Posted last year about my EQ-4 worm gear (RA) binding in cold weather, wanted to see if anyone can give me some ideas, one last time.

[Trippelforge]

(sorry long post)

Last year I was never able to get my mount to work in temps below 2'C. As once the temps dropped near there my RA axis simply got so tight the motors could no longer turn it. I spent the entire weekend making a last ditch effort to fix it (without luck obviously), and at this point even if it's impossible I simply want to know WHY it's doing this. And in all honestly I am finally starting to come to grips that I need a new mount 😕. 

So I am pretty much well adept at adjusting the worm gear / housing itself. As I probably got a solid 20hrs on tweaking it, both in warm and frigid temps. And at "normal" temps I can make the mount turn smooth as butter, with almost no backlash and very little resistance. I mean it's pretty much perfect. Yet as mentioned once it gets cold it tightens up, so much in fact that it's hard to even turn the gear by hand that the belt goes on. 

When that I happens I start adjusting the worm gear itself, as if I unlock the axis it spins freely by hand and does so with no noticeable difference in tightness. Yet no matter how much I tweak the worm gear it never loosens up enough to continue tracking. That is until I bring it inside and come back 20 minutes later.... like magic it works again.

Fast forward to last weekend and I finally broke down the entire mount head. I didn't do it last year, but figured that was my last shot at this, maybe something was messed up? Due to how the mount was behaving I didn't have a lot of hope though. But I broke it all down, heavily cleaned each internal component and applied superlube, which is rated to -44C. No internal components looked damage, and everything went back together perfectly. Back on went the worm gear, tweaked it, and stuck it back in the fridge and tried again at low temperature. And... once again it seized.

At this point I finally came to realization that perhaps it was simply the worm gear itself and it's housing. I felt stupid that I hadn't even tried cooling that alone and seeing if it turned. So I did only to find out that it functioned perfectly at cold temps. So at this point I swapped worm gears all together as they are identical. Nope... didn't make any difference.

I am simply out of ideas. But my only guess at this point is that SOMETHING is shrinking and causing the issue. But if I am right.. what is it? I assume if it's simply the mating of the worm gear to RA gear it would ease up when I loosen? This is driving me insane... 😡

If anyone has any ideas on what's going on I would LOVE to gear it!

Thanks everyone! 😃

 

 

 

 

 

[AstroKeith]

Sounds like you are looking at the wrong end of the gear train. You've pretty much established its not the worm.

Check out the motor end, and the motor itself. At the beginning of the reduction train, the impact of bad forces will be proportionally much bigger. Could even be an electronics problem.

BTW what mount is it?

[Trippelforge]

11 minutes ago, AstroKeith said:

Sounds like you are looking at the wrong end of the gear train. You've pretty much established its not the worm.

Check out the motor end, and the motor itself. At the beginning of the reduction train, the impact of bad forces will be proportionally much bigger. Could even be an electronics problem.

BTW what mount is it?

All this testing is without anything extra installed (no motors).

I am using a CG-4 w/ EQStarPro drive system. The crazy thing is that it worked fine during the 2021-2022 season. I purchased the mount new, and prior to the last few years it has very little usage. I would say a total of maybe 12-13 sessions @ 4hrs or so each.  

[AstroKeith]

I see.

How about misalignment of the worm with the gear? If there is a significant lateral shift or twist, then the efficiency of the gear drops off quickly.

[Trippelforge]

19 minutes ago, AstroKeith said:

I see.

How about misalignment of the worm with the gear? If there is a significant lateral shift or twist, then the efficiency of the gear drops off quickly.

The worm gear itself does not wiggle inside of the housing, and it seemingly is squared up when installed. However there is no way obviously to see inside once it's bolted on. I never tighten the bolts really, I just do so just enough that they don't wiggle. I have of course tried various torque on them though, but once tightened up the worm gear is hard to turn as expected. Do you think there is a tiny bit of misalignment going on anyhow? I tried both gears with the same result. Thanks for helping me!

[AstroKeith]

There's not much left to be out of alignment  if both worms are the same. Possibly the main gear has moved up or down the RA shaft a little?

Is there a chance that when you think you are adjusting (ie slackening) the worm gear, in fact you arent?

[Trippelforge]

3 hours ago, AstroKeith said:

There's not much left to be out of alignment  if both worms are the same. Possibly the main gear has moved up or down the RA shaft a little?

Is there a chance that when you think you are adjusting (ie slackening) the worm gear, in fact you arent?

I did make sure the main gear was fully seated when I rebuilt it. Can it float to another position? I don't know, that's a good question but I have honestly spent hours tweaking it. You would think that at some point I would've had it in the sweet spot? I had it in and out of the fridge probably a dozen times over the weekend. 😕

This has been so frustrating... it doesn't make sense either that a few years ago it seemingly worked in colder weather. And nothing happened to it, wasn't dropped or even went traveling.