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Help before I screw up my LXD75

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#1 Jimmy2K63

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Posted 15 July 2009 - 07:17 PM

I was discussing with a fellow amateur some time back about my mount and he mentioned to me about checking the lash on the RA motor. I've used the scope a few times now and I think I have broken in the gears a little with all the slewing that I have done and I have a tiny bit of play in the RA shaft. How do I go about adjusting this, that is, removing the covers or whatever, etc. I don't want to ruin anything as this is practically brand new.

Also, I do think it's a good idea to remove the counterweight anytime the mount is moved. I'm hoping this has not contributed to this play in the RA shaft, but I have not screwed anything up yet, at least not damaged.

Your assistance is greatly appreciated.

James

#2 David Pavlich

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Posted 15 July 2009 - 10:05 PM

I tore mine apart and polished everything, new grease, and worked the lash. It's a $500 mount and you'll be hard pressed to get all of the play out of it. I found that when the lash seemed good and the mount had no play, it was too tight. Back it off just enough to loosen the mount up to where the motors didn't come to an abrupt stop when it stopped slewing, the slop would be back. So...I found the happy medium and let it go.

The secret is to always have it loaded slightly east heavy so that the RA worm is always engaged.

David

#3 Jimmy2K63

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Posted 16 July 2009 - 05:36 AM

I'm guessing that I have roughly 1 to 2 mm of play at the end of the shaft - not the part that threads into the mount but the other end. Is this a normal amount after break in and does this require any adjustment? I've heard that there is a break in period.

#4 Eddgie

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Posted 16 July 2009 - 07:46 AM

There are two different adjustments. One is the worm gear mesh with the worm wheel. As one of the other posters mentioned, this one can be difficult. At some points around the revolution of the worm wheel, it might seem rather tight, and at other points, it migh seem rather loose.

I typically turn the worm wheel through a full revolution and try to find the tightest spot, and set the penetration tight. This way, as it goes around the wheel and the gap opens, it doesn't get too bad.

The other adjustment is the end float on the worm. I am not sure, but is SOUNDS like this is the adjustment you are talking about.

When you take off the worm gear housing, you will see that the worm gear rides in a cup at the end opposite the gear end. If you pull in and out on the gear along the axis of the shaft and the shaft moves in and out, this is called "End Float."

I set my worm gears to ZERO end float. To set it, you will see a big brass bolt on one end with a slotted screw inside the head. You loosen the outer bolt slightly and then turn the inner one clockwise until all of the float is out. Watch that it does not move when you tighten the outer bolt. You want all of the play out, but you still want the shaft to turn freely.

And finally this. Three are screws that pinch that clamp the worm housing down, and there are screws that MOVE the worm. The three screws that move the worm are in a line. The outside two screw PULL the worm closer to the worm wheel, and the middle screw LIMITS the travel. I find that you should keep the lock down screws rather snug when you are using these screws to set the worm penetration, but sometimes when you tighten the lock scews, it will change the setting. If you are tempted to keep the clamp screws tight, be aware that the screws that you use to adjust the worm penetratoin are in soft metal. I recently sold an LXD55 and I think that I might have stripped one of the screws because I had the lock screws too tight. I had a spare worm housing that I gave the buyer, but in retrospect, I think that I may have damaged the worm housing without knowing it.

So, my point here is don't get the lock screws TOO tight when adjusting, you might do some damage. Better to keep them very lightly snugged, and re-adjust the screws if the clearence changes when you tighten the lock screws (usually it will get tighter when you tighten these).. SO, some trial and error to get it right.

But don't be afraid. It is not all that hard to do.

Also, don't forget to check the spur gear backlash when you have the motors off, and make sure that the set screws on the spur gears are tight. Some non-hardening lock-tite might not be a bad idea in this area.

Regards.






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