FRAME, BOOM and SKIDS
The frame appears to be well made and basically in accordance with the Construction Prints. Being able to physically look at it helped to clear up some of the questions I had from just looking at the prints. An owner of a steel fabrication plant who is also involved in aviation had a chance to look at the frame and commented that he was impressed with the quality of the welding. Needless to say, since I'm not qualified to make this judgement I appreciated the feedback from this individual; it definately increases my confidence.
One area I was surprised at is the main transmission mount as I had witnessed one being physically jigged and welded when I visited Ear Falls. This is one of the very key alignment points, yet when I checked it carefully the mounting tabs are not in alignment with each other. From my non-millwright perspective, I believe this is due to bending the 1/8" steel parts after they have been cut which forces a curl at the bend line to edge point and a difference across the center notch ... this is compounded with heat warping from the welding. The factory response was to just torque the bolts and it will align, however this goes against my thoughts and I may end up fabricating shims. For such a critical joint, I would have also expected to see a light end-mill cut taken on the transmission casting mating surface; this was not done, but I'll also admit that I haven't checked the accuracy of the casting which may preclude the need for this operation.
(The focus and shakes are the pits here ... If I remember I'll take another photo.)
The construction manual goes into detail about how to drill a hole at all tube intersections before welding and then pouring in corrosion protection (tubeseal supplied) to protect the inside of the steel tubes. While the fill nipple was welded in place, it has not been through drilled into the interior of the tube. I don't know if this was intentional to keep the tubes sealed until the corrosion protection stage (after painting) or whether this was an oversight that would also make one suspicious of all the inaccessible holes that should have been drilled.
Update: I've drilled and tapped the fill nipple for the 1/8 NPT plug and also done a basic pressure check. There were at least two significant leaks several tubes removed from where the plug hole is, so I think its safe to assume that the holes were drilled. One of the leaks is the result of an incomplete weld, while the other is coming from the right collar junction on the tube that has the right pedals. The fabricator at CHR chose to deviate from the plans and make a single weld instead of two welds. It would appear that the tube inside the collar does not have a sealed weld to the collar as the air is coming from the junction of the rotating/fixed tubes; unfortunately there is no obvious way to try fix this except by cutting the collar and tube. I can only hope that the tubeseal does its magic without getting into the rotating pedal tube. This appears to indicate that the final assembly order should be: paint, grease, then apply tubeseal.
Update 2: It would appear that the single collar weld is going to cause me continuous problems. A good six months plus after the tubeseal was introduced, this junction is still weeping tubeseal every time that I pivot the frame to work on the bottom and I assume this will also occur in flight. I sincerely wish that CHR would update their plans and that their fabricators would follow them ... they saved five minutes during fabrication and now I'll have to deal forever with a frame that won't seal and weeps tubeseal. Needless to say, I'm not impressed and truly hope that CHR has changed the way they weld this joint. If they were to actually pressure test the frames after fabrication then this discrepency would have been found immediately while the factory jigs were available to re-weld this area.
If I was welding a frame up, one place I would slightly change is where the top of the seat back tubes meet the frame. These are currently centered on the frame, but there are two layers of .032" and one of .063" aluminum which meet on top at the sides and a .032" and .063" sheet at the center. If one was to try using a brake on the headboard to accomodate the bend for the upper frame area, this causes a compound bend line. I chose the simpler method of just snugging down the mounting screws and allow the aluminum to curve naturally, but I would not call this either a crafted or ideal solution and the seat back does not sit flush along the full length of the center tubes. If the seat frame uprights were welded off-center (slightly forward), this could create a situation where only the headboard required a slight but straight bend.
Both the oil cooler mount tabs and the lower boom
attachment plates showed evidence that the frame had seen a lot
of dragging around on these points during construction (during
cab fabrication its easiest to position it with the nose pointing
straight up). While I don't know if this was a contributing
factor, but the oil cooler mounts were not at 90° to the frame (see
Oil Cooler in the ENGINE
section). I don't believe there has been any damage to the boom
alignment, but time will tell.
Update: I could have fabricated at least one tapered shim, but
these were carefully bent back into position trying to avoid
undue rotational pressure on the tube. The easy solution for
prevention is to just position some plywood or other wood scraps
under the lower points and a 2x4 under the upper attach plates
when flipping the frame. A simple piece of cardboard should allow
everything to slide around without grinding the frame.
These same flattened scrape marks were also noticed on the bottom of all the skid feet where it appears that the frame had been dragged around on the feet without the use of ground wheels or any other protection ... certainly not what I would expect from a factory environment that might be interested in delivering high quality parts.
Originally the fuel tank supports were fabricated from tube as shown in the construction manual, whereas they are now fabricated from pre-cut .063" sheet steel. Both myself and others feel there is a lot of "wobble" to the new mounting style. I've now welded reinforcement gussets to each of the tank mounts and the results are amazing. Originally, just a slight fore/aft pressure on the outside of the rear mounts would cause them to start flexing whereas they are now extremely rigid even with significant pressure applied. I don't know if this has any bearing on the 2/rev vibration issue that some builders are reporting as occurring/changing with various fuel levels, but I'm sure it can't hurt.
The other concern I have in this area is with the
mounting straps which go around the fuel tanks and mount but are
held in place by bolts through tangs which are bent into the end
of the straps. My experience with this kind of tang has not been
good as the tangs tend to bend inwards putting pressure on the
underlying surface and/or open up with a resulting change in
pressure; they are also very prone to breakage. I will be
investigating getting some straps made with T-bolts; I know one
place that makes them, but I've also recently noticed that diesel
tractors (i.e. 18-wheelers) also appear to use these for their
fuel tanks. As a minimum, I'll consider welding some triangular
reinforcements for the tangs to add reinforcement and prevent
their bending by the pressure from the bolts.
Update: See the Engine/Fuel
System section for my solution.
The fuel selector mount and the adjoining mounting tab are now one piece about 3-1/8" wide and there is a tight fit between the frame and a reasonable sized "box" in the headboard to house the fuel selector lever. If this combined tab were 1/4"+ wider it would make the fitting of this "box" much easier.
There appears to be a slight frame alignment difference between the left and right side around the center cheek rib area. This was noticed as I was working on the floorboard and realized it was non-symmetrical. While this doesn't appear to have any structural significance, it is mentioned so that others can have a heads-up and avoid confusion.
If one is building their own frame (or has welding equipment), they may want to consider their electrical runs in advance and weld a few tabs in place for mounting adel clamps. Due to the seat front and firewall sheeting, the front and rear frame tubes are not completely open and making later provisions for cable runs could create chafe points for clamps, cable-ties etc.
The manual discusses under-drilling and reaming
the mounts for the tail boom attach bolts. On my frame these pre-drilled
holes appear to have just been drilled to size and actually have
significant play in them similar to what happens when using a
dull drill bit. Since there are only four AN4 bolts holding the
entire boom in place, I consider this to be a critical joint that
should have accurate holes and no play. I have obtained some AN5
bolts (both regular and close tolerance) and I intend to open
these holes up and ream them when I get to this stage. While it
is a great help that the factory has chosen to align and pre-drill
the boom, I sincerely wish they did it with AN3 bolts and let the
builder open up and ream the holes to final size. Also, since the
upper right frame attach point is not at the same angle as the
tab on the boom (~ 3/32" misalignment), it makes me wonder
how much care and accuracy took place during the alignment and
pre-drilling.
Update: I was going to change these four bolts to AN175 close
tolerance bolts. However, upon closer inspection I felt that
there wasn't enough edge distance remaining to do this. In fact,
one of the holes already only has 3/8" left (i.e. 1-1/2D or
aviation minimum) rather than the recommended 2D. I'm now going
with AN174-6 close tolerance bolts. Only one of these bolts
required a slight tap while the other three slid in with just a
little resistance.
Trivia: I was curious why the upper boom attachment points on the frame seemed overly tall and also why the boom's upper mount tabs were bigger than the lower tabs. Looking at a picture of an older Baby Belle, I noticed that there were two bolts in the upper mount and one bolt in the lower mount ... all appeared to be 1/4" bolts.
One change that I have heard multiple references
to is to allow more room for the correlator linkage clearance and
adjustment. Although the delivered correlator linkage will work,
there is very little room for adjustment by lengthening the
moment on the collective's throttle horn where the rod goes down
to the throttle torque rod. The cause of the interference is the
back center upright for the right seat frame just below where the
horizontal seat center frame tube meets. The lower vertical tube
can be cut just below this junction, moved forward a couple of
inches along the seat horizontal tube and
then welded back in place. I first put a slit at the bottom of
this upright tube which allowed it to be pivoted forward without
having to actually remove the tube. Also
note that my seat pan has a notch in this area to prevent any
possible interference. I did this modification before painting
the frame, but it would have been a lot simpler if the factory
had done this before I learned about this change and had already
fitted sheeting and mounting tabs around the center well for the
right collective.
