A different opposed piston engine

[Brian Rupnow]

Well there!! That's enough silliness for one day. I managed to squeeze in a set of timing gears, a camshaft, and 95% of the exhaust valve train. I have hidden the one standoff that would normally obscure the timing gears, just so you can see better how things are mounted.---Brian

[Brian Rupnow]

Just did a final volume check, and without taking any valve lead, lag, etc. into consideration, the compression ratio will be 5.4:1

[sbwhart]

Very interesting idea there Brian

Stew

[Brian Rupnow]

Aha!!!--Seems that we do have room for two valves and a sparkplug in there!! It just took a bit of wiggling. The exhaust valve is cam operated, the intake valve is atmospheric.

[Hugh Currin]

Brian:

Amazing how fast you're doing this design. If I could do such, it would take months instead of days. It's coming along very well.

I don't know if it would matter, but will the length of the "standoffs" be a problem? These cantilever posts could see high stresses, they are in the "connecting rod" load path. Would it be worth extending the front crank support up to support them at the front, simply supported rather than cantilever? On the down side, it would be harder to assemble and tend to hide the really cool mechanism.

Thank you for showing this development, a lot more fun and education than just seeing a final design.

Hugh

[Brian Rupnow]

Hugh--I've been doing this since 1965. If I can't do it fast now, then something is very wrong. The standoffs are 5/8" diameter cold rolled steel and are setting in 5/8" deep counterbores in the 3/4" aluminum backplate, held in place with a 3/8" steel bolt from the far side. It is only 1.25" from the face of the blue backplate to the side of the grey part which rocks on the standoff. They won't move. Remember, this is only a small "demonstration" engine, and will never see rpm's or loads that will move those standoffs.---Brian

[Hugh Currin]

Brian:

With 5/8" standoffs and 3/8" bolts it does sound like you addressed the concern. Sorry to bother.

I do like the idea of an open design, to see all the motions. Looking forward to more design, and hopefully the build.

Thanks.

Hugh

[Brian Rupnow]

This is a section taken through the center of the cylinders, and coincidentally through the center of the exhaust valve and valve cage. I have added the groove in the pistons for the Viton o-ring. The pistons never get any closer together than what is shown in this section view, and when they are fully at the other end of the stroke, the rings never get close to the slot in the rear of the cylinders. You can see where the exhaust exits through the right hand side of the green 3/4" block which holds the cylinders. I have not shown the exhaust pipe yet. The intake valve would be pretty well identical in a section view, except for the fact that it is an "atmospheric" valve, needing no cam to energize it, and the port which leads to the carburetor faces out the opposite side of the green 3/4" block from the exhaust port.

[Brian Rupnow]

As luck would have it----I was just getting warmed up with this new engine design because I don't have any "real" engineering work at the moment. This morning I got a panic stricken call from an inventor I do business with, who is "Just going to die!!!" if he doesn't get a new thing patented before the end of the year. (I don't know why.) At any rate, he needs a bunch of drawings to submit with his patent request----And he needs then RIGHT NOW!!!  Ah well, I never could turn down money!!--Engine development may slow down a little bit for a while.

[Brian Rupnow]

Wowsers!!!

[Brian Rupnow]

I don't see a great deal of sense in spending a lot of time machining a fancy flywheel for an engine like this. All of the "monkey motion" and neat stuff to see working will be on the "front" side of the engine. What I have shown here is simply a 4" diameter disc of mild steel or possibly cast iron, with a boss on each side. The boss on the side towards the main vertical plate is 7/16" long x 1" diameter, long enough to stand the main body of the flywheel out clear of the 3/8" bolt heads which are holding the stand-offs in place. The boss on the exposed side is 1" diameter x 1/8" long, and serves no purpose other than a cosmetic one.

[Pete49]

Another intriguing design Brian. I don't know how you come up with them but as usual a great write up on the way and as usual I will be watching again
Pete

[Brian Rupnow]

Due to the physical shape of this engine, I won't be able to screw the exhaust pipe nor the carburetor into the center block, because they will hit on the cylinders and not be able to turn. Consequently, they will both have to be attached with bolt on flanges and some of gasket. I like to run a bit of two cycle oil with my Coleman fuel to lubricate the cylinder and piston, so the exhaust is always messy--so---I ran the exhaust pipe out towards the back side of the engine. If I need to, I can add an auxiliary bracket from the exhaust pipe to the main vertical backing plate. The "intake manifold" for the carburetor will be an unusual shape, but it serves to move the carburetor away from both the cylinder and the sparkplug.

[Brian Rupnow]

Today I made a little time to add the snap ring grooves to the end of the cam shaft and "stand-off" pivot shafts, and downloaded some snap ring models from McMaster Carr's website. This pretty well completes the design of this engine, except for the ignition. I really wish I could just embed a magnet in the flywheel to trigger the hall effect switch for my ignition spark, but my understanding is that the magnet must be embedded in some material that is non magnetic, to work properly. I don't want to add anything more to the front side of the engine. I could use brass for the flywheel, but that would cost about a zillion dollars. Aluminum is too light to make a flywheel from. What do you think of this idea---Make the 5/8" thick flywheel from steel or cast iron, but drill a 1/2" hole 1.5" deep and Loctite in a 1/2" diameter x 1.5" long plug of round brass into the hole (close to the same relative density/weight) and Loctite the magnet in a pocket drilled in the outer end of the brass plug. I don't know if that would work or not.

[metalmad]

Hi Brian
What an amazing contraption, I have to force myself to resist the urge to build one as I have plenty on my plate as it is.
Nice one!
Pete