# Another Elmer's OCR



## cfellows (Mar 18, 2009)

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


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## Metal Butcher (Mar 18, 2009)

I'm looking forward to following your build. 

That slave exhaust piston design of yours sounds very interesting!

-MB


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## rake60 (Mar 18, 2009)

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

Rick


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## cfellows (Mar 20, 2009)

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.


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## cfellows (Mar 21, 2009)

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.


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## cfellows (Mar 22, 2009)

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


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## Metal Butcher (Mar 23, 2009)

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


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## cfellows (Mar 23, 2009)

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


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## cfellows (Mar 28, 2009)

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


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## cfellows (Apr 2, 2009)

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


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## Metal Butcher (Apr 2, 2009)

cfellows  said:
			
		

> 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


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## cfellows (Apr 2, 2009)

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


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## Metal Butcher (Apr 2, 2009)

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


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## putputman (Apr 2, 2009)

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.


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## bearcar1 (Apr 2, 2009)

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.


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## Metal Butcher (Apr 2, 2009)

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


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## cfellows (Apr 2, 2009)

Metal Butcher  said:
			
		

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



See answers in red...


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## Metal Butcher (Apr 2, 2009)

cfellows  said:
			
		

> 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.


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## cfellows (Apr 2, 2009)

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


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## Metal Butcher (Apr 2, 2009)

cfellows  said:
			
		

> 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?


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## cfellows (Apr 3, 2009)

Success!

I made another crankshaft out of a piece of 1/4" drill rod that was just a hair thicker than the first one. I also shortened the slave valve spring in the head by about 1/8". Runs pretty good now. Gotta put stops on the reverse lever and maybe twiddle with the spring some more. I'm also thinking about grooving the crankshaft on each end and fitting an o-ring to see if I can cut down on the air loss.

But for now, I'm happy! ;D

[ame=http://www.youtube.com/watch?v=BfsX2juV9O8]http://www.youtube.com/watch?v=BfsX2juV9O8[/ame]


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## GailInNM (Apr 3, 2009)

Congratulations Chuck :bow:
We all knew you would beat it into submission.
Gail in NM,USA


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## Maryak (Apr 3, 2009)

Chuck,

Pure Genius, (10% inspiration - 90% perspiration). :bow:

Winners are Grinners. :bow: :bow:

Congratulations. :bow: :bow: :bow:

Best Regards
Bob


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## 90LX_Notch (Apr 3, 2009)

Very nicely done.


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## kvom (Apr 3, 2009)

love the sound!


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## Metal Butcher (Apr 3, 2009)

Hurray! :big: Hurray! :big: Hurray! :big:

Glad you got things sorted out! :bow:

I don't think I could have handled another day of suspense!

-MB


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## bearcar1 (Apr 3, 2009)

Sounds like you threw a rod at the end.   ;D :big:

Nicely done.


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## rake60 (Apr 3, 2009)

Congratulation Chuck!
Looks and sounds great! Thm:

Rick


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## Shopguy (Apr 3, 2009)

Two thumbs up! Success with a very interesting design. 
Ernie J


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## PhillyVa (Apr 3, 2009)

Good job :bow: Chuck :bow: and it looks cool too.

Regards Thm:

Philly


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## SignalFailure (Apr 21, 2009)

I'm having trouble with my build of this engine....

http://www.homemodelenginemachinist.com/index.php?topic=4819.0

Most of my dimensions (although metric conversions) match those above but it won't quite go on around 5 psi 

The vertical air passage meets the bore right at the top as do the two horizontal passages.

The inlet tube is threaded 3mm on the outside with a 1.5mm (1/16") hole - I wonder if that's the problem?

I made a new shaft slightly tigher fit with shallower flats (around 0.75mm deep rather than the 1.25 ish on the original0 but still no joy 

Any suggestions please before it goes to the scrap box? :'(


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## Metal Butcher (Apr 21, 2009)

Paul  said:
			
		

> I'm having trouble with my build of this engine....
> 
> http://www.homemodelenginemachinist.com/index.php?topic=4819.0
> 
> ...



Oh no, don't put it in the scrap box. Tighter fits are good provided that the parts are free and smooth. The shallower flats will give you a shorter air intake timing. That may not admit enough pressure to cycle a full stroke. Check to make sure your flats are lining up with the valve ports. Check that the crank flats don't have excessive overlap at the upper port that leads to the cylinder piping. All of your port and passages openings should be at-or-above the specified size. Your piston to bore fit should be a smooth .001 clearance. Try to lap the piston and crank with a fine lapping compound. Metal polish or a abrasive tooth paste will work. Also check that the timing is correct. Check that you milled the flat for the crank disc set screw accurately in relation to the intake and exhaust flat angles. 

I can't tell you how many times I came very close to giving up. My desire to succeed was so strong that when a part went wrong I thought I was going to cry. Other times its a good thing that my shop is in a basement, so no one can hear what I need to say to release stress when things go wrong. I'm not a person that easily shrugs off loosing the better part of a day making a useless part. Its a struggle to overcome this human trait, and I'm probably not alone.

Don't give up!

You will find the answer, its just a matter of time.

-MB


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## SignalFailure (Apr 21, 2009)

Thanks for the encouragement - I only threatened it with the scrap box to try to make it work! 

I think everything you suggest is in order although I'd need to check the overlap of the flats.

I was reluctant to open out any of the passages as if it didn't work the main part of the engine would be ruined and with no milling facilities that was by far the most labour intensive part! I'll open them out with just the next or next but one number drill size if all else fails.

