The cylinders on steam engines need insulating and there are many ways of achieving this. On this page I’ve shared some ideas, options and a particular design of mine for the insulated steam engine cylinder for the wooden beam engine.
The cast iron cylinder from my wood and metal beam engine with a number of steps designed so that I could wrap the outside in wood and create an air gap.
The wooden planks in the image below shows how these then create an air gap and how the brass caps hold all of this together.
I machined the top and bottom caps from brass. In the case of the top cap I bored it larger than 1 inch so that it would easily clear the piston. It’s probably obvious, but worth noting that this is a single acting cylinder.
The hole in the bottom cap is to take the intake/exhaust pipe.
The cylinder was finally clad in bog oak and then two coats of varnish with a sand between coats.
The top ring was fixed with three brass 8BA bolts with round heads. I considered these didn’t need to be that substantial as there are no real forces acting on this ring. I fixed the bottom brass ring with three countersunk 8BA bolts. The three other holes are threaded 8BA and are designed to fix the cylinder to the beam engine frame. I tapped the centre hole M8 for the inlet/exhaust pipe fixing.
Oscillating Engine Cylinder Insulation
For my oscillating steam engine I took a more traditional approach and machined a step in the cylinder outer surface to create an air gap. The air gap is formed between the cast iron cylinder and the outer brass case. This trapped air is a good way to insulate the steam engine cylinder.
A cover was then made from sheet brass and this was then painted red and bolted in place with small brass bolts.
And so the cover and resultant air gap forms the insulated steam engine cylinder.