Two Engines in One or Elmer Gets a Makeover

[tel]

Via an offset drive Marcello, same as my Pseudo Cygnet

 

[mzetati]

Got it!
The connecting rod hub doesn't make full turns, it slides on the cranckshaft pin.
That would be the "offset drive", I suppose.
Marcello

 

[Sshire]

Marcello
My guess ( since Elmer doesn't say) is that the intake is the red line.
I did as you suggested and removed the valve housing and applied air to each intake. I did get 120 degree turns from each intake. So it appears that the cylinders are getting air.
When I try with the valve and housing in place, I feel a "push" from one cylinder only which makes the valve the problem.
After measuring and checking the plans the only difference is that the recess in the side of the valve that faces the intakes is .08 larger in diameter than the plans. I'm remaking the valve now. If I had some clear lucite, I would almost consider making the valve in that to see what's going on with the intake.
Thanks so much for taking the time to help with this.
I'll report later today on the new valve.

Best
Stan

 

[arnoldb]

Hi Stan

I took a bit of time before replying because I wanted to give the plans a bit of a study.

The valve faces must be very flat and parallel, as must be the inside of the valve housing and the face of the crankcase against which the valve runs to minimise blow-by

This might sound like a silly question, but did you put the valve in the correct way around ?

If you still have problems after checking that and/or re-making the valve and still get a lot of blow-by, try to use some thickish oil (diesel engine oil or slideway oil) to generously lubricate the valve and see what happens; this might just do the trick by providing some additional sealing.

Kind regards, Arnold

 

[Sshire]

Hi Arnold
Thank you for taking the time to decipher the plans.

Not a silly thought at all. In my numerous removals and reinstalls of the valve housing, I did once put the valve in backwards.
The faces are as flat as my face mill, very fine grit Clover, and my skill level can get. I actually face milled a bit off the valve housing until I got a slight binding of the valve. Then, with very fine grit wet and dry, polished the valve until it just ran freely. That's why I'm remaking the valve, in hopes the the new one will like it's new home better than the last one.
I have been lubricating with Starrett Instrument oil but will use a heavier oil when the new valve is finished. I won't get a chance to try it until I return home this evening from the July 4th festivities. 236 If Bogs or any others from the UK are reading this post, the festivities are a yearly reminder that 236 years ago, we won. ;D

Best
Stan

 

[Captain Jerry]

Hi Stan

I'm a little late to join in on this thread. I hope you don't mind if I comment on this valve design at this point. I have studied it and I have used it as a model on some of my wobbling engines with some variations in air flow and size. In essence this is no different than a slide valve. It just happens to slide in three different directions. It is also different in that it is an inside admission slide valve,(the pressure is in the cavity of the slide and the exhaust is outside). There is also no way to adjust the timing except by changing the dimension of the various parts. Elmer's engine runs with dimensions that he used so if you are off in any of the critical dimensions you may have changed the timing to the point that it won't run.

These are the critical dimensions

Valve travel or eccentric throw. Elmer shows the offset of the small pin on the end of the shaft as 3/32". This control how far the valve body travels in one stroke.

Steam Port. Elmer shows these as 1/16" diameter. It's location is shown on a 5/8" PCD or 5/16" from shaft center. Any error in this dimension would be the same as changing the location of the steam ports in a slide valve.

Valve disc diameter. Elmer show this to be 3/4". If this dimension is off, the valve disc will open or close the exhaust port too soon or too late.

Valve face width. This is the difference in the outer diameter and the inner diameter of the valve disc on the engine side of the valve disc so it is vital that both inner and outer dimensions be maintained. If the valve face is too narrow it will open the pressure side while the exhaust side is still open and may fail to close the exhaust side completely.

Timing angle. The offset pin at the end of the shaft must be set at 90° in advance of the crank.

This is a single acting engine so air on the bottom side of the piston has no effect. The crankcase breather equalizes this with the atmosphere.

