# Will These Motors Be Powerful Enough?

1. Apr 27, 2013

### rocketbuilder

Hi everyone,

I plan on getting a deeper understanding of this soon, but for the time being I'm just looking for a quick answer so I can order the parts needed.

I'm building a rover that in total (including all parts) will weigh about 15-18 lbs. It has six equally spaced legs, each connected to a 4.5 inch diameter by 3 inch wide wheel with rubber treads. Each wheel has a small hub connected to it where the 4mm shaft of the motor will be held. My question is, will 6 small 12 Volt DC 120 RPM motors with 60 Newtons * cm of torque be enough to move the rover around? I'm not really concerned with speed as long it can move at about a slow walking pace. My bigger concerns are will it move and will there be enough torque for it to make it up small hills of modest inclination (given that it has some traction).

Thanks so much

2. Apr 28, 2013

### Staff: Mentor

Welcome to PF!

What slope are you looking to try to climb?

3. Apr 28, 2013

### rocketbuilder

Thank you!

I guess there really isn't one set slope that I want the rover to climb. I want it to be able to move around in different environments, but let's just say the maximum slope it would try to climb would be about 35 degrees.

thanks again

4. Apr 28, 2013

### Staff: Mentor

Ok, can you use some geometry and the equation for potential energy to calculate the power required to do that? (And throw in an efficiency factor of 50%.) Then you can use that power and the RPM to find the torque required of the motors. Give it a shot...

5. Apr 29, 2013

### rocketbuilder

Ok, so I did some calculating and ended up with about 2.25 (rounding up a bit) lbs force per foot for the torque needed to climb a slope of 35 degrees and a height of about 5.73 ft given it's hypotenuse is 10 ft. I also took into account the 50 percent EF when calculating the power. Do these numbers sound somewhat correct? Also do I have to take into account the diameter of the wheels? My formula for calculating torque was T= hp(converted from power) X 5252 / rpm