[s.d.haynes@ic.ac.uk]

Has anyone ever seen a unicycle with gears? I was thinking about the various
method with which this could be achieved, the main problem being you must be
able to pedal in reverse as well, for this reason the standard gear system
on a racer would be useless. The only idea I've had which could be feasable
would be to have a infinitly variable system consisting of a smaller gear
attached to the pedals going via a chain to a larger gear on the wheel
constructed of two halves of a gear with the seperation between them
variable (see rubbish ascii picture below). I have seen a similar system on
a normal bike.

* *
* * <------- CHAIN
* *
* * *
* ** ** *
* ** ** * *** *** <------ 'TOP'-HALF OF GEAR **** ****
* * * *
* ******* *
* ** *
* ** * <---- VARIABLE SEPERATION
* ** *
* ** *
* ******* *
* * * * **** **** <------ 'BOTTOM' -HALF OF GEAR ***
*** ** ** ** **
*

The ride would not be even, as the gear is longer in one direction than the
other, but I have experimented with riding with one pedal longer than the
other, and have found this to be no problem. Does anyone know whether this,
or anyother system has succesfully been tried?

Simon Haynes.

sdh@ee.ic.ac.uk

[Richard Allen]

>>>>> On Tue, 4 May 93 09:22:39 BST, s.d.haynes@ic.ac.uk said:

Simon> Has anyone ever seen a unicycle with gears?

Simon> I was thinking about the various method with which this could be
Simon> achieved, the main problem being you must be able to pedal in reverse
Simon> as well, for this reason the standard gear system on a racer would be
Simon> useless.

You would need variable size cogs at both pedals and wheel. The similar system
used on some bikes uses spring loaed chainrings at the pedals, such that the
chain tension under heavy load compress the springs and reduces the effecive
gear. I think a something similar to a normal deraileur gear changer is needed
as well to take up chain slack as the chainring size reduces. To use the system
on a uni you would need to find another way to take up chain slack. I dont think
it would work if you used the spring loaded cog at the wheel, since it would
tend to change to a higher gear when the going got tough. I know of no way to
link two such adjustable cogs so one shrinks as the other grows.

I'm not sure, but I dont think the planatary type ('Sturmey Archer') gears
require a freewheel, so it might be possible to modify one of these hubs to do
the job. The problem would be changing gear, since I seem to remember you have
to stop pedalling. Should be possible though.

As an alternative would it be possible to mount two deraileur freewheels on a
giraffe, one in each direction. It might then be possible to change one set of
gears while moving forwards, then rock backwards to change the reverse gear set.
I'm not yet convinced it could work, let alone be feasible to build.

Would a uni with gears be legal for racing? It would still use the 20-24" wheel
size, but it could approximate to a much larger wheel.

I once wanted to build a giraffe with a 6" or smaller wheel, but driven fixed
gears to give a larger equivilant wheel. It could look strange.

I doubt if any of that was any use, but it kept me from working for a while.

Rik. "Less wheels than most"