I've installed an MD-5 single axis R.A. drive on an old Super Polaris that I've been rehabilitating. Now that I have it all together I see that something's missing: the pressure plate for the clutch. I can set it all up for the motor to drive the scope, but to disengage the gear I would need to loosen the knob and manually pull the drive gear out of engagement with the driven gear. Am I understanding correctly how this works? If so, can someone supply a clear image of this pressure plate? Perhaps I can improvise a fix using a spring or a spring washer? If not, I'll put out a call in the Classifieds.
Do you have the "clutch" device (in the PDF manual [see link in post #2 above], the clutch is pictured 3rd from the left in the bottom row of the figure at the top of page 17, and diagrammed assembled and unassembled in the figure at the top-left of page 18 ... copied + inserted below) installed on the mount's worm-screw shaft ?
If yes, then disengaging the motor (allowing manual slo-motion using a knob or flex cable installed on the outboard side of the clutch, and/or on the worm-screw shaft's extension on the opposite side of the mount) should only require loosening the thumbscrew [labelled "Setscrew" in the diagram] on the clutch device, which should allow the worm-screw shaft to be turned while the gear that's part of the clutch unit remains engaged with the gear on the motor shaft.
The "pressure plate" action that clamps the clutch gear to the clutch shaft happens when the thumbscrew of the clutch pushes down on the tapered (cone-shaped) section of the central 'gear shaft' that runs through the center of the clutch (see again the figure at the top-left of page 18, reproduced above). Because of the taper of that cone-shaped section, tightening the thumbscrew will force the clutch ring (that contains the thumbscrew) to the left in the figure, effectively clamping the sides of the clutch gear so it can't spin independently of the clutch 'gear shaft'. In this condition, the clock drive motor turns the worm screw on the mount. Loosening the thumbscrew on the clutch releases the leftward clamping pressure force of the clutch ring (from the thumbscrew pushing down against the taper), and in this condition (without this pressure) the clutch gear and the clutch 'gear shaft' can rotate independently of one another (i.e., the clutch gear can remain relatively stationary [its gear teeth still engaged with the teeth on the gear attached to the motor] while the 'gear shaft' through the center of the clutch is rotated manually by a knob or flex cable for slo-motion pointing adjustments).
Does the verbiage above help explain how things are supposed to work ? Hopefully so, and in that case hopefully you can figure out what in your setup is not working as it should. Let us know if anything might still be unclear -- copious verbiage is not always beneficial ! <sorry -- brevity is not my strong suit, unfortunately ...>
EDIT / P.S. If you don't have the little clutch assembly, and only mating spur gears on the motor shaft and on the worm-screw shaft on the mount, then [obviously] you can still loosen the paddle-shaped level on the mount that clamps the R.A. worm gear to the mount's R.A. axis (allowing you to slew in R.A. by hand), but then after re-tightening the clamping lever on the mount, for any further slo-motion fine-tuning of your scope's pointing in R.A., [without a clutch unit on the worm-screw shaft] you would need to have a hand-held motor drive / guide controller that can allow you to run the R.A. motor at a faster-than-siderial speed (e.g., 4x, 8x, 16x etc) using East / West pushbottons on the hand controller. So the little clutch assembly is not a must-have [if you have a hand-controller that will run the R.A. motor West or East at a faster rate, to center your object in the eyepiece], but the little clutch device is convenient since it allows use of the manual slo-motion knob or flex cable.
Edited by jkmccarthy, 21 February 2022 - 04:03 PM.