Doc Posted February 1, 2012 Share Posted February 1, 2012 Here's a few photo's of my barn door mount. The screw I decided on was a 1/4"UNC 20tpi thread and this made the hinge to middle of screw radius 11.43" .To get this as perfect as I could, I made the screw and tilting mechanism on a slliding plate so just by undoing a few bolts I can achieve that perfect 11.43". The whole screw pivots top and bottom so to avoid tangent error. I can vouch that it is very smooth both up and down and no binding of the threads have accured in practice. The finder is from my TAL 100r and has the crosshairs so polar aligning shouldn't be to bad as the whole lot is mounted on the TAL EQ mount. Plus I have the wixey to get the latitude spot on. Going to invest in a few small bubble levels as well. It now has an handle and a guage so I can turn it exactly quater of a turn every 15 seconds. The only negative I can say is that the piano hinge has a little play in it. Will this effect the final image I can't say as yet. If it works Ok my next step is to add a 1 RPM motor and bracket to it. Hope you enjoy the photo's and comment and advice really welcome. Link to comment Share on other sites More sharing options...
catman161 Posted February 1, 2012 Share Posted February 1, 2012 That looks great mick. Forgive my newbie ignorance but what exactly is this setup for? Link to comment Share on other sites More sharing options...
Doc Posted February 1, 2012 Author Share Posted February 1, 2012 basically stick a camera on it and rotate the screw 1 revolution every minute and it will track the sky. In theory a cheap EQ mount. Link to comment Share on other sites More sharing options...
catman161 Posted February 1, 2012 Share Posted February 1, 2012 Ahh I see. Cool Link to comment Share on other sites More sharing options...
Guest Eddy Posted February 1, 2012 Share Posted February 1, 2012 Who do you pay to turn the screw? Link to comment Share on other sites More sharing options...
Doc Posted February 1, 2012 Author Share Posted February 1, 2012 A screw Wallah thats Martyn's next job Link to comment Share on other sites More sharing options...
Daz Type-R Posted February 1, 2012 Share Posted February 1, 2012 Nice bit of DIY there Mick. A screw Wallah thats Martyn's next job PMSL - Link to comment Share on other sites More sharing options...
Doc Posted February 1, 2012 Author Share Posted February 1, 2012 Maybe we should have a list of Martyn's jobs. Tea Wallah Parking Wallah Screw Wallah Link to comment Share on other sites More sharing options...
Doc Posted February 1, 2012 Author Share Posted February 1, 2012 looks better than mine a real pro job not like the shed job i made Don't be like that, yours looks great, I bet it works better then mine. Link to comment Share on other sites More sharing options...
BAZ Posted February 1, 2012 Share Posted February 1, 2012 Iv'e just caught up with this! I have to charge being executive screw wallah, and since it's you lot, I'll do it for £28 an hour, cutting me own throat at that Iam! Link to comment Share on other sites More sharing options...
Craig Posted February 1, 2012 Share Posted February 1, 2012 Very nice DIY Mick, impressive! Maybe we should have a list of Martyn's jobs. Tea Wallah Parking Wallah Screw Wallah I think this calls for a new title for Martyn. Link to comment Share on other sites More sharing options...
Guest Eddy Posted February 1, 2012 Share Posted February 1, 2012 (edited) "Insert Job Role Wallah" Haha Craig I love it Edited February 1, 2012 by Eddy Link to comment Share on other sites More sharing options...
Rusty Strings Posted February 2, 2012 Share Posted February 2, 2012 I'm a little unclear why fitting this nicely made jobby onto a EQ mount (EQ1, 3-2?) turns it into a cheap EQ mount Link to comment Share on other sites More sharing options...
Doc Posted February 2, 2012 Author Share Posted February 2, 2012 My EQ mount was the only mount i had at the time, you can fit it to any mount it just needs to be polar aligned (Facing north pole star) Link to comment Share on other sites More sharing options...
Mark Harper. Posted February 2, 2012 Share Posted February 2, 2012 Fantastic I want one!!! ; ) Link to comment Share on other sites More sharing options...
+Graham Posted February 14, 2012 Share Posted February 14, 2012 Mick - That is an impressive piece of work. I need to tap your knowlage on this one. How long will it track for. As a replacement for an EQ mount will it stop rotational distortion on long exposure photos. I am looking for an alternative mount to an EQ for a very large Newt. The ALT / AZI type mount is preferred because of the weight involved but it will induce rotation on long / multiple exposures. I am thinking along the lines of a precision made version of this design coupled with PHD to guide it. What do you recon to the possibility of achieving an accurate mount using this type of design. many thanks Graham Link to comment Share on other sites More sharing options...
