This started out as a kind of doodle in between the pedal
generators and other renewable energy stuff I usually make. I'd been given
a small bike with a twisted frame, but the tyres were too chunky and the
wheels a bit small to make a pedal generator. A quick glance in the tat
store revealed some golf trolley wheels which were almost the same size
as the bike ones, the long heavy duty pivot from the lift mechanism of
a hospital bed, and the remains of some folding chairs. I'd recently seen
a picture of a 'Christiania' trike with two wheels at the front and a long
vertical steering head, and had the idea of making something similar out
of the bits I'd got.
The bed pivot actually made quite a good steering
head though lining everything up took two goes due to the frame twist.
I could see the wide front wheelbase making it hard to
steer so the original handlebars were widened to get more leverage.The
top frame tube had been extended to allow for the changed head angle so
the handlebars were widened and refitted set
back slightly.
The idea looked good but the first problem I discovered
was that although the front platform could take a lot of weight, unloaded
it had a great tendency to tip over if the steering was turned too far.
At extreme steering angles it could even fall over standing still! The
old fashioned 'ice cream' trikes which are in a similar format don't suffer
from this as the front part is a fairly heavy box.
The only thing to do was to severely
limit the steering angle, and then lock the freewheel so that the trike
could be reversed to get around tight corners.
A road test was carried out
by our test pilots which proved that it was still steerable with weight
on the front though it was a bit scary as the brake had been removed with
the original front forks. One of the testers discovered another problem,
trapping a finger in the steering limiter.
The next priority was restoring some sort of brake. The
only place one could go was on the back wheel, so the original front brake
was transplanted to a piece of square chair tube welded across the rear
frame. The trike was designed to split into two parts to make it easier
to transport to events, but that made it difficult to have a brake lever
on the handlebars. I had the idea of fitting a handbrake lever more like
a car's one somewhere on the frame, with a ratchet to stop it rolling when
parked on a slope.
The idea was all very well, but making or finding a suitable
ratchet mechanism was quite a problem. A secondhand lever from a car would
have been too big and the ratchet would probably have been too coarse.
Trying to make a ratchet out of a metal gear wheel from an old printer
or something would have been a lot of effort. Whilst thinking about the
problem, I suddenly noticed a cheap plastic ratchet
clamp. They cost less than four pounds so I decided to buy another
one and cut it up - it was the first thing I'd had to actually buy for
this project. After a bit of fiddling around to get the right leverage
and making up a mounting for it behind the steering head, it made quite
a passable handbrake.
A final refinement was to put a cover
around the steering stops so that no-one else could get their fingers in
them.
Next, the whole thing was taken apart again for painting.
Here it is being used at East Reading
Adventure Playground. It goes all right on flat sufaces, but the gearing's
a bit high for slopes and rough ground, so maybe a bigger rear sprocket
would be a good idea.
After having problems with the rougher sloping ground
we were on at HESFES, I decided to look seriously at the gearing which
was definitely too high. Small children couldn't get it to go with load
on the front, and on the flat it could reach speeds which the steeing wasn't
suitable for.
Another small bike was acquired at a car boot sale for
a fiver. It looked in quite good condition apart from a trashed seat but
the plastic sleeve bearings on the pedal crank and steering head were worn
out, though the ones on the wheels might just make them reusable for a
trailer (or maybe the next trike...).
The pedal crank was cut up and the chainwheel pressed
off in a vice. It still looked surprisingly flat, and even more surprisingly
the attempt to weld it onto what had been the
original front wheel from the trike worked! (I hadn't dared to mess about
with the rear wheel so I could put it back in if it hadn't worked).
Having got away with that which had almost doubled the
gear ratio, I got interested in the idea of fixing the rear sprocket from
the scrap bike onto the side of the trike's front chainwheel.
Again, I figured that if it didn't go on straight I could grind it off
again and go back to the using the original chainwheel.
That more or less worked as
well, though the sideways shift of the chain meant the back wheel had to
be spaced across to compensate which didn't really matter on a trike.
With the larger chainwheel, the overall
gearing was about three times lower than the original and there was
still the option of using the original front chainwheel by changing chains.
After sessions of slamming back and forwards, and pulling
short wheelies which certainly hadn't been possible before, I concluded
that the welds would hold and refitted the chainguard
modified by adding on bits of the one from the scrap bike.
