Brantuk Posted April 1, 2016 Share Posted April 1, 2016 Hi Folks Does anyone have (or can recommend someone) with decent wood cutting or routing facilities. I'm building a rocker box for a dob and just need to precision cut the alt bearings on each side. The wood is quite substantial being 13-ply Baltic Birch of 3/4" (18mm) thickness. The places that supply the wood don't seem to like cutting circles lol. Cheers Link to comment Share on other sites More sharing options...
Perkil8r Posted April 1, 2016 Share Posted April 1, 2016 Have a word with Graham, he did say to me once that he can water jet ply! Link to comment Share on other sites More sharing options...
Brantuk Posted April 1, 2016 Author Share Posted April 1, 2016 Thanks Mike Link to comment Share on other sites More sharing options...
Doc Posted April 1, 2016 Share Posted April 1, 2016 Try these Kim. They are in Nottingham and cut to any shape you want. http://www.cutplywood.co.uk/ Brantuk 1 Link to comment Share on other sites More sharing options...
Brantuk Posted April 1, 2016 Author Share Posted April 1, 2016 Thanks Mick - they do look quite good - I've emailed them. Link to comment Share on other sites More sharing options...
Doc Posted April 1, 2016 Share Posted April 1, 2016 They advertise on E-Bay as well Kim. Brantuk 1 Link to comment Share on other sites More sharing options...
Brantuk Posted April 1, 2016 Author Share Posted April 1, 2016 (edited) Their timber does look good - they do S/BB which is what I'm looking for - not a lot of it about. I'm hoping to replicate something like this Mick: http://dobstuff.com/lbrockerbox.htm Edited April 1, 2016 by Brantuk Link to comment Share on other sites More sharing options...
Doc Posted April 1, 2016 Share Posted April 1, 2016 That should be very easy to do Kim. Just make sure you have the measurements correct. Good luck Link to comment Share on other sites More sharing options...
Brantuk Posted April 1, 2016 Author Share Posted April 1, 2016 Lol - very good point - I'm re-measuring for about the 5th time tomorrow. Just about there now - hoping to order the wood and cutting next week. Link to comment Share on other sites More sharing options...
Doc Posted April 1, 2016 Share Posted April 1, 2016 What bearing material are you using. The original Light bridge used felt and I thought it was excellent. I got the stiction to almost perfect. Link to comment Share on other sites More sharing options...
Tweedledee Posted April 1, 2016 Share Posted April 1, 2016 I too was just about to ask about your choice of bearing materials. Very interested Link to comment Share on other sites More sharing options...
Brantuk Posted April 1, 2016 Author Share Posted April 1, 2016 (edited) The current Alt bearings are load bearing felt too Mick - not bad stuff at all but I've no idea what it is or where to get it from. If I can't find it I was going to give PTFE a try out (from AWR Technology) - just not sure if it works ok with the metal disk bearings on the tube though. http://www.awrtech.co.uk/miscprod.htm#PTFE The Az bearing I'm intending to reuse the original lazy susan so I'll be having either a square or circular bottom base board. Might augment it with the milk bottle washer mod for a little more stiction - but may not even need that. There's more to think about than I realised - it's so much more than just building a simple box lol. Edited April 1, 2016 by Brantuk Link to comment Share on other sites More sharing options...
Tweedledee Posted April 1, 2016 Share Posted April 1, 2016 3 minutes ago, Brantuk said: There's more to think about than I realised - it's so much more than just building a simple box lol. Cheers Kim. I found the same planning mine Brantuk 1 Link to comment Share on other sites More sharing options...
Doc Posted April 2, 2016 Share Posted April 2, 2016 Why don't you try something different and use ball transfer bearings instead of a lazy Susan bearing. Imagine 6 of these little housed bearings in a circle sitting proud to give a gap between your ground and base boards. Stiction is controlled by adjusting a centre bolt thus putting pressure on the ball bearings. Never tried this but in theory it should work. Have a look here: http://www.wdsltd.co.uk/categories/76/ball-transfer-units Link to comment Share on other sites More sharing options...