Minor differences in valve timing makes all the difference in performance and on this valve, the dimensions must be exact as there is no adjustment. By exact, I don't mean + or - .008". Elmer used fractional dimensions so 1/64" error shouldn't keep it from working.

I hope this is of some help but if I have not helped you understand the workings of this unique valve, I will be happy to elaborate on any point.

Jerry
In my designs, the size was changed so those dimensions are of no use to you. If you

 

[Sshire]

Jerry
Thanks so much for that excellent analysis of the rotary valve.
I checked all dimensions and all were way within Elmer's tolerances (if 1/64" is .0156). My largest error is .004 except for the valve.
I did remake the valve as the I.D. was +.008. It's now +.001.
I made it a few thou over Elmer's .250 thickness so I can reduce it and keep fitting until it just runs freely.
I expect to fit and test when I get home from the BBQ.

Thanks again.

Best
Stan

 

[Captain Jerry]

Stan

One other point about the valve. The number and size of the holes through the web are of no significance. If you make them bigger or add more holes, you can see what is happening at the valve face better. Pick any piston and set it at TDC. With the valve cover off, look at the valve port corresponding to the cyl at TDC. It should not be visible on the outside of the valve ring (exhaust) or the inside (intake) looking through the holes. Slowly rotate the shaft in the direction of normal rotation. The valve port should should begin to open on the inside of the ring and should be fully visible when the piston is at mid travel (90°) and begin to close being completely closed at BDC (180°). As you continue to rotate, the port should begin to open on the outside of the ring(exhaust) as the piston rises in the bore and is again fully closed as the piston comes to TDC.

It is wrong to consider the port and the tube as just steam (air) pressure inlet. It is also an exhaust tube and port, depending on the direction of the piston travel.

Actually, I guess I had two things to say. The hole in the center of the valve body should be a free or loose fit on the pin. Any binding at this point might tend to lift the valve body off of the port face.

Good luck with you trials. You are almost there.

Jerry

 

[Sshire]

Jerry
I think that's what's needed. I really need to see what's happening.
I know that the piston/ cylinder/air passages are ok because, without the valve, air hose directly on each hole in the port face rotates the crankshaft 120 degrees. I've tried that in both clockwise and counterclockwise and it works every time. That leaves only the valve.
I'll add 4 more holes and make them a bit larger so I can see what's what tomorrow.
That leaves only a road trip to Florida for a consultation ;D

Thanks again for all of the help.

Best
Stan

 

[Captain Jerry]

Sure Stan. Gas prices are down and Florida daytime temps seldom exceed 95°F this time of year.

Jerry

 

[mzetati]

When I try with the valve and housing in place, I feel a "push" from one cylinder only which makes the valve the problem.

You mean that by rotating the shaft 120deg none of the other two cylinders gets any air you can feel on the finger? There should be, however leaky the valve might be.
Either the valve is not rotating, or its not clearing the port. Have You not misplaced the 1/8drill into the valve crank?

Marcello

 

[mzetati]

I'd remove the covers and the valve housing, plug three of the four holes into the valve (a strip of adhesive tape on the inside should do) and apply thin air to the fourth to find out when (if ever) and in which position of the piston each cylinder gets air, by turning the crank by hand.

Marcello

 

[Sshire]

Marcello
If I remove the valve housing and valve and put the air hose over a port the crank rotates 120 degrees. Put the hose on the next port and the crank rotates another 120 degrees. Put the hose on the third port and the crank routes another 120. This tells me that the all of the cylinders are getting air and not binding. The only thing left to prevent this engine from running must be the valve.
I'm going to take Captain Jerry's suggestion on drill more holes in the valve to see what is actually happening when the valve rotates. Hopefully, this will reveal the problem.

Best
Stan

 

[Troutsqueezer]

I knew there was a good reason for my taking so long on my version of this engine and that is because all the great advice you are getting here will help me immensely as I go along. This is a worthwhile thread, Stan. Thanks to all for the inputs.

