*
I
originally made 5mm [1/5"] x 150mm aluminium, worm support plates but these
could still flex. A later find of a long length of scrap, 10mm aluminium
[also 6" wide] offered a much stiffer alternative. The miter saw will be used to cut the strip squarely to length. With a light application of lamp oil as a cutting fluid.
The original 5mm worm support plates. Holes provide clearance for the axis shafts and longitudinal 16mm studs.
That said, the 10mm thick aluminium is not a trivial material to saw, cut and drill. I had to use the lathe for the larger drills and hole saw fitted in the 3-jaw chuck. This required the very lowest back gear speed and the lathe bed as a safety stop against rotation of the plate. I then carefully feed the tailstock barrel in to slowly push the material onto the drills and hole saw. The barrel pushes squarely and the drill can safely enter the hollow MT2 barrel when it breaks through.
My dirt cheap, old pillar drill doesn't have remotely enough torque or stiffness to drill large holes. The lowest of five speeds is still far too high for larger drills. The holes can even come out hexagonal if I push my luck! Though usually the drill stalls first. Once a pilot hole has been opened out to the safe capacity of the drill I move over to the lathe for much greater safety and smooth, round holes.
The availability of scrap aluminium is not an ideal design parameter for telescope making. The builder quite literally becomes a slave to the materials available. This forces the designer to comply with what they have to hand and owning/buying the necessary tools to make it happen. Wishful thinking will not help here. I seem to have spent a lifetime wandering around scrap yards. Though not continuously, I hasten to add. I have developed a feeling for what is useful and what is beyond my capacity however hard I try. Gone are the days when I'd bring back solid 4" shafts and huge, matching, plumber block bearings. Or 24" cast iron, lathe face plates to build polar axes, for fork mountings. With each component almost too heavy to lift.
If you can afford to pay for castings and/or a skilled machinist then count yourself very fortunate. Though you probably won't save much money over a Chinese, mass-produced commercial design by the time it is finished. You will only have yourself to blame if it does not function optimally. The latest, mass produced design probably emerged after a whole series of iterations. The designers will be using CAD and enjoying feedback from the design and production team for start to finish. Many mountings improve almost annually as users complain or make positive suggestions for improvements. Though it often seems the Chinese designers do not read the forums.
One should always be incredibly grateful for whatever [scrap] materials turn up to your advantage. I don't think one should try to haggle too much. Or the scrap dealer will quickly lose interest in helping the oddball. You are the strange one who actually wants to take something away and may even pay well for it! Rather than forming an orderly queue to sell more scrap material to him for cash in hand. A degree in diplomacy helps to avoid being sent hurriedly on your way. Climbing over heaps of sharp metal to rescue one useful piece is just foolhardy and downright dangerous. Any accidents will become his responsibility. So take great care, act sensibly, be polite and put nobody at risk.
I have been extraordinarily lucky in finding enough flat strips of 10mm and even 20mm plate in [mostly] good surface condition. Alas, finding suitably heavy alloy angle has resisted all further visits. Metals can be bought on eBay UK and DE but the Danish metal stockholders will not deal with private customers. Trying to buy a few small pieces of 4mm plate from a local engineering firm proved rather costly. Though they did have to guillotine a couple of quite modest pieces to size. With digital readouts on the machine it was only a matter of moments to set and cut. A return visit provided no suitably heavy angle for worm support in their entire stock of aluminium alloy.
The new 10mm support plates will still be trapped between the bearings housings and the axes heavy flange bearings. The four equally heavy 16mm, [~3/4"] corner studs [all threads] will prevent all movement. I shall probably have to use solid blocks of metal rather than angle profile to support the worm housings.
New 10mm worm support plate beside the old 5mm. It took ages to cut the large hole to clear the axis shaft. After failing to make any depth from either side I had to drill dozens of tiny holes in the circular track to help the hole saw on its way. I made the plate slightly longer in case I need the space.
Don't waste money on cheaper hole saws. The Millarco 65mm hole saw was worn out by taking only two 5mm cuts in aluminium despite using only 45 rpm and lamp oil as a cutting fluid. With the DIY outlets closed by Saturday lunch time I shall have to wait until Monday now to buy a real hole saw. Not some cheap crap which can only manage one hole in cardboard packaging.
Click on any image for an enlargement.
*
No comments:
Post a Comment