Update: I moved this tube forward approximately 2" and this
is about the same as I've seen on a newer frame from the factory
that incorporated this change. However, I feel that it should
actually be moved forward even more ... perhaps 2-1/2" or so.
In my testing on a couple of different machines, I've noticed
that there is interference at much over about 7/8" of
correlator extension. Since several owners have reported using 1-1/4"+
extensions, this can be a problem at full up collective and very
low throttle settings. This would probably only be an issue
during a practice auto entry or the flare for an auto, but I'd
hate to see the collective sticking during these activities.
One issue that came up as a result of this change
is the routing of the passenger's center seatbelt. The other
three belts (and this one initially) can be routed from their
attach point, around the inside of the seat frame vertical tube
and then back over the outside of the seat frame horizontal tube.
While somewhat contorted, this keeps the belts away from the
collectives and presents a relatively clean / flat exit for the
belts as they pass through the sheeting. However, initial testing
has indicated that this routing does not work well after moving
this seat tube forward as it causes the belt to kink and bunch up.
Update: This was solved using a bit of an extension between the
two belts that are mounted to the center attach point ... see
below under Lap Belts.
The frame has a hard point for the possible mounting of a cargo hook. While I don't have a defined need for this, I had thought it might be wise (and easier) to install a hook and it's releases during initial assembly such that it could be later used for training and just to have the flexibility. CHR does not currently offer a hook as an option and the ones that I have looked at that are primarily designed for an R22 (~400 pound rating) are extremely expensive at several thousand dollars. For now this option is on hold, but I am keeping my eye out for a good deal on an appropriate hook.
Update: See the Controls section for how I resolved this. While I still need to fabricate an attachment bracket on the hook itself, I chose to make an educated guess and pre-drill a couple of holes in the hard point and lower rib for attachment bolts before painting and assembly. In hindsight, I also wish that I'd beefed up the CHR-supplied hardpoint before painting the frame. While the supplied welds and design should be fine for static loads, my concern is with wind gusts and oscillations of the load. I'm looking at adding some kind of a "U"-bolt strap from the hook mounting bolts up to the tube cluster right above this area.
Update 2: I found a 5/16" squared "U"-bolt that fits perfectly over the cluster just above the hardpoint. With the legs of this bolt hanging down, they're then bolted to a piece of angle stock which is also captured by the bolts in the hardpoint for the hook. Certainly not as light or clean as initially welding an extra brace to the hardpoint, but it was a simple bolt-in reinforcement that can be done after the firewall ribs and sheet are in place and everything has already been painted.
The night light kit includes a landing light
mount and bulb. Although there is no reference to this in the
construction prints or manual, from various pictures I've seen it
appears this is normally mounted on the right rear plate where
the sleeve for the skid leg is attached to the frame. Indeed this
plate has a free horizontal flat surface on it. Unfortunately the
supplied light mount is 2" x 1-5/8" while this surface
is 1-5/8" x 7/8" and cocked at a 20° angle. It would
appear that one has to either fabricate a new U bracket for the
mount or a spacer that is ~5/16" thick in order to clear the
sleeve. Also, the supplied bolts only have a thin internal tooth
lock washer and I believe these should be replaced with AN bolts
and nylon lock nuts or castle nuts with cotter pins.
Update: Rather than go to the trouble of designing a spacer
plate, I went with the same technique that most others appear to
be using ... basically the brute force way of applying enough
torque and the relatively soft mounting bracket bends to conform
to the odd mounting shape. Pretty? ... No. Functional? ... Yes (at
least for now). I'll have to wait and see what the long term
effects of this are. I added an AN toothed washer both above and
below the frame mount to try prevent rotation of the mount and
also used a nylon insert lock nut. For the horizontal bolt in the
mount, I replaced it with a longer Grade 8 NF bolt and nylon
insert lock nut (I didn't have the right length AN6 bolt).
Instead of using this mount as the electrical ground per the
original wiring, I used a separate ground wire that went to a
prepared frame ground lug.
Pitch Rod Clearance: It would appear that the
pitch link rod contacts the frame at some positions. Although the
factory knows about this and just lets the pitch rod rub on the
frame, I decided to notch the frame rail in front of the
transmission forward support bracket. Although the required depth
was probably only 1/8" or so, I made mine a little deeper (perhaps
3/16") since there is 1/8" plate material welded behind
the tube at this point. I first heated the frame tube and then
used a piece of 2" tube to make a radiused "dent"
in the heated tube. I also had a brace on the transmission mount
during this process to try prevent any shifting of the bracket.
Update: With the transmission and pylon rods firmly bolted in
place, I have now been able to check this through the full range
of required motion. Even with the "dent", my pitch rod
just touches the frame at one extreme but this does not result in
any kind of drag on the rod. I've added a strip of thin UHMW tape
to the "dent" to prevent any rattling and rubbing.
Hard to get a picture with good contrast on this
Straight Control Rods: I decided to implement the option of using straight control rods instead of the walking beams and this required a change to the tubes that support the main transmission. There is more details and pictures in the Controls section. It appears that newer kits are now shipped with this undocumented change and CHR has also chosen to change the support tube arrangement for the transmission side mounts.
If a builder chooses to eliminate the walking beams and use straight control rods, the back side of the most forward of the three tubes for the transmission side mounts will need to be modified to provide clearance for the rods. I've seen one picture where this tube was heated and "dented" to approximately 1/2 its normal diameter. I decided to try cut a notch which will then be covered with a piece of welded in flat plate. When I initially measured it, this looked about right; however, once the transmission was in place and the full throws were exercised there was still significant binding. I'm down to about 1/4" of the tube left and I can still get a bit of binding. I don't know if this is due to different frames or the fact that I don't have the final alignment of the mast, pylon supports and control throws performed. It looks like I'm going to have to totally cut out the notch in this piece of tubing and figure out how to brace it with an additional piece.
Update: On the right side I essentially removed the entire tube and ended up leaving just one tube wall thickness. I did the same thing on the left side, but there is just a slight contact at one extreme of the swashplate movement. It would appear that the full tube needs to be notched on the left side and possibley even another 1/16" more of the reinforcement.
If I were doing this again, I would try wait until the pylon support rods have been drilled and bolted in place. It would also be handy to have the pitch rod adjusted and installed. In this way, one can then find the true range of motion required and the real size of the notches.
Tail rotor cable mount: My tail rotor cable front mount was welded to the frame 7-1/2" from the rear of the pedal tube versus 7-1/4" from what appears to be the center of the tube on Construction Print #28. The dimension on the print would probably just work whereas the mount on my frame would not. Since I found this out after painting and during final assembly, I chose to make a cable extension rather than cut and re-weld the mount which would also require a change to the kick panel. I would recommend that all builders check whether their cable and rodend assembly will reach the pedal tab (and allow adjustment) before they fabricate the kick panel or paint the frame. It's much easier to make changes at the early stages.
Per the Rigging Manual ... max extension using cable nuts,
minimum rodend threading and still too short at neutral pedal
Additional Mounts:
Before painting the frame, I identified several additional mounting brackets that I had welded onto the frame. Since I elected to change the strobe system and went with a separate power supply and head, I needed to find a mount for the power supply. I chose to mount it on the right side just in front of the firewall. This keeps the cable to the head as short as possible and also keeps the power supply far away from sensitive electrical equipment such as the governor and LASAR® controllers. A wide tab was welded to the cross-tube on STA.52 and a piece of angle was used to form a front mount. There are nutplates for the hold-down screws/bolts and the actual power supply mounts about 1/2" in from the side/vertical tubes to allow room for the tail rotor control cable if I choose to run it throught that area. The one negative ... the rear screws/bolts are accessible, but will require a mirror to see them during installation.
I looked at many places to mount the ELT. It should be accessible yet protected and rigidly mounted to the frame. I ended up using tabs and a mounting plate to locate it underneath and behind the pilot's seat near the center of the frame. As noted in the Avionics section, my unit is mounted horizontally per the manufacturer's recommendation rather than at the 45° angle recommended by some other manufacturers. The location of the antenna mount still isn't finalized.
Update: Even though this plate was already painted, I decided that I wasn't happy with it. Originally it was made from .063" material and I changed that to .080" which seemed to considerably reduce the flex. I also moved the ELT back about an inch and one of the bolts now goes through both the ELT mounting bracket and the plate before being secured to the frame. This also gives a bit more room for the antenna and remote connectors.
Original mounting plate
I'm installing both the LASAR® ignition system and a governor system, both of which have control boxes that needed to be mounted. I have seen some installations where the builder chose to bolt such items to the back side of the lower seat sheeting, but this would have interfered with my seat pans. I chose to add a large .063" aluminum plate (~14"W x 11"D) under the pilot's seat to hold these and any additional similar items. Due to the cyclic brace tube, a large notch is required and not all of the plate's area is useable.
Controllers just placed to verify size and not in their final position
The use of a combined collective friction and
lock device appealed to me, so I added a mount for this. I
started with a piece of square stock and trimmed it to make an
upside down "U" shape which I mounted 6" in front
of the collective pivot point. This distance was somewhat of an [un]educated
guess and I'll update it after I have fully fabricated this unit.
