Motor gearboxes...basic questions.

[dgauthier]

Questions concering electric motor gearboxes...

1. Are there direct relationships between ratio, speed and torque? I just installed an electric drive. The torque spec on the basic drive (W/O gearbox)is given as 225 ft/lbs and the spec for the entire assembly is 2250. The gearbox is clearly stamped 50:1. Does gearing down not directly multiply torque, or is there a typo somewhere? The gearbox provides a 90 deg. direction shift.

2. What is significant about "double-reduction" gearing? Is it a reference to internal arrangements or is there a performance difference? For example,in terms of output speed and torque will the end result be the same for a "standard" 10:1 gearbox and a 10:1 double-reduction gearbox?

Thanks in advance,
DG

 

Yes torque is related to speed. Torque out of the gearbox is equal to torque in multiplied by the gearbox total ratio. So 225 into a 50/1 unit will give 11250 out and the speed will be 50 times less.

Double reduction gearing means there are two meshes ( 4 gears. As most parrallel axis and bevel gearbox single reductions are usually 5 or 6/1 then for a 10/1 unit it would probably be a double reduction and for 50/1 I would expect a triple reduction. The bigger the single ratio, the smaller (relatively) the pinion shaft so it bends more, that's usually the reason to keep it low.
The differences will be the cost and the efficiency, say 97% per mesh.

If you have a large ratio with only two reductions it's possible you have a worm box. The efficiency of these is a lot less but you will get the big ratio in less stages.

 

Can anyone tell what what the drive efficiency loss is through roller chain. For instance if I have four parallel shafts connected by individual roller chains, assuming all of the sprockets are the same size, what is the power loss between shafts due to the roller chain?