Author Topic: Compressed Air Radial Engine (Read 40825 times)

cfellows · « **on:** February 17, 2011, 11:58:58 PM »

I started posting this build over on HMEM and decided to copy it over and continue posting progress on this board as well. It'll be compressed air using my ball slave valve arrangement. Operation will be 4-stroke using a 2 lobe, coaxial cam turning at 1:4 ratio to the crankshaft. Here's the beginnings of a concept picture:

I started out rough cutting a hexagon out of 1.25" thick aluminum tool plate with my 4 x 6 band saw. Then used a 1" arbor to chuck it up in my 5C hexagonal block. I used a 2" indexable carbide mill to face off each of the 6 faces.

Wound up with what seems like a respectable hexagon 1.25" thick and minor diameter of 2.443" (Yeah, I over shot the target diameter of 2.500" :-[)

Chuck

cfellows · « **Reply #1 on:** February 18, 2011, 12:00:22 AM »

I finished a prototype of one of the cylinders today. As you can see in the drawing, I've made a change in the design. Instead of using 2 long studs on either side of the cylinder to hold the cylinder and head in place, I decided to make the cylinder and the head one integral piece and use 4 SHCS's to faster the cylinders to the crankcase through a square flange in the base of the cylinder. I don't like the look quite as much, but it will be easier to build.

I still have a little work to do to the cylinder before I'm finished with it.

Chuck

cfellows · « **Reply #2 on:** February 18, 2011, 12:01:22 AM »

I made a few more chips today. I'm proceeding cautiously since I'm still designing as I go along. The first thing I did was radius the edges of the fins and the head on the cylinder. I was trying to make a radius form tool but decided in the end I was overthinking the problem. I ended up just using a small file and sandpaper to make the radiused edges. I also started doing some milling on the crankcase. I may leave the outside profile this way or I may go ahead and finish radiusing the parts of the crankcase between the cylinders like the drawing. Finally, I started work on the master connecting rod spool. It was my first foray into machining 12L14 steel (a piece I inherited from Shred, I might add). Lovely stuff to work with.

Chuck

cfellows · « **Reply #3 on:** February 18, 2011, 12:02:33 AM »

Managed to squeeze in a little more time on the radial. I'm designing and making different components to see a)if I can, and b)whether they'll fit together as planned.

In these pictures, I'm making up the components of the connecting rod assembly. There is still a lot of finish work to do on the pieces, but there's some tips here I thought worth sharing.

First picture is an overall shot of what I'm trying to get to. You can see the master rod in the upper left. The 5/16" curve at the bottom fits snugly against the center hub of the spool.

The three little pins are 1/8" diameter and are shouldered down on the end to accommodate a 2-56 thread. The pins slide through a 1/8" hole in the top of the spool and thread into 2-56 holes in the bottom of the spool. The pins will be cut off flush with spool and a screwdriver slot cut on the top end. This was the method Rudy Kouhoupt used on his 5 cylinder radial air engine.

So the first problem is to shoulder down the end of each pin to .085" for a length of 1/8" I wanted to use my minilathe for accuracy and to take advantage of the freshly sharpened tangential tool bit.

Since I don't (yet) have a carriage stop, I engaged the lead screw and used my leadscrew crank on the left end of the lathe to control the length of the cut. Since the leadscrew is 16 TPI, 2 full turns advanced the tool bit 1/8".

The next trick was to cut a 2-56 thread (squarely) on the shouldered end of the 1/2" long pins. So, I mounted the pin in the chuck of my tapping guide and laid the die, mounted in a die holder, on the table. This worked very well to cut the threads squarely.

Chuck

cfellows · « **Reply #4 on:** February 18, 2011, 12:03:30 AM »

I'm pretty pleased with way the crank assembly is turning out, especially the 3 shouldered screws that hold the connecting rods in. This fiddly little pieces tend to give me problems, but I took my time and they turned pretty good.

I plan to do some additional milling on the center spool to remove some weight. I may also do some light shaping of the connecting rods so they look less clunky.

Chuck

cfellows · « **Reply #5 on:** February 18, 2011, 12:04:02 AM »

Today I shaped the Connecting Rod Master Spool (is there a proper name for this piece???) I used a 1.25" end mill to cut the curved part. As you can see, I used the crankcase as a fixture to hold and position the spool for cutting.

I'm going to leave the connecting rods alone for now. Next I'll be working on the crankshaft.

Chuck

cfellows · « **Reply #6 on:** February 18, 2011, 12:04:31 AM »

I hogged out the crankcase today and mostly finished the other two cylinders yesterday. Still have to round off the edges and fins on the cylinders and crop the base flanges down to size. If you like exercises, try centering a six sided piece on 3 opposing sides in a 4 jaw chuck. Had me scratching my head a few times.

You can begin to get an idea of what it's going to look like:

Chuck

cfellows · « **Reply #7 on:** February 18, 2011, 12:05:07 AM »

I hogged out the crankcase today and mostly finished the other two cylinders yesterday. Still have to round off the edges and fins on the cylinders and crop the base flanges down to size. If you like exercises, try centering a six sided piece on 3 opposing sides in a 4 jaw chuck. Had me scratching my head a few times.

