes less of a priority. However, we do get extremely cold weather here that can make starting very difficult. I have heard about just cracking the throttle a couple times which causes the acceleration pump to squirt raw fuel into the intake; however, this is an updraft carburetor system which would logically just allow the fuel to collect in the SCEET tubing used in the air intake system if the engine isn't cranking ... whoa FIRE HAZARD! In the end I decided to install a primer pump and lines with the idea that it was much easier to do this during initial construction and the worst that would happen is that I decide to either cap it off or remove it entirely. With the experience I now have, this would still be a difficult decision, but I would most likely not install a primer while leaving enough panel space for a future upgade to it.
I had already obtained the primer and various fittings before the engine arrived. Surprise ... the engine came with fittings and lines (both uninstalled) for a 3 cylinder priming system. Thus the discrepancy in the "Left-over Parts".
The primer ports are on the intake / exhaust side of the cylinders which is normally the bottom of the engine. This makes sense on a carbureted engine where the lower position should prevent any drain-down of the fuel within the primer lines into the intake passages and thus keeps the primer lines full of fuel and ready to use. The potential problem with a vertically mounted engine is the vertical distance and inconsistent height between the cylinders. I really don't know if the holes in the spray nozzles are small enough to prevent it, but I wonder if the fuel in the primer lines might eventually settle to the level of the lowest spray port. Now that everything is installed, I regret not doing a mockup test to check whether this can happen.
When using the primer ports, the lines exit to the rear in the Safari installation which is crowded with things like the intakes, exhaust system, thermocouple probes and the capped off oil pan. There are special clamps that can be used to hold primer lines to the intake runners, but I couldn't find a part number for them initially (Lycoming part # 71910). Basically, the routing looked overly complicated to me with a high potential for interference and damage.
I chose to mount my primer lines in what is normally the fuel injection ports which are located on the forward side of the vertically mounted engine. This is very easy to route the lines and they're protected by the shroud from damage. This protection is also a big negative in that the lines are not easily visible when the shroud and fan are installed. I realize that these lines and fittings will need to be carefully checked when the fuel system is completed, but I reasoned that once it has been confirmed as not leaking then it should be okay for quite a long time. After all, how many pilots with fuel injected engines remove the cowl and check all their injector lines during a pre-flight inspection? Certainly these lines and fittings are an annual inspection item where one can look for traces of the blue dye from 100LL fuel. While the ideal hard lines would be stainless steel, I used 1/8" copper. Although copper will work/age harden, these lines are relatively short and well supported. Ideally the line between th shroud and firewall should be a flexible line, but one needs to remember that primer lines only have pressurized fuel when the pump is being pushed. For now, I'm planning that the lines between the shroud, primer pump and gascolator will all be aluminum and contain movement loops.
Note that a small section of my center divider is
removeable to allow the primer line to stay in place even if the
divider is removed.
I debated over the various methods of getting the primer lines through the firewall and to the gascolator and engine. I finally decided to go with flared bulkhead fittings. Part of the reason was due to the location of where I wanted the lines to exit ... if I was just using grommets and continuous lines then I didn't want them to be in the removeable portion of the firewall. By using bulkhead fittings, the lines can easily be removed and more importantly, I could locate the lines inboard of the frame tubes where they are going to be more protected from hangar rash and other "incidents".
I constructed an engine stand similar to the provided design, but chose to add casters (2 fixed, 2 lockable swiveling) to the bottom. This allows me to both easily turn the engine around as I'm working on the conversion and shroud, and also to roll the engine out of the way when I'm not working on it. Although this works well, if I was rebuilding this stand (or at least re-purchasing the casters) then I'd use swivelling casters on all four corners.
Hoisting the Engine
I had assumed that I would borrow or rent an automotive style engine hoist to lift the engine out of the crate and onto the stand, and also for the installation into the frame. While digging around in the basement, I realized I had a cable hoist puller that had more than enough capacity ( 5'+ and 6000 pounds). After putting a couple of 5/16" eyehooks into separate joists, I found that each one could more than support my weight without concern. A short chain between them spread the load and supplied an anchor point for the puller ... lifting the engine from the crate and onto the engine stand was now a simple task and I didn't have to worry about the hassles of borrowing or renting a hoist.
A side benefit of having the frame on casters is that it appears I will able to use this same arrangement for installing the engine in the frame. Instead of the more normal method of hoisting the engine and rolling it into position, I will be able to hoist the engine and then roll the entire frame into position. Time will tell how well this works out. While this would probably work well with an overhead hoist, it caused problems when using an automotive engine hoist. I had set the caster height for minimal height while still allowing for clecos on the bottom panelling. While the hoist legs would just go under the frame, there is an interference with the throttle rod that goes from the cabin to just below the carb. The quick and simple solution was just to put some blocks under the casters while installing the engine.
While the above hoisting arrangement worked well, when I moved to the hangar it was no longer available. I've since been using just a standard automotive engine hoist and it works fine. The one problem is that I actually have to block up the casters on my cabin since the legs on the engine hoist won't fit under my frame / cabin otherwise. During the final engine installation, I used a portable frame which worked out much better.
It's hard to see in the above picture, but there is a couple of problems with the engine hoist as shown in the Construction Prints. The first issue I had is that the legs on the C-channel were slightly too narrow for my engine case. I had to do a bit of grinding in this area to get clearance. I chose to mount the lift ring centered over the end of the slot that captures the prop flange. The problem with this is that it does not allow for the weight of the C-channel and subsequently the combination is always slightly tilted ... the top to the right in the above picture. If I were doing this again, before welding in the lift ring I would weight the C-channel and find the C/G of the lift assembly. From there, one can calulate the weight of the engine and the various moment arms. The lift ring would then be welded very slightly to the right in the above picture.
Although the construction manual clearly talks about avoiding heat warping during welding, my pre-welded tank had an ~1/4" warp across the top. The flush rivets holding in the retainer plate were also not countersunk deeply enough causing the heads to stick up significantly. Once I had opened up the cover plate hole (with a combination of nibbler, shears, die grinder burr and files), I elected to drill out the rivets and attempt to countersink them deeper. This was somewhat successful, but compounded by the wavy top surface. When I do the final assembly, I plan to use a gasket under the sump cover. While the retainer plate was off, I also managed to open up a couple of the bolt holes in the top cover that were off center and prevented bolt entry into the pre-tapped holes.
