View Full Version : PM Research Model #1

06-16-2010, 04:24 PM
Anybody built this model? If so how does the steam chest work? When the valve slides back and forth is it supposed to keep all three openings covered at all times or is it supposed to open one of the end openings to vent into the steam chest. I am working from a very old set of plans and a limited knowledge. Thanks Fred

06-16-2010, 04:29 PM
Can you post pictures or links so we can know what you are talking about? Thanks.

06-16-2010, 06:11 PM
without knowing that specific engine...
The end holes connect to each end of the cylinder. The center hole is the exhaust port. Steam enters the steam chest, and enters one end of the cylinder. The othe end of the cylinder is connected to the exhaust port by the slide valve, which usually has a small hollow in its face. The slightly higher pressure in the chest helps to pust the valve onto the port face and seal it.
So yes, the valve covers 2 of the 3 holes. Lap and lead of the valve might mean both inlet ports are covered for a short period of time as the valve moves from one end to the other, that depends on the engine design.

06-16-2010, 07:00 PM
Thank you! That just about answers my questions. It is waht I assumed but the demensions on the print don't allow that. I will adjust my machining. Thanks for your help! Fred