DaveAK

10 February 2011, 1427

I've got limited knowledge on each of these and haven't paid too much attention to it. With my bike it was pretty easy, I know the motor RPM so could gear it to get the top speed I was after. I know that if I want a little more acceleration I'll lose some off the top end, and vice versa. I'm not designing for the drag strip or race track, so I don't need to put much more thought in to it than that.

Now my summer project is a little different. It's not a bike but I hope you'll help me out anyway. :) It's going to be a slow speed tracked or multiwheel vehicle deigned for pulling a load. Most of the work will be done at probably 5mph with a 15mph top end just for getting from point A to point B.

Here's the motor spec:

CONTINUOUS RATING: @ 48 Volts

•3100 rpm

•2.8 ft lbs torque

•45 amps armature

•9.5 amps field

•2.3 HP

PEAK RATING:

•4500 rpm

•14.3 ft lbs torque

•350 amps armature

•20 amps field

•8.5HP

If I run at 48V I can gear it to run at 15mph @ 3000rpm, and 5mph @ 1000rpm (approx. 7.7:1 ratio). Or if I run at 24V I could gear it to give 15mph @ 1500rpm and 5mph @ 500rpm, right? (3.8:1 ratio) This assumes that 24V will give half the rpm.

This is where I start to get confused and need some pointers. I'm designing for slow speed pulling power, so torque is the critical factor.

1) Whats the relationship between the motor specs, voltage, torque and gearing to get me the best setup?

2) To get torque you need amps right? So would running at 24V or 48V be better for providing the low speed torque I'm looking for? I'll need to keep the amps to a reasonable level for continuous operation.

3) How does gearing effect torque at the wheel vs. motor torque?

Ultimately I can just as easily run this at either 24V or 48V, or even 36V, but I just can't get my head around figuring which would be best, and what the trade offs would be.

Now my summer project is a little different. It's not a bike but I hope you'll help me out anyway. :) It's going to be a slow speed tracked or multiwheel vehicle deigned for pulling a load. Most of the work will be done at probably 5mph with a 15mph top end just for getting from point A to point B.

Here's the motor spec:

CONTINUOUS RATING: @ 48 Volts

•3100 rpm

•2.8 ft lbs torque

•45 amps armature

•9.5 amps field

•2.3 HP

PEAK RATING:

•4500 rpm

•14.3 ft lbs torque

•350 amps armature

•20 amps field

•8.5HP

If I run at 48V I can gear it to run at 15mph @ 3000rpm, and 5mph @ 1000rpm (approx. 7.7:1 ratio). Or if I run at 24V I could gear it to give 15mph @ 1500rpm and 5mph @ 500rpm, right? (3.8:1 ratio) This assumes that 24V will give half the rpm.

This is where I start to get confused and need some pointers. I'm designing for slow speed pulling power, so torque is the critical factor.

1) Whats the relationship between the motor specs, voltage, torque and gearing to get me the best setup?

2) To get torque you need amps right? So would running at 24V or 48V be better for providing the low speed torque I'm looking for? I'll need to keep the amps to a reasonable level for continuous operation.

3) How does gearing effect torque at the wheel vs. motor torque?

Ultimately I can just as easily run this at either 24V or 48V, or even 36V, but I just can't get my head around figuring which would be best, and what the trade offs would be.