Doc Posted February 14, 2012 Author Share Posted February 14, 2012 To be honest Grahram it was only used a few times and I think the longest I used it for was 4 minutes. I didn't really take much notice of how the photo's turned out as the light pollution was horrendous in four minutes, but I do remember the stars were pretty tight and round. It tracked well with hardly any flex but that was only with a Canon 1000d on it's back, if you are planning a large newt then it's going have to be alot more heavy duty. The weak point is the hinge and i did have an idea for this but it never reached the drawing board. For the Mark 11 version I was going to use plummer bearings on the the top and bottom board with the shaft going through all four of them, this way there will be no flex at all. My advice would be make it out of aluminium, place two 12mm plummer bearings on one side off both top and bottom plates then insert a 12mm shaft through all four bearings, this will give you awesome stability. To drive it you will need a 1 RPM motor as the screw was a 20TPI thread, the maths is on the web somewhere, I have no idea about PHD as I've never guided but the set up would be possible I'm sure. Anymore advice let me know and if you sell any think off me Link to comment Share on other sites More sharing options...
+Graham Posted February 14, 2012 Share Posted February 14, 2012 Hi Mick. Thanks for the response. If I went down this route for the newt I would make it out of machined steel parts and use tapered roller bearings on each end of the hinge and bronze bushes as center bearings. You say it needs to turn a 20 tpi thread at 1 rpm so I can work out the ratio thanks. When you use this do you open it out locate your target and then close it up to track. Many thanks Graham Link to comment Share on other sites More sharing options...
Doc Posted February 14, 2012 Author Share Posted February 14, 2012 Only ever took M42 and located it with the plates shut and then started turning the handle 1/4 turn every 15 seconds. As I said the weak part is the hinge but using roller bearings and bronze bushes should be perfect. Also what is critical is the 11.43" measurement from the middle of the hinge to the middle of the 20TPI rod. Of course to hold a big newt you might want to make the whole thing bigger so if you want to make it twice as big just x2. Link to comment Share on other sites More sharing options...
+Graham Posted February 14, 2012 Share Posted February 14, 2012 Thanks Mick you have just answered the one question I forgot to ask and that was the center to center measurement. I will have to run some numbers if I make it bigger to maintain the angle increase to thread rotation per min. If you don't mind I will do some drawings and run them by you. thanks Graham Link to comment Share on other sites More sharing options...
Doc Posted February 14, 2012 Author Share Posted February 14, 2012 That's fine. Link to comment Share on other sites More sharing options...
+Graham Posted February 15, 2012 Share Posted February 15, 2012 (edited) Good morning Mick. I have just been running through the numbers on this and I think it is as follows. 1 revolution at 1 rpm = 0.31 degees elevation per min. 1 inch or 25mm = 6.2 degrees elevation per 20 mins. Travel of top plate = 0.4mm per min or 8mm per 20 mins If I move the center point out to 250mm I think it becomes. Travel of top plate = 1.4mm per min or 28mm per 20 mins. Rotation becomes 3.5 rpm. I was also thinking along the lines of replacing the threaded rod with an ecentric cam. If the cam had a rising rate of 1.4mm per min it would do the same job but with far better efficiency and be a lot smoother. The cam would run against a roller bearing set into the bottom plate. This way the motor can be fixed to the top plate and direct drive the cam with a belt. What do you think ? thanks Graham Edited February 15, 2012 by Astrotec Limited Link to comment Share on other sites More sharing options...
Doc Posted February 15, 2012 Author Share Posted February 15, 2012 1 revolution at 1 rpm = 0.31 degees elevation per min. 1 inch or 25mm = 6.2 degrees elevation per 20 mins. Travel of top plate = 0.4mm per min or 8mm per 20 mins This above makes sense but you have lost me on the 250mm centre point calculations. The idea of using a cam is pretty unique I think, I never seen another one. On paper it should work and I wish you all the luck in the world designing and making it. Link to comment Share on other sites More sharing options...
+Graham Posted February 15, 2012 Share Posted February 15, 2012 Hi again Mick. Following on from my last. I have done some drawings to detail what I mean. I did decide to mount the motor and drive to the base insted. Pic 3 shows the drive system without the base plate. graham. Link to comment Share on other sites More sharing options...
+Graham Posted February 15, 2012 Share Posted February 15, 2012 Sorry Mick we overlapped there. The 250mm from center of hinge to center of thread or in my case center of roller bearing. To get the figures I came up with I drew the points on the cad. By extending the triangulation line which is created by your dimensions untill it reaches the vertical at the 250mm point in theory should give the equivilent distance needed for the top plate to travel to get the same angle of 0.31 degrees per min. I hope that makes sense. thanks Graham Link to comment Share on other sites More sharing options...
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