Can you use two identical DD hub motors front and back?

[Wolfy]

Good Day Eh?

This might be stupid to ask,but it seems to be of the same subject.
Can you use two identical DD hub motors front and back?
Have them share the throttle control through a single controller?
Have them share same batteries with regen on both?
Or do it with separate battery system w/regen while sharing conroller?

(moderator edit: split from topic "Front hub motor as regen brake?" because new topic is definitely not the same subject. Also refer to the several topics regarding dual hub motor bikes.)

 

[edcastrovalley]

Good Day Eh?

This might be stupid to ask,but it seems to be of the same subject.
Can you use two identical DD hub motors front and back?

Yes

Have them share the throttle control through a single controller?

Not with sensored controllers. You can share a single throttle with two controllers though.

Have them share same batteries with regen on both?

Yes

Or do it with separate battery system w/regen while sharing conroller?

No, but you can share one battery with two controllers.

 

[Wolfy]

edcastrovalley wrote

Not with sensored controllers. You can share a single throttle with two controllers though.

I think I get the sensored DD part......
The way I was thinking that take sensor signal from only one of the DD's (back one) and have the other simply not hooked up or sensorless.
Given the same motor winds,tires,wheel size should they not be giving extremely similar sensor signals?
Also,make sure phase wiring size and length is identacle so amperage would divde almost evenly.
Or would the load not be that even? Back wheel with more weight,hence traction.
Is the issue if the back wheel loses traction and spins? Think you would blow the controller if the sensored motor spins faster than nonsensored.
Got me thinking after reading the HS/HT Clyte thread in sensorless vs sensored versions.
If you go sensorless with both DD's would you not have the same issues if one breaks traction or even more load on one than other?
Does that mean a single sensorless controller can drive two DD's ?
Just trying to wrap my noodle around the sensorless part of things....

 

[dogman dan]

The two wheels will never stay in synch for more that a few revolutions. You'd need two controllers. I think that one is nearly set in stone.

It could be done with brushed motors I believe, but hardly worth the disadvantages of going to year 1900 tech.

 

[Wolfy]

Thanks Dogman,
I get it.......they just won't stay syncro
Had to ask

 

[John in CR]

Thanks Dogman,
I get it.......they just won't stay syncro
Had to ask

They won't even start synchronized. To use a single controller the rotors would have to be locked together with the circles of alternating polarity magnets in identical positions. The stators would also need to be locked in identical positions too. Then wiring the phase wires in parallel is likely to cause a problem for the controller, since the motor resistance and inductance would be halved. The solution to that is more tricky than it sounds, because you'd need to wire the 2 stators in series, which will make the motor easier to drive by increasing the winding resistance and inductance. I'm actually considering doing exactly that to solve my controller blowing woes, and get the side benefit of double the torque and power.

To give you an idea of the kind of motor that would result, the huge buildup about the new Crystalyte motors was over amotor with a 35mm long stator and a typical fast wind ebike motor Kv for the HS series. I'll be starting with a motor essentially identical in basic design (same diameters, and same pole and slot counts), but wound with strands totaling 8 gauge for a significantly higher rpm/volt, and a 40mm stator, and of course without the assembly flaws. They're real controller eaters. The resulting motor will retain the same high Kv and high current handling, but will be twice as easy for controllers to drive and have a whopping 80mm stator for double the torque. Rainy season has me thinking BIG with the motors I have on the shelf.

John
the guy demanding hubmotor respect

 

[dogman dan]

Right, I couldn't even think of how you'd even get the motors to start in synch. Surely it could be done, but it sure wouldn't last more than a few revolutions once you start introducing the front wheel slipping, or just taking a slightly differend path.

But just having two controllers and one throttle is pretty simple, and works fine.

 

[Alan B]

Put both motors on the same chain or shaft, with an adjustment to sync them. One problem with syncing motors is that it is not really feasible, and another is that the extra heat dissipation of two controllers is a good thing (and you can get home with one if necessary).

Speaking of which, anyone ever put a mid-drive and a rear hub both driving the rear wheel to get more torque and increase heat dissipation? Some electric motorcycles use two motors. Putting one in the frame and one in the rear wheel could be interesting... Would work on a cargo bike. Pike's Peak rig???

 

[Kingfish]

P1 Dual 12FET - A living example of two identical DD motors, two controllers, and one throttle. Wheels are 26" in the front and 24" in the rear made deliberately to avoid contention on the flats.

It never became hot, though was often very warm after long hill climbs. I dig the torque; you can tell when one motor cuts out or cuts in. Last week I had a snafu: The rear wiring was eroded by the rear tire and cut out the motor, although I was still able to make it home using the FWD.

Would love to try it (or the next incarnation) on Pike's Peak next summer!

Count me in, KF