More details are in the Controls
section.
Update: After doing some more initial checking on this it would
appear that this bracket should have been mounted a little
further forward ... perhaps 8" or so. One of the problems is
that I can't determine the exact distance using the other
components I have until after I've adjusted the up-limit stops on
the collective based on the pitch link requirements. For now I'll
just go with the bracket position I have and avoid cutting it off
and re-welding it.
As supplied, the collective trim system is just a simple tension spring held at the top by an S-hook over a tube. I am not comfortable with this as a broken spring (which has happened many times) would allow various pieces of the cable and spring to jump off the hook and who knows where they would land. I welded a tab to the tube so that the top end can be fully captured with some kind of a clevis. The eyebolt at the bottom of this assembly only has a nylon lock nut on the bottom since it is in tension and I wouldn't consider using this unless it also had a jam nut above the tab. More importantly, I now consider this system to be UNSAFE and will not even consider flying in any ship that uses this system. There is more information in the Controls section and while I will eventually be trying to implement the blade weight modification to balance the forces, I was looking for an interim replacement alternative.
I do NOT believe that a tension spring is the best choice for the collective trim system and as a minimum I'd consider a change to a safety drawbar spring ... most probably two lighter ones with one on either side of the collective assembly. I have a totally different approach to the trim system and although my implementation has a new piece welded in place, it is below the original location and should not preclude the use of any alternative that the factory eventually develops. It uses a compression spring from an R22 which will PUSH up rather than PULL down. I believe this approach is quite viable and much safer. I first tested the stock trim spring arrangement and measured the force on the end of the collective using a spring scale and various adjustment lengths on the eyebolt. The range of motion tested was the same as provided to me by an owner who is currently flying his machine. The new spring assembly is capable of duplicating the full range of forces that I measured (7 - 17.5 pounds) and has both a left and right threaded rod end which are simply rotated to adjust its initial force and position.
There are three aspects to this installation: a lower mount, the spring assembly and the upper bracket. For the lower mount I used a piece of 3/4" square tubing on the same plane as the other frame tubes and then fabricated a "tower" type support. The upper upside-down "U" bracket mounts to the stock hole for the eyebolt and also the bolt on the end of the pitch tube which prevents rotation. The bolt in the original eyebolt hole is actually upside down to gain a little more clearance for the rod-end. If I was re-doing this I'd move the square cross-tube further inboard, perhaps an inch or so, and also change the top bracket so the upwards force would be applied closer to the end of the pitch tube rather than under the stock hole for the eyebolt. The "tower" would also be somewhat smaller as I now know the required height (~2.75" above the top of the square tube) and wouldn't leave as much material that allowed for testing. Some lightening holes would also be added before welding it all in place.
Note that this spring assembly has three guide rods that keep everything aligned and slide through one end of the assembly as the spring flexes. Because of the rubbing action, these are a maintenance item and the wear on these rods needs to be monitored.
N.B. The safety wire around the spring is to aid in the spring installation / removal as there is quite a bit of force being exerted by the spring ... something like 50+ pounds. If one is working with this spring, they should be EXTREMELY careful when installing and removing it. There are a couple of spacers on the bolts / brackets that will be required when this assembly is finally installed due to the fact that I allowed allowed extra room for the prototype's adjustment. These pictures were taken during the proof-of-concept testing stage.
Hindsight: I am very happy with this spring arrangement. Initially I had the spring set a bit too soft but it was very easy to alter it by adjusting the rod ends a bit ... the result is that the collective now holds it's position in a hover with absolutely no hand pressure on it. Note that I have the swept tip blades and I've been told that they require more spring pressure than the newer square tip blades.
Most of the pictures I've seen show the air
filter box being held in place by supports mounted to adel clamps.
While I was doing the welding, I decided to add some tabs to the
frame such that the filter box can be rigidly mounted with bolts.
Note that I added both an ear above the leg mount and a vertical
flat plate between the two tubes forward of that. If I was doing this again, I'd add a
third tab on the vertical tube above the gear socket just above
where the angled tube is welded to it. Originally I wasn't sure
of where I wanted the vertical location of this tab and I
eventually resorted to using an adel clamp rather than welding
another tab onto the frame after it had been painted. Although
the clamp is strong enough, a welded tab would have added a bit
more rigidity. The other change might
be to mount the air filter box on the left side of the craft to
avoid any interference between the SCAT tube and the throttle
linkage ... time will tell if I have regrets about my current
mount. Then again, I might end up mounting a cabin heat selector
valve on the left side.
Update: Mounting the air filter / selector box on the right side
of the frame meant that SCAT tubing had to be woven through the
frame members in order to avoid the throttle rod. I'm not sure
how easy it would be to route the tubing around the oil lines but
I know several other builders have chosen to mount the selector
box on the left side. If doing this mount again, I'd also
slightly move it further forward to allow more room for a
person's foot on the upper part of the landing gear leg when
doing inspections.
I had originally planned on holding the seat pans in place with fasteners to the rolled over edges of the seat outside sheeting. I was not happy with this, both from the alignment and strength issues and the difficulty of installing the fasteners blindly. While I was doing the welding, I added tabs to the inside of the seat frames (6 per seat) to act as hardpoints when mounting the pans.
Ballast weight: The stock ship has positions for the ballast weight both near the front of the right skid and just in front of STA.187 on the boom. These two positions should be able to accommodate the normal range of C.G. requirements for both solo and dual flight. I noticed on one of the factory ships that they had a third ballast weight location just inboard of the right rear skid leg. In discussions, it would appear that this position is very handy when flying dual but with a very light passenger; i.e. a child. This location allows the ballast weight to still be carried outboard of the cabin and also to retain the proper C.G. range. I've decided to add this mount before painting. There's another example of one of these mounts here.
The two rings I used were cut from 2-1/4" x .120 wall 4130 tubing and the smaller ring is 1" wide and the larger one is 1-1/4" ... I would think that it might be possible to go with somewhat thinner material. I put a small tab at the bottom of the smaller ring to aid in putting the ballast weight in (i.e. it rests against the tab when fully seated). Although I knew there would be some heat warping from the welding, the holes for the ballast weight pin were drilled to match it before the mounts were welded ... that way I knew I had the proper spacing. After welding, a 2" flapper wheel quickly made for a smooth slide-in fit.
Collective micro-switch(s): There are several
electrical circuits I can envision that require a collective full-down
micro-switch; flight timer, maintenance timer, alarm horn
lockout, etc. I made a bracket that attaches under the pilot's
side pitch tube support and allows the installation of the switch
which is activated by the most rearward non-rotating part of the
collective. Until I've finished my wiring diagrams, I'm not sure
if I'll use one or two switches, but the bracket allows for
either configuration plus vertical adjustment. I used the micro-switch
style with the long lever which allows for some misalignment and
can be trimmed as required (Wicks part # V7-6C17D8).
Update: It now looks like I'll be using two micro-switches. One
switch is based on ground and is used to trigger the flight timer
in the GTX-327 transponder and also to record collective time on
a second Hobbs meter. The other switch is based on +12V and is
used to interrupt the power to the horns when the collective is
full down, similar to the way it is done in an R22.
Engine Ground Strap: The frame that I received had a tab welded to it for the engine grounding strap that was located near the right rear conical bushing. However, there is not a good engine mounting point near this. The bolt that holds the shroud in place could be used but the electrical connection would rely on the bolt itself and it is very confined where the bolt head (or nut) goes against the engine case. Conversely, near the left rear conical bushing there is an unused 1/4" hole in the engine case that would make a perfect attach point for the grounding strap. While the electrical path through the frame to this point is a little longer, I don't think it would be significant. If I'd really thought this through before painting the frame, I would have welded a tab onto the left rear engine support for the bonding strap.
I had thought about welding a bracket to the pillow block mount immediately behind the transmission. The purpose would be to allow the use of a sensor (or two) to measure the RPM of the tail rotor driveshaft by utilizing the ferrous heads of the Omega coupler bolts. Instead, I welded this bracket to the topmost pillow block shim.
Shoulder Belts:
The delivered kit has both lap belts and single-shoulder belts. However, the shoulder belts are of the fixed style (but adjustable in length) rather than inertia reels. It would appear that a fixed shoulder belt will be too restrictive to allow unrestricted access to the avionics and some of the switches. Since the only stock solution would be to fly with the shoulder belt very loose (unsafe) or wiggle out of the shoulder restraint when adjusting switches (again unsafe), I felt that a design change was required. I've heard of one implementation of inertia reels where they were mounted quite low and then run upwards to turnarounds before exiting the headboard, but this seems overly complicated and one has to be careful of interference with the walking beams, fuel shutoff, etc.
