# Help with Motor Selection

#### troybaxter99

Joined Jan 19, 2022
3
Howdy y’all,

I am wondering if any of y’all got any recommendations on possible motors I could buy for my robot. These motors must should preferably be 12V, lowest current possible (preferably no more than 2.5A), have a torque handling between 100 lb-in and 150 lb-in, an RPM of no more than 15, and can sustain operation for several hours continuously.

The purpose of these specs are to allow my team and I to drive a roughly 3 foot wide, 3 foot long, 2 foot high 80-100 pound rover across muddy terrain for several hours. The wheels of the rover are 10 inches in diameter. I won’t get into the details why, but there is a reason why the rover is this large and this heavy.

Joined Jul 18, 2013
25,230
With those specs and you are going to attempt it with 30watt motors?
If only 15rpm required then some high degree of gearing should be used, naturally.
You should calculate or measure the actual torque required at the output shaft and calculate input torque accordingly.

#### MrChips

Joined Oct 2, 2009
26,151
Experiment with automotive windshield wiper motors. They are 12VDC driven and come with reduction gears.
They are readily available on the surplus market.

Joined Jul 18, 2013
25,230
There are also automotive geared seat motors that are quite powerful.

#### troybaxter99

Joined Jan 19, 2022
3
With those specs and you are going to attempt it with 30watt motors?
If only 15rpm required then some high degree of gearing should be used, naturally.
You should calculate or measure the actual torque required at the output shaft and calculate input torque accordingly.
That’s what we are expecting. My team and I just don’t know where we can find motors with gearing that can match our specs. The current motors we have rate up to 50 kg-cm, and we need roughly 3.5 times that torque. That being said, they are two times faster than we need them to be, with an RPM of 27. So we know there has to be something out there.

#### troybaxter99

Joined Jan 19, 2022
3
With those specs and you are going to attempt it with 30watt motors?
If only 15rpm required then some high degree of gearing should be used, naturally.
You should calculate or measure the actual torque required at the output shaft and calculate input torque accordingly.
Based on some calculations, the motor itself should have 1000 RPM input, and a torque of around 10 lb-in. We would prefer to have a right angle planetary gear attached with a ratio between 30:1 and 50:1. Of course, we have no clue where to find the right motor with the right gearbox.