Brantuk Posted April 2, 2016 Author Share Posted April 2, 2016 Those look interesting Mick - especially the surface mount ones rather than the recessed ones (the less drilling the better lol). With a thin metal circular plate on top to save wear on the underside of the box they just might work. Link to comment Share on other sites More sharing options...
BAZ Posted April 2, 2016 Share Posted April 2, 2016 They look a great idea Mick. I would go for the stainless balls, you don't want any corrosion pitting the surfaces and making it less than perfect, which that Birch frame would be. It looks way better than the weetabix standard. Link to comment Share on other sites More sharing options...
Doc Posted April 2, 2016 Share Posted April 2, 2016 (edited) You are both on the same wavelength as me. As you say Kim a circular stainless plate about 2mm thick to stop the plywood getting damaged. The stiction will be governed by some clamping arrangement and you should be able to make it very smooth. Also for the altitude bearing material why not use bearings again. I would try three cam follower bearings on both sides. Once again a clamping arrangement to provide stiction but it could be made very smooth. http://simplybearings.co.uk/shop/Bearings-Cam-Followers/c3_4461/index.html Edited April 2, 2016 by Doc Link to comment Share on other sites More sharing options...
Tweedledee Posted April 2, 2016 Share Posted April 2, 2016 (edited) Great idea Mick Why 3? Do you mean 2 each side for bearings plus 1 each side for lateral positioning? I'm looking for a simple, smooth and very controllable friction clutch/clamping mechanism to vary tension when changing heavy accessories. Might help if I ever get any really heavy eyepieces Any ideas? Edited April 2, 2016 by Tweedledee Link to comment Share on other sites More sharing options...
Doc Posted April 2, 2016 Share Posted April 2, 2016 The Meade LB mirror box is a substantial weight. I would place three bearings each side evenly spaced through 180°, something like 40° - 90° - 140°, always over engineer when you can. Let me have a think about the friction clutch. Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted April 2, 2016 Share Posted April 2, 2016 Cheers Mick. I see, but having 3 bearings each side, they would need to be extremely accurately positioned or I would think that one of them would need to have some small amount of built-in adjustment to ensure all three acted properly as bearings. Link to comment Share on other sites More sharing options...
Doc Posted April 2, 2016 Share Posted April 2, 2016 I would make all three adjustable so you could get it spot on. Link to comment Share on other sites More sharing options...
Tweedledee Posted April 2, 2016 Share Posted April 2, 2016 11 minutes ago, Doc said: I would make all three adjustable so you could get it spot on. A bit more work perhaps, but if you are going to do it right and get it perfect, that has to be the best way to do it Link to comment Share on other sites More sharing options...
Brantuk Posted April 2, 2016 Author Share Posted April 2, 2016 (edited) In the link to the box I'm emulating - there's a design for a friction clutch if you scroll right to the bottom of the page. I think getting the ota balance right is gonna be the key thing to make the friction clutch work optimally. Edited April 2, 2016 by Brantuk Link to comment Share on other sites More sharing options...
Tweedledee Posted April 2, 2016 Share Posted April 2, 2016 (edited) Cheers Kim, that is simple enough to implement. The one on my Orion 14" looks a bit similar, except that it tightens through the altitude axis with a Teflon washer one side and three Teflon pads the other side. The altitude circles on the lower tube assembly are supported on two non-rotating nylon bushes. The system on the 14" just doesn't "feel" very good in use, so I'm sure there must be better methods. The Light Bridge version might be better as it acts around the edge of the bearing circle not the middle which should allow less pressure to have more effect at the edge than it would in the middle. The LB method would not implement easily on my 14" but might suit a new build. Edited April 2, 2016 by Tweedledee Link to comment Share on other sites More sharing options...
Brantuk Posted April 2, 2016 Author Share Posted April 2, 2016 Ahhh.. that looks quite a sophisticated braking system - the one supplied with the LB is actually much simpler - just a screw up tight knob on a lever with a bit of teflon on the end pressing on the outside of the disk bearing. Link to comment Share on other sites More sharing options...
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