I picked up a couple of AM_Safe inertia reels from Chief Aircraft and they mate with the AM_Safe lap belts that were provided in the kit. The original shoulder belt tabs were cut off the frame and larger tabs were welded on in their place at the same angle such that the inertia reels could be mounted in the relatively stock position and extend through the headboard. The new tabs were cut from .125" 4130 and are 2-3/8" wide x 2" high with the tops rounded to match the reels and positioned so that the outer edge of the tab is about in line with the edge of the upright tube on the frame. After trial fitting the reels and stretching the belts to their operational position, I figured that it was best to slightly cant the reels for a direct pull since there's no turnaround to take a side load. I've attempted to move the reels as far rearward as practical, but there is interference with both the "firewall" top rib and a bubble mounting clip if they were moved much further back. As it is, a "bump" style cover will need to be fabricated to cover up the approximately 2" that protrudes through the headboard. The headrest cushion will probably just clear this and its thickness will prevent a standalone protrusion that could be considered a safety hazard.
Update: Here's the public admission of another flawed idea. The above technique works fine on the pilot's side which is where I did all the measurements and even drilled the mounting holes. Unfortunately I forgot that the seats are offset to the right side due to the collectives and this technique is unworkable on the passenger side ... the mounted reel would extend beyond the headboard and hit the bubble. Back to the drawing board to design a turnaround system where the reels will be mounted behind the headboard and exit it the same way as the stock arrangement with fixed belts. There is enough room, but the trick will be to get the angles right so the belts will have a consistent angle on the turnaround.
Update 2: The new mounts have been welded in place as have the turnarounds. The angles are kind of wild to figure out, but I think the side-to-side positioning of everything is pretty reasonable. The angle that I blew it on is the vertical one. I used the previous attach point plates as the basis for the turnarounds and after cutting them at the appropriate angle I welded both a turnaround tube and side rails to them. I've also added an AN3 bolt so there's no way the belts can jump out of their track and get stuck or cut behind the headboard. The problem is that the original stock angle on the attach point plates is too steep so the belts ride about 3/16" above the support tube where they will eventually exit through the headboard. Ideally, the back end of the cut plates should have been dropped about 3/16" or 1/4" thus making the belts lay flat along the support plate and tube. I'm probably going to add a clamp plate here so the belts lay down along the plates and the slots in the headboard don't need to be overly large. My technique is probably getting way too complicated as I kept trying to modify and add to the existing stuff rather than just starting over with a clean slate.
Right side inertia reel
Right side inertia reel mount (front, side, above)
Left side inertia reel mount (front, rear)
The 1/8" 4130 steel inertia reel mounting plates have had several lightening holes added to them subsequent to these pictures being taken.
Hindsight: I've been discussing the use of
shoulder belts and inertia reels with a new owner who has a lot
of aviation experience, especially in helicopters. The more we've
discussed his objectives, the more I understand his desire to use
a "Y" belt shoulder harness on an inertia reel.
Certainly if I was re-doing this change I'd now use a "Y"
belt rather than a single shoulder harness as it prevents the
torso from coming out of the harness in violent motions,
regardless of direction. The difficulty in mounting this is that
the optimum location is blocked by the walking beam mount ... I'm
led to believe that the newest frames may not have that mount and
thus it would be a non-issue and a very simple modification.
Also, a new walking beam mount with a wider rear side containing
a slot could be fabricated / installed and the inertia reel
mounted below it.
Update: I've now seen a picture of a recently delivered frame and
it did not have the walking beam mount. Since mounting is no
longer an issue, I would highly recommend that builders use dual
shoulder belts ... either a "Y" or a 4-point system.
There are lots of options when actually figuring out the exact safety belt to use. Here's a link to Aircraft Belts Inc. which shows some of the options that are available. Hooker Harness also makes aircraft seat belts and offers various parts such as inertia reels. If one is considering a Y-belt with inertia reel, then they might want to check out the Schroth Autocontrol belts. These are automotive specialty Y harnesses that have an electrical lock ... with electricity applied they act as a normal inertia reel but when electricity is removed (via master off or movement sensitive control module) they lock up.
Lap Belts
The standard Safari kit includes 2" lap belts rated at 3000 pounds breaking strength or approximately 12+ G's depending on weight. If I was redoing this area, I would consider purchasing 3" lap belts. The reason being is that the strength rating is before the belts have seen a lot of use which invariably leads to a bit of rubbing and fraying. More importantly, I have personally seen a seat belt after a crash where the belt appears to have broken due to friction and heat as it rubbed against the seat edge when it went through the tightening process during the impact. In talking to the TSB investigator, he noted that this is a common occurance and immediately recognized it.
The next question is how to route the lap belts so they are both effective and convenient to use. With the factory supplied mounts, I could see a couple of ways but only one that worked for me. The passenger outer belt could either be routed direct and come through the bottom of the interior's side panel or it could be routed around the seat frame's upright tube and then exit just below the seat. Since I already had a storage bin in this area, I chose the latter. The pilot's outside belt doesn't leave much of an option since a direct routing would cause it to interfere with the collective. Due to the shape and location of the mounts, I found it best to place an AN970 (i.e. large) washer between the belt end and the frame mount. This little bit of extra standoff helped to prevent the belt from being compressed against the mount and frame tubing.
Flaking paint is due to bending the tabs for cutting the slots
... it's since been touched up.
The bigger headache is the single center mount. This works fine for the pilot side where the belt wraps around the seat frame. On the passenger side there can be a possible interference due to the vertical seat support that is moved forward to clear the correlator. I found that by stacking four AN970 washers between the two belts I got extra clearance so the ends of the two belts were not highly compressed together and this also just changed the angle enough that I could wrap the passenger belt around the frame. Note that one also needs to be careful that the passenger's center belt is not chafing on any closeout material that has been used under the center collective. If my calculations are correct, the two belts being anchored by a single AN4 bolt are roughly equal in strength to the bolt. If one were to go to stronger and/or wider belts on a single mount then it would probably be adviseable to upgrade this bolt to an AN5 or AN6 bolt ... probably wouldn't be a bad idea for the stock configuration either.
Am I happy with the seat belt mounts ... not really. While I was aware that it would be difficult to route the belts, I wish I'd added a new mount for the passenger center belt when I was still making changes to the frame. A separate mount would both prevent two belts from pulling on a single bolt and also allow for a straighter routing. I still don't like the idea of the belts wrapping and rubbing around frame members but this would take a significant redesign ... perhaps cables from the main frame to a joining tab on the seat frame where it could transition to a belt. In the meantime, I'm going with the stock CHR design but I also used UHMW tape on all places where the belts touch the frame.
Pedals:
I was concerned that the supplied pedals do not have any kind of side stop, as is the normal practice, to prevent one's foot from sliding off during operation. My solution was to weld a piece of 1/16" 4130 that was shaped something like a "?" onto the center of the uprights which then also hook over the top of the horizontal part of the pedal. For the open ends, I have turned some aluminum plugs that fit into the tubes and have about a 3/16" high lip that acts as a stop. These have been hard anodized and are held in place by a small loctited screw. If one had a very wide foot and/or boot, they could also use this technique to widen the actual footrest portion of the pedals. I'll probably cover the actual foot rests with some kind of non-skid material or as a minimum heat shrink tubing or self-vulcanizing silicone tape.
Update: I actually covered the pedals with polyolefin heat shrink tubing. While I'm sure it won't have the greatest wear cabability, this was done as an interim measure while I keep my eye open for alternative material. In fact, I actually used two layers of 1" heat shrink with the idea that if the outer layer starts to fray then it's a simple matter to slice it off and there's still another layer below it. Kynar heat shrink would have been preferable, but it's more difficult and expensive to obtain, especially in the required 1" size.
For those builders with short legs, they might want to look closely at the Rotorway pedal design. The actual footrest is a "T" arrangement with the leg extending horizontally forward and sliding into a receiver hole atop the vertical segment. Since this is held in place with a clamping bolt, it allows for fore-aft adjustment of the pedals. Also, the newer R44's have a similar "T" arrangement for pedal adjustment, but they use a quick release pin. Ideally, the vertical tubes on the Safari would be moved to the center of where the footrest is located, and possibly at a more forward rake before making this kind of change.
While turning the pedal plugs, I also made up a couple of aluminum plugs for the top of the console upright tubes. These tubes are shipped "open", but I felt they should be plugged against corrosion. After the frame was painted, a bit of tube-seal was put into the tubes and they were then sealed with the plugs and JB-Weld.
Upgrades:
Cyclic brace: It's my understanding from reading the new rigging instructions that newer factory frames have an additional brace for the cyclic added under the pilot's seat. I would suggest that owners check whether this brace is installed and if not, then they may want to consult with the factory as to its applicability. This is now documented in the maintenance area of the owners area on CHR's website and I chose to weld it in place before painting the frame.
Throttle linkage: At Sun 'n Fun I noticed an upgrade to the throttle linkage on one of the factory ships which I was told is now standard on production kits. On the torque rod that goes from inside the cabin to directly under the carb, instead of using the sleeve-type bearings as shown in the plans, this ship used rod-end bearing and hangers similar to the design of the walking beam supports. The primary purpose of this is to remove any binding or friction that can occur due to any slight misalignment during or after welding of the sleeve bearing. Instead of the bearing tubes being welded to the bottom of the frame tubes, this change has tabs welded flush with the top of the tube and the rod ends then hang down from these tabs. Unfortunately I didn't take a picture nor did I get a chance to look at the front bearing support.
