# DC-Motor calculation for Power/Torque

Hello. I wanna calculate my DC-motors strenght and see if it's strong enough to move 5kg (a bottle with liquid in it) back and forth. I am running this

https://www.servocity.com/html/60_rpm_precision_gear_motor.html#.VTzU6iHtlBc

at 12V with a L293D H-bridge and the bottle is moved by a skin like this on

https://www.servocity.com/html/channel_slider_kit_a__637108_.html#.VTzV5iHtlBc

my DC motor is pulling the rim.

So is there anyway I can calculate and see if my motor is actually strong enough to do this?

Thanks.

Skin? Rim? Are you talking about the timing belt slider you've linked to?

Your system has friction, have you any idea how much ? Is there a gravity component to overcome too? A good diagram would be mighty useful.

That motor doesn't have a continuous rating, only stall and idle, which isn't useful

And its all in tedious imperial units, gah! This is the 21st century!

As far as I can see the motor develops upto 1.4Nm at stall (perhaps it can handle 0.5Nm continuously - perhaps not? How can we tell?)

The timing belt drive has a 12.7mm radius sprocket so 0.5Nm translates to 39N linear force, if that's useful.

Weight Force = Mass * g (gravity)

Power = Torque * Speed

Torque = Force * Distance

Speed Out = Speed In / Gear Ratio

Power Out = Power In / efficiency

Power = Amps * Volts

One little thing you do need to understand - the speed used to calculate power should be radians per second, not RPM. The rest is just a matter of plugging the numbers into a calculator.

As i see it you want to lift 5 kg with a radius 13 mm wheel. Lets say: 55 N x 13 mm = 715 mNm. At stall your motor gives 1373 mNm (194.4 oz-in). Most DC motors are linear so you can draw the torque in a graph, where Y is torque and X is RPM, as a straight line from point X=0;Y=1373 to X=60;Y=0.

Y=715 will occur at 31 RPM pretty much in the middle of the graph.

Without knowing other losses this motor looks like a good candidate...