Popular Post Doc Posted September 14, 2017 Popular Post Share Posted September 14, 2017 (edited) It's autumn and about time I made a start on my new Alt/Az Mount build. The plan is to get this up and running before winter sets in so the quicker I start it the better. It's going to a Alt/Az mount similar to the american DiscMount, I have looked at Robs (Binoviewers) DM6 and have decided to put it on steriods so to speak. It's going to be made of 3/4" thick aluminium, six inches square. The discs are 5 inches in diameter and 1" thick. The bearing will be PTFE and 1/4" thick. It will be held together by a 1" stainless Steel shaft running in oilite bearings. I have made a start and the here's a few photo's. They are a little foggy as my phone camera got wet, and even though it's dried out it's still foggy. Here is some of the material involved. Squaring up the material. Milling to size. The metal looks white as it has a protective film on it. Once again milling the plates to size. These are 6" x 6" x 3/4" Doing some measurements. Just one thou over. Perfect. That's it for now. Edited September 14, 2017 by Doc +Streetbob, Tweedledee, +Graham and 2 others 5 Link to comment Share on other sites More sharing options...
Brantuk Posted September 14, 2017 Share Posted September 14, 2017 Looking forward to seeing this one take shape - nice start Mick Link to comment Share on other sites More sharing options...
philjay Posted September 14, 2017 Share Posted September 14, 2017 Nice one Mick. There is something special about plain stock metal, I reckon it's because it can potentially be so many things. Link to comment Share on other sites More sharing options...
+Graham Posted September 14, 2017 Share Posted September 14, 2017 Nice one Mick. Will watch this one with interest. Seems to be the season to build things. Link to comment Share on other sites More sharing options...
+RonC Posted September 14, 2017 Share Posted September 14, 2017 Good start Mick, also watching this build Link to comment Share on other sites More sharing options...
Tweedledee Posted September 15, 2017 Share Posted September 15, 2017 Looking forward to watching this come together Mick. What a great project. Link to comment Share on other sites More sharing options...
Doc Posted September 15, 2017 Author Share Posted September 15, 2017 Done a little more today. The plates are getting to size now and it's all looking good. Making a mess Milling controls of the power feed I built. All sides squared and to the correct measurements. With front piece included. Just need to drill, tap and bolt it all together. Link to comment Share on other sites More sharing options...
+Bino-viewer Posted September 16, 2017 Share Posted September 16, 2017 (edited) Just found this Mick (thanks for the message.) Impressive start to an interesting project ! I will follow your progress closely. My discs are 6" in diameter with the PTFE the same at 1/4 inch. The DM6 is designed with a 40 lb payload capacity / with OTAs upto 12" SCT class or 6" refractor class. Remember Mick, if you want to borrow my mount, i'll drop it off anytime on my way home from work. If you plan on using a biggish refractor and i assume you are (on a tripod) you may need to factor in some sort of extension piece between tripod & mount. Theres also (on my extension), a cork layer between extension and tripod / to give some extra purchase to stop the whole setup from rotating / becoming loose. A handle arm is handy too. I can manually track with mine at high powers quite happily. Not sure if you've considered it Mick, but encoders and Digital setting circle / computer are a great addition. I have encoders on each axis, and they are really very simple, easy to install and take up little room. They are not too expensive either. Good luck with the build Edited September 16, 2017 by Bino-viewer Link to comment Share on other sites More sharing options...
Doc Posted September 16, 2017 Author Share Posted September 16, 2017 (edited) Thanks Rob. There's no need to borrow yours yet Rob, might have a look later regarding the encoders. I have considered a cork washer and will use one, also it will sit on a 6" riser made hopefully out of solid aluminium to give it some weight. Where is your handle arm secured onto the mount? As for encoders I'm still researching them, you have the original ones sold by disc mount, these were the originally Sky commander encoders I think. Edited September 16, 2017 by Doc Link to comment Share on other sites More sharing options...
+Bino-viewer Posted September 17, 2017 Share Posted September 17, 2017 (edited) Edit : to my previous post : The cork layer is between extension and mount, not extension and tripod. Below are a few images of the mount, encoders, saddle etc The saddle is made by Discmounts and has a Losmandy style fitting. It is somewhat over-engineered, but when you consider payloads, and the price of some of these OTAs it probably needs to be. The base of the saddle plate is smooth, but has the dovetail cut in above. The bottom smooth part is where the handle is bolted on. At the top of the altitude disc, a small 90deg finder bracket is attached, with means to fit a generic finderscope or RDF. Its all very nicely machined and engineered, but is effortless to use. I love the DM6 ; it probably the best Alt-Az mount on the market. But maybe i'm biased ? Edited September 17, 2017 by Bino-viewer Link to comment Share on other sites More sharing options...
Doc Posted September 17, 2017 Author Share Posted September 17, 2017 Thanks for the pics Rob. Regarding the bearing, I'm considering two 5" x 6mm discs of PTFE rubbing against each other. I read somewhere that this combination has less friction then PTFE on Aluminium. I think PTFE has very low coefficient and is ideal for this sort of application. The other option regarding low coeeficient bearing material is UHMWPE but this more expensive. The stiction will be via tension on the nut connected to the shaft, the more you tighten the less movement you will get. DM has the same application and it works pretty well. Link to comment Share on other sites More sharing options...
