Crankshaft for opposed twin 5cc CI aero engine

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Hi people way more knowledgeable than I. I have made several single and one inline twin aero CI engines but would really like to have a go at an opposed twin or simultaneous firing V-twin.

I could use some advice (PICTURES!!) on making the crankshaft.

My dilemma is this: I can easily make the crankshaft one-piece in the lathe. No probs. Trouble is then I need to make the conrods 2-piece and, at that small size, any screwing together at the bottom-end is likely to be weak and and require enough material for screws etc making them heavy (tapping an m1 screw hole in aluminium anyone? Anyone?). I saw the FigTree Pocket engine from the MotorBoys which does just that but not totally convinced as the rods are so big and heavy.

The other option is to make the conrods 1-piece and the crank 2-piece (like on commercial 2-stroke engines). I prefer this option but have no idea how to make jigs to keep the whole thing perfectly aligned and get the tolerances right for a strong press-fit that wont self-destruct at 13K RPM plus. This option is great as I could use super hardened chrome steel roller bearing rollers as the crankpins which would last for ages.

Anyone out there with some ideas?

Thanks,
Patrick
 
I made the crank for my 15cc sidevalve boxer as a pressed assembly, using hard dowel pins for the big end journals.
I'm the end, I had to lock the assembly together by TIG welding.
There is a build thread on this site.
I will be making a smaller, 10cc version of the engine. For that, I will be making a one piece crank with split rods, just for a bit of variety.
Pete
 
I made the crank for my 15cc sidevalve boxer as a pressed assembly, using hard dowel pins for the big end journals.
I'm the end, I had to lock the assembly together by TIG welding.
There is a build thread on this site.
I will be making a smaller, 10cc version of the engine. For that, I will be making a one piece crank with split rods, just for a bit of variety.
Pete
Thanks Pete. Did you have any warping issues with the TIG weld?
 
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