Brian builds a Corliss

[Brian Rupnow]

We're half-way thru February and I need to build something. The Corliss steam engine is a very interesting design, and it seems that there are two designs available on the net. One is as per the original full size Corliss engine, with two auxiliary "dashpot" cylinders to aid in closing (or maybe opening) the intake valves. The intake valve mechanisms have a complex design, incorporating a  two piece rotationally slotted mechanism which works with these "dashpot" cylinders.---Then there is the simplified version, which does not have the dashpot cylinders nor the complex mechanism on the intake valve apparatus. Instead, it has two adjustable links driving the intake valving and two adjustable links driving the exhaust valve mechanism. I will be building the second simplified version. A gentleman was kind enough to send me a 3D assembly of the second type of Corliss engine and I will be revising the design to suit my own fancy. This is the engine as it was sent to me. The first obvious change I see is that all 4 of the bearings for the valve shafts are using 1/16" diameter hex head bolts. These will be upgraded to #4 socket head capscrews. I like the look of socket head capscrews better, and I seriously doubt that I could drill and tap sixteen 1/16" diameter threaded holes without breaking off the tap. Stay tuned---it should be an interesting journey.---Brian

[Craig DeShong]

Corliss models seem to abound.  I have a friend who's building one from a casting kit, though he doesn't post here.  I'll be watching, Brian.

[crueby]

Will be watching along here too!

[Art K]

Brian,
This sounds like a very interesting project. I intend to build a steam engine some day, but think I'll do a standard one first.
Art

[Brian Rupnow]

I have built quite a few steam engines, but they all had the more conventional slide valve on the cylinder. This one will be something totally new for me. When I import a model that was made in some other software than mine, every individual component has to be fixed in place, as none of the mates that position the parts in relationship to one and other get imported. And since this is something totally new to me and was never built by the man who sent me the design, I have to basically recreate the entire engine from parts to which I add all of the mates. This lets me rotate the flywheel and see the piston move thru the correct stroke to make sure that everything is correctly positioned. As I recreate the parts, I will also make any changes I want as I model them.

[Brian Rupnow]

At this point in time I have opened a lot of the individual components and saved them into a new assembly file, adding proper "mates" as the parts were added. This shows me that as the flywheel and crankshaft rotate thru 360 degrees that the piston will travel correctly and remain centered in the cylinder. That is a GOOD thing. Tomorrow I will start changing the things I want to change, and add them into the assembly as I build it.

[kvom]

Dashpots close the input valves when there is cutoff by a mechanism that frees the valves momentarily.  The cutoff mechanism is difficult to attain in model scale.  As shown in your 3D model, the alternative is to have the governor control the timing of the valves.

[Brian Rupnow]

The flywheel shown on the original model is 7 1/4" diameter. The largest piece of pipe I have is only 6" diameter. Before I do any actual "building" I will call my steel suppliers tomorrow and see if anyone has a short length of larger diameter pipe. I don't care for the 2" thick baseplate on this existing model, but I have to decide on the flywheel diameter before I start changing anything.

[Brian Rupnow]

The cylinder block is 2 1/8" square. I have a chunk of round aluminum here that is 3 1/2" diameter x 3" long, which would allow me to cut a 2 1/8" square out of it. I don't want to make the cylinder from aluminum because it has a high coefficient of friction, but I also have some 1 1/2" diameter cast iron from which I can make a thin walled sleeve and epoxy it into place as a liner. I have to look thru all the build threads on this. I seem to recall reading about someone who did the same thing.

[crueby]

On mine I made a center sleeve with blocks around it, since I couldn't turn the full size block easily. May have been others too.
Remember that the valve bores also have turning valves in them, you may want to sleeve them as well.

[Brian Rupnow]

Chris---Couple of questions for you.-- What material did you make the cylinder block from, what did you make the liner from, and what was the outside diameter of the liner you used? It looks to me like the maximum diameter you could go to on the liner would be 1 1/4" or you would be into the threaded holes to attach the small diameter end-cap on the non rod side. This would only leave a 1/16" wall thickness on the liner---unless you went to a larger size end-cap with larger bolt pattern on the non rod end of the cylinder. This is all assuming that your cylinder had a 1 1/8" bore same as the MEM Corliss.

[crueby]

Chris---Couple of questions for you.-- What material did you make the cylinder block from, what did you make the liner from, and what was the outside diameter of the liner you used? It looks to me like the maximum diameter you could go to on the liner would be 1 1/4" or you would be into the threaded holes to attach the small diameter end-cap on the non rod side. This would only leave a 1/16" wall thickness on the liner---unless you went to a larger size end-cap with larger bolt pattern on the non rod end of the cylinder. This is all assuming that your cylinder had a 1 1/8" bore same as the MEM Corliss.

Hi Brian,
I used 303 stainless steel for the engine block parts, all built to the same dimensions as the MEM plans. The liner started as a piece of 1.5" diameter bar, stepped down at both ends. The build is here, showing how I pieced things up, the first post includes a diagram with the dimensions I used (obviously long before I had any CAD software! )

https://www.modelenginemaker.com/index.php/topic,5980.msg117702.html#msg117702
The way I did it was more complicated since I fit the liner into a multi-piece block, to keep the block parts small enough for the Sherline, plus I was still learning how to handle larger pieces. If I was going to do it again today, I'd start with the full size block and bolt one end to a faceplate for boring rather than trying to use the chuck. Learned a lot doing that build.
Oh, and in that build I made two cylinders, and extended the crankshaft to make it a twin version, pistons offseet 90 degrees.
Chris

[Brian Rupnow]

Thanks Chris---I hadn't seen that build before. Fantastic stuff!!!---Brian

[Brian Rupnow]

Probably I will go with a 1/2" thick baseplate supported by four legs (which I haven't shown yet). This will let me keep most of the mechanical components the same as originally designed on the MEM website.

[Jo]

the same as originally designed on the MEM website.

Our MEM Corliss model engine was designed by our moderator Bob  Holme (Maryak) who we sadly lost at the beginning of 2020 

Jo