-dennis

 

[Sshire]

Dennis
I agree. Jerry's troubleshooting analysis is excellent. I'm determined to make this a runner.

 

[Captain Jerry]

Stan

In spite of what I said earlier, it is hotter than blazes in Florida, and my shop air conditioner can't keep up with the afternoon heat when the shop roof looses the shade of the big laurel tree on the south of the shop, so I will entertain myself by thinking about this engine and valve. Here are a couple of other thoughts.

When you send air directly to the cylinder through the face port, you get 120° of rotation. You should get very close to 180° of action. The force may be smaller at each end of the range due to con rod angle but with no resistance, air at the top of the cyl, force should kick in just past TDC and should drive the piston all the way to BDC. True, in a 3 cyl engine, each cyl is only responsible for only 120° but they all operate closer to 180° with some about 60° of overlap.

I found it very difficult to get this valve to operate reliably with a face groove and instead came to rely on flat valve faces and a very close fit on the opposite valve faces with the valve face and cover, lapping to final size as you have done.

I also prefer to use a lighter viscosity oil and generally use 10wt or lower. There is almost no load on these faces and 10wt gives better coverage and penetration between the faces.

Don't overlook air leak at the valve cover joint. Oiled paper works just fine. You can lap the valve to a tight fit and then add the gasket at assembly to provide clearance.

If you have to make the valve body again, I would leave the inside diameter slightly under and the outside diameter slightly over. This might rob some power at TDC as it will cause the valve to open slightly past TDC but the improvement in performance of eliminating air leaking over to the exhaust side of the valve face through the incompletely closed port will be beneficial.

While you have the paper and scissors out, you might think about a paper head gasket as well.

Another place to check is piston blow by which is very easy with a single acting acting cylinder and a closed crankcase. Just put your finger over the breather and apply air to one of the clinders. Any pressure in the crankcase has blown by the piston. If it is much, you may need to add O-rings to the pistons. You may find that
plugging the breather hole or restricting it will allow the engine to run but I would only do this as a test and at low pressure.

In my experience, a loose engine is a smooth engine. There is no oil circulation and no oil filter. I generally like to leave bearing caps just snug during run in with plenty of oil. Flipping the flywheel with a finger should get at least three full revolutions before stopping. I am happy to see contaminated oil flowing from the bushings. I like to put a tachometer on the engine and watch for speed changes as I snug up the bearing caps. If I can stop the engine by doing this, it is time to look at the shaft alignment.

This turned out to be longer than I had planned but it is really hot outside.

Jerry

 

[Sshire]

Jerry
Excellent! More to try. I've used Teflon sheets in other engines as gaskets and they seem to work well. I make a custom punch for whatever size I need.
I am only getting 120 degrees per port when air is applied directly.
Since I'm getting really quick at making valve bodies, I'll try one with your ideas.
I did drill extra holes in the valve and did as you said. My results match what you said should happen on each cylinder.
Even though I detect no binding, spinning the flywheel only gets me a bit over one rev. I can put the pistons back in the 5c collet and use wet n dry to very slightly reduce the O.D. it's a whole lot easier to make a new piston than my round, fancy cylinders if it gets too loose.
More to come.
Best
Stan

 

[Captain Jerry]

Stan

Ignore much of what I said. I'm going to sober up and try again tomorrow. The error? Air is supplied to the radial input, not the axial one. The valve is outside admission, not inside admission. I don't know what I was thinking. Everything else that I said is true except that the direction of rotation is reversed. When the shaft is turned in the direction of normal rotation, the face port should appear outside of the valve ring. There may be other errors in my thinking.

I will issue you a credit, good for any additional doubtful information that you may need.

Jerry

 

[bearcar1]

I will issue you a credit, good for any additional doubtful information that you may need

Will there be any sales or promotions for that item anytime soon? *beer* Rof} Rof} Rof}

BC1
Jim

 

[Captain Jerry]

Jim

For members in good standing on HMEM you will always get a substantial discount by including the PROMO CODE "WTF" with all request.

Jerry