Quote:
Originally Posted by Tallstock
My SW dob azimuth mount has typical sticking and jerking problems.
I have tracked down a lazy susan type bearing (which I reckon I can install) but can't help wondering if the movement in the centre bolt/washers will remain a problem.
Peter
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Hi Peter,
It has not been so in my case. I've since fitted the same mod to a 300mm Bintel with success, and it has Argo Navis on it as well.
Think of it this way: with the original teflon pads there is any amount of sideways movement allowed, governed only by the fit of the centre bolt and its metal sleeve. Even if you don't do anything to the centre bolt the situation is actually improved somewhat by the bearing.
The lazy susan bearing has an upper and lower semi-circular track made of pressed sheet metal, with ball bearings between. If not subjected to any appreciable horizontal (sideways) load, this arrangement will always tend to settle into the same alignment under the (mostly) vertical load. So, when panning the telescope around in azimuth, any small amount of misalignment should settle out as soon as you stop. However the bearing ring does have to be installed concentrically around the centre bolt to within a few millimetres, say two.
What this bearing can't handle is eccentric loads, that is, rocking movements. The elevation movement of a Dob is OK because that axis is compliant and does not transmit much rocking-type load to the base, but you can elect to limit such movement anyway between the two halves of the base plate by installing teflon pads outboard of the bearing, of a thickness just less than the thickness of the bearing.
Hope this assists
Cheers