Question: Dual motors

[ryan_lirui]

This may come across as a stupid question, but is it possible to match two different types of motors together to propel the same wheel? If so, would it be possible for example to use an outrunner motor in combination with a hub motor with a sprocket on it?

 

[amberwolf]

No reason why not, as long as they both drive the wheel to the same RPM if they are to be used together.

If you intend to use one as a high-torque low-speed startup motor, and then use the in-wheel hub motor at closer to full speeds where higher torque is not needed (except on hills), then their RPMs do not even need to match. You'd just want to freewheel or clutch the slower motor so that it will not place a drag on the faster motor once that one kicks in.

 

[etard]

I think thats an excellent idea, Amberwolf! You could gear the RC motor to top out at like top pedal speed, say 15 mph, and then kick over to the Hub motor for cruising. 8) Use an RC controller for the Hub motor and a Sensored Controller for the outrunner. Or what about a smaller brushed motor connected directly to a battery for burst acceleration? Would that work? Personally, I would never do it. Ebikes seem a cluttered mess with a hub motor on it usually, let alone both.

 

[JEB]

On one of my trikes I have a direct drive to the rear wheel with one motor, the other motor drives through a split chain to the rear cluster for steep hills. I know this adds more weight etc., but I like haveing a backup motor, both have freewheels

 

[TylerDurden]

Markcycle's first motorbike had a rear X-5, then he added a motor via chain-drive to help it get started.

 

[ryan_lirui]

I wonder if there is a way to throttle engine speed directly rather than how much power is put into them. If you could do this then I suppose you could put two engines in series and have them produce a combined, continuous high torque output until one of the motors reaches its maximum speed at which time the freewheel kicks in and allows the other motor to continue to accelerate.

I guess one alternative way of approaching it would be that the motor with the least aggressive profile would be your guide motor, and then using the output of its hall sensor you'd use this to gauge how much power to input into the second motor.

Maybe none of this is necessary. Maybe all you'd need is freewheels on both motors so that when the two motors are in sync then they would be producing a combined torque, and when either motor is at a point in its rpm range at which it can produce more torque than than the other motor the other motor just disengages.

 

[John in CR]

Ebikes seem a cluttered mess with a hub motor on it usually, let alone both.

??? It's only the bike frames that are the problem spacewise, and a hub motor + an RC helper is really no different than just an RC motor alone other than the extra controller. I can't build a better motor, and I sure as hell can't build better electronics, but I do think I can come up with better frames tailored specifically for ebikes. Examples to come, including a whole new class that is a more practical car replacement. I'll leave the performance stuff to guys like Recumpence and LiveForPhysics, et al.

Regarding the original post, a hub motor with a helper motor to aid in acceleration and mountain climbing has been on my short list for a while now. It's a great idea. A 15-20mph top end for a power RC seems like gearing you want to be able to do steep ascents. Another benefit of the 1+1 alignment is if the hubbie is direct drive, then regen braking is easily accomplished. One more benefit is the silent running, though the RC experts are getting their stuff pretty quiet now.

Since my bikes are long and low, near impossible to end over, so my 1+1 would be a front hub, and the out of wheel motor driving a geared hub to be able to climb virtually any hill. Once our resident experts develop the idea bike motor, the need for a second motor will go away with speed and low rpm torque all in one.

John