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Thread: The Bucket Foundry

  1. #4186
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    Quote Originally Posted by WilDun View Post
    Yes, 39B I always found was a delight to machine. - In my later days I worked part time in a gearcutting shop and most days I trudged through the traffic from Mt Wellington to Mt Albert with shafts and gears to have them hardened at Heat Treatments, then trudged back with hardened ones.
    On the odd occasion we might get a slightly banana shaped shaft (after hardening) which tended to piss us off somewhat!
    I once had one out of 6 shafts come back bent. They were machined more or less identical, except the bent one had a wee witness mark from where a chamfer hadn't quite cleaned up the end of the bar stock.
    Ever since then I've avoided the last couple of inches and haven't had any significant issues.

    Oh, except for a bit of Chinese shit, the remainder of which went in the bin at tolerably high speed.
    Go soothingly on the grease mud, as there lurks the skid demon

  2. #4187
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    I find pre machine close, stress relieve, then finish machine leaving stock for grinding works well with minimal distortion.

  3. #4188
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    Quote Originally Posted by Flettner View Post
    I find pre machine close, stress relieve, then finish machine leaving stock for grinding works well with minimal distortion.
    Yeah I'd done that, but there was an inclusion in the last inch or so of the bar.
    Still, better it bent then than broken in service, it was a fucking expensive bit of kit.

    The other problem is you can't trust certificates nowadays, a significant quantity of them are forged. I'd expect that to be a real concern for aviation supply traceability?
    Go soothingly on the grease mud, as there lurks the skid demon

  4. #4189
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    It was a worry, my supplier tested the waters on Chinese steel. Quickly changed back to the original German stuff. I get to find out if its not worthy at heat treatments, if it doesn't come up to spec. A bit late, has cost a lot before that point.

    Some of my gearboxes are over 1000 hours now. EN39B is good material for gears to be made of.

  5. #4190
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    Quote Originally Posted by Flettner View Post
    It was a worry, my supplier tested the waters on Chinese steel. Quickly changed back to the original German stuff. I get to find out if its not worthy at heat treatments, if it doesn't come up to spec. A bit late, has cost a lot before that point.

    Some of my gearboxes are over 1000 hours now. EN39B is good material for gears to be made of.

    We often did boxes with chunkier teeth for the rally and off road (car) guys etc. they didn't have ground lobes and made a helluva racket, but that didn't seem to bother those guys a bit! - guess in their application that didn't really matter!
    Sorry - I don'i consider myself an expert on gears - no, I was just the (very interested) old part timer who turned up the blanks for the gears and shafts - amongst other stuff - even things eg. like ringing up guys who were a little reluctant to pay their bills!)
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  6. #4191
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  7. #4192
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    Is this a quiz? or is it a concoction you are working on yourself - what is it? - it looks to me like a piston with a cylindrical deflector on the crown! and I think if that's the case, then the only situation where it might work well is with HCCI! or .........could it be a central passage instead of the normal transfer passage ???????

    If it is a new project of your's, then give us some clues (like a pair of shorts and knees! ) and of course both end views!
    Freedom of speech is important but if what we say is considered incorrect by our peers, they will quickly put us right.
    P.C. will eventually destroy our right to tell the truth.

  8. #4193
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    Will, sorry, the jolly Kiwi Biker had been play up so I was experimenting with posting Youtube links.

    Its a new piston, machined from solid unobtainium, with a special gudgin connection leaving no external holes for gas recirculation, exhaust transfer, with real large exhaust ports. Lump is just so I can still hang on to it while I finish machine its outside, ring groove and side cutaways. Piston will be flat top or perhaps slight conical.

  9. #4194
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    Yeah, thanks Neil, I should have figured out what the lump is, but me being me will tend to get carried away and read a lot more into it ...... was even tempted to ask if it was a double diameter piston at one stage! ......... still interested in what it is (or is going to be) though also finding out about the pin setup!
    Freedom of speech is important but if what we say is considered incorrect by our peers, they will quickly put us right.
    P.C. will eventually destroy our right to tell the truth.

  10. #4195
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    Quote Originally Posted by Flettner View Post
    Will, sorry, the jolly Kiwi Biker had been play up so I was experimenting with posting Youtube links.

    Its a new piston, machined from solid unobtainium, with a special gudgin connection leaving no external holes for gas recirculation, exhaust transfer, with real large exhaust ports. Lump is just so I can still hang on to it while I finish machine its outside, ring groove and side cutaways. Piston will be flat top or perhaps slight conical.
    Have KTM hit the like button yet



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  11. #4196
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    Quote Originally Posted by Flettner View Post
    Will, sorry, the jolly Kiwi Biker had been play up so I was experimenting with posting Youtube links.

