MECHANICAL POWER QUESTION

Power = torque X speed. 1 HP = 33,000 lft_f/min. 1 HP = 746W. Watts = Volts X Amps.

It is unclear what the traveling speed is of your mechanism, but as far as I can tell, it may be as much as 60 rpm X small wheel diameter X pi. Just for fun, let's say that your small wheel diameter is 4 inches. That means that the cart will move about a foot per revolution. At 60 rpm, the cart will move 60 feet per minute. The torque at the wheel must be at least 9 lb-ft to get the cart moving and a little less to keep it moving. The HP required is 9/33,000. 9/33,000 is insignificant, but it's got to drive the gear train, etc., so let's say you need 1/10 HP. 1/10 HP = 75 W. 75W at 24 V yields Amps = 3.

What else?

<What else?>

Nothing Else--end of story!

For the purpose of clarification, the motor has the 4" dia. gear and chain. The other end of the chain is the 4" dia. idler gear. The bins are attached to the chain. The small wheels ( 2" dia.) are not driven but are under the bins to take the weight off them and permit them to roll smoothly. The 54 lb. weight was measured by attaching the scale to the chain so that the filled bins, gears, weight of the chain, rolling weight and all other frictional losses were included in the measurement.

Can you give me the calculation used to determine the 9 lb-ft torque at the motor. Thanks

It's still not quite clear how your mechanism is set up, but I think I can assume a couple of things (even though I know what "assume" can do for me).

IF the load, which requires 52-54 lbs force to move it, is being driven by a 4" sprocket and motor, then the 54 lb force is translated from linear to rotary motion via the lever-arm moment of 2" radius. 54 lbs X 2" = 108 lb-in torque = 9 lb-ft torque. Speed, at this point, doesn't have anything to do with the calculation, and therefore power (or horsepower) doesn't have anything to do with the calculation either.

Power is torque times speed. Horsepower is torque times speed also, but it has specific units of measure. 1 HP is 33,000 lb-ft force/minute, for example. For a given speed, 60 rpm, the power required to move the chain with a 4" diameter sprocket is 9/33,000 HP.

The problem with sizing a motor to do this work is that it is based on ideal stuff. If you put a 1/1000 HP motor on this mechanism, I'd bet it wouldn't work long, if at all. One reason is the power loss in the gearbox of the motor, which you may think isn't significant if it's well lubricated, but it certainly isn't friction-free.

60 rpm, 1/10 HP motors are cheap and should have enough overhead to last a long time.

Thanks for the information, Bill. It was very helpful.