Help w/ repairing/refurbishing an equatorial mount

[DaveC426913]

TL;DR Summary

I should have quit when I was ahead.

My eq mount was not behaving - the RA joint was slipping in its socket. There was too much play. So I repaired it once, tightening the axial bolt. The problem is that if I tighten it too much, it binds. So I've taken it apart a second (actually, third) time and cleaned it and regreased it. And this time I made sure the worm gear was properly engaging.

But in doing so, I've made it worse. Both the RA and the Dec joint now spin freely. The worm gear is engaging (I have double-checked this), but there is nothing to prevent the entire unit rotating on the six-inch bolt. There has to be something that locks the bolt to the barrel, so that the only rotation is via the worm gear dials.

In both joints, a piece fell out that I can't seem to figure out where it came from. It is a threadless, featureless pin - maybe 1/4" in diameter and 3/8" inch long, just like this:

It seems to me, if it had a home in the right place it could perfectly fulfill the task of stopping any free rotation of the mechanism. But I can't find a hole anywhere it might sink in to.

To be clear: I am not talking about the external manual locking pins, that lock the rotation completely, as indicated here:

The pins I knocked out (if these are what's wrong) are (presumably) internal.



I'm trying to find an exploded view of an eq mount to examine, but no joy.

Help!

This appears to be my scope - an Orbitor 4000:

 

[Baluncore]

There has to be something that locks the bolt to the barrel, so that the only rotation is via the worm gear dials.

You should have some friction in the clamps, so you can physically move the telescope to a target, then allow it to track without slipping. That freedom to move, also protects the worm gear from excessive force.

 

[DaveC426913]

You should have some friction in the clamps, so you can physically move the telescope to a target, then allow it to track without slipping. That freedom to move, also protects the worm gear from excessive force.

Yes. That's the way it was before.

But it is now so loose that it won't even hold up its own weight.

I am wondering if I should not have greased the parts I greased. I find it hard to believe the axial bolt gripped the gear by friction alone (it was very tight - I had to use some gentle taps of a hammer to take the axial bolt out of the gear). If it is supposed to be gripped by friction alone, then I have done A Bad Thing with the grease.

That freedom to move, also protects the worm gear from excessive force.

Yeah. Upon further reflection, this makes me sad, because it makes me realize it cannot be held in place by a pin. It's got to be friction.

OK so these pins are probably still the right thing but they must be on a spring, to provide the necessary friction. I wonder if the springs saw a chance at freedom and made a break for it without me noticing.

Or is it possible that the pins fit inline with the manual locking knob, like a spacer?

 

[Baluncore]

I am wondering if I should not have greased the parts I greased.

I would wash off the grease with white spirits, then see if I can make paper washers to provide friction between the metal surfaces.

I find it hard to believe the axial bolt gripped the gear by friction alone (it was very tight - I had to use some gentle taps of a hammer to take the axial bolt out of the gear).

I have little idea what the pins might have done. Maybe they pinned the worm wheel in place to counter torque.

 

[gmax137]

Stating the obvious: it's not going to work right until you figure out where the pins go. Put the grease question aside til then.

 

[DaveC426913]

Stating the obvious: it's not going to work right until you figure out where the pins go. Put the grease question aside til then.

Yeah. They've got to be in the same hole as the manual locking knobs. i.e. per the diagram.
(Not the same as my mount, but at least we can talk to the diagram)

I'll try that tomorrow.

 

[DaveC426913]

No sign of the pins here...

Nor here:

 

[DaveC426913]

Stating the obvious: it's not going to work right until you figure out where the pins go. Put the grease question aside til then.

That seems to have done the trick. They seem to be an extension of the locking knobs. I stuck them in there and now the scope seems to work fine. We'll see how it works with first light.

Thanks!

Now I'm off in search of a camera-USB eyepiece and a collimator, each ideally for <$100. (If this works out, I can always upgrade them).