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[Brian Rupnow]

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]

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.

[Brian Rupnow]

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]

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

[Gas_mantle]

I'd be interested in seeing how this develops Brian 

I have contemplated trying to make something similar from bar stock, my thoughts were to fabricate the standards from 5 pieces - the crosshead guide cylinder, 2 supporting legs and the 2 outer webs being soldered in place.

I've never made anything like that so not sure how practical it is but I'd like to give it a try 

Peter

[Brian Rupnow]

Follow along Peter. I will post the results that I get. The hardest part of the entire engine is probably those two fabricated stands.

[Nick_G]

.
That looks to be modeled upon the Stuart D10

If you are looking for a simpler (and IMHO more elegant) solution you could look at something based similar around the Stuart 'Twin launch' or the 'Compound launch'



Nick

[Ye-Ole Steam Dude]

Beautiful engine Brian. Would it be possible to have the lower post made by 3-D printing. However, your 3-piece design looks fine. Looking forward to you build.

Thomas

[Brian Rupnow]

Thomas--If I cared to spend the money, I'm sure I could have it 3D printed. However, I would rather fabricate the parts.  For me, the important aspect of making something like this is more about making a functional part with the machinery I have in my little shop.--Brian

[Brian Rupnow]

This is going to get interesting. Although the solid models have been designed in inches, it appears that in some places the numbers used may be direct conversion from metric. Also, the bolts used are 7BA and 8BA, which I am not familiar with. I will be converting the fasteners to Imperial sizes, mostly #5-40 and #4-40.:eek:

[Johnmcc69]

Hi Brian, I think I have the plans for the engine shown in your 1st post. Somewhere along the line I downloaded them. (Free) I created a 3D model of it in Pro-Engineer years ago as an "excercise". I'll see if I can find them for you. I think the plans were in German though. But, the details & dimensions are there...

 John

[Brian Rupnow]

Hi Brian, I think I have the plans for the engine shown in your 1st post. Somewhere along the line I downloaded them. (Free) I created a 3D model of it in Pro-Engineer years ago as an "excercise". I'll see if I can find them for you. I think the plans were in German though. But, the details & dimensions are there...

 John

John--Thank you for the kind offer, but no thank you. I never trust 3D models downloaded from Grab-cad, and by the time I get finished changing everything to suit a fabricated assembly with #4 and #5 bolts, it will be changed so much that drawings would be meaningless.  ---Brian

[Jasonb]

Easiest way to fabricate the trunk and standard would be to turn the flange and guild as one piece, legs cut from 1/8" tee and bent to form the vertical ribs, solder all these onto a flat bar and then cut that to form the feet after soldering.

[pgp001]

I made the one for my barring engine from cast iron bar, and just made the webs as separate decorative parts glued into some shallow slots.



Phil

[Gas_mantle]

Easiest way to fabricate the trunk and standard would be to turn the flange and guild as one piece, legs cut from 1/8" tee and bent to form the vertical ribs, solder all these onto a flat bar and then cut that to form the feet after soldering.

Jason, have you uploaded a build log of doing this or something similar ? Now that my Grasshopper is just about finished I'd like to try fabricating parts so I'm interested in how you did it :-)