Engines > Your Own Design
Freelance Inline Twin
yogi:
Hello everyone,
The days are getting shorter and the temperatures cooler, which draws one back into the shop. So it’s time to introduce you to my next project. After the hit ‘n miss engine I built last, I want to build a multi cylinder engine. I’ll keep it relatively simple, as it will be a two cylinder engine.
The engine is totally freelance and designed by myself. The main part of my design is the built up crankshaft. The inspiration for the crankshaft comes from H. Shillings. It utilizes large thin section ball bearings to register the different parts accurately. The idea is to have easy to make parts that will be assembled to a true running crankshaft.
The goal will be to have a slow idling, well running engine. I set the compression ratio at 5.5 : 1. This figure is just a stab in the dark, as I haven’t built an engine like that before. 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.
It will be liquid cooled, requiring a full set up with pump, fan and radiator and all. That’s another first for me.
A few dimensions to get a feel for the size; Bore 32mm, Stroke 34mm, Flywheel diameter 90mm, Height to top of cylinder head 178mm
Below, I have some CAD renderings for you guys. This is how the finished engine should look like. There are still a few little details that need attention, but I feel confident enough in the design to have a go at it.
I hope you will be along for the ride..
Yogi
Roger B:
Looks an interesting project :ThumbsUp: :ThumbsUp: Is that the waterpump behind the fan? I'm not sure that you will really need the number of crankshaft bearings that you have unless you will be running the engine with high loads/speeds :headscratch:
Jasonb:
Looks Intertesting, Malcom Stride had a couple of basic designs using the Schillings type crank but never got round to making them, not unlike your engine in many ways.
Roger the bearings form part of the crankwebs and without them the built up crankshaft would not work, Schillings used the method in a number of engines upto V8 or maybe even a V10. Though I think it should only need the centre bearing and two small outer ones.
J
yogi:
Roger, yes, that is the pump behind the fan.
Like Jason said, the bearing are an important part of the built up crankshaft, and not only for the load bearing. Especially for our small engines.
The outer bearings could be smaller, but when I started to draw up this project, it was a four cylinder, which I then reduced to two. I left it modular like that to test the design.
It is an experiment, even though I have confidence it will work well. I guess the only way to find out is to build one... 8)
Yogi
Zephyrin:
Very nice project, i enjoy to follow this thread...
I didn't see any output from the camshaft to drive the distributor, are you planning to use glow plugs ?
I have an inline four (still unfinished) with this sort of crankshaft and when all the pieces are apart on the bench, it looks very tricky to assemble in the engine bloc...but really clever at the end!!
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