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Old 07-06-2018, 07:18 AM
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bojan
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Lazy Susan for Dobsonians, could be interesting for DIY

For quite some time I was looking for something to fix the issue with my dobsonian mount that I had from the start - relatively weak vertical shaft (I modified the drum assembly from front loader washing machine for that purpose), so the whole telescope was behaving somewhat like the vertical pendulum. The Lazy Susan bearing always looked like the obvious solution to this problem, but I never found anything suitable, until now.

Some time ago I stumbled on very interesting item on ebay... and last week I decided to bite the bullet and purchased 18" version (last one it seems..).

Anyway, Lazy Susan arrived yesterday, it is as advertised - quite good quality, well machined, steel balls all around (they can be replaced from one side hole, which is closed with M5 hex grabscrew), it turns smoothly.

I intend to mount it under the cage as additional bearing, in hope the vibration will be removed... will post how it went when finished.

Last edited by bojan; 07-06-2018 at 08:13 AM.
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Old 07-06-2018, 10:40 AM
astro_nutt
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Hi Bojan. I've used Lazy Susan bearings on some of my dob base projects. Since the largest I could get was a 12" ball bearing type, which has a slight rocking movement, and the only way I could correct the movement was to use 6 tiny 25mm castors, (Bunnings), 60 degrees apart outside the bearing.
With my last dob mount mod, I removed the bearing and just used 6 tiny castors recessed into the dob base. The castors contact a metal ring cut from 0.50mm gal sheeting fitted to the underside of the mount. An adjustable centre axle bolt, (secured to the mount and adjustable at the base). to keep things in place. It moves smoothly enough with one finger.
A tap on the secondary section stops in about 4 seconds.
Hope this helps.
Cheers!
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Old 07-06-2018, 10:39 PM
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tempestwizz (Brian)
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Living in Laos, there seems to be abundance of Chinese eateries, most of which feature a king sized version of lazy Susan that I’ve often thought would fit the bill. I’m viewing those with a Susan size of around 900mm. Admittedly, the weight of the vittles is unlikely to reach more than 10kgs in normal use, if the load could be arranged to fall more onto the balls around the rim rather than into the centre, I think it would make a fine azimuth platform. Likely to be inexpensive too. The only drawback I can think of would be the possible accumulation of gritty stuff in the bearing channels that may cause roughness in the rotation.
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Old 08-06-2018, 02:20 AM
DarkArts
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Thanks for that heads up and report, Bojan. That's a great idea.

A quick search on eBay shows a few of these sellers with stock up to and including 20", and one even has a 24" (last one at the time of writing, though).

Just search eBay for "aluminium lazy susan".
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Old 13-06-2019, 02:19 PM
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JRX82 (James)
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How is your Lazy Susan mod working? Are you happy with the result?
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Old 13-06-2019, 02:40 PM
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Still on ToDo list...

My problem apperas to be too much friction (it should not be the problem for "normal" Dob.
I need to increase the friction of transmission wheel (vertical axis), to be able to use this lazy susan.
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Old 13-06-2019, 08:53 PM
Wavytone (Nick)
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IKEA have a cheap lazy Susan too, two pieces of pressed steel with 1/8Ē ball bearings in a circular groove maybe 150 diameter. Canít recall what was on top - I think it was just a wooden disk and was under $10.

Bought one many years ago and fashioned it into the azimuth bearing of a compact mount. The fork arms were made from laminated wooden shelf brackets ... their L shape had a rather obvious alternative use.
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Old 13-06-2019, 10:51 PM
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mswhin63 (Malcolm)
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Quote:
Originally Posted by bojan View Post
Still on ToDo list...

My problem apperas to be too much friction (it should not be the problem for "normal" Dob.
I need to increase the friction of transmission wheel (vertical axis), to be able to use this lazy susan.
I had the same problem. I felt that if I could reduce the friction, I could put less stress on the motors and use smaller ones. That part worked well although there was a problem with low resistance causing some issue with backlash mostly.

I stopped the build, and as it appears, I may be moving to Adelaide soon, I will spend more time there to get my astro-gear running again. I have the listed bearing I picked up from an old bit of shop cabinet. I can't wait to get a good job to continue and more time available for astro stuff.
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Old 14-06-2019, 08:48 AM
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Allan_L (Allan)
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I did this "Lazy Susan" mod from IIS Projects and Articles section, on a previous DOB and found it to work quite well.
http://www.iceinspace.com.au/63-378-0-0-1-0.html
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