Care should be taken when tapping the pipe threads in the cover plate since it is very easy to go too far when trying to get maximum depth with only one thread plus showing. I also chose to add another 1/4" NPT tapped hole to the cover plate to allow for the possible future use of an oil separator return line. For now, this hole is just plugged, but I thought it was much easier to do it at the same time as the other holes and before final mounting. Note that this was done after this photo was taken.
Opening up the filler tube hole was thought provoking; originally I thought about using a drill-type hole saw, but the necking down didn't allow for a convenient fit. After drilling a hole of about 1/2", I was able to get a round file in there and then eventually open it up enough with a round file to get a larger half-round bastard file in. Eventually it was smooth with the walls. I found that by wrapping the top of files with duct tape I didn't have to worry about gouging the threaded top area of the neck. One concern I have is for the o-ring or gasket holding the cap in place. I used the o-ring from the original filler tube, but I'm not totally happy with the fit and resistance to turning. I had a chance to look at the factory ships and they have chosen not to use any kind of o-ring under the cap and just rely on the metal-to-metal friction. One thing I chose to do was to turn/mill a lot (over half) of the aluminum off of the cap. I felt this cap was just too big and heavy for our needs and just added mass where it really wasn't required.
The rod that actually measures the oil was a press fit into the pre-drilled hole in the cap. I chose to slightly roughen it and add a bit of JB-Weld to lock it into place. I also found that it was quite difficult to get a good reading when initially calibrating the probe ... mineral oil on a silver rod is very hard to see and I had to be extrememly careful not to let it touch the side of the filler tube. After several tries, I eventually got what I felt where good consistent readings and added a filed groove at both the 6 quart and 8 quart mark.
Trivia: I was wondering about the large size of the threaded portion of the cap ... turns out it's the same (or very close) to that on the neck of a one quart oil bottle. I found that the Scottish blood in me allowed me to slighty screw the bottle into place so that the last part (drop) of it would drain into the tank.
I drilled a safety-wire hole in the drain flange and plan to use the supplied plug at first. After a couple of oil changes I will change this to a Curtis CCA-1650 3/8" NPT fitting. I figure that anything that makes maintenance easier will be one less excuse on why to delay it. My reasoning on the delayed installation is that the Curtis fitting is somewhat more restrictive and I would prefer to ensure that any metal chips etc. from initial running are more easily extracted and visible with the used oil during break-in oil changes.
As an alternative, I found a reference that several RV owners are using the Fumoto T202N valve. I have not seen one of these but can appreciate that the ball valve style would definitely give a better flow and eliminate the O-ring in the Curtis valves. Note that the T202N is for 1/2" NPT as used in a Lycoming sump and the F110N is for 3/8" NPT.
Originally I'd planned on using a 1/16" cork gasket under the cover plate. When I looked carefully at this after painting, the irregularities weren't as bad as I'd thought they were. Instead of a cork gasket, I just used some Permatex gasket maker under the cover. Although there will be an oil mist inside the tank, it isn't a pressure vessel.
I know ... it's still missing one safety wire in this picture
The oil pickup fitting supplied in the kit was an AN842 right angle hose fitting. I had seen where another builder changed this to an AN844 45° fitting and this seemed a good way to try reduce some of the restriction that is imposed by a 90° fitting. In hindsight, I'm 50-50 on this change as the hose is just starting to oval ... perhaps it's just the angle of the fitting on my sump plate.
The fittings for the valve cover drains supplied in the kit and shown in the above picture are AN840 straight fittings. I found that by using these that I had a lot of trouble trying to route the hose to the right side (i.e. cylinder #4) in order to get the hose horizontal or preferably a downhill run to the tank. By changing it to a 45° fitting, I was able to get this hose horizontal and it routed fairly easily. Since the tank was already mounted and the other fittings and some hoses were in place, I actually used an AN915 45° elbow to achieve this ... it could be installed without removing any other fittings. I left the fitting to the the left side (cylinder #3) as a straight fitting but a 45° fitting would also make the routing of that hose much straighter.
For me, the hardest oil line to route was the large vent hose. I had a couple of places that were likely candidates but they caused too sharp of a bend in the hose and caused the hose to flatten. I have seen where a builder chose to use a metal hoop to make a sharper 180° bend that avoids this kinking. While that will work physically, I would worry about whether the metal inside the tube would cause water vapor to condense before making it around the bend. Perhaps placing the metal hoop so it is in the hot air exit from the cylinders would prevent this. I ended up routing the hose as high as possible then forward and down to a point about half way between the oil tank and the firewall. As to a whistle slot in the hose ... I need to do some more research or get some informed feedback on that.
Once I'm operational, I want to monitor the amount of oil that is vented by the tank. If it is excessive, I think that one might be able to add a baffle to the cover plate such that there is not a direct path from any of the return lines to the vent fitting. In hindsight, I wish I'd just welded this in place before anodizing the cover plate. I've also talked to an owner who indicated that 8 quarts of oil is actually too much for his installation and that his system quickly settles in at about 7 quarts after which he needs to add another quart about every fifteen hours. His recommendation was to mark the stick at six and seven quarts and use these as the full / add lines.
I had some qualms about removing the original sump's oil screen from the system and had a couple of thoughts on how to install one. That's an issue for a later time but in the meantime I hope my full-flow oil filter will suffice.
The mounting tabs are narrower on my tank than on the frame.
Rather than just suck the difference up with the bolts, I chose
to fabricate a filler shim of ~ 1/16"+ which I'll verify
after paint whether it's still required.
Update: A shim still looks appropriate after the painting.
However, I found that I had some .028" stainless that made a
perfect fit.
Similar to the fuel tanks, the welds on the oil tank need to be checked. I found one corner that had a fairly major leak from a very poor weld.
Now that everything is installed in it's permanent position,
it would appear that the crankcase oil return tube on my tank is
not centered below the return on the engine. No dimension is
given on page #33 of the Construction Prints but it would appear
that the boss on my tank is centered approximately 3-1/4"
from the edge and would need to be about 1/2" further over (about
3-3/4") to be centered. If one is building their own oil
tank per the plans, my suggestion would be to defer welding this
boss until the engine is installed and the tank can be positioned
in place to measure where the boss needs to be. I'm hoping that
this offset will be okay with the provided hose, but since my
engine is still pickled and sealed, I don't want to install the
hose until just before I'm ready to run the engine.
