A Corliss Mill Engine.
I have always had a liking for big, relatively slow running mill engines and I am also fascinated by different valve gears. So far having built small slide valve and piston valve engines the idea of Corliss with a radically different approach to valves seemed an interesting challenge.
Casting around for possible designs there is the very large Southworth engine with castings from Blackgates that can be built in various formats, however the casting costs are horrendous. I also came across a project on Model Engine Maker’s forum website. A few members had worked together to create an engine design built from stock rather than castings and the model developed the complex aspects of the valve gear and a barring system.
This looked like a doable project so I started gathering materials and doing more research. That involved a visit to the Chamber Street Museum where resides a small Corliss built in Kircaldy. This has a different approach to operating the valve gear, two eccentrics driving inlet and exhaust valves rather than the American design using a single eccentric and a wrist plate with many tiny linkages operating the valves together. The engine also has a single piece trunk guide and brace back to the crankshaft bearing.
So would it be possible to use the fundamentals of the MEM Corliss design? Well I am giving it a go!
The key part is the cylinder block. This is a lump of mehanite riddled with holes many more than a Swiss cheese however all needing to be very precisely sized and positioned! Having been somewhat unsuccessful with accurate positioning on my mill using the hand wheels and the spectacular improvement in accuracy I had when putting a DRO on my lathe I caved in and bought one for the mill. Thus equipped I set to and have made the cylinder block with only 2 minor and survivable mistakes!
Meanwhile adapting the design from the Original design to the “Scottish” version has been proceeding not on CAD but with pencil and paper tracing over the MEM drawings and adapting as I go along. Watch this space!
Kevan Shaw Nov.5, 2023
