Engines > Your Own Design

Another Simple Single Acting Engine

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PaulR:
I've drawn up a some of the plan for my next simple bar stock engine which will be single acting, using a piston type valve controlled by an eccentric (for a change). The piston will have a wrist pin connection to the con rod and the valve rod will need one of those funky bends somewhere along its length to make room for the crank, bearing and thickness of the eccentric itself - I need to work out what sort of jig will be needed....

Here's the cylinder and valve chamber. Air will be admitted past the end of the valve and expelled via an internal hole within. I plan on drilling through from the valve rod end then plugging the bottom of that already threaded hole. I might make the holes on the surface of the valve into slots to give a bit more time for exhaust to escape, can't do any harm!

Hope to start work on it later today or Friday.

PaulR:
Found time to make a start  ;D Made the cylinder, valve chest and the two end caps. A test piece of 8mm silver steel fits nicely for the valve, next will be the MS piston. However, measuring the bore I find that there's about 0.15mm difference between the ends (~ 0.006"), probably due to the weedy 6mm boring bar I have. It might be ok, I'll see what it's like when I've made the proto piston :D

Sanjay F:
Good to see you off and running on another design; I'm not visualising it yet, but then again I'm lost without a General Arrangement diagram. Good job you've got that in your head!  :Lol:

PaulR:

--- Quote from: Sanjay F on June 03, 2026, 08:58:32 pm ---Good to see you off and running on another design; I'm not visualising it yet, but then again I'm lost without a General Arrangement diagram. Good job you've got that in your head!  :Lol:

--- End quote ---
Cheers! Maybe I should rely less on what's in my head... in the middle of the night I realised my original idea for the valve rod/eccentric won't work as despite being cylindrical, the valve has to stay in the correct orientation. A clevis on the end is probably the way to go instead but getting the length of the rod exactly right while it has a bend in the middle will be tricky (could put an ugly block in the middle instead of a bend I suppose).

PaulR:
Short of time at present but found enough to finish the eccentric rod and make the eccentric itself, apart from the hole for the grub screw to set the timing.

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