I am building Ray HasBrouck's No.3 Horizontal Mill Engine. I have a cast iron block and would like to hear from builders with experience of running semi-rotary steam engines on steam. In particular I would like to know about the selection of materials for the valves. If simply corrosion, friction and running together are considered then bronze vales working in cast iron seems a good choice but further in his book Ray mentioned the effect of heat and expansion of materials in connection with running his engines on steam.
I am concerned about steam leakage with the semi-rotary valves. So far I have only found video of engines with semi-rotary valves running on air when leakage would not be apparent.
A similar situation must prevail in the popular MEM Corliss engine. Could anyone with experience of running these engines on steam comment on what valve material they selected?
Many thanks
Bob