Opposed 4 Compressed Air

[Kermit]

Chuck,
I may have overlooked it, but I'm wondering what you use between the brass manifold an the aluminum valve housing. Is it just a lapped metal to metal joint? The picture shows a tight seam there where the two meet.

I'll go back to lurker mode now. Beautiful engine too.


Thank you,
Kermit

 

[cfellows]

Chuck,
I may have overlooked it, but I'm wondering what you use between the brass manifold an the aluminum valve housing. Is it just a lapped metal to metal joint? The picture shows a tight seam there where the two meet.

I'll go back to lurker mode now. Beautiful engine too.

Thank you,
Kermit

Actually, Kermit, it's not even lapped. Just flattened on some wet or dry sandpaper over a piece of glass. We'll see how air tight it is when I get the engine running.

My biggest problem with air leakage is usually around the rotary valve and its housing. I tried to get a really close fit on this one, so we'll see.

Chuck

 

[kustomkb]

Great progress Chuck.

Its looking pretty sweet!

 

[cfellows]

Chuck,

I really like your engine. :bow: :bow:

The prop as a flywheel is a great idea. :bow:

Personally, I like the cylinders as they are.

Best Regards
Bob

Thanks, Bob. The prop will be more for aesthetics and I will probably not have much of a pitch on it. I'm more interested in having some weight and not so much on actually pulling air. Having said that, I don't want it to look to bulky.

I found a piece of cold rolled steel plate, 6" x 6" x 3/16" thick, so I'm planning to carve the whole thing out of that one piece. Going corner to corner, I should get a prop just under 8" from tip to tip. I'm still thinking about the best way to transfer the pattern to the steel blank. Once I figure that out, I'll use the band saw to cut the rough X shape out, then use the belt sander to shape the profile of each blade. At that point, I may put a small twist near the base of each blade. Next, I'll grind the air foil using an angle grinder, then shape and smooth with a file. We'll see how all that looks before I worry about final smoothing and polishing.

Chuck

 

[ref1ection]

Very nice looking engine. Can't wait to see it all come together. I also feel that you can't go wrong on the cylinders, tapered or not, still gonna look right.

Ray

 

[cfellows]

Got the propeller cut and smoothed to the profile today. For some reason, it looks like it's made of aluminum in the photo, but it's actually cut from 3/16" thick cold rolled steel. The prop is 8" diameter from tip to tip.

Here's the prop with the paper pattern still glued on. This is after I cut it out on the bandsaw and sanded up to the lines on my belt sander. I've got it mounted in the mill on my rotary table getting ready to mill out the thinner sections connecting the blade to the hub.

Heres a picture with the milling done and some filing also done to smooth up all the edges.

Now I have to noodle over what and how much will be done to it to finish it.

Chuck

 

[putputman]

Daaang Chuck, yesterday you were just talking about the prop and today here it is. :big: ;D :bow:

Can't wait to see & hear this one run. Always fascinated with your air engines.

 

[Deanofid]

Nice start on the prop, Chuck. It's quite a hunk of iron, and should give a fine flywheel effect.

Dean

 

[cfellows]

Well, I screwed up my courage, clamped the prop in my vise and put a 20 degree twist on each blade. Think it tuned out pretty good. Now I have to pull out the grinder and grind the proper airfoil curve on each blade.

 

[joe d]

Chuck

That's looking good! Do NOT get you fingers in the way of that one :big:

Joe

 

[cfellows]

Chuck

That's looking good! Do NOT get you fingers in the way of that one :big:

Joe

Thanks, Joe. Yeah, it's a bit of a brute. I'm planning to knock off all the sharp edges and corners so hopefully if I do get my fingers in the way, it'll just be a bruise.

Chuck

 

[cfellows]

This is actually going faster and easier than I thought it would. It's all hand work at this point, but I forgot how much I enjoy the hand work. I did a bit of wood carving a few years ago and, of course, a lot of wood carving as a kid. You can really get lost in this kind of stuff. I understand how GBritnel can get wrapped up in the file work.

I ground and shaped the leading edge of the prop blades in the last hour and a half or so. I used my 2" belt grinder to do the rough shaping, followed by draw filing to even it up and remove the grinder marks, followed by a light sanding with 220 grit wet or dry paper. Tomorrow, time permitting, I'll shape the trailing edges and smooth them up.

 

[cfellows]

Here's the prop, pretty much finished. Still have to balance it and decide on a finish. I've got it sitting on the engine crank to give an idea of size & scale. My first impression is the prop should be bigger. Any opinions? Regardless, I'm probably not going to make another one. :big:

Chuck

 

[slick95]

Chuck,

Actually the diameter looks just right. Typically a four blade prop would be shorter/smaller (like yours) diameter due to the added load from the additional blade(s). Also, a polished prop is generally only polished on the front (side away from the engine) and painted flat black on the other side (reduces reflection to the pilot).

Looking real nice. You're putting in some significant shop time in the this project. Thank for the pics...

Jeff

 

[Metal Butcher]

Here's the prop, pretty much finished. Still have to balance it and decide on a finish. I've got it sitting on the engine crank to give an idea of size & scale. My first impression is the prop should be bigger. Any opinions? Regardless, I'm probably not going to make another one. :big:
Chuck

That,s a mighty fine lookin prop there Chuck! What you could use is a spread water tower style stand with a wooden base, hint ,hint. ;D

And it looks plenty big to me.

-MB

-MB

 

[stevehuckss396]

Here's the prop, pretty much finished. Still have to balance it and decide on a finish.

send it out for chrome!!!

 

[Maryak]

Chuck,

Lovely job on the prop, (and the engine too). I agree with others. It looks proportional, (making it a pee pee i.e. proportional propeller), to the engine. :bow: :bow:

Best Regards
Bob

 

[NickG]

Looks brilliant! :big: :bow:

 

[stevehuckss396]

Hi Chuck!!

I am going back thru some of the old threads. Where are you at with the engine? Is there any plan to get back to work on this one? Just wondering.

 

[cfellows]

If you get the idea I'm jumping all over the place with my projects, you're right. I'm kind of working on different things as the mood hits me. This is an opposed 4 cylinder compressed air engine that I started a couple of years ago. Yesterday I completed the larger timing gear and got it installed. Today I made the pistons. I am very close to having this engine running (assuming it runs! :-[). I'm intent on getting this thing finished before I go on to something else, so I may actually get it running within the next few days.

Chuck