"Tom Gardner" wrote in message
...
I need about 67 rpm on a shaft.
An 1800 motor with a 40 to 1 gearbox = 45
An 1800 motor with a 20 to 1 gearbox = 90
Of course, Automation Direct doesn't have a 30 to 1 box and I want to use
them as a supplier.
The output of the gearbox will have a belt to drive the shaft but should I
use the 40 and step up the speed to the shaft with the appropriate sheaves
or step down the speed from the 20? Or, does it not make any difference?

Torque doesn't factor into this, I'm upgrading from 1/10hp single phase to
1/3hp 3-phase...and it's CHEAPER!!!

For no particular reason I seem to believe that two reductions are better
than one reduction and one increase. Just for fun, you might calculate it
both ways to see if one is easier with stock pulleys. Even if you use an
adjustable pulley, you might find one way easier or cheaper to implement.

Don Young