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Thread: Back to Steam--

  1. #1
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    Default Back to Steam--

    I have always been intrigued by the Stephensons Link reversing mechanism that was used on some steam engines. While searching for information about it, I was directed to "GrabCad", a site where 3D models can be downloaded free of charge. There is a complete and very detailed model of a small two cylinder steam engine, 3/4" bore x 3/4" stroke, with the reversing mechanism on it. It is quite a lovely model, and it is obvious that many of the major components are castings. This afternoon I have been playing on my CAD system to see what would be involved in making this engine from bar stock. This is what the engine looks like as downloaded.
    Brian Rupnow

  2. #2
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    The most complex casting is that of the cross-head and the two supporting legs which hold it in position. If I was a real fanatic about it, I might be able to carve this from one lump of metal, but it would be a very trying exercise---and there are two of them.
    Last edited by brian Rupnow; 09-04-2017 at 05:17 PM.
    Brian Rupnow

  3. #3
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    It appears to me that this could be fabricated from three pieces of either steel or brass, silver soldered together. It wouldn't be nearly as pretty as the casting, but should function the same, and be much, much easier to fabricate. The round portion is pretty straightforward lathe work, and the legs could be fabricated from either one or two separate pieces. It might be tricky to turn the radius in the leg where it has to match the outside diameter of the round cross head, but that is simply a matter of fixturing.

    Brian Rupnow

  4. #4
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    Like I said--Not nearly as pretty, but much closer to the scope of what I feel I can fabricate from bar stock.
    Brian Rupnow

  5. #5
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    Quote Originally Posted by brian Rupnow View Post
    The most complex casting is that of the cross-head and the two supporting legs which hold it in position. If I was a real fanatic about it, I might be able to carve this from one lump of metal, but it would be a very trying exercise---and there are two of them.
    That doesn't look like an insurmountable weldment...got the component part lines, fillets & all.
    Len

  6. #6
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    Well, maybe not insurmountable if you are an experienced tig welder with your own tig set-up. Keep in mind though, that the small outside diameter of the round part is only 13/16" in diameter.
    Brian Rupnow

  7. #7
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    Brian, how about milling some holes or slots in the RHS legs?

  8. #8
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    3D print the GrabCAD parts with a suitable filament and get then cast as 'lost filament' bronze or iron castings. Some PLA filament is suitable

  9. #9
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    Stephenson valve gear gave way to Walshaerts(sp)? which later started to give way to... I forget... Anyhow, if you want to experiment with different valve gear, look up Charlie Dockstadter's programs. He has a ton of them, both inside and outside expansion. I.E. Piston valve vs traditional.

  10. #10
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    That's a Stewart model. 10 double v I think.
    My first casting based steam was the Stewart single 10V.
    Some of pu U.K. Folks should recognize it

    Very good castings at the time.
    Should be relatively straightforward to duplicate

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