Incidentally I deliberately didn't make a flat for the crank disc screw as it would allow me a little more leeway when setting the timing (it'd also mean filing a third flat exactly perpendiculr to the two flats...not easy!). In fact I've yet to come up with a foolproof way to get the flats exactly 180 degrees apart as it is.

Thanks again, more tweaking to follow...


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## Metal Butcher (Apr 21, 2009)

Elmer has the timing correct, and its very critical! On my modified build I milled the flats accurately. On one occasion after I took it apart for cleaning the motor would not cycle a full stroke. Upon close examination I found the set screw slightly off and not perpendicular to the flat. Its THAT critical!

With no other way to get accurate flats, lock a shaft in a square block using a brass screw. Clamp the block in a vise and file or mill the flat. rotate (index) the block in the vise and file the other flat(s).

Here's a link to my up sized version of elmers #3 O.C.R. If you haven't seen it.
http://www.homemodelenginemachinist.com/index.php?topic=4412.0 

Best of luck.

-MB


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## bearcar1 (Apr 21, 2009)

Hi Pul, Would it be feasible to file the leading edge of that flat in order to obtain some 'degree-ing' of the valve opening? The same could be done to the lagging edge as well if required. A very shallow angle and very fine cuts, followed up by a stone would seem to be the order of the day. You'll get it, I have the faith in your determination and can not wait to see this one fire off!

BC1


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## cfellows (Apr 21, 2009)

Paul, what kind of compressed air source are you using?

Chuck


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## SignalFailure (Apr 21, 2009)

Metal Butcher  said:
			
		

> With no other way to get accurate flats, lock a shaft in a square block using a brass screw. Clamp the block in a vise and file or mill the flat. rotate (index) the block in the vise and file the other flat(s)



Doh! Why didn't I think of that?

Bearcar1, I'll open up the airways a tad first and see if that helps but a little 'lead' would seem to be a good idea.

Chuck, it's an aquarium pump that probably outputs about 5psi (it's rated at 10psi but I doubt it's accurate). I can get the engine to turn over with a car tyre footpump so maybe I'm expecting too much from this little air pump?


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## cfellows (Apr 21, 2009)

Paul,

With compressed air engines, the volume of air is as important as the pressure. You can have a lot of PSI, with very little volume and it might not be enought to run your engine. You need a combination of both to get adequate power.

Using an electrical analogy, PSI is like voltage and volume of air is like amps.

Chuck


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## Metal Butcher (Apr 21, 2009)

I would think that a diaphragm type aquarium air pump would not be sufficient.

If you have a piston type aquarium air pump it would probably be sufficient on a small engine.

I have a diaphragm type on my wish list as a way to do demonstration runs away from the mess and chaos of my shop. I don't think it will produce the pressure to run a single acting engine and especially one like #3 O.C.R. that uses a single cylinder port for both intake and exhaust. That's a bit of a problem as far as I'm concerned. I have a few motors that can run for short bursts on lung power alone. I tried this a few times and nearly passed out. The guests found it entertaining, but I did not!

I'm sure Chuck will be along shortly to shed some light on this subject.

Edit. This design of motor would run better at very low speeds in an inverted position. Gravity would benefit the up stroke (down stroke when inverted). Maybe I should consider mounting mine to the ceiling? Now that would be entertaining! ;D

-MB


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## mklotz (Apr 21, 2009)

Aquarium pumps are indeed low volume. Just look at the feeble bubbles they produce in an aquarium.

For on-the-go demonstrations, you can't beat an air brush compressor, e.g.,

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93657

All (~12) of my versions of Elmer's engines and others of similar size run nicely with this compressor. It's very quiet too. You can hold a conversation with it sitting on the bench next to you.

If the air brush compressor exceeds your budget, consider getting a refillable air pig, e.g.,

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41712

although you'll need access to a conventional compressor to fill it.


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## SignalFailure (Apr 21, 2009)

The aquarium pump will run my twin oscillator and 'Double Scotch' but as I mentioned above it wouldn't run 'Scotty' or the Elmer's Opposed I built (can't run that on anything!) so maybe a single-cylinder single-acting rotary-valve *is* too much to ask. I'm going to try all the tweaks and maybe remake some bits and see it it'll go nevertheless.

Thanks again for the pointers, appreciate it! 

EDIT: Thanks Marv... I was eyeing up a £25 ($25?) compressor the other day but maybe the £100 'proper' version would be sensible...

MB: Rest assured i've tried it every which way  My twin oscillator would only run when up-ended until it was well broken in!


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## SignalFailure (Apr 21, 2009)

Opened up the inlet 'tube' from 1.5mm to about 1.7mm. Opened up the horizintal passageways about the same and the vertical passage to about 1.8mm (I think the vertical passage isn't quite centred precisely over the top of the shaft). Lapped the face of the valve. Re-fitted the original shaft which I think was better. Re-soldered the flange to the copper tube as not certain it was 100% airtight. Fitted a brass spacer between crank disc and bearing.

Managed to get it running for a few strokes on the aquarium pump while held upside down! More tweaking should do it. Thanks for all the tips!

[youtube=425,344]2OlTK-oKS7c[/youtube]


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## mklotz (Apr 21, 2009)

On the OCR and other of Elmer's engines that use the OCR valve style, you can improve performance by replacing the spring that friction holds the valve disk in place with a small thumbnut. This requires loosening said nut to change direction but the pressure of the nut holds the valve down tight when running and prevents leaks.


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## rake60 (Apr 21, 2009)

When I built Elmer's OCR I didn't have a spring that fit the pressure
requirements. I cut a very short section of aquarium air line to fit under
reversing valve in place of a spring. It works just fine!

Rick


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