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Electronics => Electronics => Topic started by: soninja8 on May 05, 2013, 07:11:34 PM

Title: Will this work?
Post by: soninja8 on May 05, 2013, 07:11:34 PM

I am making a large scale rc tank/car and I happened to stumble on these cheap motors:
http://www.ebay.com/itm/Fasco-24V-Electric-Brushless-Motor-7103-0113-DIY-/171031701843?pt=LH_DefaultDomain_0&hash=item27d248a953 (http://www.ebay.com/itm/Fasco-24V-Electric-Brushless-Motor-7103-0113-DIY-/171031701843?pt=LH_DefaultDomain_0&hash=item27d248a953)

Will 24v at 5.2 amps be enough to carry, say, 50lbs?

Also, is anyone familiar with these Fasco Brushless motors and the motor controller that comes with it?

Thanks again!

Title: Re: Will this work?
Post by: jwatte on May 05, 2013, 10:04:54 PM

What you need to move a rolling wheel is torque.
What you get from voltage and amperage is power.
Without knowing the gear ratio and kV ratio of that motor, and also not knowing how much of an incline you want to climb, nor how much friction losses you'll have in your drivetrain and wheels, it is not possible to do the math.

Any motor, no matter how weak, can move any mass, no matter how large, if it's doing it on a perfectly flat surface with a perfectly lossless drivetrain. This is a fact that trains on rails use to move relatively large amounts of mass, with relatively small engines/motors (relative to the train -- they're actually massive compared to the motors most of us actually interact with :-)

If there is no gearbox on that motor, I would hazard a guess and say that, no, there will not be enough torque to start a 50 pound load riding on solid plastic wheels on a flat concrete pavement. And your use case may be worse, with deforming rubber wheels on a lawn, climbing at a 20 degree incline.

If you use a gearbox, yes, you can make it carry that load; the question is then how fast you want to go.

Title: Re: Will this work?
Post by: soninja8 on May 05, 2013, 10:30:10 PM

You were very informative, and your response was what I was thinking. I'll go with the heavier duty brushed motors instead.

Thanks again!

Title: Re: Will this work?
Post by: jwatte on May 06, 2013, 11:58:01 AM

Quote

I'll go with the heavier duty brushed motors instead.

Brushless motors are a fine powerplant. What you really need is a gearbox.
Typically, brushed motors can be had with integrated gear boxes easily, whereas I haven't seen that readily available at hobbyist prices for brushless motors.
If you can find a way to get sufficient gearing out of that brushless motor, it could work fine. For example, a chain or timing belt drive, with a small pinion on the motor, and a large driving sprocket on the drive axle, might give you 8:1 or so, which *might* be enough. (Specifics are important here!)