DC-Motor calculation for Power/Torque

Other Hardware Motors, Mechanics, Power and CNC
1

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.

2

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.

3

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.

4

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...