I will be making this change to my ship as I do have a slight binding in this linkage which I'd like to eliminate in order for the governor to have as friction-free a linkage as possible. The retrofit for the rear bearing will be relatively simple as it should be a matter of just adding the tab to the top rear of the lower tube on STA.76 and an inner sleeve to the torque tube that can be tapped for an AN4H?A bolt. It looks like the rod will need to be shortened about 1/2" at the rear and the inner sleeve will be made from 3/8" (.375) x .083" tube which will need to first be turned down in a lathe before inserting into the 1/2" x .083" (.334 ID) throttle rod. As an alternative, 5/16" (.3125) x .095" rod might work as the insert but the ID would need to be enlarged with a #3 drill before tapping. At the front end, it looks like I'll extend the tube forward (3-1/4" minus room for the rod-end) so the bearing can hang from the tube in front of where the current sleeve bearing is welded. I'll probably use a combination of 1/2" x .083" tube with a 3/8" x .083" turned insert that extends through the joint and into the existing rod.
Update: I've now upgraded this torque tube. The first surprise was that the original tube was not .083" wall as shown in the construction prints, but rather it was .049" wall. Since I had to extend the front end and I didn't have any 1/2" x .049", I decided to just replace the whole tube. Also, using .049" whould have meant that I'd have to figure out a different insert arrangement and I already had some 3/8" x .083". I considered using either .058" wall whose ID is about .009" larger than the 3/8" insert or .065" wall which is .005" undersize. I ended up using a 3' piece of 1/2" x .065" wall due to availability, but in hindsight it would have probably been easier to wait for the .058" wall and not have to turn the inserts down. The original horns were saved for re-use.
Note that this change still does not balance the throttle linkage. If one had an essentially friction-free linkage, there is still the fact that there are four rod-ends, three bellcrank arms and a couple of short lengths of tubing located on only one side of it. Since there are no flight loads on this linkage, it is probably reasonable to change the rod-ends to 3/16" ones that are considerably lighter. A counterweight could be used to balance these forces.
Update2: As I was tightening this in place during final assembly I noticed one problem with my implementation of this new setup. The torque tube sits between two rod ends that are designed to not have side play and unless the tube is of the exact right length, it will exert a side pressure and a binding force. While I'd purposely made the tube short by a thin washer width, I still spent a lot of time trying to get the perfect position as I was tightening the nuts. Also, the plans call for the link between this rod and the throttle on the passenger collective to be 7" in length. I started with mine at 7-1/4" and would have preferred it to be even a bit longer; i.e. closer to 7-1/2".
Hindsight: As I was making the above changes, I considered whether to change the throttle linkage to a push-pull control cable as is used in nearly all other aircraft. In the end, I decided to just go with the tried and proven Safari approach. In hindsight, I wish I had further explored the cable option. In addition to being more balanced, lighter and simpler, it would have alleviated another issue that came to light during final assembly. My LASAR® magneto cap with the four leads coming out of it is just over one inch directly above the throttle torque rod. This means that I had to install extra clamps on these plug leads in order to make sure they wouldn't rub on the torque rod.
Miscellaneous:
After being around R22s, one of the interesting things I noted was the front jacking point which protrudes through the belly sheeting. At first one may wonder why this is required, but it becomes apparent when you need to lift the front of a completed craft for items such as skid leg removal. The rear of the main frame is easily supported for jacking, but there is no obvious front lift point on the Safari. I think one could devise some sort of cross-brace that fits under the belly sheet and catches on to the gear legs in a way that does not interfere with the skid legs, but it would also be cumbersome. I haven't looked carefully to see what would be entailed in adding a hard point to the frame that goes along the front of the seats and I haven't seen this done on a Safari yet, but I'm sure it would come in handy if one ever had to remove the skid tubes or is using a heli-mover. A simple change during construction may end up saving a lot of trouble later on.
Update: I talked to a builder who has just recently lifted a nearly completed ship onto the skids. His technique was to put a jack under the frame cluster just behind the cab and then raise one side at a time and install the legs and skids. Since this is relatively strong area near the CG, it worked well for him.
I figured that most of the construction work was in the cab and main frame areas and that the boom could be stored until the end of construction since most of the work on it is simply bolting parts on. In hindsight, I would consider doing any modifications to the boom first and then painting / corrosion proofing it before putting it aside for storage.
One concern I had during the uncrating was an
apparent "dent" in the top tube near the tail rotor.
The factory informed me that this is done on purpose for tail
rotor gearbox clearance; this is not indicated on the
construction prints and I'll wait for assembly to confirm this.
Update: The "dent" is definitely required in order to
clear a rod end on the tail rotor assembly.
While tapping the tubeseal hole for 1/8 NPT, I realized that it would be relatively easy to do a pressure test on the boom. I found that an easy way was to jam a rubber-tipped air nozzle against the hole, pressurize the frame and then cover the hole with a finger while listening carefully. Sure enough I could hear an air leak. Closer inspection revealed a weld that had scalloped into a tube and had a pin-hole in the center. No other obvious leaks were detected, but perhaps there are other much smaller holes that the tubeseal should handle. An additional advantage of doing this is that the chips from the tapping process will be blown outwards when the finger is removed ... BE VERY CAREFUL of your eyes!
One other area of concern I have is with the mounting tube for the horizontal stabilizer. This tube is welded in place with two small beads ~1/4" long and a small center weld ... shorter beads than are on the tail light mount! Since the forces acting on this tube have a lot of leverage, I've added small braces under the tube on each side so the weld area can be increased and assist in preventing any torqueing and potential failures.
I'm still not sure which radio antenna postion to
use (under belly or boom mount) and I've also decided to change
the strobe light assembly. In order to accomodate these changes,
I've modified the original strobe mount so it now becomes an
antenna mount and I've fabricated another bracket that will be
attached to the next intersection rearwards of this (and on the
opposite side) that will become the new strobe head mount.
Update: I'm happy with both of these mounts but I do feel that
they're a bit close together. With the angled whip antenna in
front of the strobe, the antenna is relatively close to the
electrically noisy strobe ... I'm glad that I chose to go with
the shielded version of the strobe head. I'm not sure what the
optimum combination of locations is ... perhaps moving the strobe
head one bay rearwards.
Update 2: The new antenna mount might be just a
bit too far back for some antennas. With the main rotor blade
against the bump stop in the rear direction, I think it may be
possible for the blade to just contact the tip of the antenna
while still clearing the boom by perhaps 4"-6". Since
this is getting the blade too close to the boom for my comfort,
I'll probably leave things as they are ... if I clip the top of
the antenna then it's a great indicator that I've been trying to
cut my boom off. Other antenna's might have a bit more of a rake
and not be a problem in this position.
Update 3: It looks like the blades will just clear the antenna
unless there is something major happening with them.
One of the concerns I had with both the antenna and the strobe head is the fact that there are electrical connections exposed to the elements which could eventually lead to corrosion. I fabricated small extensions to these mounts with a grommet in the bottom so that these connections would be protected from the direct influence of things like rain or snow.
I have heard of one builder who had a problem with vibration in the aft end of the boom and also balancing problems with the tail rotor. He tracked this down to the long vertical braces that run from the bottom of the hoop then upwards at ~45° forward. These tubes have ~31" of unsupported length and his solution was to weld a small cross-brace about half way up. I tapped on these tubes and noticed that they have a high frequency "buzz" with a very long decay time. I then cut a piece of tube to fit just a bit higher than the center (~1") of the unsupported area; the idea being to not induce a 1/2 frequency vibration due to equal lengths. When repeating the test with the tube just pressed in place, the result was that the resonant frequency appeared to be much lower and decayed much quicker. I've welded this piece in place as a pre-emptive move against tail area vibrations.
In preparation for mounting the tail rotor driveshaft, I noticed that several of the pillow blocks rocked when placed on their mounts. After further checking, I determined that most of the pillow blocks mounts were not square and/or parallel to the driveshaft. Each mount was then individually checked using a long straight edge over two or three mounts and "tweaked" till it was both flat and parallel to the other mounts. I suppose this really should be checked again after the shimming has been performed. Lateral rotation of the mount is not an issue but longitudinal error will cause the bearings to run off their axis and even though they are rubber mounted it can put an excessive load on the bearings and/or the driveshaft.
Two different pillow block mounts with longitudinal discrepencies
The tailrotor gearbox chip detector (and often the tail light) use the frame as an electrical ground in order to function properly. If one is using a boom mounted radio antenna then it also relies on a good ground plane. Thus it is important to have a good electrical bond between the boom and the main frame. Instead of just relying on the boom's attachment bolts (possibly isolated due to paint), I added a bonding wire between these two frame segments. Before mounting the tail rotor gearbox, it would have been helpful to have mounted a ground stud (i.e. a 6-32 stainless flush head screw) centered at the very rear of the gearbox mount and hanging downwards. Since I hadn't installed a stud before mounting the gearbox, I had to remove a bit of paint and then use star washers to get a good electrical ground for these devices.
