Another Simple Single Acting Engine

[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  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

[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! 

[PaulR]

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! 

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.

[Sanjay F]

The eccentric sheave/strap and 'bent' eccenric rod turned out nicely; all coming along 

[PaulR]

Thanks Sanjay. Still not finding much timer to progress but at least I got some standards roughed out and the bearings made. Might do some shaping and certainly remove the lathe marks, also need to put some threaded holes in top for the combined retaining pins/oilers and in the bottom to fix them to the base plate.

[PaulR]

Adapted some stainless screws to hold the bearings in place and allow lubrication.

[PaulR]

Piston and con rod finished, crank disk just about done, needs a grub screw to hold it on. I made the piston twice, the first time the cross drilled hole for the rod was way off, the second time it's quite a bit better but a long way from perfect so might end up making that again.

[PaulR]

I was planning to join the valve chamber and cylinder with screws but as there would be only about 1mm between the hole and the valve bore I decided to sweat them together instead.

[Minh Thanh]

 

[PaulR]

Cheers 

Here are the parts placed together, need to finish the support under the cylinder, fix it all to the base plate and make a flywheel. Not much seems to have gone right with this engine, from small design errors to mistakes when making parts, if it works it'll be a miracle!

[Sanjay F]

Looks great, fingers crossed for you that it will turnover. 

[PaulR]

Due to other projects I haven't had time to spend on model engineering until this afternoon. In my last short session I made a basic flywheel, this afternoon I've been trying to get it going with limited success. I've rerouted the exhaust passage on the valve and made the port a lot bigger. I remade the piston although I'm not convinced the new one is any better as I think the bore is not accurate or smooth enough. I spent ages fiddling with the timing (had to move the flywheel well away from the sharp edges of the standards as they've wrecked my thumb! Here it is, swimming in oil and turning over but it will only run for a few seconds at present, hope to get more time to devote to it and catch up with the forum in the coming week or two.

<a href="https://www.youtube.com/watch?v=81BXf7-22Hc" target="_blank">http://www.youtube.com/watch?v=81BXf7-22Hc</a>

[Sanjay F]

At least it's running, so hopefully some adjustments will keep it running for longer