O
optimistx
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.).
---
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:
http://www.tip.csiro.au/Machines/success/sc.html
The pages contain a thorough description of the motor at
http://www.tip.csiro.au/Machines/papers/iwscem/index.html
No gears are needed.
The bike might resemble this solar car, but would be narrower and shorter.
Cyclone bike motor 360W at
http://www.cyclone-tw.com/dc24.htm
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
http://www.crystalyte.com/Mspecs.htm
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?
---
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.(?).
---
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? ;-)
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.).
---
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:
http://www.tip.csiro.au/Machines/success/sc.html
The pages contain a thorough description of the motor at
http://www.tip.csiro.au/Machines/papers/iwscem/index.html
No gears are needed.
The bike might resemble this solar car, but would be narrower and shorter.
Cyclone bike motor 360W at
http://www.cyclone-tw.com/dc24.htm
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
http://www.crystalyte.com/Mspecs.htm
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?
---
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 restrictionsfor 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.(?).
---
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? ;-)
