Compressed Air Radial Engine

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cfellows:
Took a break from the small rotary table to get some work done on the crankshaft for my radial. Here it is, clampted into a v-block while the loctite cures (Thanks for the v-block idea, MB). Tomorrow I'll drill it out and insert a roll pin. A taper pin would be better, but I ain't got none of those nor do I have the needed reamer so a roll pin will have to suffice.

Chuck

cfellows:
I've decided to go ahead with the overhead valve arrangement on this engine. It will be 4 stroke in operation and will use a combination of my slave exhaust valve and a ball inlet valve similar in operation to the Liney Halo radial. High pressure air will be presented to the top of the cylinder where it will be stopped by a ball bearing check valve. To "fire", a valve stem which is an interference fit with the ball valve will open the valve by pushing it to the side when the stem is depressed. This will admit air into the head where it will push a second ball bearing to the side, exposing a hole which leads into the cylinder. This will push the piston in a manner similar to my other slave valve engines.

So here is the first series of pictures on work done the past couple of days. Here is one of the cylinders with the valve stem hole drilled down through the top into the and a 1/8" hole drilled radially all the way through.

Here I've milled a flat on both the intake and the exhaust sides to receive the input and exhaust pipe flanges. I've also enlarged the hole to several different sized. The intake side is 7/32" so the 3/16" ball bearing is a very loose fit. This allows air to flow around the ball bearing when it is unseated by the valve stem. Then the hole is stepped down to 5/32" where it passes around the valve stem. Finally, on the other side of the valve stem, it opens up to 3/16" so the slave ball bearing is a close sliding fit.

Inlet side, showing the step down to 5/32" around the valve stem hole.

This shows the inlet side on the left and the exhaust side on the right.

I will be attempting to emulate the layout of the Anzani radial engine as close as I can, perhaps without as much detail. Here, you can see that on the rear side of the cylinders, there is a tube going up the back into an elbow at the top which leads into the cylinder head. This is the air/fuel inlet manifold.

On my engine, the high pressure air supply will go up a tube on the rear of the cylinder and into an elbow, similar (or at least as close as I can get it!) to the Anzani. So, in the next series of pictures, I am making my version of the elbow.

I'm milling all three manifolds in one piece of brass and will cut them apart later. Here I'm using a 1/4" end mill with radiused corners to cut out the sides.

Next I use corner rounding bitto round off the top edges.

And, the finished manifold before cutting in to three separate pieces.

Here they are cut apart and the holes for the tube have been drilled. There is also a hole on the bottom which will lead into the cylinder head.

And, here they are with tube soldered on, mounting holes drilled and pretty much ready to mount, well, after I pickle them and get them polished up!

I'm still figuring this thing out as I go along, so progress is a little slow.

Chuck

cfellows:
Thanks for the comments, Stew, Dave, Deanofid. After a lot of noodling and mind changing, I think I've worked out the details for the back end of the engine. The cam will have two lobes, 180 degrees apart and will turn at 1/4 the speed of the crankshaft. The cam will be coaxial to the crankshaft with double reduction gears 12/24, 12/24 to arrive at the 1:4 reduction. So here are a couple of pictures of the back crankcase cover. Here I'm machingin the back side and the timing gears will be inside the hollowed out part. The valve lifters will be set into the ring that has been formed. Further maching will be done on the ring and, in the end, it won't be a ring. Hard to explain what I have in mind, guess you'll just have to wait and see it. ;)

The ring part, btw, is 1 7/8" OD x 1 3/8" ID.

Chuck

Bogstandard:
Hi Chuck,

I'm glad you have decided to show us over here what you get up to.

As you know, I have followed your designs for a while now, and it always amazes me how well your little engines sound and run, and as yet, I have still only got one engine with your design of poppet valve made. Maybe a little further into the future, I will be able to make another one.

But please remember, on here, we would like to see your other projects as well. Anything goes.

John

sbwhart:
Hi Chuck

Thanks for showing your engine build I have a weekness for radials, the poppet valve looks interesting, just finished reading an engine book that has a design for a single cylinder poppet valve engine. hmmmmmmm :proj:

:D

Stew

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