You can begin to get an idea of what it's going to look like:

Chuck

cfellows · « **Reply #8 on:** February 18, 2011, 12:06:05 AM »

Did a little softening and finishing work today. This first series of pictures shows the radial set of holes being drilled which will hold the front crankcase cover to the main crankcase. I thought the group might like to see the indexing fixture I have built into my drill press. I picked up this round table at a scrap yard a number of years ago. It already had the 24 holes in the sides (well, two holes on opposite sides are missing, but I work around those). I had to turn the spigot down to fit my drill press. Then I bored out the center to fit a 5C collet. Finally, I made an indexing pin and lever from some strap I had on hand.

And here are some pictures of the engine in its current state:

cfellows · « **Reply #9 on:** February 18, 2011, 12:07:00 AM »

I spent most of today doing remedial work. Paying the price for getting in a hurry earlier on. I discovered the cylinder openings in the crankcase were .010" closer to one edge than the other. And, they varied in size by + / - .005". So I set the crankcase up again and enlarged all the openings so they were centered and equal in diameter. Of course, that meant that the spigot at the bottom of the cylinders was now too small, so I had to build them up by soldering short lengths of brass pipe on them and re-turning them to fit the new openings. Now they are all consistent and fit nicely. I feel much better now! 8)

So, finally some pictures with the engine in an upright position. They always look better when you get some fasteners in place.

Yeah, I know, including the picture of the B-17 which adorns my shop wall is a bit over the top!

The overall diameter of the engine is a tad over 6". Here's a picture with a soda can for size reference:

Chuck

cfellows · « **Reply #10 on:** February 18, 2011, 12:07:45 AM »

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 · « **Reply #11 on:** February 18, 2011, 12:08:42 AM »

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 · « **Reply #12 on:** February 18, 2011, 12:09:24 AM »

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 · « **Reply #13 on:** February 18, 2011, 01:11:13 AM »

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 · « **Reply #14 on:** February 18, 2011, 02:02:04 AM »

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

Stew

cfellows · « **Reply #15 on:** February 19, 2011, 03:17:38 PM »

Got some work done since the last post. Here are some pics of the timing gears. The two larger ones are 40DP, 24 teeth, 1/8" thick and about 6.5" OD. The smaller gears are on the 3/8" rod and haven't been parted off yet. They will be 12 teeth and are .35" OD.

One of the 12 tooth gears will be loctited onto the crankshaft and drive a 24 tooth gear below it. The 24 tooth gear will be ganged to a 12 tooth gear, which will, in turn, drive the other 24 tooth gear which turns freely on the crankshaft. The double lobed cam will be attached to the second 24 tooth gear on the crank and will turn at 1/4 the RPM of the crankshaft.

Chuck

Brass_Machine · « **Reply #16 on:** February 19, 2011, 03:24:53 PM »

Stunning ofc Chuck

I have an idea for an engine... Might work well with your valve design... Hmmm...

Eric

saw · « **Reply #17 on:** February 19, 2011, 03:56:06 PM »

Nice, good work.

cfellows · « **Reply #18 on:** February 19, 2011, 06:45:08 PM »

Quote from: Brass_Machine on February 19, 2011, 03:24:53 PM

Stunning ofc Chuck

I have an idea for an engine... Might work well with your valve design... Hmmm...

Eric

Come on, Eric, you gotta share...

CallMeAl · « **Reply #19 on:** February 19, 2011, 11:06:08 PM »

Hey Chuck,

Just found this build, beautiful and intriguing work. I aspire to make something as nice as engines someday.

AL

cfellows · « **Reply #20 on:** February 21, 2011, 07:35:43 PM »

Got all the timing gears done. I decided to make the primary gear and shaft one integral unit rather than trying to loctite or solder the gear to a shaft. The second and third gears are ganged and soldered together. Then, the fourth gear rides on the crankshaft at 1/4th the speed of the crankshaft. The cam will be attached to the fourth gear, probably with a mechanism which allows for timing adjustments.

Chuck

greener121 · « **Reply #21 on:** February 21, 2011, 09:58:13 PM »

Very nice. Show the cutter for the gears, I'm assuming a Sir John cutter?

Brian

cfellows · « **Reply #22 on:** February 21, 2011, 10:03:38 PM »

Just used commercial involute gear cutters. I have a complete set of 40 DP cutters as well as an assortment of 24 DP, 32 DP and 16 DP. I want to try making my own hobb one of these days.

Chuck

cfellows · « **Reply #23 on:** February 23, 2011, 10:47:26 PM »

I think I've wrestled all the remaining design questions to the ground so the worst part is over. Today I made the back timing gear cover or back cover for the back crankcase cover which is confusing, I know. I've also drilled and tapped the holes.

Next, I'll be cutting away a significant part of the back cover and the sides of the ring to look something like this:

Chuck

saw · « **Reply #24 on:** February 24, 2011, 05:06:01 AM »

Nice

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Author Topic: Compressed Air Radial Engine (Read 40825 times)