Elmer's 43 "Build" Questions

[Bear]

Some progress. Pretty much finished the cylinder assembly; except for an exhaust pipe and a little cleanup. Now to progress to the eccentric assembly parts.

[Bear]

Although gradual, I have made some progress. Connected the connecting rod today. Turns nicely. I can feel some compression. May try to hook up some air for a little test. Need to tidy the screw that mounts the connecting rod to the flywheel. Next to move on to the eccentric rod.

[RReid]

Looking good Bear. I too chose that engine as my second build.

[crueby]

Getting close, very nice!  Just looked up a video of one running (flyboy Jim's), very interesting eccentric motion on that engine.   

[Bear]

Thanks, Ronald and crueby.

[Dave Otto]

Looks like great progress!

Dave

[Bear]

Thanks, Dave.

[Bear]

Tried it out with some air. Piston pushed back with valve movement; however, I can not get the piston to move in (compression stroke) with valve movement. First of all, I think this should be doable at this point; please correct me if I am wrong, and I hope I am  .

If it should have movement on the compression stroke, any ideas on what went wrong?

[crueby]

Two things I would check first (I've had both issues in the past). First, is the port on the valve face for the compression stroke being opened as the valve rod moves forward? It could be that the valve slider is not centered properly, or the slider itself is too long. To check, take the cover off the valve chest and turn the engine over by hand, and see if the port at either end is exposed and covered again.
The other possibility that comes to mind is if the port at the end of the cylinder that connects to the port on the valve face is blocked by the gasket. I had en engine where that was the issue, trimmed the gasket and it ran.

[crueby]

Just looked back to earlier in the thread, noticed that there is a valve plate as a separate piece on the cylinder block. Check that all three ports are open, could be the one at the inner end is blocked by the gasket.

[Bear]

Thanks, crueby. I did check, and the port was not visible when moving the valve forward, so I elongated the port and it now opens when the valve is moved forward. However, that did not make it work. Also, as a reminder, I have not yet made the eccentric. By the way, no gasket on this engine, at least not that I saw in the plans.

[crueby]

Hmmm. Is the passage that leads from the port down to the end of the cylinder on that end lining up with the port in the valve face? Or could the opening into the cylinder be blocked by the cylinder cap on that end? Got to be a blocked or missing opening somewhere if the air is not getting through.As for the gaskets, unless there is a perfect mating surface on both sides, usually there is one between parts, the gaskets are commonly not shown on plans since they usually just show metal parts, and the gaskets are just made to match the shape/holes of the parts.When you apply compressed air, and move the valve, the piston is not moving - do you hear escaping air hissing from anywhere? How much pressure is the compressor supplying?

[Flyboy Jim]

Thanks, crueby. I did check, and the port was not visible when moving the valve forward, so I elongated the port and it now opens when the valve is moved forward. However, that did not make it work. Also, as a reminder, I have not yet made the eccentric. By the way, no gasket on this engine, at least not that I saw in the plans.

With the slide valve at one end of the throw is one port open and the other closed and then the same for the opposite port at the other end of the throw? I just looked at mine and as the slide valve is at one end, one port is open, the other is closed. Then as the slide valve is moved the other way both ports are closed for a bit and then the other post is opened with further movement to the other end.

Jim

[RReid]

Thanks, crueby. I did check, and the port was not visible when moving the valve forward, so I elongated the port and it now opens when the valve is moved forward. However, that did not make it work

The risk in enlarging a port is that now that port could be opening while the opposite port is not yet closed. Then there is pressure on both sides of the piston. It is usually better to remove material from the offending side of the valve, without changing anything on the other side.

[mklotz]

You can check that the air passage is clear by removing the valve, blocking the exhaust port and the input port to the opposite end of the cylinder with a bit of modeling clay and then applying air.  If the passage is clear you should be able to feel the air pressure on the piston.

It's conceivable, but, IMO unlikely, that there is a leak between the offending air passage and the exhaust passage.  Air meant for the piston would escape directly into the exhaust before reaching the piston.  Also, check for burs on the valve plate.  A bur that lifts the valve as it moves could cause such a leak.