After the last couple engine builds were single cylinder engines, I felt it’s time to build a multi cylinder engine. I settled on a 2 cylinder engine of my own design.
The unique part of the design is the built up crankshaft. The inspiration for the crankshaft comes from H. Schillings, a german model engine builder. It utilizes large, thin section ball bearings to register the different parts accurately. The idea is to have easy to make parts that will assemble to a strong, true running crankshaft. If this crankshaft design proofs to be successful, I already have plans to utilize this design in future engine projects.
The goal for the engine will be to have a well running, slow idling engine. I set the compression ratio at a modest 5.5 : 1. This figure is a stab in the dark, as the compression ratio is a compromise between performance and idle characteristic of the engine. The slow idle is important to me, and I feel I can achieve what I’m looking for with the mass of the flywheel and crankshaft combined.
The engine is built up from bar stock. Throughout the design, I tried to simplify the parts as much as possible without compromising the look too much.
The engine will be liquid cooled, requiring a full set up with pump, fan and radiator.
A few dimensions to get a feel for the size; Bore 32 mm, Stroke 34 mm, Flywheel diameter 90 mm, Height to top of cylinder head 178 mm
I modeled the engine in CAD. To illustrate what the finished engine should look like, I’ll start with a few renderings:
The built up crank shaft:
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