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A ball bearing for a Dobsonian mount
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Tony Legge
Joined: 13 Oct 2006
Posts: 9
Location: Cambridge, England
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 Posted: Fri Oct 27, 2006 12:35 pm Post subject: A ball bearing for a Dobsonian mount |
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Hello all, I recently aquired an Orion Optics 10" Europa on an equitorial mount, but too heavy to move! I converted this to a Dobson mount, using an old (chip board) table top. To make the base swivel freely, I use a router on a radius arm with a half inch round bit to cut circular grooves in the two base pieces, and glass marbles run in these grooves as a ballbearing. A spacer cut from 4 mm hardboard sits between the two base plates to hold the marbles apart, and a bolt passes though the centre of the two base plates to secure the bearing. The OTA is set in a close fitting box, held by pads of firm plastic sponge (old packaging material). The OTA box pivots on two 110 mm plastic pipe plugs from the local building supply. These have flanges wide enough to take countersunk screws. The plastic plugs sit in semi-circular bearings on the side plates of the supports. I turned a bearing ring from an old 1" oak plank, then cut the ring in half to give 2 accurate bearing surfaces for the plastic plugs (better than a jig sawn half round). If you don't have a lathe, a section of the appropriate plastic pipe might work if this is cut down the side and sprung open a little. The eyepiece is 48" when the OTA is vertical, so under most conditions it can be used while sitting. Total weight is 20 kg and total cost about £15. I will post some pictures when I can. Best, Tony Legge
Last edited by Tony Legge on Thu Nov 23, 2006 12:49 pm; edited 2 times in total |
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Nightowl
Joined: 09 Aug 2006
Posts: 6
Location: Bristol, UK
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| Posted: Wed Nov 08, 2006 11:49 am Post subject: |
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Hi Tony
I was going to ask for photos but I noticed that you have posted them but they don't show up on the forum only in the "Topic Review" panel.
Looks like a job for the Admin.
Nice job |
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Tony Legge
Joined: 13 Oct 2006
Posts: 9
Location: Cambridge, England
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| Posted: Thu Nov 23, 2006 12:53 pm Post subject: |
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| Hi, The Dobson photos do not show in my message above on "Ball bearing mount." If you want to see these, try clicking on the "quote" box on the original message above, then scroll down. Best, Tony Legge |
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