Upshur twin crankshaft

[GordonL]

I am in the process of building an Upshur Opposed Twin engine. After four failed attempts to make a one piece crankshaft I think that it is time to go to a built up crankshaft. This is small. It has 5/16 dia shaft and 3/16 thick side plates. Every time I get half done and try to turn the second journal it catches and bends something. I have tried soldering a spacer bar between the first journal plates but that has not been too successful. I just ruined try number four so it is time to rethink. My question is on how to join the pieces. On larger crankshafts I have silver soldered the pieces together but I am afraid of warping on these small pieces. Others have used loctite with and without pins. My experience with locktite has not been great. Any advice on this from someone who has built this engine or something similar? I am planning on running the main shaft all the way through and cutting it out after everything is together.

Thank you: Gordon

[Roger B]

I don't know this engine but how are you supporting the crankshaft? At the start of this thread I am making a slightly bigger shaft:

https://www.modelenginemaker.com/index.php/topic,7883.0.html

This and the alternate 360° shaft were turned without problems.

[GordonL]

That is a possibility. The crank is made from a flat bar 1/2 x 1 1/4 x 4 1/8 lg. I have been machining between centers with a face plate. Starting with a round piece and turning down one end and supporting that end in the four jaw would eliminate the problem of having the throw collapse because of pressure from the center in the tail stock. Food for thought anyway.

[GordonL]

Thanks for the information. I have never heard of a Keats angle plate before but now I am sure that I need one. 😁

[Roger B]

There are two Keats angle plates I am aware of. One is available from a number of import suppliers, shown below. This is too big for my Hobbymat but fits Minilathes and upwards. The other is a casting kit from Hemingway which has a neat adjustment mechanism. This is my build log:

https://www.modelenginemaker.com/index.php/topic,4275.0.html

[rklopp]

Check out https://www.homemodelenginemachinist.com/threads/turning-a-one-piece-crankshaft.6743/post-73306 for some ideas and links to further threads on making cranks.

[GordonL]

That is a much better solution than what I have used. Thanks.

[GordonL]

After seeing that set up I realized that I have a 5c collet fixture. If I mount that to the face plate I can use that to hold the crank while I machine it.That should work well and be versatile enough for other cranks. My problem was the result of trying to machine between centers which put end pressure on the crank.

[Roger B]

That sounds like a good solution