My question here is. Would this be a better way of building a high performance motorcycle then running 2 brushed motors? My reason for thinking this is that you could gear and select a brushed motor for better low speed performance and design the hub motor for better high speed performance. I searched but I didnt quite find what I was looking for.
Running a bldc hub motor and a brushed dc chain drive
- Thread starter sparkvark
- Start date
Ricky_nz
10 kW
sparkvark said:
You would need a freewheel of some sort to stop the brushed motor being overdriven at high hub speeds.
I think it all adds unnecessary complexity. Two different controllers, are their throttle responses similar.
How will the torque share? You could end up with the motors fighting each other. You would need more expensive controllers to avoid this.
Whats the fascination with brushed motors, there are decent brushless motors available is similar power levels that will give lower maintenance.
The only reason I myself would go for such a solution is to have a backup motor on the bike for "emergencies", and one that could be run without a controller if it came to that (which the brushed could do, in theory, though practice could make that difficult depending on conditions). Also because it would be very cheap for me to do, in that I already have the brushed motors and have used them for thru-the-gears drive successfully. 
But if I were to have a budget to just get whatever I wanted, I'd do it with brushless motors for both, as they're more efficient. I'd actually use a hubmotor for both of them, too, though one of them wouldn't be in a wheel, it'd be in the chain loop somewhere, to drive thru the gears. The other hubmotor would be a freewheeling geared motor, most likely.
For much of my riding, the hub works fine, and is simpler. But some of it, like cargo hauling or hills, the thru-the gears method works much better, and in start/stop traffic it would also be more efficient than the hub, due to the lengthy high currents pulled by the hub to get to speeds where it doesn't do that.
If I didn't need a "spare" motor, I'd just go with a thru-the-gears setup. But having a freewheeling geared hubmotor in the front wheel as a "spare" limp-home motor would be nice, as it doesn't add that much weight or complexity, and doesn't add any noticeable drag to the bike even with pedalling, let alone a main thru-the-gears motor.
The only other thing having the front hubmotor be a direct drive rather than geared motor would be especially good for is regen braking--when coasting down a hill or stopping under heavier loads or from higher speeds, that'd sure save wear on the brake pads.
I do not know if I can safely or easily make a thru the gears motor do regen; I'd have to do it without a freewheel anywhere in the system from wheel to motor, which means no coasting, unless I add a clutch in there somewhere. Also no derailer/tensioner, as it'd get messed up with power fed backwards thru the system, probably. So an internally geared rear wheel hub for shifting, and perhaps another one for more gears in between the pedals and/or motor and the rear hub, if I need further gearing down for hills and such vs flats, and then a simple pre-tensioned fixed-gear chainline from rear wheel up to motor. THen tension could be maintained both directions on it, and would work under drive or regen.
But if I were to have a budget to just get whatever I wanted, I'd do it with brushless motors for both, as they're more efficient. I'd actually use a hubmotor for both of them, too, though one of them wouldn't be in a wheel, it'd be in the chain loop somewhere, to drive thru the gears. The other hubmotor would be a freewheeling geared motor, most likely.
For much of my riding, the hub works fine, and is simpler. But some of it, like cargo hauling or hills, the thru-the gears method works much better, and in start/stop traffic it would also be more efficient than the hub, due to the lengthy high currents pulled by the hub to get to speeds where it doesn't do that.
If I didn't need a "spare" motor, I'd just go with a thru-the-gears setup. But having a freewheeling geared hubmotor in the front wheel as a "spare" limp-home motor would be nice, as it doesn't add that much weight or complexity, and doesn't add any noticeable drag to the bike even with pedalling, let alone a main thru-the-gears motor.
The only other thing having the front hubmotor be a direct drive rather than geared motor would be especially good for is regen braking--when coasting down a hill or stopping under heavier loads or from higher speeds, that'd sure save wear on the brake pads.
I do not know if I can safely or easily make a thru the gears motor do regen; I'd have to do it without a freewheel anywhere in the system from wheel to motor, which means no coasting, unless I add a clutch in there somewhere. Also no derailer/tensioner, as it'd get messed up with power fed backwards thru the system, probably. So an internally geared rear wheel hub for shifting, and perhaps another one for more gears in between the pedals and/or motor and the rear hub, if I need further gearing down for hills and such vs flats, and then a simple pre-tensioned fixed-gear chainline from rear wheel up to motor. THen tension could be maintained both directions on it, and would work under drive or regen.
