The No-Chain Bike

[Andre Jute]

The Mando Footloose NO-CHAIN folding bike has two power circuits linked by a battery. On the first circuit you pedal gently but have no direct connection to the rear, driving wheel. Instead you pedal a generator, which charges a lipo battery. The battery in turn drives the second circuit, which consists of itself for power and the motor in the rear wheel, plus its associated electronics of a throttle and some sensing mechanism which increases output up hills. It weighs 48 pounds...



Click the photo or this link for more info: http://www.bbc.com/autos/story/20140924-an-e-bike-that-breaks-the-chain

It's a goodlooking bike, properly developed, but the question does arise of what level of losses once can expect in this two stage process. Generators and batteries are simply not that efficient at storing and releasing power.  What do you reckon, Jim, around a third gone in unavoidable losses?

[triaesthete]

  I suppose the next question is will the load smoothing benefits offset the drop in efficiency?  This looks to have some characteristics of Diesel electric traction in locomotives. Friction brakes seem to be missing a trick though as this surely demands regenerative brakes to square it's circle??

Interesting
Ian

[Andre Jute]

  I suppose the next question is will the load smoothing benefits offset the drop in efficiency?  This looks to have some characteristics of Diesel electric traction in locomotives. Friction brakes seem to be missing a trick though as this surely demands regenerative brakes to square it's circle??

On another forum Jeff Liebermann, a reliable engineer, calculated with rough guesses from experience of efficiency at each point in the chain:

****
                     Minimum    Maximum
                     Eff %      Eff %
Pedal DC generator     75         90
Charger & control      80         95
LiIon Battery          80         85
DC to AC inverter      90         95
AC motor               50         80

Multiplying the efficiencies together, I get 22% to 55% drive train
efficiency.  By comparison, the drive train efficiency of the common
gear and chain system runs between 85% and 96%[1].

***

The footnote ref is to the famous Kyle & Berto article in IHPVA No. 52 of 2001, already several times discussed on this forum.

55% efficiency makes it a bike for trendies who want to brag they're saving the earth, and 22%... nothing I can say that will pass the mods on a family forum read by Jawine and other ladies.

Pity. It looks good enough to pose with.

BTW, I looked into recovery of braking energy a few years ago, and on a bicycle scale it would be very hard to make it work. Very expensive too, with current technology. The return even when it does work would be marginal, both technically regardless of cost, and in relation to the cost. Another idea for trendies, not real-life cycle-tourists. Some ideas just don't scale to bicycles.