Recumbent Bike Project

DB Econbent (Short Wheelbase Under Seat Steering)

(Sold to my friend Kobi G and shipped to Israel May 2006)

Me On Econbent

This page is a brief description of why and how I ended up building my own
Recumbent bicycle, the fun and pitfalls along the way.

The project began in mid 1998 as a whim, I had seen recumbents
being ridden around Vancouver and had decided that as due to physical limitations
I could no longer ride a conventional bike that one should be rented to try out the
general style and decisions could be made as to whether long or short wheelbase under
or above seat steering, etc
I went down to a local recumbent dealer (Cambie Cycles) and met with Brock the owner
who kindly allowed me to trial ride two , a long wheelbase and a shorty. I settled
on the shorty as the one to rent and rode it around all day. The fun and ease of
the ride was immediately evident and I determined at that point to build one as soon
as a plan could be found.

That was where the real story begins

I searched the web and came up with many designs finally settling on the DBEconBent
from a picture kindly posted to the IHPVA web page by Don Boose. After emailing Don
and finding out the original plans were no longer available I determined it to be
possible to build a pretty close clone from the picture.
I started into the design / layout phase by measuring the lock plate of a Dodge Caravan
side door as this was what Don had leaned his bike against for that shot. The lock
plate was 5.5 inches and I was able to use this measurement to determine all frame
dimensions while double checking them against the rear wheel which was 26 inches
dia. A picture was printed off the web and lines were drawn through all major frame
tubes to ascertain all the relevant angles. I started by cutting up my old mountain
bike, as my theory was simple, once committed by cutting up my old wedgy, I'd have
to finish or be rendered bikeless.and half a man :-)

Well, once the first hacksaw cut was made the adrenaline started to flow in copious
quantities and the rest of the old mountain bike was soon lying lifeless in a heap
on the car port floor.

A quick trip the local muffler shop and I soon discovered it imperative that one
must check around and say as little as possible as to the intended purpose of the
pipe one needs bent. As prices varied wildly, once they knew I was constructing a
bicycle the price somehow soared to unreasonable heights. So one soon learned to
repeat the phrase, I just want a short piece of pipe with three bends
It ended up costing me around $60 Canadian (not bad really) as I got lots of bits
of scrap with which to practice welding. As I had welded years before with gas and
a buzzbox the decision was made to get the six main structural welds done professionally.

After a week or so of hunting around I lucked upon a contact via a friend, the fellow's
name was Paul Brodie, I was told he'd do the job for me and I have to say that not
being a bike enthusiast I had no idea who Mr. Brodie really was. As it turns out he
is the local mountain bike guru and hand builder of bikes extrordinaire, a really
nice fellow and very helpful.
Paul took my heap of crudely jigged together parts (the welding jig was made of wooden
2 x 4's) and transformed them into a veritable sculpture of steel. His expertise
and knowledge of what was needed to make a bike function was invaluable and much
was learned during my two hours in his workshop in rural British Columbia.

His trusty dog sat at our feet while we listened to loud rock and roll on his stereo
and all this while I watched him glue the bits together with the skill of a true
artist using a TIG welder as his brushes. (Total cost of TIG welding $100 Can).
As I left Paul's workshop the bike suddenly looked like the beginnings of a real
machine rather than a heap of muffler pipe. I hurried home and took a couple of pictures
while I thought through possible designs for various brackets which were required
to hold key parts.

The decision was made to go with aluminum brackets milled / drilled or turned out
of solid (billet) blocks rather than welding bits onto the main frame for one simple reason,
as this is my first bike construction project I have no experience on which to draw
as to where and how certain things should be mounted.

The easiest and most appropriate method seemed to be to manufacture brackets which
could easily be moved or modified if required instead of hacking the main frame.

Well, the idea seemed good at the time but it turned out to be a lot of work as the
various designs came and went, it did indeed take up some serious machining time
and added a fair bit of weight to the bike.

As I have built the bike primarily as a means of getting exercise I don't mind the
extra weight.... :-)

Once the correct positioning is determined all the brackets could conceivably be
removed and much lighter bits welded to the frame to achieve similar results without
the weight.

The seat was a challenge too, due to physical requirements for a comfortable design
I went with a standard chair shape and merely bent / welded it up out of
steel tube. I decided to make the position (back and forth) variable along the main
frame rail and the pedals are also adjustable in and out.
The steering (USS) was to be another key point for many hours of painstaking brainstrain.

Eventually I settled on a design put forward by a good friend, Brad Britton, he suggested
mounting the steering bearings on the same bracket with the bottom of the seat so
it would move as the seat was adjusted. Ahha (great idea me thinks :-)

A suitable shape came to mind and several hours were spent milling the device from
a solid hunk of aluminum. The original concept was to have suspension both front
and back but logic won out and I settled for a hard frame first time around due to
lack of experience of basic bike geometry.

A few good books were purchased and read religiously for weeks, many ideas came and
went but slowly the beast took shape as more bits were added.

