Thorn Cycles Forum
Community => Non-Thorn Related => Topic started by: Andre Jute on September 28, 2014, 07:21:40 AM
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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...
(http://ichef.bbci.co.uk/wwfeatures/624_351/images/live/p0/27/85/p02785pj.jpg)
(http://www.bbc.com/autos/story/20140924-an-e-bike-that-breaks-the-chain)
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?
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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
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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:
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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].
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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.