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High efficiency DC motor for a bike?

Where to find a DC motor with high efficiency for a bike?

How to find (or build?) a bike motor of 250 - 500 W with the 'overall' efficiency as high as possible, e.g. 97-98 %? ( here overall efficiency = ratio of power received by the wheel / electric power from the battery e.g.).

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When googling many hours I have found: Aurora solar car has a csiro motor / generator 1.8 kW and claims 98 % efficiency without bearing and without controller losses:

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The pages contain a thorough description of the motor at

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No gears are needed.

The bike might resemble this solar car, but would be narrower and shorter.

Cyclone bike motor 360W at

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boasts the top effiency of 97.6 % (without gears 9.33: 1 , the gear assumably takes away 10-20 % , 10 % if one stage reduction,20 % if 2 stages ?).

Crystalyte motor specifications for motor 408 at

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give output power 344 watts , when input power is 48 V *10 A= 480 W, and thus efficiency 344 w*100/480 W = 72 % (rpm=383 ). Sounds very low, could this be easily improved by changed design of the motor?

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The purpose of this hobby project is to make a power assisted bike for my own use with these goals:

a) aerodynamic drag coefficient about 0.1 and cross sectional area about 0.1 square meters , excluding wheels and pedals

b) regenerative braking

c) to be used on public cycle paths and public roads in flat terrain in southern Finland, where hills might be typically 20-40 meters high; including towns with numerous traffic lights (stop & go)

d) possibility to use solar cells and wind as power source

Ultra capacitors have efficiency of over 99.9 % (e.g. bcap2700 of Maxwell?), when storing or retrieving energy . If motor / generator can charge / unload / utilize them with the efficiency of 98 %, it becomes practical to utilize downhill and traffic light braking to store energy. The weight and volume does not seem to be a problem. Thus one could travel with astonishingly low total power consumption and high speed. Dreaming around 100-200 W and 50-60 km/h :) (legal restrictions for bikes and scooters in European Union will be followed of course).

If ultra capacitors can be charged in some seconds from 220V electricity outlets ( anywhere! ) then even the range would not be a problem. But if motor / generator efficiency is only eg. 70 % , one gets 0.7 * 0.7 =

49 % of the energy back. If the storage is a battery, then the loss is even higher, perhaps only 25 % left. Then regenerative braking is useless. But with ultra capacitors and high efficiency generator / motor the situation sounds promising.(?).

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I have studied theoretical physics and mathematics in Helsinki University 40 yrs ago, worked since then with computer programs and simple circuits for process control etc, but electric motors are new to me. Learning and tinkering in this hobby project is as important as the possible end result :)

Could solar car 'Aurora' principles to be copied to a bike? Bying NdFeB magnets and Litz wire and designing and building the motor on a kitchen table? If so, which url? ;-)

Reply to
optimistx
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Theoretical physics ? It is not all numbers. Plus the number should also make sense. An aerodynamic drag coefficient of 0.1 is a bit low. A cross section of 0.1 m^2 is also a bit low, a mere 30cm in square. As to the motors. Bigger motors have higher efficiencies.

It is rather hard to achieve the 99.9% on ultracaps. The electronics doesn't run on nothing. Regenerative braking makes sense when the traffic is stop and go plus in hilly landscapes.

Plus don't forget the drag of the wheel when the road is not as smooth as a railway track.

Rene

--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
Reply to
Rene Tschaggelar

nice to get your comment, and so soon.

Air drag coefficient, cross sectional areas, and rolling resistance coefficients are based on asphalt road tests on my real recumbent 2-wheeled bicycle equipped with a pc to measure parameters, and with a capability to travel in it feet first with body completely straight in a horizontal position, 0 degrees. My width is 45 cm and 'thickness' 20 cm, 45 cm * 20 cm = 0.09 m2. With a suitable hard clothing as fairing I would resemble a seal and dive through air :) .

Theoretically this has much smaller cross sectional area than world record bike 'Diablo',

which at 4500 ft altitude with 0.006 slope made 132.3 km/h (with 500 W human power of Sam Whittingham, assumably)

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In theoreticl physics I learned about electricity and magnetism, but professors never mentioned 'electric motor' as far as I can remember :). As in linear algebra the word 'matrix' was a forbidden word (being too practical, too much applied science).

Reply to
optimistx

The 500W are not to be made "completely straight". Some muscles have to be moved and the suboptimal shape lets the drag coefficient quickly rise above 0.1.

I remember having heard about such a seup with 4 wheels where they achieved 300km to the liter with a little hydrogen motor.

impressive numbers. I realize the motivation is the numbers, less whether the whole is useable. It doesn't need australian outback rough road to increase the drag of the wheel. Further I'd assume the measured power to be calculated from a pull-wire. Power is equal pull times speed.

500W mechanical means several kW thermal, which are not doable flat, feet first, the searing sun overhead, and little convection. The air drag of 0.1 means little convection, doesn't it ?

I'm aware of that. An additional [set of] engineer(s) might help in effectively applying the available technology of electronics.

Rene

Reply to
Rene Tschaggelar

I think he was talking about the case when his bike is being powered by the electric motor.

- Tom

Reply to
tomg

Yes, that could be so. The term HPV suggested that the vehicle was thought to be human powered.

Rene

Reply to
Rene Tschaggelar

True. During coasting or with motor only legs are kept straight within the 'fairing'.

In competitions like

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the winner got this year 7759 mpg (miles per gallon), or 2746 km/litre . The average speed is low.

Yes. A group of volunteers would be ideal, because this is not a commercial project, and there are no sponsors.

--
Are there people interested in bike motors like there are lots of
enthusiasts in radio controlled
airplanes, assembling motors like they do in

http://www.powercroco.de

e.g. reducing the rpm and increasing torque with

http://www.aerodesign.de/peter/2001/LRK350/Warum_dreht_er_so_eng.html#Anker1164462
Reply to
optimistx

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