Gears

George said:

I am in the design stage of a multi person "bicycle" and am looking for information on gearing
systems. Basically I need a system that allows the different cyclist to pedal at different speeds
and therefore supply different levels of power.

There is a false assumption here that two cyclists pedalling with the same cadence cannot supply
different levels of power.
--
David Damerell <[email hidden]> Kill the tomato!

George said:

I am in the design stage of a multi person "bicycle" and am looking for information on gearing
systems. Basically I need a system that allows the different cyclist to pedal at different speeds
and therefore supply different levels of power. And for as much of this differential power to be
transfered to the drive train.

Can anyone point me in the right direction? Does anyone know of any good resources?

A conventional tandem forces the same cadence for both riders, but not the same power. Each rider
can pedal as hard or easy as he/she desires.

I've seen a tandem with ratchets in the cranksets which lets either or both riders coast
independently of the other. I think these were Shimano cranks, not sure, and don't know if they are
still made. The pedals are not forced to stay in phase.

Differentials would allow each rider to choose the cadence, but force the same torque from each
rider, or at least a fixed ratio of torques. Good luck finding any differentials light and strong
enough for bicycles.

I don't know the configuration of your vehicle, but it might be possible to provide each rider with
an independent complete conventional drivetrain, driving a common axle. Each rider could choose
gears and coast as desired. You could probably machine adapters for old-style freewheels to fit on a
common axle.

Good luck.

Dave Lehnen

Dave Lehnen <[email hidden]> wrote in message
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Quoted message said:

George said:

I am in the design stage of a multi person "bicycle" and am looking for information on gearing
systems. Basically I need a system that allows the different cyclist to pedal at different
speeds and therefore supply different levels of power. And for as much of this differential
power to be transfered to the drive train.

Can anyone point me in the right direction? Does anyone know of any good resources?

Others have pointed out that there are tandems that allow independant *coasting* (the DaVinci and
Vision recumbent types). The Bilenky/Counterpoint Opus tandem features somewhat-independant gearing
for each rider driving the rear wheel. There are a couple custom recumbent builders that build
tandems with elaborate drivetrains that allow independant gearing for each rider. One of these is
Lightfoot Cycles: lightfootcycles.comtandembikes.htmOpen ↗ Some recumbent tandems have
completely independant drivetrains: the captain powers the front wheel, the stoker powers the rear
wheel. ZOX makes one like this: zoxbikes.comindex e.htmlOpen ↗

Interestingly, at last May's HPV races in Portland, only one of the five multi-rider entries had a
"normal" tandem drivetrain. The rest had independant drivetrains for each rider:
ohpv.orgcalvin18.htmOpen ↗
ohpv.orgdon008.htmOpen ↗
ohpv.orgdon080.htmOpen ↗
ohpv.orgneils106.htmOpen ↗

Jeff