I’m not sure whether this question would be better suited to here, or one of the steam engine forums, but as I am a complete beginner I guess here is a good place to start.

I am currently thinking about how to build a small stationary steam engine model (half inch piston diameter sort of size), and was thinking about ways to construct the cylinder that doesn’t require lots of machining from a single large piece of stock or from a casting. I have come up with a couple of possible ways of constructing it from a couple of pieces of smaller stock, and am wondering what the shortcoming/limitations of these methods might be as they don’t appear to be commonly (or at all) used.

My first thought was to bore the cylinder channel through the centre of a piece of round stock, mill one side flat and then attach a flat block (the cylinder base) to the milled face with the steam inlet and exhaust channels already milled in it, as shown below (with a gasket between them in yellow).

Here I am assuming that there are bolts (studs?) that screw into round stock to which the cylinder base, steam chest and steam chest cover are attached. Also note here that I haven’t given any consideration to dimensions yet (inner/outer dimensions, bolt holes, steam channel sizes etc).

Are there any immediate issues with this approach? One thing I feel might be an issue would be that the cylinder heads (and gasket) would be sealing across multiple parts (including another gasket).

To solve this, I thought of instead not milling the entire cylinder flat, but instead leaving say a few mm at the outer diameter to provide a solid face to which the cylinder heads can seal against, as shown below (only shown on one end). The cylinder base piece could be extended in height so the cylinder heads didn’t overhang.

However another immediate issue I see here is that now the steam inlets to the cylinder would come out of the sides of the base, and as these can’t be bolted together I doubt there would be a good way to get a decent seal. I suppose I could bore the inlets in the cylinder such that they still meet top of the cylinder base (where the gasket is) but this seems a bit fiddly.

So this leads me to my current idea – mill the cylinder as above, and instead bond the cylinder base to the milled face to effectively create a block similar in shape to a casting, which can then be bored, drilled, have the steam channels/exhaust put in in the same way. Are there any issues with this approach?

In terms of how these pieces would be bonded I am not too sure yet. Assuming the whole cylinder assembly would be made of cast iron I have the following thoughts:

• Welding:
  • might be quite a lot of heat into a relatively small component – risk of warping?
  • welding would only create a seal around the edge, so there would be no seal around where the steam channels cross the base/cylinder interface
• Silver soldering:
  • possible similar concerns as welding – heat distortion, only sealing around the edges (or at least as far as the solder wicks in between the pieces
• Adhesive:
  • JB weld seems a good option as it would cover the entirety of the mating faces and so should provide a seal around  the steam channels.

So I guess this is a long way of saying my current idea is to JB weld to pieces of cast iron together into a ‘pseudo-casting’ and then progress from there as normal. Does this sound viable or should I just stick to the tried and tested methods?