It seems to me hub motors generate torque in two ways: one "electrical" (more copper windings give greater effective current flow past magnets & slow down the motor's ungeared rotation speed while increasing torque) and one "mechanical": using internal cogs & rings to gear down the motor speed from thousands to hundreds of rpm.
Question is, since motors vary in the proportion of torque derived from each means, what difference (if any) does it make to motor performance how its torque is generated?
For example, two motors, same voltage & current limit, magnets layout etc. one has a higher winding number (and so higher "electrical torque") runs at around 2000 rpm and is mechanically geared down by around 7:1 to around 280rpm; another has less windings, runs at about 3300 rpm but has a higher mechanical geared reduction ratio of ~12:1 to give the same 280rpm approx. What performance difference could be expected, in principle (if any), between these two motors, in the same size wheel eg 20"?
One thing occurs to me, that "mechanical" gearing is more voltage-related & so may require less current and hence less heating - could that make it more efficient: lower losses as heat? But then, would torque originating from current be somehow inherently more "torquey" & better for hills, say?
Please feel free to correct if my terminology is incorrect or inaccurate: I'm only just starting to find out about these things and I realise the picture is incomplete and probably vastly over-simplified! having said that, I was rather satisfied the other day when I grasped the relationship of "torque" to the rpm and power output of the motor, and the turning force of the wheel on the road (though torque graphs don't get mentioned here, so I'll not go into it, but will post what I found if anyone's interested )
Stuart.
Question is, since motors vary in the proportion of torque derived from each means, what difference (if any) does it make to motor performance how its torque is generated?
For example, two motors, same voltage & current limit, magnets layout etc. one has a higher winding number (and so higher "electrical torque") runs at around 2000 rpm and is mechanically geared down by around 7:1 to around 280rpm; another has less windings, runs at about 3300 rpm but has a higher mechanical geared reduction ratio of ~12:1 to give the same 280rpm approx. What performance difference could be expected, in principle (if any), between these two motors, in the same size wheel eg 20"?
One thing occurs to me, that "mechanical" gearing is more voltage-related & so may require less current and hence less heating - could that make it more efficient: lower losses as heat? But then, would torque originating from current be somehow inherently more "torquey" & better for hills, say?
Please feel free to correct if my terminology is incorrect or inaccurate: I'm only just starting to find out about these things and I realise the picture is incomplete and probably vastly over-simplified! having said that, I was rather satisfied the other day when I grasped the relationship of "torque" to the rpm and power output of the motor, and the turning force of the wheel on the road (though torque graphs don't get mentioned here, so I'll not go into it, but will post what I found if anyone's interested )
Stuart.