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worm gear adjustment


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#1 cmjrff

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Posted 04 July 2011 - 03:24 PM

Does anyone have suggestions or how-to's to adjust the lxd75 worm gears?  I have tried several times and still have signs of backlash and some jumpy movement.  Thanks for any help with this.

#2 DSOMAN

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Posted 04 July 2011 - 05:36 PM

This is one of the best tutorials on adjusting the LXD75 that I have seen:

http://www.thestarde...enance_101.html

Be sure to re-grease them with a decent lubricant.

Brent

#3 cmjrff

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Posted 05 July 2011 - 08:32 AM

Thank you for replying to my post, Brent.  I've used that how-to and it is very helpful.  I seem to have a situation where as I carefully adjust things so that the axis moves when first turning the gear, as soon as that adjustment is reached, it kind of binds up or something.  Whatever it is, it seems like I cannot get the backlash out without getting some jerky movements in.  Is there some backlash (or lag in response) to the turning of the gear that is necessary so that over-tightening is avoided?  Thanks for any thoughts on this.

I noticed in one of the yahoo groups a post by a guy who modified the worm gear housing for his lxd 75 and added some ball-bearings.  He was going to put some photos and step-by-steps on the site after checking it all out, but never did as far as I can tell.  His initial outcomes were positive from what he said.  Are you familiar with some kind of modification like that?

Thanks for any input.

#4 DSOMAN

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Posted 13 July 2011 - 10:04 AM

I have read about various mods to the LXD75 mount but have never tried them. You will never get all the backlash out of the gears but it can be reduced to an acceptable level.

It sounds to me like the three worm tension screws are not correctly set-up [these screws interact and the adjustment is touchy]. Also the tension adjustment on the ends of the worm drive screw might be too tight. Those are the only adjustments that control backlash in the LXD75. The three worm tension screws are the most critical and the most difficult to get right.

When properly set-up you should be able to turn the worm drive gear with your fingers over the full slew range without binding.

Brent

#5 MistrBadgr

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Posted 13 July 2011 - 04:53 PM

For metal gears you have to have some backlash or the gears cannot move.  If backlash is too tight, the gears wear out prematurely.  With plastic gears that can flex, you can come closer to no backlash because the gears can flex some.  If you are trying to take out as much backlash as possible, when things geyt jerky, it is a sign the backlash is too tight.  This assumes that the gears are in proper allignment otherwise.

That is what the gear training excersize is for, to tell the brains of the scope how much backlash there is.

Hope this helps.

Bill Steen
Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#6 cmjrff

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Posted 13 July 2011 - 04:58 PM

Thanks for all the replies.  I will continue to try and get this right.

#7 SmokeyJoe

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Posted 24 October 2016 - 04:48 PM

I’ve also heard mention of certain gears (I’m assuming it must be the worm ring-gear) being out of round from the factory. The result of this is sloppy backlash in one zone and tightness 180° around from that. In such cases the best you can do is kind of average things out by trial and error – a little sloppier-than-desired in the ‘loose’ zone, so it’s not too tight at the other end of the spectrum. Sound like a royal pita. I hope I don’t have to ever deal with it. But when you’ve got lemons…






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