Best available steppers, boards, controllers, etc?

Guy Brandenburg

We have a venerable but beefy and smooth university-grade German equatorial mount from the 1970s, whose “dumb” electro mechanical drive has clutches and variable-speed controls that have been an intermittent problem from Day 1. The RA drive is currently on my desk; the old clutch pads had come off. Adjusting the new pads and gears and solenoids is not trivial!

We are therefore looking seriously into converting to an OnStep drive. One major problem: the various boards, controllers, etc recommended on various parts of the OnStep wiki either seem to have compatibility issues or else are not in stock and/or not being produced.

we are neophytes at building anything this complex.

I have the RPM measurements for the various gears. For example, tracking speed on the worm gear that sticks out in that photo is 5 rpm with no load. The synchronous motor that drives all this is rated at 60 rpm with a torque of 1/900 HP. 

So does that mean that the worm gear would need a torque of 12 times 1/900 horsepower? And we could use a belt with two sheaves of equal size, and a geared stepper mostly running at 5 rpm, or a 1:2 pulley ratio with 10 rpm?

what are the current driver and controller and board recommendations for something like this?

thanks so much.

Guy Brandenburg
Hopewell Observatory

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