Update: I managed to get the hose in place and it appears that it
will be fine. Note that if the engine has been properly pickled
and standing for awhile with this port capped then there will be
oil pooled above it when the port is uncapped ... and yes I
learned the hard way when I wasn't prepared for the amount of it.
New Pancake Tanks
Note that owners of the new "pancake" oil tanks ... they appear to use a different venting arrangement from what is shown in the Construction Manual(s) and Prints and I've yet to see any factory documentation on this. More information is in the Safety section.
I've now seen a factory installed version of this oil tank. While it's my understanding that originally it did not use a crankcase vent line from the stock cylinder draindown fittings, this one had a vent line. It went from the crankcase #1 draindown fitting to a welded "Y" connector which was inline with the drain line from the #3 rocker cover. Personally, I would prefer an extra boss on the tank rather than the "Y" fitting and extra connections.
I have only done a trial fit of the supplied oil cooler at this time. Although the fit is tight around the hose area, it looks like it will be useable with some shimming. Neither of the welded mounting tabs on the frame uprights were at 90° to the frame in either axis. Rather than just torque the bolts a little harder, I will be making some wedge shaped shims to take up the ~1/8" gap on one side and ~3/16" gap on the other. It seems to me that if I just torque on the .125" mounting tabs they will force the .049" wall tubing they're welded on to twist and be under constant stress. Since the factory both welds these tabs and provides the oil cooler, it would help a lot if they created a jig so these pieces actually fit and didn't require wedge-shaped shims.
I finally decided it was actually easier to try bend (i.e.
straighten) the tabs rather than mill tapered shims. After the
tabs were straightened, various combinations of shims were tried
in order to find the best fit and clearance for the inlet/outlet.
Eventually I ended up with a .063 shim on the left side and a .090
shim on the right side. Note that the tabs on the cooler itself
are different widths and the bolt hole locations should be marked
individually. Also, be aware that the tabs on the oil cooler are
a relatively soft metal. Since I was drilling from the outside
in, this means that on the left side I went through the 4130 tab
into the cooler tab while on the right side I went through the
cooler material before the 4130. One has to be careful doing this
on the right side; if I were doing it again, I'd probably use a
90° drill here so I could go through the 4130 first on both
sides just to be safe.
Update: I've noticed on a newer frame that these tabs had quite a
visible offset bend in them that I assume was done before the
tabs were welded to the frame. It would appear that these are to
prevent the requirement for shims.
I don't have an answer yet as to why the oil cooler lines have
reducers at both ends since it would seem logical to try create
as unrestricted a flow as possible. Superior also must believe
this as their manuals talk about using large diameter oil lines
and avoiding things like sharp bends in order to minimize flow
restrictions. One thing I am aware
of is that this particular type of cooler did have some issues
with cracking around the hose fittings when used in it's original
application. Perhaps the reducers are to alleviate this kind of
problem.
I am now aware of one Safari owner who has experienced this
cracking around the hose fittings and it should serve as a
warning to all builders not to over-tighten these fittings. When
installing the reducers (or fittings for those using flared lines),
one should use lots of thread lubricant/sealer and be careful not
to over-tighten them. If the NPT threads aren't deep enough or
don't have the correct orientation then they should be carefully
tapped deeper rather than just tightening them some more. When
the hose or hose fitting is installed, it should be done using
the double-wrench technique whereby one isn't trying to further
tighten the threaded portion in the actual oil cooler. If one
spots a bit of oil weeping from these connections, resist the
temptation to further tighten it and always check first for
possible cracks.
The cooler has a thermostatic valve which would appear somewhat redundant as the engine also has a vernatherm controlling the diversion of oil to the cooler once it reaches a pre-set temperature. This thermostatic valve in the cooler also acts as a pressure bypass valve, but I still wonder if this setup is just creating the opportunity for double the chances of failure. Primarily because of the pressure bypass function, I will leave it in place for now. In sticking with the aviation use of this device, I added a safety wire to this valve.
I have couple of concerns with the MIL-H-6000 hoses:
I realize these are relatively low pressure lines, but I'm tempted to change them to AN flare fittings and Stratoflex 124[K] or Aeroquip 666 teflon hoses which have a virtually unlimited shelf and service life. With a bit of torque seal one can also easily see if the fittings are loosening at all. Routine and annual maintenance then becomes an issue of inspecting for chafing, rather than this plus keeping track of service times. Definitely a more expensive way to go, but it would probably add a lot of peace of mind.
Update: I think I've finally come up with a reasonable compromise between cost and reliability. The sump to engine pickup hose and the oil cooler lines will use flare fittings and teflon hoses while the valve cover and engine return lines will use MIL-H-6000 hoses and clamps. Thus the critical pickup line should be protected against air leaks and the pressurized cooler lines will have secure connections. The engine return line can't easily move and the fittings on my valve covers have a "bumped" design that should prevent them from slipping off.
The question for the oil cooler lines becomes what size of braided hose to use. The MIL-H-6000 hose and fittings are 3/8" (.375" ID hose) but -6 braided hose has an ID of .312" and -8 hose has an ID of .406". I decided to go with the -8 lines so as to not restrict the flow any more than required. I'm using AN816-8 (N.B. steel not aluminum) straight fittings on the engine and AN823-8D 45° fittings on the cooler ... the hose has 90° fittings at the engine end and straight fittings at the cooler end. While the AN 45° fittings aren't too bad, I prefer to use smooth 90° hose ends rather than the 90° AN fittings which have a sharp lip on the inside. The actual hose lengths (flare to flare) were 37-1/4" and 38" but these could be slightly different for other engines and hose routings ... I could have probably made both hoses 37-1/4" without problems. While teflon hose would be the Cadillac solution, their fittings are expensive and hard to find ... Aeroquip 601 should be fine and I'm choosing to use AQP hose and fittings since it's available locally.
Update2: I tried changing the fitting on the engine's sump plate from a hose fitting to a flared fitting. Unfortunately I'd tapped the sump plate to get the hose fitting as deep as possible and the flared fitting bottomed out before fully sealing. While I could have partially filled the hole and re-tapped it, for now I'm going to stick with the hose fitting and make sure there is enough excess in the bent hose to prevent it from ever coming off. This doesn't solve a potential leak in the pickup line or fittings and I'm thinking I'll probably eventually change these fittings and hose; perhaps at the first annual.
