Overcrank Single Cylinder Engine

[cfellows]

Great looking engine, Brian. To my eye, it's one of the prettiest you've built.

Chuck

 

[Brian Rupnow]

Thanks Chuck. Here we are in "Run-in" mode. 10 minutes at mid range rpm with the bolts all just snug, everything drenched in oil. Then 15 minutes with all bolts snugged up "fairly tight"---Then 20 minutes with all bolts torqued down to finished torque. Then it should be very free to turn over.

 

[lazylathe]

Go Brian!!!

I leave for one day and when i check in the engine is done!!! :bow:

Looks great and can't wait for the video to hear what it sounds like.

Is it going to get the blingy treatment plan??

Andrew

 

[ShedBoy]

Nice!!
Brock

 

[Brian Rupnow]

Now I'm at the difficult time. The engine overcrank mechanism works beautifully, and is totally free, to the point where a flip of the flywheel carries it through two or three revolutions. I am again fighting issues with my slide valve. The cylinder extends quite marvelously under air pressure, but doesn't want to retract when I shift the valve. The last time this happened, I took the cylinder end caps off and shifted the valve, resulting in a blast of air out of the cylinder passages and clearing a peice of what Marv so aptly called "Splooge"---and that fixed things. I can only hope that repeating this will clear anything remaining and fix it again. When I first assembled the cylinder, I didn't want to use a cardboard gasket between the slide plate and the aluminum cylinder, so I resorted to using some liquid silicone from a tube. This has now came back to bite me on the butt. The silicone extruded into the air passages when I tightened the four bolts holding the steam chest in place, and I think (hope) thats what is causing my issues with the piston not retracting properly. I won't be posting anything more on this build untill I have a video of the engine running. I can just tell from the action of the mechanism that its going to be a beautifull thing under power. And no, I'm not going to "bling" it out. I find that its quite enough to design and build these engines without the "blinging" process.

 

[JorgensenSteam]

Brian-

Good luck with sorting out the valve.

Perhaps a more obscure reason for making the ports and passages plenty big is to prevent obstructions.

Looks like it is going to turn out nicely.

Pat J

 

[SBWHART]

Good luck with sorting the valves out Brian, I'm shure it will be a great runner.

Just a few suggestions that may help:-

Slide valve rod where it goes into the back of the steam chest, it may be acting as a damper, just file a small flat on this part of the rod to let stuff escape.

I put the sealant stuff on with a small paint brush that way you can control how much and whare a lot better.

Good look again

Stew

 

[Brian Rupnow]

Now I'm stuck!!! I know what is happening, I just don't know why. When the slide valve is positioned in such a manner that it causes the cylinder to extend, everything works fine. I have lots of pressure, no problem. Now here is the strange part---When I move the slide valve over .100" (which is the full movement as per Elmers #33 engine which I copied the valve mechanism from), I know that air is routed to the other end of the cylinder. I have confirmed this by removing the end cap where the piston rod comes out of, and I get a good blast of air there. But--at the same time air is leaking past the valve into the other end of the cylinder, creating a back pressure, which keeps the piston rod from retracting. I confirmed this by putting the valve into the "retract" position and loosening off the bolts which hold the outboard end cap in place. As soon as I did that the air in that end was free to escape and the rod retracted with no problem. I have tried numerous positions of the valve rod, my parts are all built "on spec", I have lapped the valve sliding face, I have opened up the slots in the back side of the valve a bit to make sure its not binding on the nut or the valve rod, I have lapped the face of the slide plate. I'm running out of things to try. If anybody else out there has built Elmers 33 please let me know if the retract stroke worked okay. Science and logic tells me that it should. I have looked at the wear pattern on the slide plate where the valve slides on it, and it has a nice uniform shiny surface from the valve sliding on it.

 

[Captain Jerry]

Brian

This may not be the answer but just a place to look. When the port to the rod end of the cylinder is open to the steam chest, the other side of the piston (the head end) should be open to the exhaust and not able to hold any pressure. I would double check the width of the cavity on the slide valve to be sure that the exhaust port is uncovered and check for obstructions in the exhaust passages.

