motors and gearing

thetoddjohnson

Imagine that you had 3 identical sparky carts.

Cart A you leave untouched and it has a top speed of X.

In cart B you swap out the motor for a “high speed motor” and at the same time you reduce the gearing (either using a different rear or shorter tires or some combination thereof) such that the top speed remains X.

In cart C you swap out the motor for a “torque motor” and at the same time you increase the gearing (high speed rear or taller tires or some combination) such that the top speed remains X.

What would be the pros/cons with respect to efficiency? heat generation? longevity of equipment? acceleration?

Thanks,

TJ

BGW

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Gregorio

Interesting discussion.

I would have to believe that the longevity/durability differences would be hard to quantify. You would, however, be shifting the failure points from one place to another. The motor on cart C is doing the same work but at a lower RPM which shifts the stress point to the transaxle, etc.

From a performance perspective, you would have to study the area under the torque curve to determine which combination makes more sense. You can't always make up a lack of torque with gearing.

Revolution

I have contemplated this issue for more hours than I care to admit. I know from real world experience that high rpm motors out perform low rpm motors on their output, once their rpm is reduced to fit the requirements by suitable gear reduction. I am looking forward to the conversation from here out.

thetoddjohnson

If you were to use a high speed motor, high speed gears, and large diameter tires then try to climb a hill with 4 people on the cart it wouldn’t work. I’m assuming the result would be a fried motor. Correct?

What would fail if you did the opposite—high torque motor, low gearing, standard size tires, traveling on flat ground, with only one person. Would this simply be a robust setup and would work fine, or would something break?

Thanks,

TJ

Gregorio

It would be a fried "something" as the RPM drops and torque rises, so do the AMPs! I'd put money on the cables or batteries as most controllers have limits.

Revolution

Most likely nothing would break ever, but low gears with a torque motor at normal voltages might be 5 mph on level ground.

Revolution

If Plum Quick or D&D wants to loan me a stock, torque and a speed motor, Ill buy the gears and test it out!

Nate

cgtech

"the opposite" (high torque motor, low speed gear, small tire), the result "should be" a cool running motor & controller, and climb any hill or tow anything at the same 5mph it does on flat ground. The big "if" here is the torque handling ability of the axle. Some issues remain, the stresses endured by the "top half" of the axle would be decreased (input shaft and intermediate shaft "drive" gear), but the "bottom half" would be increased (intermediate shaft "driven" gear, ring gear, spider gears, axle shafts) due to the change of the mechanical leverage on the axles and such. Some engineer will be along shortly to shoot my theory full of holes...