ptwizz Posted January 21, 2014 Author Share Posted January 21, 2014 The principle is simple: Kepp cutting metal away from the billet until I'm left with a crankshaft. The reality probably involves some wailing and gnashing of teeth. Quote Link to comment Share on other sites More sharing options...
ScoobySnacks Posted January 21, 2014 Share Posted January 21, 2014 I'm surprised you're milling, rather than turning on a lathe using an offset jig. Fantastic work though, that hub, rod and cylinder assembly is awesome! I don't think I'd want to hide it away in a load of cylinders, it looks too good! Quote Link to comment Share on other sites More sharing options...
ptwizz Posted January 21, 2014 Author Share Posted January 21, 2014 I'm milling because I don't fancy swinging 15kg of steel 20mm off centre on my Drummond round bed. It wouldn't swing over the cross slide anyway. I'll cut the billet to a rough approximation on the mill, then finish turn on the lathe with a fixture to set the throw and provide dummy centres. Picking swarf out of my beard! Quote Link to comment Share on other sites More sharing options...
ScoobySnacks Posted January 28, 2014 Share Posted January 28, 2014 True, swinging large off balance masses on a lathe is always a worrying time. Who was it who said about their sculptures "I just look at it and chip away all the bits that don't look like a horse" ? Can't wait to see the trike when it's all done. Quote Link to comment Share on other sites More sharing options...
bingreed Posted January 28, 2014 Share Posted January 28, 2014 "I saw the angel in the marble and carved until I set him free" - MICHELANGELO I imagine Pete's approach is not dissimilar - can't wait for the next instalment Sent from my iPad using the rather marvellous PMC Forum mobile app Quote Link to comment Share on other sites More sharing options...
ptwizz Posted March 19, 2014 Author Share Posted March 19, 2014 Some of the operations involved in machining the drive half of the crankshaft: The billet had to be roughed out on the mill so that I could get it onto the lathe. The first operation in the lathe had to be a series of facing cuts, reducing the main shaft to a diameter that would clear the lathe's cross slide. With the mainshaft turned, the billet was mounted on a faceplate with the crankpin centre running true. Note the counterbalance bar bolted to the faceplate. This job was just possible on my ageing lathe. All the turning was done at low speed (~300RPM) to keep distortion of the eccentric mass down to a tolerable level. To bore the taper in the crankpin, I had to rig up a fixed steady. This uses one of the connecting rod side plates and it's bearing. For some reason, the pictures have appeared in reverse order. Quote Link to comment Share on other sites More sharing options...
Guest Posted March 19, 2014 Share Posted March 19, 2014 Very nice I just can't wait to hear her thump into action. SW Quote Link to comment Share on other sites More sharing options...
ScoobySnacks Posted March 27, 2014 Share Posted March 27, 2014 Engineering porn. Simon, are you sure this classes as "clean" What an amazing project though, your skills and knowledge are enviable! Quote Link to comment Share on other sites More sharing options...
ptwizz Posted March 28, 2014 Author Share Posted March 28, 2014 I have to keep this in perspective: I am building what is essentially a copy of a 100 year old design. I have a motorised lathe and a milling machine with digital readouts. 100 years ago, the first of this type of engine were built by men in sheds with considerably less resource than I have available. Those guys were the real heros. The only skill I would claim credit for is patience. Everything else can be easily learned. Quote Link to comment Share on other sites More sharing options...
ptwizz Posted April 23, 2014 Author Share Posted April 23, 2014 6kg of crankshaft assembly. Convincingly chunky. Next - pistons. I've only made one piston for an internal combustion engine before - and that was a copy of an existing part. For this engine, I have rejected the original four ring pistons which go with the Dnepr heads - mainly because the valve pockets are in the wrong orientation. I have designed a slipper piston with oil control more suited to a radial, in which the pistons have to work in all orientations. Quote Link to comment Share on other sites More sharing options...
Neilzy Posted April 23, 2014 Share Posted April 23, 2014 Pete sent ya a pm Neilzy Quote Link to comment Share on other sites More sharing options...
