A Smokebox Vacuum Test for Romulus "Lesley"
As part of some research for the work on Lempor Ejectors elsewhere on this site, I decided to find out what level of vacuum my more-or-less-standard Romulus locomotive was generating. I built a water manometer, mounted it temporarily on Lesley's cab roof and went for a run.
The manometer was a simple loop of 3/8" (9.5mm) i.d. clear vinyl tubing clipped to a board and hooked up to an unused smokebox connection (photos one and two). In photo two you can see that the difference in water level is 1-3/4" (44mm), the maximum vacuum attained with the blower full on at 90 psi boiler pressure (photo three).
Photo four is a view inside the smokebox. The bright bit of tube is the manometer probe. The visible steam is from the four blower jets. No petticoat pipe is fitted and is not specified for Romulus on the drawings.
The maximum vacuum attained whilst running was 2-1/4 inches of water or 57mm of water or 560 Pascal or .08 psi. Pick your units, whatever makes sense to you!
Richard Stuart (near Perth, Western Australia) has measured 60mm maximum vacuum on "Como" a 2-6-0 with 2-1/2" diameter x 3-1/4" stroke cylinders, 7-1/2" drivers, 8" diameter steel locomotive type boiler, no superheat. He describes it as a "first generation 'couldn't be worse' design". Click the thumbnail for a larger photo.
Como 
For comparison, Romulus is an 0-4-0 with 2-1/8" diameter x 3.3" stroke cylinders, 6-1/2" drivers, 8" diameter steel locomotive type boiler, no superheat and also of the FGS "couldn't be worse" draughting style.
Richard's new Lempor-ejector-equipped Garratt locomotive has attained a smokebox vacuum of 85mm water.
On Saturday November 13th 2005, I track tested Romulus Lesley with her new ejector. Results were mixed. The four-hole nozzle did less well than the single hole one but the diffuser and mixing chamber were a phenomenal improvement, reaching 5 inches of water vacuum (127mm) over the old stack's maximum of 2-1/4" (57mm). Click here for The Lempor Ejector for Lesley page.
This is just a cool shot taken through Lesley's open firehole.
It does seem to show that the gases continue to burn within a 5/8" diameter boiler flue tube.