One of the things that I noted when installing the oil lines is that it is impossible to route the lines so that all the oil is drained from them when doing an oil change. The line from the right rocker cover (cylinder #4) would have had a significant upwards bend if using a straight fitting on the oil tank ... by going to a 45° fitting it is about horizontal and by using the wheel on the right skid it will drain downwards into the tank. The issue that I couldn't resolve is the lines to / from the oil cooler. Since they come downwards out of the bottom of the accessory case and then go up to the oil cooler there will always be some kind of a "U" bend in them. As a result, there will be perhaps a cup or so of oil in these lines that is not changed during an oil change.
I chose to purchase the factory built exhaust system. While I have heard about others who developed their own performance style exhaust system, I had two considerations:
At this time I have only done an initial trial fit of the exhaust system. It was definitely a little tight with it's fit on one cylinder, but the ball joints took care of some of this and it seemed to fit better as the various bolts started to get snugged down. The bigger issue which I haven't resolved at this time is that it would appear that the system is out of alignment and offset to the left side, possibly a little before the "can" and more so from the "can" to the actual tailpipe. Since the engine and boom are not installed on the frame it's hard to actually verify the fit, but the tailpipe eventually rides in a relatively narrow channel in the boom. I was having trouble with the shroud fit when these pictures were taken so I can't tell yet whether the top of the "can" will align with pre-installed flange in the shroud's heat collector.
Note that the above images were enhanced. Since the center line marker (dropped from the case halve part line) that I used didn't have enough contrast, these images were first blown up and a black line placed over it. In the right image there's a shadow from the dropped line which I didn't remove; look for the weight at the end of the dropped string, not the string's shadow.
I had sent the above pictures to CHR and asked them about this since I was aware that another builder had a 360 exhaust with an offset tailpipe which they chose to remove and re-weld at the correct angle (that was after he decided not to use the factory recommended solution of just heating and bending it with an oxy-acetylene torch). The response I received was that I should wait until the engine was installed and tailboom attached to verify the angle / clearance before they would consider a warranty repair. Well, several years later and with the boom attached, the exhaust is still off center the exact amount shown in the above pictures ... I really do know how to project a centerline and measure offsets. Needless to say, I'm not happy with the outcome or the delay in dealing with this. Although the tailpipe does clear the frame, it would make mounting the support bracket somewhat difficult and it looks pretty crappy to me.
Interesting effect of dust on the boom due to the flash ... not nearly as noticeable to the eye
In one respect its actually good that I delayed shipping the exhaust back to CHR as I've now found an even bigger problem that could only be identified with the engine in the frame ... the ball joint on #1 cylinder is somewhere between touching and 1/16" away from the frame (the exhaust can be moved a bit during installation due to CHR's use of oversize holes on the flanges) and it's impossible to position the two flanges and their three bolts!!! While it's obvious that CHR's jig is/was out for the tailpipe, it would also appear to me that they never mounted a finished exhaust system in a frame with a 360 to verify whether it would actually fit. Considering their stated policy that they won't release anything (including replacements for unsafe items) until it's had 100 hours of test time, it might seem hypocritical that they'll sell a $1,500 exhaust that's never even been trial fitted. I debated about getting my local welder to re-position the #1 stub and the tailpipe versus incurring the delay and costs of shipping it back to CHR (the only question is whether for repair or a refund). Just one more ill-fitting piece in an ever-growing list that needs to be dealt with by the builder rather than quality control ... what a waste of time, effort and money. If I'd wanted to custom build and fit an exhaust then I would have just planned on this from the outset and built a tuned system that yields performance gains. At least if I'd built it myself I would have used proper sized holes and properly faced the flanges the way companies like Vetterman do ... in addition to a lousy fit, obviously CHR doesn't think these kinds of things are important.
Also notice the non-standard CHR markings ... this is actually #1 and #3 cylinders using Lycoming's numbering
I decided not to send my exhaust back to CHR. After all, they're the ones with the bad jig and I have no reason to believe that it would be any better after they work on it some more. Instead I'll just slice & dice then have my local welder correct it. This will also correct another issue whereby all four ball joints won't fully seat at the same time. I can also have him weld on some tabs to try prevent cracking of the tailpipe (more about this further down). As I said before, what a waste of time, effort and money to correct factory mistakes on an expensive component ... it probably took me as long to prepare these changes as it did for the factory to tack the system using new clean parts (cutting off both sides of a ball joint, clean them up, try bend a tube a bit, fabricate an extension, cut off the tailpipe and prepare it for re-welding).
With the tailpipe cut off, one of the things I
noticed is how heavy it is ... it's 2-1/2" OD x .065"
wall which is ~ 2.34 pounds (at 1.7 pounds/foot). The runners are
only .035" wall and I can possibly understand the main can
being .065" wall due to structural support. However, I see
no reason why the tailpipe couldn't be thinner ... 0.049"
wall would save over 1/2 pound and .036" wall would save
over a pound (~ 1.11). Similarly changing the inner can tubing to
.036" would save just under a pound (.93) and changing the
outer can to .036" would save over two pounds. This weight
is behind the CofG on an already tail heavy craft and it's this
kind of attention to detail that would help correct the balance
and save extra lead in the ballast weight. It would appear to me
that the tailpipe is made from 304 stainless rather than 321
stainless which is more common for aircraft exhaust systems ...
since 304 is normally available in 1/16" wall increments
this could be the reason for the thick tailpipe. Although 321
tubing isn't as commonly available as other alloys, Wag-Aero's printed catalog
shows it in sizes from 1-1/2" OD through 6", including
2-1/2" x .036"/.049", 3" x .036" and 5"
x .036" ... wished I'd seen this before
welding my tailpipe back on.
Sidenote: Although I didn't do it, I wish I'd changed the angle
on the tailpipe more downwards when I had it welded back on.
There are two reasons for this: firstly it would allow me to use
a more flexible retention mechanism to allow for more movement
and secondly it would keep the exhaust further away from the boom.
One builder has told me how the heat and soot from his exhaust
has permanently affected his paint on the boom.
