Tweedledee Posted September 24, 2016 Author Share Posted September 24, 2016 Thanks Martyn and Stephen. I'm rather proud of it so far. It has taken a good deal of research and head scratching to fully understand the design requirements and studying other people's mirror cell constructions. Then drawing it accurately to full scale in accordance with the PLOP program, then sourcing the materials and finding out what I am capable of engineering with my own DIY equipment and what to sub out. I could have got one ready made very similar for $1500 plus shipping from the US. I had a local engineer price it against my drawings at a minimum of £1300! Apart from water jetted trefoils from Graham, laser cut whiffletrees and some aluminium welding, I have done the rest myself investing a bit of time and effort. I also had my welding guy accurately mill out and press fit the 6mm plain end bearings into the centre of each trefoil. Not having an engineering background, this has been very rewarding since I have learnt new skills and techniques of working. My costs are running at under £300, if you exclude the cost of extra power tools and equipment I have bought. This equipment will more than pay for itself as it will also be used to build other parts of the scope and for household DIY jobs. Good job I enjoy working with non-standard stuff like circles and triangles, not many right angles in this project . The most tedious part so far was tapping 18 no. M5 threads in the trefoils for the 18 suspension pads. It took a while as I had to be so careful not to accidentally cross thread any. More difficult than tapping M10. I ended up with a couple of blisters after two and a half hours of non-stop tapping. The aluminium mirror cell feels more rigid and heavier than I expected it to be, but that has to be good when it needs to properly support a heavy 20" mirror and maintain alignment. Loved every minute of this project so far, and now starting to see pleasing results. Hoping this inspires others. Link to comment Share on other sites More sharing options...
+Bino-viewer Posted September 24, 2016 Share Posted September 24, 2016 Hats off to you Pete Looking forward to seeing more as you progress with it. Tweedledee 1 Link to comment Share on other sites More sharing options...
Doc Posted September 24, 2016 Share Posted September 24, 2016 Just one word. AWESOME Tweedledee and BAZ 2 Link to comment Share on other sites More sharing options...
Brantuk Posted September 24, 2016 Share Posted September 24, 2016 Very impressed Pete - you're making a fabulous job of it. Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted September 25, 2016 Author Share Posted September 25, 2016 Had a bit of fun with the mirror box geometry with a dry run to check that things fitted roughly in the right places. Very pleased with my wood butchering so far. Moved indoors when my workshop suffered intermittent showers this morning, and got a slapped wrist for putting it on the dining table. Last week I won an ebay auction for a hardly used Dremel 4000 with router frame and loads of other accessories for a bargain price. Hoping to use it for some of the finer work on the scope. It looks to be a very fine and handy tool. Wondering if I might be able to rig it up to do some half decent biscuit jointing on the mirror box to save me buying an expensive biscuit jointer. Smithysteve 1 Link to comment Share on other sites More sharing options...
Smithysteve Posted September 25, 2016 Share Posted September 25, 2016 I have been following your thread Pete, enjoying the coming together of a great project! You are making great progress! I will have to pop over and take a closer look! Just as long as it doesn't set me off thinking too much cheers! ?? Tweedledee 1 Link to comment Share on other sites More sharing options...
+Graham Posted September 27, 2016 Share Posted September 27, 2016 Very nice Pete Thats coming along well. Tweedledee 1 Link to comment Share on other sites More sharing options...
BAZ Posted October 4, 2016 Share Posted October 4, 2016 You can buy tools that fit the router that would allow you to biscuit joint Pete. It saves buying anther power unit when you already have one. http://www.screwfix.com/p/erbauer-biscuit-jointing-kit-47mm-4-pcs/65290?kpid=65290&cm_mmc=Google-_-Product Listing Ads-_-Sales Tracking-_-sales tracking url&gclid=CIvonsDJwM8CFQ2ZGwodmQ8Cdw Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted October 4, 2016 Author Share Posted October 4, 2016 Thanks Martyn, that would do the job but would need a bit of jigging for the 60 degree mitres. Link to comment Share on other sites More sharing options...
catman161 Posted October 8, 2016 Share Posted October 8, 2016 This is coming on brilliantly Pete! Really nice work. Very inspiring indeed. Sent from my iPhone using Tapatalk Tweedledee 1 Link to comment Share on other sites More sharing options...
