Another Elmer's OCR

[cfellows]

Not to be outdone by MetalButcher, I too am building an Open Column Launch engine, however, with a 5/8" bore (outdoing MB by a handy 11%!). Take that, MB! . I was actually going to do a 1/2" bore, but just happened to have a round piece of brass very nearly the right size with a 5/8" bore. Always like to use up those "Mistakes" before cutting into the new stuff.

I'll also have to concede that MB is outdoing me in the design arena with his inclusion of hex shaped parts.

I'm going to use my slave exhaust piston design in the head which will simplify the reverse plumbing by about half by eliminating the exhaust holes and slots. I'm hoping it will also add a little bark to the exhaust note. Engines seem like more fun when they make a little noise! 8)

Chuck

 

[Metal Butcher]

I'm looking forward to following your build.

That slave exhaust piston design of yours sounds very interesting!

-MB

 

[rake60]

Interesting design changes.
Please do keep up updated on the progress.

Rick

 

[cfellows]

Decided to remake the block. The first attempt turned out badly with the crankshaft hole out of parallel in just about every direction. I tried drilling the hole using a toolmakers vice to hold the piece while I drilled the hole in my drill press. Bad idea! I try this method every few months, and it never works. Isn't the definition of insanity trying the same thing over and over and expecting different results?

I made the new block out of brass, and machined the valve body extension on the side, similar to MB's design. Elmer's original plans called for a 1" x 1" x 1/8" piece to be silver soldered on. With the new piece, I chucked the block into my 4 jaw and used the tailstock to drill the hole. Came out near perfect.

 

[cfellows]

Got a little more work done tonight. Started on the columns. Shouldered them down from 3/16 and threaded them 6-32 to screw into the base. The base is made from is 1.25" x 3/8" cold rolled steel. I also got all the air holes drilled in the block.

 

[cfellows]

Still more done today. Got the head finished and mounted, the crank disk turned and mounted, and the reversing valve turned and fitted. Still have to mill the slot in the back side. And, I'll probably see about milling the crank disk out on the crank throw side to help the balance and the bling. Never did that before, but looks like there's lots of help available on this forum!

Chuck

 

[Metal Butcher]

Hi Chuck. Its looking good! :bow:

Your moving along at a pretty fast pace, And its looks like your in the home stretch!

Remind me to never, ever, get into a contest with you! ;D

-MB

 

[cfellows]

Thanks, MB. You know, I honestly feel more like a blacksmith than a machinist most of the time. I'm always amazed when one of my creations actually works!

Chuck

 

[cfellows]

Got a few more things done in the past week or so. I'm in the home stretch and ready to start the plumbing. This always seems to be the tricky part and will determine whether the finished engine looks like crap or a thing of beauty.

By the way, how do you like the decorative extra holes in the top of the head? :-[ Not exactly as planned but not bad enough to do over! Maybe I'll drill matching holes on the other side of the head bolts...

Chuck

 

[cfellows]

Got the engine pretty well put together, but sorry to say, it won't run. There is just too much air leakage around the crankshaft. It won't put enough pressure into the head to move the slave valve.

So, it's back to the drawing board. Pretty engine, so I'll have to figure out another way to make it run!

Chuck

 

[Metal Butcher]

Got the engine pretty well put together, but sorry to say, it won't run. There is just too much air leakage around the crankshaft. It won't put enough pressure into the head to move the slave valve.

So, it's back to the drawing board. Pretty engine, so I'll have to figure out another way to make it run!

Chuck

Hi Chuck.
Would it be possible to drill and ream the crank shaft bore oversize? By press in two pieces of solid rod w/ Loctite to seal it from leakage you could drill and ream for a tighter fit.
If the existing crank is slightly under size then its replacement could be a solution.

I thought I would mention just a few ideas just in case they could help.

I'm very interested in understanding how your " exhaust slave valve" works.
Have you posted this information or a picture somewhere else on this forum?
Thanks.

-MB

 

[cfellows]

MB, here is a link to a diagram and explanation:

http://www.homemodelenginemachinist.com/index.php?topic=3268.0

This valve arrangement works very will when the high pressure air is controlled by a poppet valve.

Maybe I'll consider a valve disk on the end of the crankshaft... something like your 3 cylinder elmer's radial works.

Chuck

 

[Metal Butcher]

Thanks for the link Chuck.

That's a very clever design!

It explains the puzzling piece on the opposite side of the cylinder head. I would imagine that the spring tension and timing is VERY critical for proper operation.
This could be the area to experiment with in you effort to get your engine running.

Please post your progress and ideas.

-MB

 

[putputman]

That design certainly looks like it should work. You know the ball valve works because you have used it on the horizontal & John Deere.

The only problem I see is a possible timing problem. Would it be possible to bore the mount block larger and then use a bushing, with a shoulder on it, between the crank shaft & the mount block. This would allow you to rotate the flat portion separate from the crank for timing. It might also be easier to replace than a crank if you would have to change the size or shape of the flat.

Just another thought if all else fails.

 

[bearcar1]

Chuck, I have to agree with the others. Unless the spring pressure is way too strong for the application, it would seem to be a timing issue. That is if your fit of crankshaft to body is very good. It would seem that there is no accurate method of adjusting the lead/lag of the opening on the crankshaft. Where is ll of your pressure leaking from exactly ???

Jim B.

 

[Metal Butcher]

Chuck.

1) What is the diameter of you crank shaft?

2)How deep did you mill the flats on the crank shaft?

3) Does the center line of the intake port going through the bearing block intersect exactly at the top center of the outside diameter of the crank shaft bore?

4) What is the diameter of your intake port going through the bearing block?

I might be able to rule out a few things by comparing this information to the design changes I made on my version.

-MB

 

[cfellows]

Chuck.

1) What is the diameter of you crank shaft? 1/4 "

2)How deep did you mill the flats on the crank shaft? .050"

3) Does the center line of the intake port going through the bearing block intersect exactly at the top center of the outside diameter of the crank shaft bore? Yes

4) What is the diameter of your intake port going through the bearing block? .093"

I might be able to rule out a few things by comparing this information to the design changes I made on my version.

-MB

See answers in red...

 

[Metal Butcher]

See answers in red...

The specs on my build.
1) the same, at .250

2) Close, at .047

3) same, yes

4) Close, at .086

I don't see anything significant enough to draw a conclusion.

I should easily run on 1 or 2 p.s.i.

I its leaking significantly at that pressure, and refuses to run, it might just be the ball valve spring is too heavy.

Have you tried a spring with a smaller wire diameter?

If you have a spare spring, then trim off a quarter of a coil at a time to test the theory of too much spring pressure.

 

[cfellows]

I think the problem is a combination of the spring being too strong and the fit of the crankshaft in the block is too sloppy. I'm going to play with it some more to figure out what's wrong.

Chuck

 

[Metal Butcher]

I think the problem is a combination of the spring being too strong and the fit of the crankshaft in the block is too sloppy. I'm going to play with it some more to figure out what's wrong.

Chuck

Check to see if there is an exhaust port leak during the pistons downward stroke,
caused by the ball valve or its bore.

On your motor there is no exhaust porting in the leak area that would be affected. A slight pressure loss could be overcome with a little more intake pressure.

-MB

EDIT: Is it possible that there is a flow restriction caused by actuating this valve design with air pressure vs a more direct and unrestricted mechanical method?