Vertical Stabilizer
I debated whether to mount this on the same side of the tabs as the tail rotor or on the opposite side. While it appeared that lazy feet in cruise would cause pressure on the tail rotor side and logically the skin should be pushing on the tabs, I opted for the opposite side with the idea that if I pop a rivet or the skin were to come off then it would have some protection from the blades. One thing to watch out for is that if one were to center the rivet holes in the provided tabs then there really wouldn't be enough rivet edge distance in the aluminum sheet. This is partially due to the tabs being welded on both sides and not being able to use the full tab for mounting due to the fillet. I chose to move the holes in the tabs further from the center in order to maximize the aluminum edge distance.
The rivets on the vertical stab should be part of the daily inspection as I'm aware that some builders have discovered loose rivets here. I'm not sure if this was the result of a vibration problem or improper rivets ... I know that the rivets supplied with my kit were borderline in length and about 1/2 size too short for my liking in this critical area ... I used longer ones. I'm also aware that some builders have chosen to double the number of tabs holding the stab in place and/or use some kind of adhesive. I went with the stock number of tabs and will probably add a short bead of silicone or other adhesive mid way between each of the tabs. The adhesive may not be structural but it should dampen any vibrations that may be trying to work on the rivets.
Update: As an experiment, I directed an air hose towards the vertical stab and looked for any kind of movement or drumming. It is definitely present and indicated to me that the number and/or position of the stock mounting tabs is wrong. I now believe that extra tabs are warranted ... for existing installations, the use of adhesive between the tabs may substitute as an alternative since it will form a bit of a U around the boom tube and should be able to adhere to the other side of the adhesive via the gap between the stab and the frame.
Tip: One may want to defer the riveting of the vertical stab until after they've done the initial routing of the tail rotor push-pull cable in order to possibly add some slots in the stab for adel clamp clearance. I made my vertical stab with minimum clearance to the frame (perhaps 1/32") and since it was already riveted to the frame, it meant that I had to either cut a clearance slot in place or find alternate locations for any adel clamps. I ended up using a Dremel tool with a cutoff wheel to create a clearance notch for the clamp.
Horizontal Stabilizer
The construction prints show the horizontal stab to be 10" x 22" in plan view while the construction manual states to start with a 20" x 22" piece of sheet before bending it. Obviously there is a discrepency as there is no allowance for the leading edge bend radius. I started with a 20.5" x 22" piece of sheet and that appears to result in pretty close to a 10" final chord.
I was somewhat worried about how to drill all the rivet holes that hold the sheeting to the spar while retaining alignment. I thought about various ways to hold/clamp the two pieces, but there was still the concern of drilling through aluminum sheet into the harder steel spar. I decided to try pre-drilling the two pieces separately. First I made a #40 drill guide out of a flat strip of 1/8" x 3/4" steel and used this as a template when drilling the two pieces. The sheeting was easy to do this way. For the spar, I first drilled one end hole and then made sure there was no rotational twist as I drilled the other end hole. The drill guide made it easy to align/drill all the intermediate holes. The resulting pieces matched very closely and the holes were then opened up to #30 ... with hindsight, the drill jig was accurate enough that I could have made it with #30 holes initially. I then used a brake hone on an extension to deburr the holes on the inside of the spar ... thanks for the tip Rick.
As another builder pointed out to me, one may want to think about offseting the holes on the top and bottom of the spar to try minimize the possibility of cracking. Unfortunately this tip came a little too late for me and I'll just have to be very careful to include this check in my pre-flights.
One of the concerns I have about the final assembly is that there is a piece of essentialy thin flat sheet riveted to a round spar. Since there is very little bearing surface, this can eventually lead to a "working" of the rivets in their holes and eventually movement. I put a bead of Hysol 9430 mixed with a bit of flox along the spar between the rivet holes just before riveting the pieces together. JB Weld could possibly also work for this. The adhesive should squeeze out and create a much wider contact / bearing area between the two pieces and prevent any "rocking" once it has hardened ... mine squeezed out to about 1/2" wide or so. Instead of using the no-name "pop" rivets that came with the kit, I used Cherry Max CR3213-4-2 pulled rivets in this critical area ... certainly not cheap but it does give me better peace of mind. Since this is a ribless structure, I found it was very prone to slight twisting and warping of the trailing edge during riveting. I used a couple of pieces of 1/16" x 1" angle held in place with double-sided tape during riveting to try prevent this.
Bottom riveted and ready for top & trailing edge riveting
I installed an end cap (optional on the plans) of .063" aluminum both for aesthetic reasons and also to add a bit more vertical stabilizer area. The basic size was about 7/8" larger than the airfoil and then a fudge factor of "looks about right" to taper the rear to about 1" diameter (actually an AN970-4 washer). One of my concerns was that if the craft is being flown out of trim in cruise there could be a significant side load on this plate. I ended up making brackets and installing three nutplates / screws to secure it: one each as far forward and back as practical, and a third one just behind the spar. Once the craft is flying, this will be monitored to check for any bending of either the end cap or the brackets. The use of nutplates versus rivets was to make it easier to inspect the full spar for any signs of problems.
I used what may be a slightly unconventional assembly order as I was concerned about getting a good seal of paint on all of the surfaces. After drilling all the rivet holes, my paint and assembly order was as follows:
The fit of the spar into the tube on the frame is relatively tight. I used the brake hone to knock off most of the high spots of paint on the inside of the frame tube. I then sanded the topcoat on the spar where it sits inside the tube ... pretty well all of the topcoat was removed in order to get the spar inserted with a tight fit. A heavy coat of Corrosion-X was also applied to both surfaces since there were a few places where pretty well all the primer had also been taken off.
Ready for final fitting and installation
I don't remember seeing any reference in the rigging instructions for the initial angle of the horizontal stab. I do remember reading various discussions about this, including some radical extremes and even in-flight adjustable systems. As I remember, the only definitive number I can recall was to use 7° leading edge up as a starting point. Before drilling the spar, I actually rotated it slightly so this starting point would put the adjustment bolt in the center of the slot.
I also have some concerns that a single bolt in a
slot is all that holds the horizontal stab in place. While the
use of a large washer should help to spread out the load across
the slotted area, there is still the possibility of rotational
movement if the bolt were to loosen at all. I will look closer at
this during final assembly and may consider adding something like
a small roll pin or second small bolt after confirming the angle
in flight.
Update: One of the things I noticed with
just a regular washer on the slot was that the stab could be
moved unless the bolt was fully torqued to at least
the specs for an AN4 bolt. I cut down a large washer so it just
cleared the weld and it covered much of the slot which also gave
a larger bearing surface. Although this appears to prevent
movement, I'll still look at adding something like a second small
bolt in a separate hole once the final angle has been determined.
I really don't want to experience this moving in flight!!!
I was talking to a builder who had a couple of hundred hours on his Safari. One of the things he mentioned is that he had several chips in the paint on the leading edge of the horizontal stab. This is certainly understandable when one looks at the amount of debris that a helicopter can kick up during operations close to the ground. I'll probably add some leading edge tape to ward off some of the chips.
One builder has chosen to make a substantially
larger horizontal stabilizer and there are some pictures of it here.
I haven't personally talked to him about it and don't know how
much of a difference it really made.
Update: I now have more information about
this craft. The simple answer is that this change was an
experiment that attempted to try fix a different problem. The
horizontal stab on this craft has now been changed back to the
same size as shown in the construction prints.
I have talked to another builder who tested various stab angles all on the same day/flight and he was surprised at how little difference the various angles made on the cruise pitch and to the cyclic forces. Before contemplating major changes to the size and/or angle of the horizontal stab, the builder should be fully aware of the potential downside ... namely what happens during a sudden loss of power. I am aware of other craft where builders have experimented with the horizontal stab and found that their changes could induce a radical pitch up/down effect ... not a nice way to start an unexpected auto and could lead to disasterous results.
The skid legs were pre-drilled at the factory and while this is one less thing for the builder to do (especially since one would have to build a jig to hold the frame, legs, feet and skids in alignment), I was disappointed that these holes were not drilled squarely with the tube centers. Since no reinforcement bushings or collars were added per the option in the construction manual, this means that the entire weight of the completed ship will be on four (well eight if you count top and bottom) 1/4" bolts in shear; note that the actual legs are .065" wall. These eight bolts are one item that I will be adding to the annual inspection and assume that I'll just replace them as cheap insurance.
If I were designing these legs or welding them myself, I would consider using a larger diameter tube on the foot where the leg attaches which would then slip over the leg rather than inside the leg. The reason is twofold:
Without a collar, the bottom of the leg could actually rest on the foot for two additional points of contact.
If the leg ever has to be replaced, it will be very difficult to drill the new lower holes since they have to mate with a pre-drilled blind hole. With the legs on the inside, the foot attachment stubs would actually be used for drill alignment.
