Crayford troubles - does this sound fixable?

[billyharris72]

Hi all:

Today I decided to improve my scope (130 P-DS) by fitting a Skywatcher auto focuser (you know, the one that doesn't fit it but does with a bit of fiddling). After a bit of fiddling I managed to dismantle the focuser - this needed a bit of rough treatment as some of the allan bolts were very badly rounded and I did try to move it by tapping a screwdriver in (gently!) with a hammer. In the end it was a hacksaw and flat head screwdriver job.

After fitting the autofocuser I put the thing back together only to discover that the focuser now barely gripped the tube - any pressure on it at all and it would just slide back into the focuser. I wasn't able to get at the adjustment screws with the autofocuser attached, as the bracket that attaches it obscures them. In the end I had a go at reassembling the focuser in the original (manual) configfuration.

I still have the issue with the tube slipping, but also it seem to catch and "grind", like metal is rubbing against metal. It doesn't feel right at all - it would be barely usable for visual and not at all for AP (it won't support the camera).

I guess my question is, does this sound like something that can be readilty fixed (and if so how) or does it sound like I need a new focuser?

Thoughts appreciated.

Billy.

[SkyGibbon]

Sounds like something in the drawtube pressure area. I cannot find a good picture of that focuser, but I would think you can undo the allens on the backside of the focuser. The ones that hold the pressure plate, and has the focuser lock on it, (the larger silver thumbscrew). Sounds like maybe the pressure shaft may have gotten tweaked somehow. It seems to be the area to take a look at.

 

There also seems to be a pressure adjustment allen just under lock thumbscrew too. That is adjustable, but the grind is worrisome.

[billyharris72]

Thanks for the suggestions SkyGibbon. I was pretty worried about it but I think I just need to slow down, step back and work it out. Not at home for a couple of days but when I get back the first step will be to replace the screws (a couple of them - not the tension ones - are so mangled I couldn't put them back), then check the tension. Maybe also the other bearings - if one of them was damaged I suppose that could account for it.

From what I can see the Crayford design is not that complicated, so it ought to be fixable, even for an incompetent bodger like myself.

Billy.