Stephen Posted October 9, 2016 Share Posted October 9, 2016 Very nice work Pete very impressive Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted October 9, 2016 Author Share Posted October 9, 2016 Thanks for the encouragement everyone. Bought a biscuit jointer and love it, so easy to use. Had some practice with it and made a very accurate right angled fence thingy to help with alignment on other joints. Now the glue has reached max strength after 24 hours, the joint is rock solid like it had been hewn out of one lump of wood. Much stronger and more rigid than I had expected. Smithysteve, Brantuk and BAZ 3 Link to comment Share on other sites More sharing options...
Brantuk Posted October 9, 2016 Share Posted October 9, 2016 Oooooo - now that looks like a nice tool. I was thinking of getting one sometime back - wish they did one for dowel pins. Hmmm..... wot to do..... Link to comment Share on other sites More sharing options...
Tweedledee Posted October 9, 2016 Author Share Posted October 9, 2016 2 hours ago, Brantuk said: Oooooo - now that looks like a nice tool. I was thinking of getting one sometime back - wish they did one for dowel pins. Hmmm..... wot to do..... You can get dowel jigs much cheaper, about £20 or less, but they are just guides for your drill. I looked at that method but after a bit of research found that you need to set up the dowel jig with great accuracy in the first place to make sure the holes match perfectly. If the holes were slightly off then you are stuck with it or start again. The biscuit jointer seems easier to set up, quicker to use and altgough very accurate, allows a little bit of wiggle room, if you need it, to get the joint perfect while glueing and clamping. Looking on youtube I found that the biscuit jointer seems much more versatile on the types of joints you can do. Each biscuit cut takes about 1 second once you get the hang of it. I say, use the biscuit method Kim. Brantuk 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted November 4, 2016 Author Share Posted November 4, 2016 After seeing the super smooth edged job Graham had done water jet cutting the aluminium trefoils for my mirror cell, I was not happy with the rough edged laser cut finish (done by a local company) on my whiffletrees. I ended up changing the design for my whiffletrees, so I sent Graham my new design drawing... Graham suggested a modification to round off the edges slightly to alleviate possible stress fractures on the sharp corners, (something that had not occurred to me). Graham's addition not only makes them better structurally engineered but also makes them look better... The new whiffletrees are cut from 12mm thick aluminium plate. I got some ball transfer units with a 20mm nylon ball from China, couldn't find any similar ones in the UK, without spending nearly £50 per unit! The Chinese ones were about £3.00 each including delivery and arrived just a fortnight after ordering. These will allow the mirror edge to move un-impeded in any direction on temperature changes without causing pinching. These provide lateral support as the mirror tilts on the alt-az mount. The stud on the ball transfers screws into the whiffletree allowing precise position adjustment by simply screwing it in or out. I will probably use some threadlock when I have them perfectly adjusted for my mirror... In the following pic the original whiffletrees are on the right. They were to have a nylon roller fitted on each end. Apart from finding a better method than an elastic band to properly orientate the trefoils, the mirror cell is about done... Link to comment Share on other sites More sharing options...
+Graham Posted November 4, 2016 Share Posted November 4, 2016 (edited) Looking good there Pete. If you screw a nut onto the ball transfer unit before you fit it to the whiffle tree you can then lock it off at the required position. Instead of the rubber band cut your self a circle of thin plastic with holes in at the relevant positions to hold the trefoils in position. The plastic will not degrade and can be a permanent fixture. Edited November 4, 2016 by Graham Tweedledee 1 Link to comment Share on other sites More sharing options...
Doc Posted November 5, 2016 Share Posted November 5, 2016 (edited) Coming along really well Pete. Considering you have never done anything like this before you should be well chuffed. Great idea about the transfer units, most people just use ball bearings but I have never seen your idea before. When you make your ground and base boards why not incorporate transfer bearings instead of lazy susan bearings into your design. Transfer bearings come in all sorts of shape and sizes and can handle huge weights so say you put 6 transfer bearings in a circle 60° apart and then the same again but further in and offset with the first circle. This way you will have 12 transfer bearings, the weight of the scope would be balanced perfectly, just an idea. Great job Pete. Edited November 5, 2016 by Doc BAZ and Tweedledee 2 Link to comment Share on other sites More sharing options...
Brantuk Posted November 5, 2016 Share Posted November 5, 2016 This is looking really professional Pete - excellent job! Thanks for the tip on the biscuit jointer - it's a no brainer at £20. Very enjoyable thread mate. Tweedledee 1 Link to comment Share on other sites More sharing options...
