First install was to keep the centre bolt, fix the bearing to the mount, and let friction keep the other part of the bearing in place on the base. Play in the bearing meant that any breeze caused the scope to wobble about, and friction was too low. Fix was to place teflon pads on the mount to bear on the laminex top of the base. Pretty good outcome, but the base/bearing surfaces were not perfectly planar, so variation in friction and stiction became annoying.
Current set up is no teflon pads, no center bolt, bearing attached to mount and base; and a lot of time spent with hammer and drift carefully knocking the rolled upper edge of the lower plate into close clearance with the upper plate; and reintroduction of the centre bolt with a nylon washer and wingnut to vary tension. This has virtually eliminated rocking and produced very nice friction/stiction - but lack of concentricity with the upper and lower bearing plates means occasional variation in friction. This has reduced by use of Lanoguard lubricant (not effected by moisture, seems not to attract too much dust). I expect that the tighter bits will go away with more use.
Still not entirely happy, thinking about little nylon swivel wheels used on furniture. Might be off to Bunnings again.......
When I started thinking on the wheels issue, fine movement of the base becomes a consideration....was fooling around with an electric screwdriver today, nice little output shaft... low rotation speed..... hmmmm!!!???
My old 12" had a homemade altazimuth fork which used a 20 cm diameter stainless roller thrust bearing, with rollers about 5mm diameter sandwiched between 2 thin steel rings - the whole bearing being 8mm thick. Dust was a major problem and the best way to keep it out was to put a thick felt ring, with neat fit around the bearing. This also provided adequate friction drag too.
I had a lazy susan bearing on my 10" dob mount, and even had some "carpet bits" for added stiction, but the mount still moved far too easily and acted like a weather vane, so I removed the bearing altogether and added some furniture glides. The furniture glides are too "sticky" I find and I have to nudge harder eventually knocking my target out of the eyepiece.
I still have the lazy susan and I can still put it on the mount, but I'd like to know what I could do / use to make the azimuth motion less prone to moving so easily.
I have a lazy susan bearing assembly (from Bunnings) on my 10"DOB base too.
What I have done is to secure (the original) bolt to the base (I screwed a small bike spanner in place to hold it firm) and I put a big washer and wing nut on the top. Easily accessible and (so far) good enough to increase the stiction as required.
Hi there, i used the Bunnings lazy susan bearing for a 10 dob base. As with others, it moved too freely, so i put a couple of upturned bolts through the base which had a couple of threaded furniture inserts, glued felt to the flat surface of the bolt and put a nyloc nut on the end i can use to wind the bolt up and down with. Now i can vary the speed of rotation as much as i want.
Hi there, i used the Bunnings lazy susan bearing for a 10 dob base. As with others, it moved too freely, so i put a couple of upturned bolts through the base which had a couple of threaded furniture inserts, glued felt to the flat surface of the bolt and put a nyloc nut on the end i can use to wind the bolt up and down with. Now i can vary the speed of rotation as much as i want.
Cheers,
mark
Could you provide pics, I don't know what you mean?
Not sure if the attached pic will help....you'll see four upturned bolts in each corner with a nyloc nut on it. Use the nyloc nut to wind the bolts up and down as needed. On the underside where there is the lazy susan bearing, there is also felt on the top surface of the bolt, so the more you wind, the greater the resistance.
Hope that helps,
Mark
