Inline Twin Engine Ep. 3

In today’s episode, I’ll be making the crankshaft.

This whole engine is built around the crankshaft, and it’s design. It will be a test bed for future use of this idea.

Please refer to Inline Twin Engine Ep. 1 for a CAD rendering of the crankshaft.

The individual parts are turned on the lathe first. This will be the rear, the flywheel end of the engine.


Second side finished turned.


The crank discs were turned next:


What will be the front end of the engine (the accessory end):


After all the parts are finished turned, it was over to the mill. I machined a set of soft jaws, to be able to hold the part accurately on the bearing seat. It is very important the hole for the crank pin is not only accurate in diameter, but also exactly perpendicular for everything to line up when assembling the crankshaft. Any misalignment would result in binding of the bearing.


Two of the discs were drilled to be tapped, and two countersunk.


The front and rear parts being finished as well:


The different parts, ready for assembly:


…and the assembled crankshaft:


The crankshaft installed in the crankcase:


To demonstrate how well it turned out, a short video:

I’m very pleased how free the crank is running. This part of the build has exceeded my expectations, and I can already envision this type of crankshaft in future engine builds.

Thank you for visiting my shop.

If you have any questions about the engine or any of the other projects, please leave a comment below, or email at yogisworkshop(at)

For other projects from the shop, please check out the projects page in the top menu.



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