The front forks were cut down from the original mountain bike set and had new lugs
welded on , I have used V brakes on the front to ensure good stopping ability from
the alloy wheel. The tire / wheel came as a used unit from Cambie Cycles
($90 Can) and was the single most expensive part of the whole project, I already
had an alloy rear so I figured to keep the rims the same to assist braking.

The seat was a challenge as living in British Columbia one has to have a waterproof
seat, I concluded that a heavy nylon mesh would be best, and after much searching
and even eyeing up local folk's back yard trampolines.

Eventually during a trip south of the 49th parallel to Seattle I was visiting REI
a huge sports / outdoor store just off the waterfront I was passing the Repair Dept
and asked if the fellow had any idea where I might get some heavy mesh, a few moments
later he returned with a large off-cut piece of the ideal material (cost $10US).
Yippee, I thought, here goes the seat at last.

Well, it was to be more difficult yet, to explain, I'm no seamstress and our old
antique sowing machine was resurrected from the garden shed and a new needle inserted,
after spending around 1.5 hours figuring out how to route the thread I finally managed
to get it to sew a few trial bits well enough. The method used is a folded edge with
a strip of 1/8" steel rod as an edge support sewn inside. Holes are poked through
the nylon with a hot soldering iron, this serves to provide an aperture for the lacing
twine while sealing the hole to stop unraveling of the nylon. I purchased 100 feet
of nylon rope and used this threaded through like a giant shoelace to hold the cover on the
steel frame.

After a short sit in the seat two layers of firm monocellular foam were
added over a solid sheet of polyethylene to firm up the seat a
bit (this type of foam is water repellant).

Next it was time to sort out the transmission. The gears are basically what were
on the mountain bike already, IE. 6 on rear wheel cluster and 3 on pedal crank plus
3 intermediate gears midway along the frame, giving a grand total of 54 possible
gear ratios.

Not being a pro at this nor a mathematician I have to confess to not having done
the math to see if there is any redundancy here in the set up or not, I will simply
ride it and see what needs to be changed and then rework the cogs when and if necessary.

The original bike had straight indexing shifters but I have purchased for ($25 Can)
a set of twist type indexing shifters and will put them on later. I will of course
keep one standard shifter for the intermediate set, its currently located at the left
rear edge of the seat, a handy out of the way location (which may change if it proves
too difficult). Please understand that this exercise is a real tease as it gives
me the chance to explore all sorts of mechanical avenues without the encumbrance
of a set of preconceived idea's that is more often than not a real pain for designers
who've run out of new concepts to try. The thing is simple, if it doesn't work I
shall change it.

A few days have passed since last jotting down thoughts and the bike had its first
test ride....and Yes, to the surprise and astonishment of my neighbours the
beast was rideable and as luck would have it I didn't even fall off...(yet)!

The gears definitely need some tuning and the rotary changers will soon be installed.
The brakes worked fine but again need some tuning and re-routing of cables etc. The
steering was as functional as the bike I rented (a Vision??) but was still twitchier
than I'd like.

I will adjust the fork-end swivel outwards on the bracket by 2 holes and try again.
I have also decided to shorten the main frame by 2" at the pedal clamp area
and do away with the alloy clamp I had made in favour of a pair of welded on tabs/bolts.
I will also remove the chain idler bracket and replace with a lighter and more efficiently
positioned welded on bracket, involving a slight redesign of the idler spindles
I'll also re machine the bottom and top seat clamps in order to lighten them as much
as possible, as well as narrowing the area adjacent to the steering shaft bearings
to allow for more rotational travel in the handlebars. I have similarly shortened
the rear top seat mounting rails by around 2"

The current plan is to strip the bike and get the frame glass beaded and zinc phosphate
coated, then have a local bodyshop paint her up. During this period I will rework
the remaining aluminum parts and have them hard anodized. Rather than ramble on endlessly
here are some pictures to show various stages of the project. I will be glad to send further
details to anyone interested in the project. As this is an ongoing development
there will be additions to this info as time permits.

Bare Basic Frame

Frame and Forks

Rear Triangle

View from right side front

Right side rear of unpainted beast

Right side finished unpainted frame

The project is still incomplete but is undergoing a slow metamorphosis
into hopefully a comfortable, fun to ride machine.

Thanks for taking the time to look at this page and I sincerely hope the information
contained will serve to inspire you to build something yourself.
Dave Barrett ( VE7PCC) Vancouver B.C. Canada.

Click Here

Part II The Ongoing Econbent Saga.....

Its now mid 1999 and the bike has taken on a new character. As mentioned
in part one the initial intention of all the alloy clamps and brackets was to allow
experimentation and to find optimum placing for various bits-n-pieces that needed to be
attached to the frame. I ended up removing almost all the original clamps and redesigning
welded on lugs from steel, (much smaller and lighter).

One of the main area's of redesign was the seat adjustment, I have retained the top
clamp but have modified it to be more streamlined and drilled holes on
the underside to lighten it substantially. The original nylon webbing seat has also
been supplemented with a good quality plywood (painted black) and aluminum bodyformed shell
supplemented by closed cell (black) foam covered with the original nylon webbing and drawn
tight with rope straps across the rear.

