Tom Gardner wrote:

I have an application that I need to rotate a shaft at about 3 rpm. The
shaft is 2.5" dia. x 5' long and has a number of cams on it. A ratchet
wheel will move the shaft incrementally through 98 steps and there are 104
teeth on the ratchet. I want to use a gearmotor and chain drive to move the
last 6 steps stopped by a limit switch. I don't think I'll need a brake and
the ratchet wheel has 2 pressure brakes on it to take the jar out of the
ratchet. I also want the gearmotor to "walk" the shaft around for
troubleshooting. All my other machines use an 2.5" air cylinder mechanism
to advance the ratchet the extra teeth. One of these cylinders is $600 plus
the rest of the mechanism for $1000. I think the gearmotor will be cheaper
and better.

My question: I want a one-way clutch so the chain drive will just coast
while the machine ratchets. Is there a one-way clutch that I can mount on
the output shaft of a 1/4 hp gearmotor and just bolt a sprocket to the
clutch?

Perhaps check the one way bearings on http://www.mcmaster.com

The overrunning clutch couplings they have don't seem to quite be it,
but at your low speeds might work.

Pete C.