Doc Posted September 17, 2017 Author Share Posted September 17, 2017 (edited) A few more photo's of the bext stage. This was to drill through so to spot the side plates. Doing it this way made the job pretty easy and everything lined up. The sides were then tapped M6 Drills inserted in to the holes to align everything up. More tapping M6. Below shows all the holes were counterbored with a M6 counterbore and M6 ccap head screws used throughout. So far I have a very well made cube 6" in size. Edited September 17, 2017 by Doc philjay and +Bino-viewer 2 Link to comment Share on other sites More sharing options...
+Bino-viewer Posted September 17, 2017 Share Posted September 17, 2017 (edited) Nice work Mick. I'm sure we are all jealous of your engineering skills. I know i am !! What sort of weight are you thinking the finished product will be ? I think the more mass the better ; certainly if you are going to be using a 5" class refractor. Here are the Discmount specs for both the DM6 & smaller DM4. http://www.discmounts.com/specifications.html The DM6 has a listed 40 lb payload capacity, which is pretty high. My refractor + rings, dovetail, binoviewer & eyepieces is around 10kg (22 lb) i think I have actually mounted my 12" Newtonian on it. This is around 16kg. But it probably foolhardy of me and my tripod is not beefy enough. So........why don't i upgrade my tripod ? Edited September 17, 2017 by Bino-viewer Link to comment Share on other sites More sharing options...
Doc Posted September 18, 2017 Author Share Posted September 18, 2017 (edited) Regarding weights I'm not sure yet, even though it's made of aluminium is pretty substantial and feels well made. The idea is if it works really well and is accurate with the encoders is to sell my Losmandy AZ8 and tripod and invest in a Barlebach Planet tripod. I think this would be a great combination. I'm still not sure how to finish the mount either polished aluminium to a shine, anodize, paint, or powder coat. Why don't you pop round one day on your way home from work and have a look Rob. Edited September 18, 2017 by Doc Link to comment Share on other sites More sharing options...
+Graham Posted September 18, 2017 Share Posted September 18, 2017 Powdered coating is the way to go. If you Anodised it you will have to strip it all down unless you are using all stainless steel fittings in the build. Link to comment Share on other sites More sharing options...
Doc Posted September 18, 2017 Author Share Posted September 18, 2017 Graham if I powder coat how much prep needs to be done. Do all the scratches have to be removed or is the powdercoating thick enough to cover these. Link to comment Share on other sites More sharing options...
+Bino-viewer Posted September 18, 2017 Share Posted September 18, 2017 One other thought Mick.... Are you planning being able to adjust the friction levels on the mounts discs ? Its a nice feature on the DM6 to be able to tighten / loosen either (or both) axis when required. For instance, with a heavy binoviewer & eyepieces i need a little bit more, just a touch more friction than when i'm just viewing with a smaller mono eyepiece. Thats why the top and back panels on the mount are perspex and simply slide out to gain access. They even supply a small magnetic spanner if you need to adjust in the field, and it only takes a few seconds to do so. Just a thought. Link to comment Share on other sites More sharing options...
Doc Posted September 18, 2017 Author Share Posted September 18, 2017 The back on mine isn't slidable but is only secured by two thumbscrews and then the back comes off. This allows access to both axis which you can tighten or loosen depending on how much friction you require. The end of the shafts will have plastic "D" inserts fitted so a encoder with a 6mm D Shaft can just slide in to place. I do like the idea of a spanner inserted inside the box, I will have to have a look into that. +Bino-viewer 1 Link to comment Share on other sites More sharing options...
Doc Posted September 18, 2017 Author Share Posted September 18, 2017 A little more done. Making sure the edge is aligned. Milling the edges so I can fit a removable back panal so to allow access to the shafts. All four sides done, and bolted back together. The finished article. The space inside will be where the encoders and friction nut will be. Next is a cover to sit within the recess area so it's flush with the outside. This will be secured with M5 thumbscrews. +Bino-viewer 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted September 18, 2017 Share Posted September 18, 2017 (edited) Looking great Mick. When you bolt the finished aluminium box sides together, is there a need for a particular torque setting or will you use a thread locking fluid? Edited September 18, 2017 by Tweedledee Link to comment Share on other sites More sharing options...
Doc Posted September 18, 2017 Author Share Posted September 18, 2017 (edited) Not as far as I know Pete, I just tighten them tight, it's not going to move at all. I've been looking at bearing material and have gone with UHMWPE mainly because it has an exceptionally low coefficient of friction which offers superb sliding properties and is one of the best materials for wear and abrasion resistance. I bought it from Direct plastics. https://www.directplastics.co.uk/uhmwpe-sheet Edited September 18, 2017 by Doc Link to comment Share on other sites More sharing options...
Tweedledee Posted September 18, 2017 Share Posted September 18, 2017 (edited) Useful info about the UHMWPE. Could you check out that link please Mick. It goes to their website but reports that they can't find that page. EDIT... I think their website is playing up at the moment, as a lot of its menu system does that. Edited September 18, 2017 by Tweedledee Link to comment Share on other sites More sharing options...
Doc Posted September 18, 2017 Author Share Posted September 18, 2017 Works on my laptop. Try there main page. If it works scroll down to UHMWPE Sheet. https://www.directplastics.co.uk/ Link to comment Share on other sites More sharing options...
Tweedledee Posted September 18, 2017 Share Posted September 18, 2017 It's working now thanks. Link to comment Share on other sites More sharing options...
+Graham Posted September 18, 2017 Share Posted September 18, 2017 6 hours ago, Doc said: Graham if I powder coat how much prep needs to be done. Do all the scratches have to be removed or is the powdercoating thick enough to cover these. It's like everything else. The better the finish before the better the finish after. Link to comment Share on other sites More sharing options...
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