4 Cylinder, 2 or 4 stroke, compressed air engine

[cfellows]

Been making some progress on the engine.  I got the crankshaft assembled with the pistons and rods.  Everything fits in the block, and although it's all a bit tight, there's no binding.  I've no doubt a little running in powered by a drill or the lathe will loosen things up.



I also finished the crankcase bottom / engine mount.  The crankcase will be open on the bottom, for easy lubrication and to make things visually more appealing.  The tabs on each corner will be mounted on top of 1/4" diameter posts about 5/8 inch long. I like to see moving parts moving...



I shaped the timing gear end of the block.  The protrusions will cover the outer diameter of the timing gears.  More for interest and a finished look than actual functionality.  The two main  timing gears will be connected with an intermediate idler.  This lets me use smaller gears, more in proportion with the rest of the engine.



And here's a final group photo...



I expect the next job will be the timing gears, then the cam tube.

Chuck

[cfellows]

Got the timing gears and valve tube done.





Here is a back view of the valve tube.  This part will be enclosed in a threaded housing to which the air line will be attached...



On to the slave valves.  Getting close to having this thing ready to run...

Chuck

[cfellows]

We have a runner!   I'm not finished with it, but did get it to a point where I could test it.









Today I finished drilling the air feed holes in the cam tube and made the exhaust manifolds as well as the springs.









The ball valves are 3/16" diameter.  I made the springs by using the threads of a 3/4" 6-32 socket head cap screw as a form.  I mounted the SHCS into my 3 jaw chuck and wrapped .010" music wire tightly around the thread grooves as I spun the lathe slowly under power.  when the spring was released from the form it unwound just enough to make a spring that's about .160 OD.

I have to finish mounting the engine on a base and do some tuning.  I think the timing could be tweaked a bit and I also believe the exhaust springs need to be shortened by 3 or 4 windings.  These changes should result in smoother running at low rpm's.  I'll make a video when I get the changes made. 

The engine is currently set up to run as a 4 stroke.  I will have to make another cam tube with double the number of exit holes to see how it runs as a 2 stroke.

Chuck

[AussieJimG]

Congratulations Chuck, it is always nice when they come to life the  first time. No doubt we will have video soon.

Jim

[cfellows]

Here's some pictures and a video of the finished engine...











<a href="https://www.youtube.com/watch?v=dYALQvq4FPA" target="_blank">http://www.youtube.com/watch?v=dYALQvq4FPA</a>

Still have to make another cam to run the engine in 2 stroke mode and see how that works...

Chuck

[BillTodd]

Great  - It sounds much bigger than it is :-)

Bill

[Roger B]

Looks and sounds good, congratulations   

[sco]

That's super neat Chuck - nice job, sounds just like its ready for work ;-)

Simon.

[Kim]

Pretty neat Chuck!  Congratulations!
And very nice video too.
Kim

[cfellows]

Thanks for the comments, folks.  Here is a second video where I've drilled a second set of holes in the cam tube.  Each cylinder now has 2 holes at 180 degrees in the cam tube which is turning at 1/2 the RPM of the crank.  This gives each cylinder a power pulse on each revolution, basically mimicking 2 stroke operation. 

<a href="https://www.youtube.com/watch?v=jiYGQ74AO90" target="_blank">http://www.youtube.com/watch?v=jiYGQ74AO90</a>

The engine does run smoother, has more power, and is self starting.  You be the judge which version sounds better...

Chuck

[PStechPaul]

I have driven a Ford 9N tractor, years ago, and I seem to remember it sounding very much like this model engine. And it seems to have a little bit of the distinctive Ford "lope" when idling.
 
[edit] I prefer the sound of the four stroke when idling, but I think the two stroke is smoother and sounds better at high speed.

[zeeprogrammer]

Very cool Chuck.
Sounds like an IC!

[b.lindsey]

Well done Chuck!!  Both versions sound great but I think I favor the 2 stroke for smoothness. Are you still planning on shortening the springs any to see what effect it has on the lower rpm range or would that mess things up when using higher pressure? Nice design and excellent execution as always!!

Bill

[dvbydt]

Super job, novel as is usual with your engines, well done.

Ian

[mnay]

Amazing work.  I love the sound as much as the way they look.
Keep em coming.   
Mike