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

[Dan_the_Chemist]

Looking forward with great anticipation.

[sid pileski]

Brian- the dash pots aid in closing the valves quickly.
the Corliss design was probably the high point of steam design and efficiency for reciprocating engines.
Is this the MEM design?

Sid

[brian Rupnow]

Sid--I'm not really sure. A fellow from the States sent me this model, but he said that he had never built it. I don't know if the MEM one had the more complex intake valve mechanisms or not.

[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.

[J Tiers]

That should be a very interesting build.

[Bluechips]

Subscribed to this one. A Corliss is on my bucket todo list if I ever get around to building models. If I remember correctly, there is a full size Corliss mill engine at a park about 60 miles from my house. Last time I saw it was many years ago (at least 15) and grass was growing up around it. It might not even be visible anymore. It was a very big engine. There were several other engines on display, too, but It didn't look like anyone was keeping the display up.

[Doozer]

....... 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

I do appreciate Corliss uniflow engines, but you're right.
Be dammed if I am going to machine up 1/16" dia screws
to make something look scale model correct. Smart idea
to use 4-40 screws. Time is short, and I would rather make
engine parts, not microscopic screws. HeII, even watchmakers
buy screws. Some of these model guys have OCD that is
crippling to their attainments in life. Good choice.

-Doozer

[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.

[Richard P Wilson]

Nothing looks worse than an engine with a flywheel thats too small. IMHO

[Bluechips]

Brian, just a thought to simplify the valve bearings with the 4 tiny screws since this doesn't sound like pure scale model build. Could they be made to slip into the cylinder body and be locked into place with a small set screws from the top (on the top bearings) and bottom for the bottom bearings? The green plate on the top of the cylinder could be enlarged to cover the screw holes. The ones on the bottom would not be seen anyhow. Might need to mill a flat on them to prevent them from trying to rotate.

BTW - I will look to see if I have a section of tubing that would make a 7" diameter flywheel. No guarantees, but I have some large short stuff stuck back. If I do have it, I would be happy to give you a piece.

Edit: I should add that I'm working today and it would be tomorrow before I could get out to the shop and look.

[brian Rupnow]

Thanks Bluechips.--Where are you?--Brian

[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.

[Doozer]

Nothing looks worse than an engine with a flywheel thats too small. IMHO

How about a woman who was in a hatchet fight, and she didn't have a hatchet ? ? ?

-D