    Its a new piston, machined from solid unobtainium, with a special gudgin connection leaving no external holes for gas recirculation, exhaust transfer, with real large exhaust ports. Lump is just so I can still hang on to it while I finish machine its outside, ring groove and side cutaways. Piston will be flat top or perhaps slight conical.
    Not being able to see the youtube stuff, I looked at the still you posted, for which, thanks. Very curious about the pin....Nicely staged pic too, leaves all sorts of questions, LOL.
    One benefit of a conventional pin is that it makes holding and machining much easier. I've got a couple of jigs which pull the piston down onto the open end via a threaded clamp onto the pin.
    Doing a taper ? Camming ?
    Reason is a tool - remember where you left it..... The late, great, John Clarke

  12. #4197
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    Quote Originally Posted by Grumph View Post
    Not being able to see the youtube stuff, I looked at the still you posted, for which, thanks. Very curious about the pin....Nicely staged pic too, leaves all sorts of questions, LOL.
    One benefit of a conventional pin is that it makes holding and machining much easier. I've got a couple of jigs which pull the piston down onto the open end via a threaded clamp onto the pin.
    Doing a taper ? Camming ?
    Taper yes, camming no. There is no big lumps on the side of the piston to cause uneven piston expansion. Should expand concentrically.
    Greg, you don't have a GN bottom end or know where a free / cheap one might reside.

    Interestingly that is how I used to make my pistons also, pin through the gudgin, with a short rod and camlock down onto the boring and facing head face fixed into the
    lathe headstock. So not only taper but you could offset the boring head a few thou one way then the other, crude but effective camming, worked real well on my home made uniflow 440 pistons.

  13. #4198
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    Quote Originally Posted by Flettner View Post
    Taper yes, camming no. There is no big lumps on the side of the piston to cause uneven piston expansion. Should expand concentrically.
    Greg, you don't have a GN bottom end or know where a free / cheap one might reside.
    125's yes, but 250's no. There's more wreckers left up your way than down here and there's been plenty wrecked. The 125's are too light. And too wide a gap to 6th.

    Not entirely sure of the soundness of your argument against the need for camming....proof of the pudding, etc...

    Piston holding - mentioning no names, LOL, one big name down here did a piston for a 450 ducati I was building for a customer. Built it up, all fine, pulled it down for a look as it made strange noises. Top of piston was .035in higher one side to the other. He wouldn't believe it till I measured from the pin each side...
    It had just touched the head that side.
    He held pistons for crown machining by the pin hole - against a Vee block. He still doesn't know how it came to be out, LOL. I finished up remachining it myself as he washed his hands of it.
    Reason is a tool - remember where you left it..... The late, great, John Clarke

  14. #4199
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    Quote Originally Posted by Grumph View Post
    125's yes, but 250's no. There's more wreckers left up your way than down here and there's been plenty wrecked. The 125's are too light. And too wide a gap to 6th.

    Not entirely sure of the soundness of your argument against the need for camming....proof of the pudding, etc...

    Piston holding - mentioning no names, LOL, one big name down here did a piston for a 450 ducati I was building for a customer. Built it up, all fine, pulled it down for a look as it made strange noises. Top of piston was .035in higher one side to the other. He wouldn't believe it till I measured from the pin each side...
    It had just touched the head that side.
    He held pistons for crown machining by the pin hole - against a Vee block. He still doesn't know how it came to be out, LOL. I finished up remachining it myself as he washed his hands of it.
    If you want a job done properly, do it yourself. That's the bloody truth these days.

  15. #4200
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    Quote Originally Posted by Flettner View Post
    Taper yes, camming no. There is no big lumps on the side of the piston to cause uneven piston expansion. Should expand concentrically.
    Interestingly that is how I used to make my pistons also, pin through the gudgin, with a short rod and camlock down onto the boring and facing head face fixed into the
    lathe headstock. So not only taper but you could offset the boring head a few thou one way then the other, crude but effective camming, worked real well on my home made uniflow 440 pistons.
    Yes I used to do that too - I figured if they used that little step at the factory, then I could as well ......... but wouldn't uneven heating by the exhaust port still require camming?.........I didn't have any posh boring head though - just a dummy pin with a tapped cross hole drilled through it and a piece of threaded rod.

    Or ... you could use an even more crude method (as I used sometimes in my very early days) - ie wait till it starts to pick up and if you managed to detect it before it seized solid - (dicey business!), file it down!

    How long will you keep us in suspense with the gudgeon arrangement?
    Freedom of speech is important but if what we say is considered incorrect by our peers, they will quickly put us right.
    P.C. will eventually destroy our right to tell the truth.

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