One of the decisions I'll have to make is whether to have the exhaust system ceramic coated in order to reduce the temperatures in the heads and the exhaust system and possibly gain a little performance. This decision has been deferred until after I'm certain that it will fit and not require additional welding to be performed ... from what I understand, parts cannot be welded after ceramic coating. Based on what I've read and the experience of others, the only two coatings I know of that I would consider are Jet Hot 2000 and HPC's HiPerCoat Extreme. I am aware of one builder who used a local coater for a product that they claimed was good for 1500°F and it started to discolour and flake off over the first foot or so within the first hour of running time. At this time I have not tried to get a cost estimate but I have heard that Jet Hot will no longer do work on anything related to aircraft due to insurance reasons. This needs to be checked out, as does getting some more information from Performance Coatings. I am also aware of one Safari builder who had his exhaust coated with HPC's HiPerCoat Extreme and I'm waiting for feedback as to how it holds up.
If I get the exhaust system coated, I will probably not get the stub from the #2 cylinder to it's ball joint coated or alternatively, just the exterior of it for cosmetic purposes. The reason being that this is where I'll be placing the carb heat muff and one wants a good source of heat. I've seen promotional literature which show the temperature of an exhaust tube reduced by over 60% in some cases and 300°F to 600°F in anothers due to ceramic coating.
Update: Well I finally made a decision and am
having my exhaust system coated. After a bit of self debate, I
contacted HPC about getting it coated with HiPerCoat Extreme.
Email does not seem to be an overly effective way of dealing with
them but things went very well on the phone and I didn't consider
their price to be out of line. Until I've got a couple dozen
hours on it I can't really say how durable the results are but I
don't anticipate any problems.
Tidbit: Although I'd been dealing with HPC, the package actually
went to Jet Hot. If you check the corporate ownership you'll see
that they've both been bought out by nCoat, Inc. On that note, I
looked at the corporate filings and it did show me something that
scares me in this economy. In their quest to corner the market
they are carrying a huge debt and are currently in default on
some of their payments. Will they survive? I don't know as I'm
not an economist but it would be a shame to see two successful
companies destroyed by a third party's vision of dominance.
The exhaust is finally back (FedEx Ground is
extremely slow) and installed. I think the appearance is great
but I'm now dealing with a chipped area about the size of a dime.
I really don't think I did it, but it is possible that it was
done as I unwrapped their packaging if the ball joint plate
scratched this area ... I certainly don't remember doing or
hearing anything that should have caused this. Although Jet-Hot
is willing to redo it, the shipping could be more than the
original coating cost. They already chose to originally return it
via 2-day express versus the ground shipping that we'd discussed
and that added an extra $100 to the cost ... one of the major
pains when dealing cross-border. I had clearly noted in writing
and with tags / tape that there were two areas that I did not
want coated: the inside of cylinder 2's stub and the inside of
the main can (i.e. cabin heat). These turned out to be coated.
One more reason that I will now only deal with local coaters
where we can discuss this type of thing while looking at the
physical parts and they can include whatever markings they
require.
Trivia: I was surprised to see that the inside of the tubes were
greyish and not black. I have talked to their customer service
and it would appear that this is a two-stage process ... the grey
is the base protective coat and the black is a decorative top
coat. If I'd known this before hand then I'd probably have just
gone with the grey ... it wouldn't have a chipping issue and if
it did then it wouldn't be very noticeable against the stainless
substrate.
The other issue I would like to address with coating application is whether it's possible to coat the interior walls without coating the inner "can" surfaces since this is the one place where one does want thermal conductance for the cabin heating system. If one is welding their own exhaust system similar to the factory system, they may want to consider making the inner can removable (or at least defer installment) to allow for this coating. As a thought, if the lips on the top and bottom were made a little bigger in diameter and only above and below the can, they could have slits added and after coating an inner can tube could be slid into position and held with clamps.
Food for thought: There seems to be a group
within the Van's RV camp that thinks that ceramic coating is not
a good idea. Their reasoning is that this is an air-cooled engine
and the exhaust actually helps to shed heat ... unfortunately I
haven't seen any test data to back this up. At this time I don't
have a good handle as to whether ceramic coating would raise or
lower the cylinder temperatures in the Safari configuration.
Perhaps a compromise solution is to just coat one side of the
pipes ... the interior only would probably allow more heat
dissipation while the exterior only would look better
cosmetically.
FWIW: I haven't worked a lot with stainless but I have seen
references that state it does not conduct heat nearly as well as
4130. While doing some cutting on stainless tube with a grinder,
the end became a dull red ... obviously it was very hot near the
end and way too hot to touch, but just a few inches away it was
at ambient temperature and comfortable to hold.
Another reason that one may want to coat their exhaust system is if they are conscious of the looks of their machine and/or trying to create a "show special". Although it is made of stainless steel, it definitely takes on a "rust like" appearance very quickly.
A stock Safari exhaust system after approximately 20 hours of
running
I've received information from another builder who stated that it is very important that the clamp that holds the very back end of the tailpipe should not be tight. While it should be restrained enough to prevent much movement, there should be perhaps 1/32" or more from the tailpipe to the top supporting plate. Without this slight clearance for movement, the exhaust may break. More about clamps / hangers further down ...
I've also received information from a different
builder about potential cracks on the sides of the main vertical
"can" where the tailpipe joins it. He noticed signs of
cracking here within a few hours of operation and also noticed it
on a factory ship. His recommendation is to weld gussets on each
side where the tailpipe joins the "can". The more I
look at this, the source is pretty obvious ... the engine is
mounted on rubber bushings to allow movement and due to the
transmission essentially locking the top of it, any vibration
will most likely have a large rotational component around the
crankshaft axis with a much smaller vertical component that will
then be magnified over the length of the exhaust system. The rear
of the stock exhaust system is mounted in such a way that it
allows fore-aft movement but essentially no side-to-side or
vertical movement. The ball joints would be of neglible help in
dampening this movement and thus all the stresses will be focused
where the tailpipe meets the "can". All in all, a very
poor mounting design. While the gussets would help in preventing
or just delaying the cracking, I think a different hanger system
is required which will allow for side-to-side and vertical
movement at the end of the tailpipe.
Update: I noticed that the customer ship at Sun-n-Fun '08 had
addressed this issue. The tailpipe had been welded on at a
downwards angle and the two side supports at the end were
actually springs going to the adel clamps rather than being
solidly mounted. I'm thinking that automotive exhaust "rubber"
hanger material could possibly also work.
