Opposed 4 Compressed Air

swilliams · Nov 30, 2010

very nice engine Chuck, sounds great too, Congrats :bow: :bow: :bow:

cfellows · Nov 30, 2010

Many thanks to all for the kind words. For those that asked, the engine does use a ball bearing slave valve which is located in the head. Here is a diagram:

The performance and sound of the engine can be varied by changing the type of spring. A heavier spring lets the engine run faster and makes for a beefier sound. Right now, the springs I used are pretty light weight making for slower speeds with less air pressure.

Chuck

ttrikalin · Nov 30, 2010

what a sound!
What do you mean you want to do some more work? Looks pretty finished to me. :hDe:

take care,

tom in MA

cfellows · Dec 4, 2010

Been thinking about the stand for my engine and started work on it tonight. I made it from a piece of magnesium I've had laying around for a few years. Gotta say, that stuff is a dream to machine. It's (a lot) lighter than aluminum and it doesn't gum up or stick to your bits at all. Nice, crisp shavings and beautiful finish, even with carbide end mills. It does cut slower than aluminum with my 4 x 6 bandsaw, not sure why. Yeah, I know it can cause a pretty exciting fire if ignited, but the kindling point is 883 deg F. so it's not likely to spontaneously combust. Too bad it's not more available.

This piece will mount to the underside of the engine, hollowed side down.

Chuck

Blogwitch · Dec 5, 2010

Very nice build and runner Chuck, just what we come to expect from you nowadays.

You've really cracked that system of operation now, the skies' the limit.

John

cfellows · Dec 7, 2010

Here's another video of my opposed 4 engine. As you can see, I've finished the base for it. From the bottom up, the first piece was made from 3" channel iron. The next piece was carved out of chunk of aluminum, 1 3/4" x 3/4" x 4" - the holes are 3/8" diameter. The vertical piece and the piece supporting the engine are both made from magnesium. Again, I really like machining that stuff.

[ame=http://www.youtube.com/watch?v=nFs24p4jYvQ]http://www.youtube.com/watch?v=nFs24p4jYvQ[/ame]

Had a bit of excitement in the shop yesterday. I was grinding and polishing the steel base for the engine on my belt grinder, and I forgot that I had been grinding and sanding the magnesium pieces on the same belt grinder. A few seconds after the sparks start flying from the steel piece, I had a wall of fireworks move across the top of my bench. there was quite an accumulation of magnesium dust on my bench top and it made quite the sparkler. Luckily there was nothing flammable on the bench top and the fireworks didn't really generate enough heat to cause any damage, but it was breathtaking for a few seconds.

I also had one of the silver solder joints on my built up crankshaft let go a couple of days ago. I cleaned it up and locktited it back together. I also pinned it with a 3/32 roll pin. I think it will hold now.

Chuck