The one negative I can think about with this arrangement is that any moisture dripping down the legs could actually pool in the foot sockets, possibly even if one added a collar. They'd need good corrosion proofing and a tiny drain hole.
Update: It's amazing how I can see this much differently when reading it a year or two after having originally written it. I now think a much better change would be to initially make the attachment stub from 1-3/4" x .125" material. Before/after the fish-mouth has been formed, the upper part of this piece could be turned down in a lathe to 1-5/8" x .065" to just above the fish-mouth (perhaps 1/8" to allow for welding). This would automatically create the leg support as part of the stub and not require the optional collars that are talked about in the construction manual. There's still the holes for leg replacement issue, but it would eliminate the bolt shear issues. Note that the stubs on my frame had already been turned down slightly to provide a slide-in fit. Since the ID of some material is slightly different and some tube is .120" vs .125", it would be necessary to carefully measure the various dimensions before turning these stubs.
The skid feet I received had been pre-drilled at the factory for the cross-bolts that go through the skids. Unfortunately they were drilled at 90° to the legs, not horizontal as shown on the plans. Although the factory claimed that this would not pose any kind of problem, I chose to have these holes fill welded and then I re-drilled them horizontally since I was not comfortable with the bolts/nuts being in such close proximity to the ground, rocks, etc.
WARNING TO BUILDERS - Read the following carefully!
Think the following step out carefully before starting it. If you have the trailer option, you can use the rear blade mount tube for trial fitting, otherwise be very careful as failure to get the required clearance will definitely gall and scratch your skid tubes. How do I know? Well, the obvious answer is the correct one and I now have one skid tube with all sorts of gouging in it.
I had a *LOT* of trouble fitting the skid tubes into the feet. When I first looked at this I realized that the ends of the feet had been slightly ovaled by the welding. Closer inspection also revealed a bump on the inside of the foot bore around the welds. Although there should have been a theoretical .010" clearance here, there was a negative clearance! I ran into trouble with the machine shop that was going to bore the tubes so both myself and a machinist friend spent a lot of time working with a flapper wheel, hones etc. trying to get the clearance. This is definitely not a precision way of doing it, but I was trying to go forward. During this sequence, I contacted the factory and got the following reply that I'll let the reader evaluate for themselves:
" ... We tried boring the tubes after welding, inserting a stub while welding, boring the tubes out before welding and nothing has worked. ..."
In my opinion, the simple solution to this problem is to use a 2" expansion reamer inside the skid feet after they've been welded. The trouble is that anyone who knows the price of this tool has probably also been hit with a major dose of sticker shock ... certainly not a tool that a builder would buy for a single use, but if one has access to one of these then it should make for a trivial task. As to why the factory hasn't invested in one, who knows?
Update: I've now seen a picture of a newly delivered quick build kit (i.e. bubble mounted) and the frame was mounted on the legs and skids. It would appear that the factory is now delivering the skid feet ready to use.
One thought I had was that if I was welding up my skid feet I'd change them to .063" walled material instead of .125". The factory feet are very heavy and I assume most of this is an attempt to get some wear protection for them. By going to .063" material then it would be quite easy to fabricate 1/2 feet (i.e. bottom only) from stainless steel that would wrap under the main feet and be captured by their bolt to act as replaceable wear pads. The front feet should be fine but the rear feet would probably require an extra bolt at the forward end to use this same concept and prevent the wear pads from flipping out of position. The net result of this change would be that the overall weight would be reduced and there would also be replaceable wear pads on the skids. Those of us that operate from an airport with paved runways (or a paved helipad) can certainly appreciate the benefits. Although my skid feet are painted with an epoxy urethane, I know that the first landing on pavement will remove some of the paint and expose bare steel which will start rusting as soon as it's exposed to moisture such as on damp grass. A bit of blade might temporarily delay this issue.
After finally getting clearance to slide the feet on, I then tried to mount the feet and skids to the legs/frame so I could drill the holes through the feet and skids for the cross bolts. The right side was coaxed into position and held with shop bolts. The left side however has a problem. I have tried all the permutations, but when the skid tube is slipped through the front foot it does not want to match up cleanly with the rear foot without putting a slight bend into the skid. I don't have an answer yet, but it appears that it may be due to either the angle of the welded attach tubes on the feet or the angle of the leg sockets at the top of the legs. Without realizing it, it would appear that I've also bent the last ~3" of the skid just by hand pressure or that the tube had a spiral high spot. After probably 20 hours to just slide the skids into the pre-drilled feet and legs, I still haven't achieved this seemingly simple task. For now I've put this on hold till I can approach it rationally.
One thing I still haven't figured out (and didn't even bother to ask), is how the factory pre-drilled the holes in the legs and their attach points without being able to slide a skid tube in for alignment. There's approximately a four foot distance between the front/rear feet and as I've found out, it doesn't take much of a misalignment to cause a real pain. I also noticed at least four holes that had been fill-welded at the factory and another one that had been started about 1/3 of the way through, but slightly off of where it ended up being through drilled.
Update: After verifying all the permutations of leg orientation, I came to the conclusion that I had been trying to get everything to fit properly and in the correct orientation, but something was definately out of alignment. Eventually I discovered that I could get everything in place if I first pushed the front leg ~3/8" higher in it's socket while trying to insert the skids. I can then just lower the leg enough to get all the bolts into their holes without excessive bending on the skid tube. When I double checked all the measurements, it would appear that when the frame is on the skids it is level with the floor and the two skids are parallel to each other. There is about a 1/4" discrepency in the measurements of the two rear legs based on the weld position in the middle. What I didn't do is to carefully measure the angles in both planes of all the skid tubes. My feeling is that one of these is slightly out and this may be due to the amount of heavy material and welding that is required on the sockets.
It looks like I now have a workable solution to installing the skid legs and tubes. Unfortunately, one tube has gall marking from the initial installation attempts and the other has a kind of spiral bend/bump in the rear where the bear paws attach, in addition to various galling. I was concerned about the tube with the bend/bump as I would have had to either remove significant aluminum from the skid or opened the foot up more (the other tube slides through it easily). When simple "straightening" attempts failed, I finally spent the $122 plus shipping and ordered one new skid tube. It turned out that the new tube is not really round (typically .010"+ difference) and also had problems sliding into either rear foot. I finally just cleaned up the original tubes and moved forward. The moral of this appears to be that fitting the tubes is not as straight forward as it appears and will probably require significant time to remove various high spots and actually fit them for drilling.
The primary purpose of getting the feet to slide over the skids the first time is to mount the skids and drill the bolt holes in the skids. In my case, while the skids were mounted I drilled the four bolt holes for the feet, four for the bear paws and two for the ballast weight. Once these were done, I removed the skids and opened the holes up from 1/4" to 1/2" to allow for anti-crush cross-tubes. To try keep the alignment, I used a unibit in a drill press and interestingly enough I discovered that my #3 unibit is slightly over 1/2" while my #1 bit is slightly under 1/2". Luckily, I had access to a 1/2" reamer so the holes were under-drilled and then reamed. Afterwards, the anti-crush tubes were welded in place. Unfortunately, the welding did cause some heat warping, especially at the extreme back, and I had to go through the whole process of re-checking all the slide-over fits as I was grinding the welds down. This re-fitting process actually required some new high spots on the tubes to be levelled out.
I chose to attach the end caps via a couple of sheet metal screws on the underside rather than being welded on as shown in sheet #7 of the construction prints. This was primarily done to avoid any more heat warping at the rear of the skids. Hmmm ... I'll have to rethink whether I want to have the silver look at the front of the skids if I hard anodize them which results in a dark colour or whether the front caps should be welded in place.
Update: I've chosen to have my skids hard anodized and dyed black in order to try protect them somewhat. The biggest problem I had was finding a supplier that had large enough tanks (8'+) to perform this. While there are several local contractors that can do hard anodizing, the largest tank that any of them had was only six foot long. I finally sent them away to Surf-Tech Industries who have ten foot tanks and are willing to work with various shippers. After they had been shipped, I started rethinking whether I should have had them Teflon impregnated. I didn't order this service, but I can understand how it could help when operating in snow and muddy surfaces.
Painted & ready for installation
The landing gear legs are a relatively tight fit over the gear feet and also into the sockets on the main frame which creates a problem in how to paint and/or protect the steel tubing. On the gear feet, I chose to paint inside the skid tube opening, inside the ground handling wheel pivots and most of the stub that goes into the leg with a thin coat of Perma-Slik G. The rest of the feet and legs are painted with my normal epoxy urethane. Even this created a bit of a fit problem and I had to sand areas of the topcoat and even some of the primer off. I'll be assembling these with a heavy coating of Corrosion-X since some of the hidden paint will be scraped off due to the tight fit. After installation, one may want to consider adding some kind of sealant around the various edges, especially where the feet meet the skid tubes.
Having gone through the painful process twice of trying to get the feet to slide easily over the skids, there is no question in my mind that if I were doing this again that I would try use a split-foot arrangement. Perhaps one of the builders who has done this will provide me a good photo of the bolting mechanism and I'll include it here.
