Motor size not sure.?

Help & Support Robot Parts
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Hi there I am a new member and this looks like an awesome site for projects I would like to build in near future.

My question is I am building a remote controlled 22" lawn mower. I know I am nuts. but its a challenge so I got to do it. LOL

The unit weights about 70 lbs. I have a 3-4% grade in my front lawn. I would like to use my existing Pistol grip remote control from my RC car with its receiver. My question is what 12 VOLT DC motors do we have that would work. I think the Sabertooth Dual 2X32 motor controller should work well to run 2 DC motors in DIFFERENTIAL DRIVE MODE. It seems the controller will do left / right /forward / back / stop operations via the remote control. So this should work really great for me. The 2 motors will be mounted with sprockets & chain so I would say there will be maybe a 3:1 reduction in speed. I believe that the mower normally cuts at about 3ft/sec while being pushed and the wheels are approx. 6" in diameter. My ruff calculations are about wheel speed of 140 rpm required.
I am looking at some cheap motors dc brushed that would have the torque to accomplish this task. Unless brushless is the way to go. But cost is limiting factor.

So I have provided as much info as I can think you would need to help me in my quest. Any comments are appreciated. If this will not work for some reason please voice in and let me know. I have tried to cover all my bases. Thanks so much.

oh PS the front wheels will be self pivoting as well.

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Hi Smooth99,

The setup is viable, make sure you can have a “FailSafe” value whenever the signal is lost between the TX and RX.
Otherwise you might have a lawn-mower run away…

Here are two nice Blog regarding motor sizing for projects:
Drive Motor Sizing Tool
Drive Motor Sizing Tutorial

Once you know more about the specs of the needed motor, we might be able to see what’s available.

:slight_smile:

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thank you the links are perfect

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I have the same project and have used electric 24VDC motors from a power chair. They work really well. Nice thing is no chains or sprockets are required and the motors go for about $150 each when they’re new. You can but old ones or buy a used power chair and scavenge all of the electrical and motorsoff of it.

I also highly recommend that you have a remote shutdown of the mower itself not just the drive wheels. If it ends up on smething you don’t want cut to crap or will damage the blades you can kill it.