BAZ Posted November 5, 2016 Share Posted November 5, 2016 That is a work of art Pete, it not only looks great, but will perform superbly. Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted November 5, 2016 Author Share Posted November 5, 2016 11 hours ago, Doc said: Coming along really well Pete. Considering you have never done anything like this before you should be well chuffed. Great idea about the transfer units, most people just use ball bearings but I have never seen your idea before. When you make your ground and base boards why not incorporate transfer bearings instead of lazy susan bearings into your design. Transfer bearings come in all sorts of shape and sizes and can handle huge weights so say you put 6 transfer bearings in a circle 60° apart and then the same again but further in and offset with the first circle. This way you will have 12 transfer bearings, the weight of the scope would be balanced perfectly, just an idea. Great job Pete. Thanks very much Mick, and yes, I am well chuffed. I haven't really done anything like this before, but I just read up a lot on the best methods of making a good cell, and then sussed out what I could do myself and subbed out the the bits that are beyond my limitations. In doing so I have learnt some new skills and gone down some blind alleys, but have found it all great fun, especially since it isn't my day job. I think it was one of your posts from a while back that put me onto ball transfer units in the first place, cheers Mick. I do intend to use them on the ground board, however I think I will need some form of friction clutch mechanism to prevent the movement being too easy. Great idea Mick, but maybe you have analysed it in a different way to me. As I figure it, I don't think any more than three ball transfers could be used on the ground board, without a complicated floating system (similar to an 18 point mirror cell for instance). No matter how many ball transfers you put on, the base board will only ever sit properly on 3 of them, and the problem is that it would be difficult to establish which three. This could mean that the base board might not be perfectly balanced. I know that most ball transfers are specified to carry a substantial amount of weight, often like 200kg or more each, so I'm not sure that using any more than three would be useful anyway. I'm still open to discussion on this matter in order to establish the best way to proceed. Link to comment Share on other sites More sharing options...
Tweedledee Posted November 5, 2016 Author Share Posted November 5, 2016 10 hours ago, Brantuk said: This is looking really professional Pete - excellent job! Thanks for the tip on the biscuit jointer - it's a no brainer at £20. Very enjoyable thread mate. Cheers Kim. Please check out my biscuit jointer post again. I meant that the dowel jigs are cheaper at about £20, but in my opinion a bit more fiddly. My biscuit jointer was £60 from Screwfix... http://www.screwfix.com/p/erbauer-erb372bjc-860w-biscuit-jointer-230-240v/33513#_=p It is a cheaper one but has some great reviews, and I reckon it's a bargain. On 04/11/2016 at 22:34, Graham said: Looking good there Pete. If you screw a nut onto the ball transfer unit before you fit it to the whiffle tree you can then lock it off at the required position. Instead of the rubber band cut your self a circle of thin plastic with holes in at the relevant positions to hold the trefoils in position. The plastic will not degrade and can be a permanent fixture. Thanks Graham. I couldn't have done it without your help and advice. Thanks for the tip. Brantuk 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted November 5, 2016 Author Share Posted November 5, 2016 10 hours ago, BAZ said: That is a work of art Pete, it not only looks great, but will perform superbly. Thanks very much Martyn. As the saying goes - "Form follows function". BAZ 1 Link to comment Share on other sites More sharing options...
Brantuk Posted November 6, 2016 Share Posted November 6, 2016 (edited) Thanks Pete - yeah I did misread - but I'm sure I saw biscuit jointers in BnQ for £20 or thereabouts - not so fancy as yours though. I'll recheck it next time I'm down there. Edited November 6, 2016 by Brantuk Tweedledee 1 Link to comment Share on other sites More sharing options...
+DaveJW Posted November 7, 2016 Share Posted November 7, 2016 Beautiful mirror cell Pete, I'll be coming to you for advice when I start mine! Tweedledee 1 Link to comment Share on other sites More sharing options...
Tweedledee Posted November 13, 2016 Author Share Posted November 13, 2016 On Monday, November 07, 2016 at 17:41, DaveJW said: Beautiful mirror cell Pete, I'll be coming to you for advice when I start mine! Thanks very much Dave. I'd be happy to help. I feel pretty confident about mirror cells now after doing a lot of research on them. Link to comment Share on other sites More sharing options...
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