Update 2: I've received information from another builder
with low hours on his ship and a crack on his factory exhaust
where the tailpipe meets the can.
Since my exhaust had not been coated, I was still thinking about the multiple reports of cracking that I'd received. I decided that I'd add gussets before final installation as a preventative measure. Looking around, I had some 1-3/4" SS tube that I used to cut a couple of sections out of which were then welded to the side of the main can and the tailpipe. This is similar to the gusset that is used on some production aircraft exhaust systems.
I've now heard from an owner with a similar factory exhaust system who has experienced the start of cracking at the joints where the runners enter the main can. Perhaps I should have added gussets to these as well just a preventative measure. Since my exhaust is now coated, it would be much harder to do it at this time.
It had been bugging me trying to figure out how
to make an effective hanger for the end of the tailpipe and I
considered many alternatives. Eventially I came to believe that
the only reason for a rear hanger is to try support some of the
excessive weight of the tailpipe itself as the main "can"
and runners are totally locked in position by the exhaust studs
in the cylinders. I don't believe that one wants to make the
tailpipe rigid in any direction with the use of a hanger. Due to
embrittlement when welding stainless, I also wanted to try avoid
any welding of tabs to the tailpipe for the hanger. Eventually I
decided to add a stainless clamp band round the rear of the
tailpipe. This band then has a hole in it to receive two springs
that go up to adel clamps on the middle set of boom tubes above
it. Time will tell how effective this is and as an initial safety
guard I'll be adding a piece of thin cable through the springs in
case they break.
Update: I think the basic approach has merit but my
springs didn't last very long. I chose to form loops at the top
of the springs which were then clamped by the bolts on the adel
clamps. This made for a very rigid attachement and it couldn't
withstand the vibration from the springs. Both sides broke right
where they were locked to the adel clamps. By changing this
attachment to a loop-on-loop junction I think it would last much
longer.
Update 2: I changed the top of the springs from loops around the bolt heads to loops that went through holes in short extenders. This arrangement has about 5 hours of run time on it now and there doesn't appear to be any problem with spring breakage. Just to be on the safe side, I have a piece of safety wire looped through the springs and adel clamps to capture the spring in case it breaks.
One can also see some of the exhaust residue on the frame in this
picture
There also seems to be some question whether the exit tube on the CHR-supplied system is too small for the O-360's and is creating excessive back pressure. This is second-hand information, but it was a hypothesis put forward as a result of excessive soot in the exhaust collectors but perhaps it could have been the result of an excessively rich mixture. With the tailpipe cut off the "can", I can see that there isn't a lot of exhaust gas clearance and it has to make a sharp 90° bend to move down the tailpipe. I'm sure that if one could increase the room in this area that it would promote a better flow. Perhaps a necked-down or "dented" cabin heat inner tube or a bell flange leading to the tailpipe would help.
I am aware that there are several Rotorway owners
who are experimenting with the Aero
Turbine mufflers with built-in resonators. If I was going to
try a tuned exhaust sytem then I'd look carefully at their
products. Note that these mufflers are about 6 pounds or about 9
pounds with the built-in resonator.
Update: There is at least one report of this muffler loosing it's
effectiveness with time. The hypothesis is that the higher
exhaust temperatures in aircraft are causing some of the internal
parts to change and/or come loose.
Another source for aircraft exhaust parts is Sky Dynamics Corporation. Their ball joints are considerably cheaper than what is listed in various other catalogs and they are the only place where I've seen a very nice 4 into 1 adapter.
Maintenance Item: It should be noted that Larry Vetterman recommends that the type of ball joint used on the Safari exhaust should be lubricated with Mouse Milk every time the cowl is off (obviously this relates to fixed wings). The rational is that these joints will stick otherwise and that there will be no movement in normal operation. I'm not sure how this affects exhaust systems that have been ceramic coated, but I would assume that it is less critical.
Sidenote: One may want to consider using anti-seize on the exhaust bolts/nuts. I've read various horror stories of people trying to remove exhaust nuts after a lot of running and ending up messing up the studs.
Operational Issue: Now that I've got a few hours on my machine, I've discovered a very unexpected side effect of this exhaust system ... there's a lot of exhaust residue on the boom and cables behind the exhaust exit. I would have expected that the blade downwash would have swept this away as there is a fair gap between the exit and anything else. The heaviest part of this residue is in the first foot or two behind the exit but I can also see signs of it much further back. Perhaps one could try angling the exhaust downwards but that could introduce a possible fire hazard in tall grass. I'm going to try build a bit of a deflector to keep the worst of this residue off the frame and cables.
I have heard from some that carb heat is not required when using the factory exhaust system due to the heat from the oil sump cover and the exhaust system being in close proximity. While this may be true under some circumstances, I'm not willing to gamble a forced autorotation on it since I've also heard from others that they have experienced ice on the exterior of the carb and icing temperatures in the venturi. Icing is a very real condition in carburated aircraft engines and the Canadian regulations require a source of carb heat. I'm sure that anyone who has flown with an instructor in an R22 has had the use of carb heat drilled into them and I've personally seen how quickly the temperature can drop into the icing range when carb heat is removed.
As part of the pre-fabricated shroud option, I was surprised to see that one side of the air filter housing was included. While this was an unexpected bonus, I didn't think this piece was useable without some changes since at one end there was an ~1/8" gap. It would appear to me that there is a discrepency in the CAD templates and the marks for the bends on one end of the top plate are ~1/8" longer than at the other end. Instead of matching the bends on the top plate to the actual side pieces, this plate was pre-bent to the marks which resulted in the gap.
I started to work on this piece and was planning
on just trying to move the bend line and see how the modified
piece fit. About this time I looked at my scrap bin and noticed
some square tubing which gave me an idea. I took some 1"
square 6061-T6 tubing and ran it through the band saw to make a
squared "U" channel whose legs were about 1/2"
wide. This gave me a consistent height for the side pieces and it
was then straight-forward to fabricate the top piece and make a
nice solid square unit that fit perfectly. Its a little
heavier than the original due to the .063 wall of the tubing vs.
bent .032 sheet, but not enough for me to even think about. I
added four 3/32" rivets in the corners to firmly hold this
collector to the filter frame. There's no need to remove this
piece during filter changes and the extra fasteners will help
prevent any bowing and/or air leaks.
