Using Front and Rear Motors

[erdurbin]

Can you use both the front and rear at the same time with the same pack and controller? If not, how would you accomplish this. I am guessing it would only give you better acceleration and climb hills better (each motor helping the other). Any input is appreciated. I do realize you must have 160mm for the rear dropout.

Also, I see that the motor only has 5 gear settings. I have a 21 speed (7 gears on wheel). This would make my 21 speed a 15 speed right? Would my shifter work properly with this?

[OneEye]

I believe you will need a controller for each motor, however you should be able to connect the signal wires from the throttle to both controllers.  You will certainly need a hefty battery to run under this configuration.

You should be able to run as a 15 speed (3 front x 5 rear), however if you have index shifting you will probably need to change it to friction shifting.

[mustangman]

 If you have a front hub motor, how about a gas motor on the back to extend the range and possibly recharge the battery pack making the bike a hybrid. 

[Gregory]

or using one controller and two BRUSHED Golden motors.

In series they'll halve the voltage, in parrallel and they'll each use half the amps.

[myelectricbike]

What happens to the torque and speed?

[mustangman]

What I would be concerned with is the additional weight may not equal additional performance especially if you have to add more batteries. This additional weight would mandate the use of LiPo or LiFePO4 batts to save wieght.

[OneEye]

Thinking it through, it's a nice hypothetical to have two motors on a bicycle, but I'm not sure I see the value added.  You are asking for a lot of additional weight and complexity for little gain.  If you are looking for higher torque with the same top speed it would probably be more efficient to get a geared hub motor or a center mount motor with gearing.  I think there is a "puma" hub motor with three gears that might be suitable.  Otherwise you can go with a beefy Crystalyte 50x series hub motor with a beefy torque for hills and a decent top speed using high voltage.

A gas motor with an electric hub motor is another interesting hypothetical but perhaps impractical at best.  On short trips you are hauling around all the extra weight of the gas motor for no reason, on long trips the electric system is pointless.  To me it would seem better to build two separate bikes, one electric one gas, and take out the one you prefer for your chosen destination...the electric for a medium distance quiet ride, the gasoline version for a long distance noisy trip.

Of course I may be entirely missing the point.

[myelectricbike]

Well then there is also traction. If you add double wide rims and tires then there might not be anywhere you can't go, except of course in water deeper than the motors.

[OneEye]

Of course I may be entirely missing the point.

Bah,

Seems the world does not necessarily agree with me about a motor in each wheel being of only limited hypothetical interest.  A series of similar discussions just erupted over at Endless Sphere, so there is certainly a fair amount of interest. 

One such thread: http://endless-sphere.com/forums/viewtopic.php?t=2293

As an interesting side note about gas-electric hybrids, someone on that forum suggested for long trips putting a small gas-powered electric generator in a bike trailer for long-distance riding.  I guess I just have a hard time envisioning spending more than an hour getting somewhere without switching travel modes and jumping in the car.  Perhaps another area where I am simply being short-sighted.  It might be just what it takes to go completely car-free.

[Dalecv]

Check it out here why they are doing it on gas powered motorcycles;

http://paultan.org/archives/2006/08/08/ktm-tests-two-wheel-drive-motorcycle/

If it doesn't improve fuel mileage I don't really see a reason why one would want to do it with an electric bike. I guess if you were riding off road up steep hills and such you might want to try it, but the weight to power ratio of electric bikes and the current status of battery technology this doesn't seem make much sense to me.

Maybe if there is some kind of timed electric bike hill climb competition.

[myelectricbike]

Check here.

[cerewa]

One of the suggestions I read for how to set up a two-motor electric bike is to use a hub motor with high torque on one wheel, (for hill climbing) and a motor with high maximum speed on the other wheel. 500 watts is easily enough to give you higher speeds than the goldenmotor hub, but the only way to do it without sacrificing low speed torque is either:
-have a separate motor for high speeds or
-have the motor run through a multi-speed gearing system