The only additional alloy bits were a headlight bracket and a few large washers machined
up to look nicer than the old steel (off the shelf units) that they replaced. All
have been anodized in a nice burgundy colour to complement the canary yellow frame
and semi gloss black seat / steering rod and handlebars.

I must be honest, I didn't pick yellow to copy Don's choice, I merely went to the nearby
paint shop and enquired as to the cost of powder coating only to be informed that if I went
with whatever colour they were running that day, it'd be $75 per colour, and if I went with a
specific colour it'd be $150 per colour......
Obviously as I was trying to build to a tight budget the colour of the day won out.....
two days later I was pleasantly surprised to get a phone call saying the frame was ready.
I have to say, powder coating is a fantastic paint process and well worth the money.
All the bits were sandblasted before painting and only handled with white cotton gloves to
prevent the oil from one's hands contaminating the steel.

The sandblasting process itself is worth a mention,
I rented space at a local machine shop, it turned out to be around $10 per hour plus
sand at $10 per bag, all equipment supplied, he said on the phone.........yeah, right!
I arrived (never having used a sandblaster before) in jeans and jacket. (Bad move)
You need a good head cover and overalls and boots and seal the cuffs and bottoms
of your pants into your socks.
I put in the ear plugs and put on the face mask and heavy gloves, started up the motor
and begun, hhmmm, sand everywhere within the first two minutes, I had sand in places
I didn't even know I had, Its extremely fine silicon sand and boy is it invasive.
(I'll leave the rest to your collective imaginations) (Chuckle :-)

As can be seen the steering mechanism has changed to a welded-on post above the main
frame rail (still behind the seat clamp) and the handlebars also got a more ergonomically
pleasing shape. The bars were a modified pair of rear tandem bars turned upside down
(donated by a friend Paul Erickson VE7CQK), I added 4" into the width.
The old gear changers have also been replaced with rotary click action types
with one old style retained for the center (intermediate) gear set.

After much deliberation and watching the HPV list for comments, a rear light panel
was thrown together utilizing an attention grabbing pair of out of phase rear flashers,
the top horizontally mounted unit has a slower rate and good visual coverage in the
horizontal plane, the other unit is vertically mounted and has a faster flash rate
with superior visibility in the vertical plane, the two units are flanked by two
panels of white 3M reflective tape (also in strips on the front forks and just under
the rear top seat bracket (both sides) and under the headlight for
improved side visibility / protection). The out of phase flashing concept is a real
attention grabber, I drove behind a few wedgies with rear flashers and found the
flash rate to be really easy to visually ignore, however the dual flasher wasn't
the answer either so a dual with different flash rates was tried and adopted due
to the fact the brain finds it really intriguing and actually concentrates on it
to find out what exactly is causing this phenomenon, the units are mounted to get
best overall visual coverage.

The headlight is a 10 watt unit with the switch on the handlebar (right side) and
rechargeable battery unit behind the seat.

All cables were replaced with Shimano good quality units and are smooth as silk.

You will notice the front chain tensioning derailer position has moved forward to
facilitate better chain control, I also added (after much thought) an extra chain
guide pulley at the rear of the front chain (under the seat). I debated long and
hard (with myself :-) over whether to use guides or not due to the obvious mechanical
preference of having nothing interfering with chain movement but decided to go with
the nylon and bearing guides and very shallow angles to create minimal drag and still
achieve the chain geometry required, The guides are quiet and as far as wear goes,
I'm going to wait and see.....if they wear too fast or become noisy, they'll be replaced
with units machined from hockey puck rubber.....its cheap, hard and long wearing :-)

Due to a lousy spell of weather here in the Pacific North West this spring I have
been unable to get the bike on the road, but last weekend I finally ventured out
and took my first tentative peddle strokes up the road, the beast is a pleasure to
ride, is less twitchy than the Vision I rented when deciding to build, and I think will be
a blast to boogey around on

The next possibility is the addition of an electric assist, I have researched many
types and a solid coupling to the rear wheel has been chosen, it entails machining
up a disk of alloy with slots cut at angles to take the spokes and a hole bored to fit over
the axle on the non gear side of the rear wheel.

A suitably large gear will be added to the outer surface, I may go with small bike
type chain or toothed rubber belting. many motors have been looked at and the favorite
at the moment seems to be a 1 hp model aircraft motor suitably geared down and controlled by a
homebrewed Pulse Width Modulated controller and Gel cell. More on this addition later.......
Below is a picture of the beast as it stands now

As a final note.....the Electric assist was never added :-( (Comments about laziness from
my wife deterred further experimentation on that front) also the intermediate gear set changer
was removed as it proved to be redundant.
The nylon chain guide rollers have proven extremely hard wearing and have caused no problems
other than being a tad noisey .

I'd like to take the opportunity to thank all the many people who have
emailed me after seeing the first part of this story and who incidentally
have almost all begun their own creative processes in the ongoing Econbent
saga. Thank you all !! and keep on building.
Dave VA7DB (was VE7PCC when this saga started) Vancouver BC Canada
Last updated: 20/May/06
Left Side View of Econbent