Update: If one is mounting this housing on the right side of the
craft then the SCEET tube to the carburetor will probably
interfere with the throttle rod. The solution is to route the
SCEET tube forward and around one of the engine mounting tubes.
If the selector box outlet ring were mounted low and forward then
it would make this routing easier. Another lesson learned the
hard way but I'm not going to go back and refabricate this piece.
I actually did use a couple of universal head rivets during construction
The harder part to fabricate is the actual heat control flapper assembly. I had some ideas for a different design but finally just went with the basic design in the construction prints. Of course I had to play with some changes that I felt would make it more solid and reliable ... I used 1/2" x 1/2" x 1/16" angle along the long edge, reinforced the flanges where the bolts go through and used oilite bearings for the flapper. One of the decisions is which side to put the control arm on since without all the other equipment in place it's hard to visualize the routing of the control cable and what it may interfere with ... my control arm ended up on the rear side. The filter housing has tangs on the element retaining screen that create 1/2" wide "bumps". Because of my side rails, I just added metal spacers on the ends but it would be much quicker and easier to just bond on some 1/16" gasket cork (shaped liked two squared "C"s) to the filter housing.
The actual flapper was made from 4130 plate welded to a 1/4" rod. After seeing the weight of this, I debated whether to remake this piece from aluminum ... something like .080" on an aluminum rod. In the end, I didn't and would still need to consider the effect of heat on an aluminum flapper and how much the pivots would wear. After everything has been assembled and painted, it will be noted that there is a gap between the flapper and the SCEET flanges. I used some high temperature RTV and release tape on the flapper to seal this which also prevents the metal-on-metal clunk at the limits.
The filter housing has a drain hole on the long
side, which is normally on the bottom. I plugged this hole with a
rivet and drilled a new drain hole on the short side that will
become the new bottom. I've seen various installations that used
bolts and all sorts of brackets to hold the filter main housing
in place on the frame. I just riveted some 1/8" aluminum
straps onto the housing and the two lower ones are then bolted to
tabs that I'd previously welded onto my frame. The top rear strap
is attached to an adel clamp since I wasn't sure where exactly to
place this tab on the frame when I was welding the tabs on. The
one thing that I really hadn't paid attention to when I was
making the brackets is the routing of the throttle rod ... I'm
not sure if it is going to cause me to do some extra routing of
the SCEET tube. In hindsight, it might have been better to mount
the selector box on the left side of the craft.
Update: The throttle rod has caused me problems in routing of the
SCEET tube. If re-doing this part, I'd delay fabricating the
mounting brackets and actuator arm until I was ready for final
assembly and then make the determination as to whether it's
easier to route the SCEET tube around the throttle arm on the
right side or around the oil lines on the left side.
The actuator arm could just be welded to the shaft, but I wanted separate pieces for the assembly and painting process. I wish I hadn't sold my surplus Robinson collective friction lever (p/n A332-1) as it would have been perfect for this use. I ended up fabricating a 2" arm that is very similar and mounted upwards (pull for hot) and used a CE1 cable attachment. Since my cold air is on the bottom, in the event of cable or arm slippage / breakage the flapper will fall to the full hot position. When mounting the control cable, the last adel clamp could be on the frame tube, the filter housing or the flapper housing. I'm going with the flapper housing and hopefully I'll be able to swing this whole assembly out of the way to change the filter element without having to disconnect the control cable.
Mike Smolek found the following item for a leaf guard and kindly provided me with one of them when I couldn't find it locally. Hopefully I don't ruin a small business opportunity for him, but this item is actually sold as a pencil cup! Perhaps CHR will invest in a case of them and supply them with the basic kit as they're very cheap, light, easily adaptable, not readily available to all builders and save some fabrication.
Tip: If a builder is thinking about removing the gasket on the Brackett BA-6210 in order to paint the housing, they should be aware that the frame has an ~1/16" safety lip on the inside of the gasket area. The gasket either has to be saved for re-use (difficult to do) or a new gasket will need to be made after painting. I chose to use a 1/16" cork replacement gasket and also some Permatex gasket sealer.
Ready for cable clamp and final installation
The hot air source to the selector box is supplied by a duct around one of the exhaust collectors and there are a couple of different examples shown in the construction notes. One tip that was passed on to me from a builder was to not clamp the supports too tightly to the exhaust header. I'm not sure if it's due to thermal expansion or vibration, but supposedly this duct is prone to cracking if it is clamped too tightly.
There are at least two different heat collector duct styles shown in the various construction prints / notes; a simple tube with a slot and a more traditional muff style. I have received feedback from one builder who found that the simple tube with a slot style was not very effective and he switched to a hybrid. I've also noted that various R22s I've flown have different styles of collectors but most were either of the full muff or half muff type ... in both cases they are quite effective. Because of the bend in the header and trying to maintain clearance for the spark plug, construction of a full or half muff isn't as straightforward as it appears at first. I started making a half muff and then ended up scratching my head as I was trying to figure out exactly where to place it. Meanwhile I was looking at the spare metal box and noticed some 3" x .065" wall aluminum tubing. In order to move the project ahead, I did a quick and dirty slice on the tube to make a collector that should be useable for initial testing. A couple of pieces of stainless were then riveted on to act as both standoffs and mounting ears. Hopefully the fact that it is on the bend should help to produce a bit more heat than if it was only on the straight part of the header. I'm fully expecting to have to revisit this piece and fabricate a new collector, but for now I have a useable piece that will allow me to pass the inspection.
One needs some way to connect the SCEET hose from
the selector box to the intake side of the carburetor. Ideally, I
can see how one could mill a custom piece to do this but I don't
feel comfortable with the accuracy of the mill that I have access
to ... plus it would take a lot of work. There used to be a
potential source of these adapters here, but
unfortunately they're no longer available. Because
of the size mismatch, I chose to mount one of the SCEET flanges
to a piece of .080" aluminum which is then bolted to the
carb with a 1/16" cork gasket between them. I wanted to try
keep the flow as smooth as possible and due to the irregular
shape, I used a piece of clear acetate to trace the carb flange
and then transfer it to the sheet aluminum. In addition to
rivets, Araldite was used to bond the flange to the plate and
also to smoothen the inside transition edges.
