Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Hi,

I am in the process of scratch building a two-cylinder, 90Degree "V" steam powered wobbler. The bores are 3/4 inch, and stroke is 1-1/4. Cast iron cylinders, brass pistons, steel frame. I have the cylinders, covers, pistons, connecting rods completed with no known issues. My question relates to the inlet and exhaust ports in the frame. I know how to align them above and below the cylinder pivots, however I am unsure about the lateral positions. As the port in the cylinder makes its arch, at what point along that arch, should the port in the frame align with it? I know the steam should ideally enter a bit before TDC. Is there a placement that relates to the crank? for example; the ports should be in full alignment when the crank is about 5 degrees before TDC. I hope I am making sense to at least some of the experts here.

Your engine is double acting and will it need to reverse?

Usually on a oscillating engine when the piston is at TDC both inlet and exhaust ports are closed and only start opening together after the cylinder moves a few degrees past TDC.  The only oscillating engines that I know of that emit steam before TDC are single acting and are designed for high speed, often they are also uniflow. Given the size of your engine I assume it will run at a normal speed?

Take care.

Tony.