One tip I had picked up on the old Safari forum was to carefully check the fit of the legs into the upper sockets on the frame. If there is any play at all, it will be magnified by the length of the legs and the weight of the feet/skids/ballast weight and could lead to vibration issues. The contributor's solution, which I followed, was to drill and tap for two bolts that fit into each upper socket collar and are 90° apart. I used AN4H-3A drilled head bolts and placed these so they are on the inside of the sockets and out of the way ... the drilled heads can be safety wired together. They definitely prevent any movement of the gear legs once everything is installed and tightened down. I've also seen a newer factory ship where they used a single bolt with a lock nut for this purpose.
I chose not to add a front step on my skid legs although I have seen pictures where a step has been installed. This wasn't done with a lot thought but rather a choice to go ahead with the painting before actually checking out a finished craft to verify how much help it would be. I've also seen a neat arrangement on a different helicopter for a simple clamp-on step and if I later decide that I'd like a step then the clamp-on style makes for an easy retrofit.
One thing I did do was to add some non-skid wing walk material on the top of the rear legs. This allows one to step on this area when doing a daily inspection (DI) around the mast area and not worry about their foot slipping. While I was working with this material, I also added a bit of it on the top of the skids just ahead of the front feet. Although I prefer not to step on the skids when entering or exiting a helicopter, I know others do ... if there is any moisture or mud around the skids then this material will prevent slipping and it should also prevent scratching from this activity. I found that a 6" x 12" piece of it (part # 09-31665) was all that I needed.
Hard to get good black on black contrast for a picture
From the pictures I've seen, it would appear that the frames that have been built in New Zealand are using a split-foot arrangement. While I haven't seen how the wrap-over strap/bolting is done, I can think of several advantages:
These frames also appear to be more builder-friendly as the pictures I've seen would indicate there are extra mounting tabs located in strategic locations, curved cyclics, and other subtle changes such as a split collective pivot tube center support. At least one of the ships also has a collective friction device added.
I've also seen pictures of other ships and talked to one builder who opted to make longer gear legs (i.e. high skids) that raise the ship approximately 6". At this point I don't have any real feedback to add here. There are two basic ways to accomplish this and I've seen examples of both: make new gear legs or add extensions to the existing gear. If I were going to try this, I think I'd take a combination approach on the first pass: it's very easy to make new longer legs in the front since they're just straight pieces of tube whereas it would be quicker to just make an extension for the rear ones rather than try get the weld angle and bracing to match the requirements.
Ballast Weight
Since my skids had been hard anodized black, I chose to also paint the forward ballast weight mount black with the idea that it is very visually obvious when the bright stainless steel weight is installed or removed. I also chose to paint the inside of the hoops and the inside bottom of the "tray" with Perma-Slik G in order to make the ballast insertion / removal smoother. That decision was made after having spent some time with flapper wheels etc. trying to resolve a binding that I'd had. I've since learned that others have had this same issue and a neat solution (from Pete via Rick) is to use an automotive tailpipe expander ... too bad I'd already solved this the hard way when I heard about this simple solution.
Miscellaneous Skid Thoughts:
I'm aware that some builders with the O-360 have had their ships come out slightly tail heavy and have done things like move the battery ahead of the instrument pod supports. One thought I had was whether to consider changing the skid tube(s) from aluminum to stainless steel. This would add some weight ahead of the CofG while also resulting in stiffer more durable skids, especially on the right one with the ballast weight. Another option might be to insert a 4130 steel tube inside the aluminum or stainless right skid extending from just behind the front skid foot to the forward bend area and it is my understanding that this is done on Rotorways.
I am aware of a couple of owners with flying machines that have chosen to add a brace to the right skid which extends from near the front of the skid to the top of the gear leg; one is as shown in this photo and a different one goes down to the front mounting bolt for the ballast weight. It's my understanding that there was quite a noticeable vibration at the tip of the right skid before this change and that afterwards there is no apparant vibration. While it is also possible to do this change to the left side for cosmetic symmetry, it's my understanding that there is no visible vibration there. I will be making this change to the right skid which has the ballast weight on it.
I added the brace from the upper leg bolt to the forward ballast mount bolt. Since I used 1/2" stainless steel for this, I've currently left it natural rather than another item to paint. Flattening the front so the bolt could attach is relatively easy with a strong enough press (I used a 12 ton model). For the back end, I first fabricated a hoop out of 1/16" stainless plate which was then bolted in place. Everything was then carefully clamped in place and it was removed for welding, including a box section on the bottom of the hoop for strength.
Bear Paws
Within a short flight from my location there's both muskeg and various lesser degrees of "wet soil". There's also the issue that in winter the ground is usually white with that fluffy cold stuff. The use of bear paws was a non-decision, but I did look closely at alternate construction methods from those shown on the plans. There's some really interesting certified bear paws made from some of the fancy "plastics" but their price tag reflects their intended use on commercial turbine ships. I quickly realized that the aluminum ones should be fine and are easily rebuilt if they get bent.
It seemed to me that the construction prints useage of a 1/8" rib riveted to 1/2" angle was probably more for material availability with some increase in strength due to the 1/4" combined laminate. I had some 1" x 2" x 1/8" 6061-T6 angle that I used to make the "ribs" from. The more I looked at them, I wasn't happy with the fact that this angle material was of the sharp 90° inside corner type so I eventually chose to replace them with angle that had an inside radius corner. My local supplier didn't have any 1" x 2" in this style so I chose to get 2" x 2" angle and just run it through the band saw. After the angle stock rails had been formed and drilled, I chose to have them hard anodized since they will be exposed to scuffing and various other abuses when they're installed.
One thing I've noted when looking at some of the commercial units is that the front edges are angled back at perhaps 45º. I can definately see where this would be an advantage during any kind of a run-on landing or takeoff as it should hopefully prevent any snagging action. I decided to angle back the front edges but I'm not sure of the exact angle ... somewhat less than 45°, perhaps 35-40° as that "looked about right". For those that are curious ... my bear paws weighed about three pounds total when finished and ready to mount.
Cross brace is to try reduce any splaying of the rails at the rear
After I'd had a chance to land in relatively deep snow in an R22 I can really appreciate the need for these. During confined area practice I got the chance to land in both powdery snow and embedded crusty layers; each of these have unique characteristics which relate to the skids settling and how they break through the layers until eventually the weight of the ship can be supported. Since the majority of the weight is on the heels of the skids, the craft tends to settle tail low and its entirely possible to get a tail strike. Hopefully the bear paws will allow a more level attitude under these circumstances. Liftoff through crusty layers is also tricky and one has to be VERY careful not to hook a skid and create a dynamic rollover scenario.
Ground Handling Wheels
Because the axle / handle assembly is pre-welded, the assembly of these should be simply a matter of drilling the holes for the cotter pins and the lock ring clips. Before drilling for the lock ring clips, the alignment should be verified on both rear skid feet to verify that they're symmetrical since there really isn't a right and left wheel assembly. I found that I actually had to grind a bit of a relief onto the rear skid feet pivots in order to allow the lock ring clips to fully close. When using these for moving the ship on the the ground, it's probably best to have the handle to the rear when the ship is on the wheels whereas if one is to fly with the wheels attached (i.e. for transport purposes) then one still wants the handles to the rear but the axle assemblies are on the opposite sides.
One thing to note is that there are two pivot areas on the axle/handle assemblies and these are a relatively close fit to the wheels and the pivot bushing on the skid feet. If these areas receive a heavy coat of paint then they will become too snug of a fit and won't allow for free rotation. I ended up painting these pivot areas with a coat of Perma-Slik G so they had some corrosion protection but would still turn freely. I also added a very thin coat of MoS2 grease to the pivot areas. For those that haven't been around ground handling wheels before, be very careful when lowering the craft off the wheels since the jacking bar will try to "snap" over. Is it easy to prevent this ... yes, but one needs to be aware of it. When the wheels are fully down, I found them to be quite stable while trying to install the locking pins.
I've been told that the Safari is harder to move around on
wheels than an R22 which is roughly the same weight and that part
of this is due to the tires that are provided. Increasing their
pressure to make the tires harder seems to help make it easier. I
can now personally confirm this. Perhaps if we could find
narrower wheels (like those on the R22) which could take higher
pressure (the supplied ones are max 20 psi) then it would be
easier to move the ship around. I don't believe that low pressure
garden tires are the best solution.
Update: My tires now have closer to 40 psi
in them and it makes the craft MUCH
easier to move around. Will the extra pressure result in
problems? Time will tell but I'm aware of others who also run
this much higher pressure and haven't had problems.
Tip: When ordering the material for the extension handle, order enough for two of them (i.e. four feet total). Although one may only want to carry a single extension handle in the craft when flying, the extra handle is very handy in the hangar. This way both wheel assemblies have their own handle and there is no need to keep moving it back and forth the way one has to do with a single handle.
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Last updated: May 03, 2009