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| cidrontmg:
Hi Nick, I have been reading the whole thread once again, and figuring out what to suggest. But havenīt come up with anything obvious or show stopping. Itīs difficult to make remote diagnoses :doh: That displacer seems to me rather heavy. Styrofoam, polyurethane, balsa, something a lot lighter would probably be better. The displacer rod also seems to be touchy. Itīs prone to leaking, and that will make quite a difference. The power piston leaking slightly wonīt be nearly as harmful. The all-important thing is, it must be free-running. Reducing friction is far more important than reducing leaks. I guess the bearings are OK, but if you have any oil/grease(!) in them, you should wash it all away. With my engines, I rotate the flywheel back and forth in +/- 10o steps, through the whole circle, and listen and feel if thereīs any scratchy noises or stiffness anywhere. And do my best to find the causes, and reduce them as much as possible. If I give the flywheel a flick with my finger, the engines make some 8-10 rotations, accompanied by a "swoosh-swoosh" noise, coming mostly from around the displacer rod. I cannot make it completely airtight and still make the engine run. But itīs not a LOUD noise, barely audible, and it is more when the displacer is moving towards the hot end. The engine might need a bigger heat difference. If you cooled the top cover, by putting some ice (snow... I guess that could be arranged... :) ) on it, it might show some vital signs... Other than that, and without seeing/feeling it, quite hard to suggest anything. Wish you the best of luck with it! :wave: |
| NickG:
John, many thanks fir the reply. Now that you've explained about reamers I think I've seen you explain in another post but I'd forgotten. This could very well be the case as it was a hand reamer I used, I don't think I wound it all the way through and the cover is relatively thick. My new reamers are also the hand variety but look a bit longer so hopefully will have a longer parallel section. I'll be sure to wind right through and use it as a floating reamer supported by tailstock if that's a better technique. Olli, thanks for the trouble shooting techniques, and the displacer material will definitely be as suggested by a number of people this foam next time. I will also try to lighten all of the rotating / reciprocating components. Cheers guys, Nick |
| madjackghengis:
Hi Nick, as John said, reamers are fickle things, and while one seldom finds a less than straight machine reamer, if of decent quality, one does get by occasionally. Most of the time, a machine reamer reams taper because it is held too rigidly, and for instance, my tailstock dangles about two or three thousandths, from sixty odd years of wear, so a proper reamer holder would improve their performance much. With regard to the eighth in shim in the three jaw, you effectively only moved the radius a sixteenth, this was the error I made in turning my cam in my Duclos flame sucker, twenty years ago, and prevented it from ever running until this year. Were I you, I would look for a piece of balsa wood to make the displacer out of, as that seems to be generally available in hobby stores, and it has been proven out many times. My wife hates it, but I have no problem digging in the "green boxes" and rescuing someone else's trash, if I see machine parts available, or scrap metal for stock. I only buy metal when I have to, but I've got tons of iron and steel from years of a machine shop, and quite a few hundred pounds of aluminum of various sorts. One should never let a printer or computer go in the bin without being disassembled, and all the useful parts kept. You might need to practice more scrounging :poke:, if you're going to build engines. None the less, it is nice looking, and I'm sure you'll get it all sorted out soon, after the holiday rush. :bugeye: :thumbup: mad jack |
| NickG:
Thanks Madjack, I think I will have to wait until after the holiday rush! More car trouble and it's just becoming so annoying now. I managed to get the dealership to do a straight swap for the citroen that had all the issues with it for a Vauxhall Vectra SRi. Despite the dealership being a bunch of incompetent ***** I thought I'd got a good deal out of them in the end. I picked the new car up on Christmas eve, it was a year newer than the other and a petrol this time - 3 days later the engine management light was on on the dashboard, had a friend plug it into the vauxhall diagnostic (thanks to him as just doing that normally costs Ģ65 + vat!) and it says there's a fault with the 'cam phasing mechanism' - another engine with daft variable valve timing ... why does everything have to be so complex these days?! So I'll no doubt have more trouble getting that repaired and getting the dealership to pay for it, but they better do, only had the car 4 days! I have sketched the thing with the 1/8" packing to get the right offset and I still don't understand why it wouldn't give me the right offset, surely you are just moving it 1/8" off it's original centreline by doing that, I can see that if you put it under 2 jaws it wouldn't move as much but just under the 1, shouldn't that have worked? Nick |
| andyf:
I think you said you were putting 1/8" packing under one jaw of a 3-jaw chuck. With a 3-jaw, you only get an offset which is 2/3 the thickness of the packing, so 1/8" packing offsets by 1/12". If you want 1/8" offset, you need 3/16" packing. It took me a while to get my head round it :scratch: :scratch: There's an explanation of a sort three-quarters way down this page: http://homemetalshopclub.org/news/aug03/aug03.html Andy |
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