It will not run.....

[Jmccrack]

Hey guys how open should each port be when it is in the open position. 100% 50% 25%?. I am sure I do not have enough offset.

 

[Ken I]

I always design mine for 100% open but as Charles Lamont stated yours should work perfectly well if properly timed.
When you stated that each cylinder runs perfectly well on its own - that begs a really daft question :- When you run them on their own are they running in the same direction ?
If not they are "fighting" each other.
Perhaps the more efficient cylinder dominates occasionally and it runs but roughly - it would also explain the apparently frictionless knocking.
My apologies but I had to ask.

Another diagnostic you can try is to hold the engine stationary by hand - apply pressure - then turning the flywheel by hand diagnose where the pushing and pulling occurs as well as any bypass, leakage or any other inappropriate flows.

Is your "D" valve sealing against its running face - are they both perfectly flat - show us a photo of the running surfaces.

Regards, Ken

 

[Jasonb]

With a port width of 3mm you will never get 100% opening as the eccentric throw is less, add to that your loss of movement and that reduces the opening even more.

The loss of movement you have measured will mean that air is not getting to the cylinder until it is say 25% along it's stroke and will then be shut off at say 75% of the stroke so you are only getting power for 50% of each stroke.

One way you may gain a bit more valve movement is to adjust the position of the arms. At mid valve travel the valve are wants to be vertical and the arm that goes to the eccentric rod wants to be at 90 degrees to that rod. If you still find this does not give enough movement of teh valve then increase the offset of the eccentric to say 0.125"

 

[Jmccrack]

Jason , Ken
I want to thank you both for your patience. I put a dial indicator on all the moving parts of the steam chest linkages and what I found was .098” everywhere except the slide valve itself. It was about .080”. I got the drawings for this unit off GrabCad. And as Brian Rupnow stated these engine are drawn but not built or tested. When I started to build this engine I ask to see if anyone had built it and not said they had. There could be slight errors. I am convinced now that .098” throw on the eccentric is not quite enough. I am going to make 2 new ones and put them on. It will only take an hour or so and with the time I have in this engine it is worth it. BTW can either of you guys point me in the direction of plans for a complicated build of a 2 cylinder horizontal with a governor and reversing.

 

[Jasonb]

Have you made the eccentrics right, you say you have 0.098" everywhere which is basically 2.5mm. the offset of the eccentric is 2.5mm which should give you 5.0mm or 0.197" movement. Did you make it with half of the offset?

Pic shows the 22mm eccentric boss offset 2.5mm as drawing and the 5mm movement you should get as it turns .

 

[Jmccrack]

Yes I should have said I have .098” travel from center in each direction. Total movement is .196”

 

[Jasonb]

In that case I assume the valve rod is also only moving 0.160" total

This may well be losses due to the angle of the levers, try it like I suggested above

"One way you may gain a bit more valve movement is to adjust the position of the arms. At mid valve travel the valve are wants to be vertical and the arm that goes to the eccentric rod wants to be at 90 degrees to that rod. "

 

[Jmccrack]

I will give that a try. by the way Jason what drawing program do you use?

 

[Jasonb]

Alibre

 

[Jmccrack]

When the slide vale is in the center position and air is applied to the steam chest it should seal will little or no air coming out the exhaust right?

 

[Jmccrack]

I I just added a short video to Media. If you look at it you see the slide valve open with air in the steam chest and then when I move the slide valve to the mid position you can still hear a lot of air escaping. The slide valve has lots of lube. Then you can see the engine run. The outer edges of the slide valve do not cover the outside edges of the ports. Also you can see the slide valve in motion does not uncover much of each port. I am thinking a bit wider slide valve and 2 new eccentrics maybe .120” offset. This is my fifth engine and my first 2 cylinder. I have never had so much trouble. But one sure learns a lot.
This is a 6 cylinder radial I am working on as well

BUT first thinks first.

 

[Jasonb]

When in mid position it should cover the inlets.

Can you measure the actual inlets as the valve I drew will cover the inlets shown on the drawing but if they have been cut wider then the small amount of lap won't be enough to cover them.

Even with the full 0.098" movement you are never going to fully uncover the inlet as that is wider than the available movement, this shows the valve 0.080" to one side

 

[Jmccrack]

.529

 

[Jasonb]

I drew the valve at 0.532" so should still just about cover your ports

Looking at the video your nut is loose in the slot and the threaded rod also looks loose in the nut all of which will loose valve movement.

 

[Jmccrack]

You are right it almost covers. When I measure they are close to the same. But when I shine a light behind the slide valve I can see a sliver of light on both sides. I have made 2 new slide valves that give me .012” lap and I have made 2 new eccentrics at .125” the old ones were .098. I have tightened up the connection points in the valve linkage. I will put it all back together this afternoon and report back.

 

[dwulfe]

Why doesn't the port face show any wear from the "D" valve?

 

[Jmccrack]

Good question. I think because I have been flipping over the copper wear plate. Since I widened the Dvalve I am getting good air retention when the valve is in mid position

 

[dwulfe]

I had trouble with D valves not seating on the port face. Irregular wear was a symptom as well as low power for given psi and hissing out the exhaust.

 

[Jmccrack]

Hey all.
HAPPY DAYS!!!!

I found my problem. When I first ran this engine I had no gaskets in it. I thought I will just see if it runs. It did. So I took it apart, painted it and put it back together ... with gaskets. I put a gasket under the copper wear plate that sits on top of the cylinder,and one between the steam chest cover and the steam chest. I put back together and there was no way I could get it to run. So I started posting to see if anyone could help. I got suggestions from all over and they were great but none worked. When I tried to run it and had the slide valve in mid position on the copper wear plate air would come out both ports and the exhaust port at the same time. I lapped the slide valve to the wear plate and still no joy,so I started looking elsewhere. Working on it today I put the slide valve back in center position air was hissing out and it hit me. With the gasket under the wear plate and slide valve on top of the copper wear plate there a .010” gap between the copper and the ports openings on the under side this is where all my air is escaping.

As soon as i took the gasket out she runs like a charm.

 

[Jmccrack]

Hey Guys
I uploaded a short video in the media section of it running on one side only. To all of you who said it was hissing to much air you were all right.
Thanks again for all the help