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Better base for an SW 250px Dob


Avocette
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After a bout of 'flu followed by light headed aperture fever I bought a 250px scope with an excellent OTA, but evidence of the effect of damp in the base woodwork (slight swelling of some of the chipboard). The base is usable as it stands, but I thought whilst I'm adding a Lazy Susan bearing for the azimuth axis, I might be more radical and replace the alt axis bearing structures with some arrangement which is smoother and more controllable than the SW thrust bearing and friction washer/melamine standard type. Does anyone have any good ideas?

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My 30" Dobsonian, because of the weight, has 6 vertical ballrace bearings fitted to the ground board, these bear on a stainless steel plate fitted to the underside of the rocker box. Because this would be too free moving, damping is provided by 3 of the bearings having PTFE friction pads, these are adjustable to give the AZ motion the same feel as the ALT. :smiley:

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Thanks Peter - bit of a scale factor change but the principle seems to be the same - to make the bearing very free running, and then add controllable friction with PTFE pads. This is pretty much what the Lazy Susan bearing with furniture sliders (unknown grey plastic but possibly PTFE) does to the SW Dob azimuth. Are there any SW Dob modders out there who have found successful ways to tackled the issue with their smaller scopes?

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Second thoughts - looks like the old Dob base can be rescued! Had time for a good clean up and careful look at the critical issue of the flatness of the melamine covered chipboard surfaces where the telfon pads on the azimuth axis and the red/brown rings on the altitude axes rub, and am now quietly confident. I have a spare Lazy Susan bearing but will try first with just the furniture sliders.

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