Jerry

 

[tel]

Did I mention those tiny exhaust ports and passages? I believe they have a lot to do with your problem.

 

[Brian Rupnow]

Further detective work shows that it is not the valve causing the problem. I put the new valve onto my existing Elmers 33 and it retracts the piston rod quite smartly. I put the Elmers 33 valve (which I know works) onto my Overcrank engine, and same deal---very weak or almost non existant return stroke. This bears further investigation. There may be something funky about my new cylinder.

 

[Captain Jerry]

Brian

Can you take the muffler off and blow air through the exhaust?

Jerry

 

[Brian Rupnow]

Jerry--Tomorrow I will take the cylinder off the engine and launch a full scale investigation. It may be that the piston is too sloppy a fit. It may be that I have pooched the hole spacing on the ports. It may be that there was enough misalignment in the main cylinder axis and the rest of the mechanism that it "oblonged" the hole in the cap where the rod exits during the "run in" period and is losing too much air around the rod. Maybe its losing too much air around the valve rod, where I didn't use a "gland" to seal it. I do know this---The pushing force developed by a piston is 3.14 x radius squared times air pressure. In my case, at 40 psi this cylinder will develop 12 pounds of "push". The mechanism moves with far less effort than that when I move it with my finger. I know that a number of tapped holes break thru into the cylinder bore. On the Elmers 33 this doesn't become an issue, because the 1/4" long piston just "skates" over the holes, and the holes are plugged by the threaded fasteners when everything is assembled. Maybe I will bore the cylinder larger and press in a liner to plug the holes and run an o-ring on the piston.
Something is very fishy, so tomorrow is investigation time.

 

[Tin Falcon]

The littlest of things can mess up the timing of the simplest of engines. Case in point I have a see through runner I call clair. Beutiful running engine I can blow in the thing and it will run. I had it at the reunion show and rough and tumble. I would not run for anthing I spent probably a couple hours over two day trying to get it to run. Simple timing I tried both directions ........ finay I figured out the problem the valve is a bicylce spoke with a teflon button . Somehow the button slipped. symetry was gone and the thing would not run a little pliers knurl button back in place an ran like a champ . I feel your pain Brian.
You will get it.
Tin

 

[RonGinger]

A few notes back you mentioned that you had the eccentric timed to be 90 degrees to the crank. Every steam engine I have built had the eccentric about 20-30 degrees off the 90 position. Look at a drawing for a reversing engine, like a Stuart Turner #1 or #4, or anything with Stevensons link and you will see the two eccentrics are at the 4 and 8 o'clock positions.

 

[dalem9]

Brian is it posabile the timing is 180 degree. or as in the one I build 120 out ? flip your ecentric over.,and see what happens. Dale

 

[dalem9]

Yea just as Ron said

 

[Brian Rupnow]

I've had that eccentric every which way but up!!! First I try it in the position suggested by Elmer. Then I rotate it a few degrees clockwise and try it again. If that doesn't improve things I move it a few degrees to the other side of the original position. This engine WANTS to run. Its just that there needs to be some good power on the retract stroke to get it "over the hump". I have even tried an extra flywheel but that didn't help. I have to sort out this cylinder retract issue before this thing will go.

 

[Tin Falcon]

sounds like something is not symmetrical and you may need to shorten or lengthen the valve rod to ballence things out.
Tin

 

[Brian Rupnow]

sounds like something is not symmetrical and you may need to shorten or lengthen the valve rod to ballence things out.
Tin

Did that Tin. The valve rod is threaded thru the nut which shifts the valve, so is adjustable. Likewise, the OTHER valve rod which runs to the eccentric strap is threaded into the eccentric strap and can be adjusted for length. The part thats making me crazy is that when I remove the 1/16" pin that holds the two valve rods together and shift the valve by hand I am seeing this hesitant/weak retraction.