Exhaust Manifold - Modern Solution

[jcbrock]

Yes, thanks Marty for both the valve info and the test setup pointer. I'd kinda figured that after John replied as the piping didn't really look like it would clear the smokebox.

[SPSteam2491]

Following up on the performance, what a difference the exhaust nozzle made! Testing the engine under steam at St. Croix for the Spring Meet, my wife was able to make 7-8 laps around the 1" track on Sunday with no issues and only having to stop at the station to service the engine (after fixing the ash pan and cleaning filters on Saturday). The exhaust that was once loud and sharp on flat track, was now subdued but came alive on the hill. We will be doing more testing with the engine during the 51st meet at St. Croix but initial feedback is largely positive.

And of course, the engineer approves of the fix

[JJG Koopmans]

Given your emphasis on performance and sound, I am wondering why you did no go any further and replaced the single orifice by a multiple one, say BigBoy style. The theory behind this is discussed in any modern textbook on fluid dynamics. I.e. four orifices give identical performance with 4 scaled chimneys as the single original as the American Buckingham already predicted in 1913. Since the 4 chimneys are replaced by the original one the relative larger length improves performance. This was investigated by MCDonald en Fox in 1966 for diffusers, tapered chimneys. So you would be on firm ground!
Kind regards
Jos Koopmans

[SPSteam2491]

The sound quality and performance were just symptoms to reviewing the root cause which was increased backpressure on the cylinders during running. I am aware of advancements made within the exhaust nozzle by increasing the number of orifices but due to time constraints and wanting to use a previously made exhaust nozzle, I was just focusing on the combination part between the cylinders. I may review additional changes to the exhaust orifice at a later date but for now, the engine runs (at some point you have to say "good enough" and move onto other projects). The next goal for this engine is to make the correct tender for it and work on detailing the engine to match a C&O F-19 Pacific.

[jeffsmith]

I made an exhaust pipe out of copper pipe. The drawing shows how this was done. I also used large radius elbows from the cylinder block. This was done on a 2.5" scale locomotive so I had more room to work with.