2 wheel drive bicycle?

[Sparky]

ok, so brads link on another post to a hubmotor running a hubmotor has given me an idea.

would it be possible to use two hubmotors to make a 2 wheel drive bicycle?

i think the extra traction gained by the front wheel would be phenomenal for an off road, mtn biking situation. relating to my jeeping experience, front wheel drive will get you up and over many an obstacle that would be impossible without.

course, i dont know anything about hubmotors. any thoughts?

[AtomicZombie]

Now that is an interesting idea. If both wheels had traction, there would be very little drag as no power is being transferred "across the wire" If one wheel lost grip, the other wheel would act like a generator and drive the slipping wheel.

This might be worth a shot if you ever have your hands on 2 identical hubmotors.

Brad

[macka]

That would be cool, but what about high speed turning? I know when your wheeling you have a smaller turning radius in 4WD, and you get some plow steering in the mud.

[Sparky]

hmm... i suppose wheels do run at different arcs in turns. i would imagine it to not be a problem though. minor slippage isnt usually an issue, especially with something as lightweight as a bicycle. perhaps you could wire in microswitches to kill front wheel power when you turn full lock.

how would you connect gears to a hubmotor wheel though?

[gbbwolf]

They sell rear wheel hubmotors complete with whatever gearing you choose.

Nelson

[rohorn]

You can run 2 brushed hubmotors in parallel from the same controller. I've done that with 2 Heinzmann hubmotors with no trouble and lots of fun.

Running 2 brushless motors from the same controller is a bad idea. I never tried to manage 2 controllers with the same "throttle".

Running a second "high speed/low torque" hubmotor won't produce any real speed increase over just one hub, but it will double the torque - if you have the battery capacity to provide the amps.

TORQUE and SPEED is GOOD.

[Radical Brad]

Brushless motors send RPM feedback to the controller in the form of pulses from a hall effect sensor or back EMF, so you would not be able to run two motors in parallel from 1 controller.

Brad

[macka]

I wonder about 2 things if you had 2 wheel drive.
1. The effect on steering the motor would have. I know in 4x4s that when the front axle is engaged, you lose steering radius because the wheels will "slip" when driven making for a wider turning circle.
2. Torque steer. During acceleration would the front wheel "pull" the bike to one side, or is that an effect found only in front wheel drive cars due to the differential dividing the power.

If both effects are non existent or minimal in a 2 wheel drive bike, then that would make for a sweet off road e vehicle.

dual drive? (http://www.electrikmotion.com/IO%20Tidal%20Force.htm)

[greenevegiebeast]

macha both the issues you have mentioned may be a 4wheeled issue. the front dif is what causes theloss of turning radius.

torque steer is caused by the difrance in legnth of the front axle shafts, the tend to twist at difrent ratets. that twisting spring action is what causes the "torque steere".(ie torqea- the twisting force)

[rohorn]

The front drive torque would have an opposite effect of braking - if the front end dosn't do anything weird while braking, then it won't do anything weird under power. It usually takes a very wide front tire and/or a bad profile to make that happen

On the other hand, if you understand how ineffective a rear brake is while going down a very steep hill, then you will understand how ineffective front drive is going up a very steep hill - especially with short wheelbases and high CGs.

[macka]

rohorn,

Yea but having both wheels driven would be a bonus for offroading, as one end would compensate for the other in those situations. In my 4 wheeling experience, I've always had a longish wheelbase (p/u truck, and cherokee) so having a short wb will be a learning curve all on its own. The other advantage that I can see is using regen braking to control descent other then having to use the brakes would allow for more options and less chances of locking a tire which is a bad thing while descending a steep grade.