Hindsight: I chose to center the flange on the mounting plate.
However, if I was doing it again, I would slightly move the
flange towards the side of the plate that goes to the rear of the
craft ... perhaps 1/8" or 3/16". This will give extra
room for the SCEET tube to clear the oil intake fitting on the
sump plate.
Blue is the carb ID, red is the flange outline and green is to allow extra flange lip width in the corners
Ready for paint
Update: It looks like this piece will end up in the scrap bin. The SCEET tube has too much interference with the oil pickup fitting for my liking and the only way to obtain clearance means that the tube has to be "crushed" which then significantly alters it's cross section area. I'm going to try fabricate a new adapter from plate and 3" x 1/16" wall tube that has an offset built right into the flange.
Much as I hate to re-fabricate pieces, I made a
new flange with a built in offset. This way the SCEET tube is
well clear of the oil pickup fitting and won't rub against it.
The only difficulty is the routing of the tubing to the air
selector box since I'd already fabricated the mounts for the
right side of the frame.
Tip: I first did a rough sketch on paper of the relationship of
the intake manifold, sump plate and the oil pickup fitting. A
couple of 3" x 3" Post-it notes made an easy way to
check the clearance and set the angles to cut the tubing.
Tip 2: On this iteration, I made the plate that goes against the
carb a bit bigger than required as there is about 1/2"
between the manifold and the sump cover. Since the carb was
installed on the manifold, the final fore-aft position was
determined by trimming the edge of the plate furthest from the
sump cover until I was happy with the clearance. Once that was
done, the rest of the plate was sized to match the carb base.
For those that are building a show ship or are just interested in the ideal solutions, there is an outfit here who will add vulcanized smooth ends onto SCAT and SCEET tubes. This should stop any kind of end fraying and make it much easier to hold the tubing to the flanges with regular clamps. Before ordering these kinds of custom tubes, I'd want to be quite sure of the actual lengths I required.
I've included this with the engine stuff since this is related to both the oil cooler and the exhaust. Since I'm going with the CHR exhaust for now, I'm running a SCEET tube from the oil cooler outlet to the top of the "muffer can" per the instructions. The bottom of the can has an outlet for the hot air and my cabin is plumbed for it ... the real question is how to build an appropriate selector valve. I've chosen to defer this until after the engine and exhaust is installed so that I can see exactly what kind of space I'm dealing with.
I am aware that many builders in warmer climates choose not to install the cabin heat source and other builders choose to remove the oil cooler heat collector during warm weather operation in order to maximize air flow through the oil cooler. In conversation with another builder recently, the topic of how to defog the bubble during high humidity operation was discussed. There is a source of warm pressurized air when the cabin heat system installed. However, without this system there is a need for a source of pressurized air such as might be obtained from a blower assembly. I've thought about how one might add a blower and a cold / hot air selector valve but for now I think I'll just go with the basic stock system.
All the factory documentation discusses and shows pictures of a heat selector mounted near the bottom of the exhaust system whereas Rick's site shows how one can mount a selector against the firewall where the SCEET tube enters the cabin area. All decisions like this are a tradeoff and I'm not sure which is best. The firewall mounted selector is certainly more rigid and moves a bit of weight forward which helps with the balance. The exhaust mounted selector creates a shorter path when cabin heat is not being used and the hot air just being dumped ... probably a slight advantage in very hot weather if one doesn't remove the tube from the heat collector to the exhaust.
I've received feedback from a builder about leaving the cabin heat system in place during warm weather operation. His valve has about 1/16" clearance on the flapper in the full off position. Due to the pressurized hot air source, he found that he was still getting a lot of heat entering the cabin. His solution was to build a form-fitting silicone gasket so the valve fully seals when it's in the closed position.
I've actually got two designs that I'm working with: a selector box similar to the carb heat selector and one made from 3" round tubing. The carb selector style has the pivot at the bottom and uses familiar construction. The tubing one is more compact but requires welding and the flapper is an ellipse that takes a bit of working out. Since the tubing one is the first one that I made, I'll be trying it initially. As I was finishing it up, I realized that the other style might have a slight advantage. Due to the angles, it's probably easiest to just leave it's exit (i.e. dump) side at ~45° pointing back / downwards ... what with the rotor downwash, there will be a tendancy to help extract air from the vent when not using cabin heat.
Although it's being a bit overly critical, I realized that movement of the control cable would try move the whole assembly if it's only held in place via SCEET tube. I added a couple of stainless tangs that resist any fore-aft movement. I also used high temperature RTV to form a seal for the flapper with most of the attention spent on getting a good seal when the cabin heat is selected COLD. If it's too cool in the cabin with the full HOT setting I'll go back and fully seal that side but I'd rather not have any excess heat dumping into the cabin on warm days. The simple way to do this was to roughen the inside of the housing where the RTV was to go and then "paint" some PVA (i.e. mold release) onto the flapper. Once the RTV was applied and set, the flapper could easily moved off the RTV and any excess cleaned up.
Routing of the SCEET tube can be a bit tricky depending upon how the various oil lines have been run. I found that since the cabin heat SCEET tube was the largest tube going through this area, I tried to route it first and then avoid this area when running the oil lines, fuel lines, plug wires, etc. It worked out fairly well for me. The first recommendation I have is to keep the exit from the selector valve as high as possible as this makes for a straighter run through the rear frame ... mine is 1" down from the top of the selector as the 1" is used for the SCEET tube that connects the selector to the exhaust. Another area of concern I had was the corner of the oil tank. Since I have the older square style tank, I actually built up a layer of RTV about 1/8"+ thick all around the front left corner as the SCEET tube rests on this area.
MISCELLANEOUS
When cutting the various SCEET tubes, I would recommend always cutting them a couple of inches too long and then trial fitting them. Although one can carefully measure the length, the outside radius does not stretch and unless there is sufficient allowance for this it is very easy to cut the hose too short ... especially if there is an "S" shape in it. This tubing is expensive and I'll admit that I cut one too short and another one was slightly short but still useable.
I've seen various descriptions of how to prepare the wire in the end of SCEET tubes before installation. I found that the best technique for me was to cut the wire and then bend about 1/2" of it at 90° which ends up inside the tube and parallel to it.
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Last updated: September 18, 2009