||The seats on both Woody & TreeBike
were constructed of salvaged 7/8" OD aluminum CB
antenna tubing. The main tubes were cut to 35" and
bent on a borrowed, hand operated tubing bender as shown
in the drawing. The front edge was joined by a straight
tube and the other two cross-tubes were bent to allow
2" of clearance below and on the back of the seat.
The dimensions given are for Woody's seat. Sue's
is similar but main tubes were bent at 3" and
13". Seat width is 1" narrower all around.
||I used a 7/8" Milwaukee hole saw
to cut the ends of the tubing to nice tight fitting
If I were to do the job over again I would take
the seat parts, assembled in a jig, to someone who does a good
job welding aluminum. What I did was solder all of the joints
into massive globs and then endlessly grind the mess down toa
reasonably smooth joint. There is a fine line between smooth,
good looking joints and weak, useless joints. The solder I used
is MG Welding Products' 'MG 470", described as a 'Maximum
strength self fluxing solder for joining, build-up and hardfacing
aluminum'. I believe that the 1/8" diameter rods cost around
$35 for two pounds.
I added a couple of aluminum tubing
braces after the first test ride. The seat reclined more
with each hard pedal stroke due to the weakness of the
main tubing. The braces are pop-riveted on and covered
with shrink-wrap. As it turns out they give a more secure
feeling by providing some lateral support and are not a
problem when getting on and off the bike.
Seat supports were made by sewing loops in
each end of lengths of 1" nylon webbing as shown
above. These straps were then wrapped around the frame
and secured with heavy-duty plastic wire ties. You can
adjust the amount of support by repositioning the straps
or adjusting the tension on the ties. More or fewer
support straps can be used as needed.
The seat material is nylon
mesh and Cordura nylon fabric purchased from an
upholstery/tent & awning shop. The mesh was cut to
fit inside the frame with 1" space all around. Then
3-1/2" strips of Cordura were folded over the edges
of the mesh and sewn on as edge reinforcement. Using a
piece of 1/4" steel rod and a propane torch, I
heated the rod and melted holes at 2" intervals
along both sides. This creates holes that are
self-finished and very strong. Finally, 1/4" brass
gromets were installed in the holes for further
reinforcement. The seat was laced into the frame using
some approx. 1/8" diameter shiny polyester cording
purchased from a fabric shop.
The seat mounts to the frame with two
pieces of aluminum angle which run between the front and
bottom cross-tubes. I cut out a lot of the angle material
to reduce weight.
of weight, this seat, complete with mounting as shown and with fabric
and lacing weighed in at less than 3 1/2 lbs.
Three of the four open ends of tubing
were finished by epoxying in short lengths of 3/4"
wood dowel then rounding the ends. This was done as a
safety measure. While testing Woody I tipped over while
hardly moving and 'apple cored' my ankle. Not a pretty
sight even today.
At left you can
see how the top left tube was finished. A longer dowel
was first drilled to the size of a light-weight
fiberglass sectional tent pole, then glued into the tube
like the others. A little sewing of some bright yellow
ripstop material and the safety flag was done. These
bikes are low and don't present a very large or
recognizable picture to car drivers. The flags are
something drivers are used to associating with bikes ...
and they make me feel a bit more visible.
Total cost per seat, not counting labor, was
less than $35. I hope this information helps you construct your
own recumbent bike seat - or decide not to, as the case may be.
These seats have worked well for us. If you have any questions or
comments please contact me.