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I was asked to start up a sperate thread on this subject, which I think is a good idea as this is a significant issue for some. After making numerous mods, I now realize I should have looked at this first. If buying a used mount I would recommend starting here with any tune-up.

Whether or not wobble in Dec, RA or both axes is a significant problem is to be determined, but I suspect it is. Most certainly it must effect backlash and most likely the ability to carry heavier loads and maintain excellent guiding performance.?

In doing some research I came across this posting from 2000.?/g/Losmandy_users/topic/g11_fix_source_for/21183709?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,1,40,21183709

I just took apart my Dec axis and was shock by the degree of play. This is? also true of the Ra axis but not quite as bad. So what to do? In the note by Neal Barry from 2 decades ago be suggests adding a third needle bearing and shimming the shaft. There is room for a third bearing in both Dec and Ra.??

In researching bearings there seem to be two designs:?full complement drawn cup and caged drawn cup.? ?

Torrington bearings used by Losmandy are the original full compliment design. I've opted to use the more expensive caged design. There advantage is the rollers stay axially aligned. This is what I ordered:?

How hard is it to removed the old bearings?

Not hard at all. On my G11 there is a brass inset end on the housing. The bearing opposite the bass end I tapped out using a piece of 1/2" dowel catching the metal edge. It came out very easily. The brass end was more difficult because less of the edge shows, so a whittled down a piece of 1.5" dowel bought at Lowes. The overall diameter was reduced a bit, a small flat was added, and the business end I reduced the diameter further. I did this on a belt sander, but one could use an orbital sander, it will just take longer.?

How hard is it to insert the bearings?

Again this was much easier than I thought it would be. I was able to press in the bearing with my hand. The new ones might be more difficult. Nevertheless, they can be tapped back in using a block of wood. On the brass end the 1.5" dowel would be used to seat it in place.?

How much play is there?

In my case a lot. The shaft appears to be in spec. 1.25 - 0.05. I will not know if the bearings are the source of the problem until the new ones arrive. If the bearing is tight to the shaft job done. If not then I will shim. I bought this material just in case.??To test the effect of shimming I used tin foil and it worked great.

What result am I hoping for?

Significantly reduced backlash, better guiding especially in Dec. My current Dec backlash is around 2500ms. With all the mods I've made I have singerly failed to reduce it thus far. Keeping fingers crossed.


Here is a quote from Neal Barry from the above thread.