Guest Posted April 23, 2014 Share Posted April 23, 2014 Don't forget you can use the instant chat when he is online SW Quote Link to comment Share on other sites More sharing options...
ptwizz Posted July 30, 2014 Author Share Posted July 30, 2014 Progress has been inhibited by other stuff recently, but not halted completely. After some investigation I've found the right material for billet machined pistons (it's Aluminium 2618A-T6511 if anyone's interested). The first piston is turned to slightly oversize, cross bored for the gudgeon pin and then the inside machined. The first is a test piston. To verify my design, I will make this one with an O ring groove in place of the top compression ring. This will be fitted to a simple test rig (a dummy cylinder with one end capped) and hydraulically pressurised to the predicted peak cylinder pressure (50 Bar) while the piston is prevented from moving by a support at the centre of the gudgeon pin. I will then measure elastic distortion of the skirt areas and the pin to establish whether I need to alter the design. Quote Link to comment Share on other sites More sharing options...
ptwizz Posted August 4, 2014 Author Share Posted August 4, 2014 More piston machining. The sides of the slipper skirt are milled, leaving 2.0mm wall thickness at the webs, 3.0mm around the gudgeon pin bosses. The piston is then supported between a centre and a fixture which ensures true running, for the crown and grooves to be machined. Quote Link to comment Share on other sites More sharing options...
Guest Posted August 4, 2014 Share Posted August 4, 2014 I am envious of your machining skills dude! Cant wait to see the running lump SW Quote Link to comment Share on other sites More sharing options...
ptwizz Posted August 18, 2014 Author Share Posted August 18, 2014 Yesterday I scrapped piston #1. It's my own design and my own manufacture, so entirely my own fault. I hadn't allowed sufficient crown thickness at the location of the exhaust valve clearance pocket, so there's a hole in it now. It's not even any good as an ashtray! Today I will saw off another 80mm of aluminium bar and start again. Quote Link to comment Share on other sites More sharing options...
alan_k Posted September 15, 2014 Share Posted September 15, 2014 Fantastic thread Pete, I am also envious of your mechanical skills. As you say you do have patience, so piston No.2 should be so much better from what you have learned from piston No.1. Anticipating more thrilling installments, Alan Quote Link to comment Share on other sites More sharing options...
ptwizz Posted October 6, 2014 Author Share Posted October 6, 2014 Some progress, at last. Before starting (again) on a set of pistons, I worked out how to set up the Drummond lathe to turn the pistons (too big Ø to pass over the cross slide) without a long overhanging tool. The new, stiffer setup allowed me to make short work of seven blanks. The finish is also considerably better than that achieved on no.1. Provided my life doesn't get in the way too much, I should have a set of pistons before too long. Then I can get onto the really interesting bits. Edit: Why do the pictures show in reverse order? I attached the lathe setup photo first. Quote Link to comment Share on other sites More sharing options...
ptwizz Posted November 11, 2014 Author Share Posted November 11, 2014 More hours in the workshop, more swarf in my socks and a satisfying pile of pistons in progress. Quote Link to comment Share on other sites More sharing options...
Norman3 Posted November 23, 2014 Share Posted November 23, 2014 I can't wait for the next episode. Particularly when we start seeing the bit about case castings. What a lovely project - nothing sounds quiet like a radial. Quote Link to comment Share on other sites More sharing options...
ptwizz Posted November 24, 2014 Author Share Posted November 24, 2014 Once the pistons are done, I will indeed get onto the main crankcase. The crankcase will not be from castings, but a bolted structure consisting of a front plate, a back plate and seven 'sides'. All will be machined from 1" thick Aluminium 5083, which I have just ordered. I had investigated the possibility of a two piece cast casing, but the design would have made for awkward assembly of the engine and I couldn't find a foundry interested in the job. Yesterday, I machined the pockets in the undersides of two pistons. This operation takes about 3 hours per piston (and since the cockup on the first piston is quite stressful ). Everything I touch is contaminated with tiny flecks of aluminium Quote Link to comment Share on other sites More sharing options...
ptwizz Posted December 26, 2014 Author Share Posted December 26, 2014 Milling the pocket in a piston. Quote Link to comment Share on other sites More sharing options...
ptwizz Posted December 26, 2014 Author Share Posted December 26, 2014 Turning the ring grooves. Quote Link to comment Share on other sites More sharing options...
ptwizz Posted December 26, 2014 Author Share Posted December 26, 2014 Boring the valve head clearances. Quote Link to comment Share on other sites More sharing options...
ptwizz Posted December 26, 2014 Author Share Posted December 26, 2014 Seven pistons Quote Link to comment Share on other sites More sharing options...
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