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This is
Betty. She's 78 years old and loves to ride. This October
(2000) she and a friend are taking an Elderhostel tour of
Wisconsin on their bikes. She can't lift her leg as high as
she used to, and she had trouble stepping over the frame to
get on and off her old bike. Even the frames on girls' bikes
are too high for her. She didn't want to stop riding just
because of that. She also wished her bike weighed less. Not
for performance, but to make it easier for her to lift the
bike onto her car's trunk rack when she takes it out on the
weekends. To solve these two problems, I built her a custom
bike with much lower step-through height and much lighter
weight than her old bike. Betty's bike is almost two years
old now. She estimates it's got about 2000 miles on it, since
she hasn't been putting as many miles in recently as she used
to.
This is the bike I built for Betty. The main
feature is very low step-through height. The forward part of
the frame is carbon-fiber and epoxy composite; the rear
triangle is lightweight steel. The finished bike weighs 23
pounds. That's 15 pounds less than her old bike. Although the
composite frame probably weighs a few pounds less than her
old one, much of the weight savings comes from lightweight
components. I've weighed a lot of bike parts; see weights.htm.
I
joined the front and rear at the time of manufacture by
laminating the carbon fiber over the bottom-bracket shell and
the bottom part of the seat tube. Carbon wraps completely
around the seat tube and the bottom-bracket shell. The rear
triangle was custom brazed for Betty's bike by Holland Cycles.
Here you can see the main feature - the low
step-through height. Betty doesn't have to lift her leg
nearly as high as she did with her old girl's bike. You can
see that the water bottle was a tight fit. There is barely enough
room for Betty to miss hitting it with her knee when
mounting.
In fact, I had to move the water bottle higher
after the frame was done to keep it as much out of the way as
possible. I did that by adding a third T nut above the
original two. Here you can see the old T nut on the down tube
below the water bottle.
After the frame was done, I had to route the
cables. I made custom carbon-fiber cable stops right on the
frame. Here is a single cable stop. I formed the back side of
the stop right on the frame surface, and the cavity for the
cable using a quarter-inch-diameter steel rod. I wanted to
bond the stop on after it cured, so I put a layer of thin
plastic packing tape on the frame as a release. I also wanted
to be able to get the rod out, so I waxed it and coated it
with release agent. To make the stop, I thoroughly wetted the
carbon plies through with epoxy, wiggled the rod through the
weave, and vacuum-bagged the wet carbon right on the frame.
After cure, I sanded the rough edges smooth and filed the
cable opening to shape. I cut the slot with a hacksaw, then
bonded the stop in place on the frame.
Here is a double cable stop on the other side
of the down tube. I made doubles the same way, only with two
rods, of course. I taped popsicle sticks together to act as
spacers between the rods. That way, they remained parallel
during cure.
Here is a stop located on the corner of the
down tube near the head tube. You can almost see the curve in
the stop where it wraps around the contour of the frame.
Betty loves her Rinard bike. Her
friends want copies of it, but I've told them it's too much
work for me to break even. Betty believes the bike industry
is missing out on a lot of sales because it fails to cater to
older folks who don't want a racing bike. Even hybrids or
comfort bikes don't solve the two main problems Betty had:
low step-through height and very light weight.
