Hello there again. I have been wondering something about the Mason Bogie type engines, specifically the ehxaust. I heard that the blast pipe moves in an ark from left to right, but with that, how does the steam shoot out perfect from the engine? Especially with engines with more slender smokestacks?
All the effective flow shaping of the entrained exhaust plume takes place in the divergent section of the front end; any offset elements in the entraining jet are transversely 'randomized' a number of diameters well short of the stack exit. See Koopmans' "The Fire Burns Much Brighter" for the relative factors in different front-end geometries.
Incidentally Koopmans has just (Aug 24) published a paper on action in multiple-nozzle front ends:
https://www.researchgate.net/publication/343694913_On_the_calculation_of_steam_locomotive_front-ends_with_more_than_one_exhaust_orifice/link/5f3a77ab92851cd302fe1e79/download
I... don't see how this answers my question. Maybe I said something off... does the blast pipe always aim upwards at a 90 degree angle? Is there a ball joint that the upper end of the ehxaust is attatched to? Any plans for inside a mason bogie?
Sorry; I thought you had done your homework. The arrangement Mason designed is set out in patent 177343A (of 1876; an improvement on what Fairlie used on his double-bogies, and this clearly shows the arrangement used and Mason's reasoning in adopting it.
https://patents.google.com/patent/US177343A/en
The exhaust nozzle is rigidly fixed to the cylinder saddle; the stack rigidly fixed in the smokebox. An extended petticoat is provided, so the entrainment area is relatively low (appropriate for a nonsuperheated engine) and this is wide enough at the bottom to accommodate the swing of the fixed exhaust pipe. Exit of the nozzle is higher than the skirt so there is no tendency once 'stack action' has commenced for backflow even at maximum stopped motor-truck rotation.
Some of the obvious practical issues, like higher gas and cinder cutting at high motor-truck deflection angle, will suggest themselves. If you were to adopt the theory of a curved diffuser bell-mouth, its entraining curve might have to lie substantially below the nozzle exit level, but it might be fun either to model the physics and flow involved or to build the arrangement (perhaps at Greenfield Village?) and test it. Combustion-gas flow shaping might ameliorate some of the accelerated wear at the sides of the petticoat that I'd expect in western narrow-gauge practice...
Note that Mason's steam arrangements, and valve-gear arrangement on curves, were far more intricate.
I have no direct knowledge of plans more detailed than David Fletcher's, but these are for models which usually have very differently proportioned exhaust flow and induced-draft arrangements. I suspect Greenfield Village may have researched the detail drawings available, or done measured drawings to reconstruct them.
(I reward Ross Crain for providing an interface to Fletcher's material but it's a trip down dawn-of-the-Internet 'aesthetics' memory lane as you do...)
http://www.ross-crain.com/rr_dsp6e-fletcher.htm
The plan for the exhaust is just what I needed! I tried very hard over a few weeks to try and find any plan. I only found one but it did not work well for me since it was from the side view and not the front. And all of what ya said makes sense now and I appreciate it!
I think part of the problem is that most of the "plans" are for models, and very few of those have any interest in modeling the inside structure that is never seen. I think there are comparable problems with modeling the flexible joints and hangers of some modern articulated and booster-equipped locomotives.
It's probably an interesting subject why the design was not made with a couple of ball joints and sleeves to optimize the draft no matter where the bogie was turned. This is a matter of first cost, but much more of maintenance.
To make a flexible arrangement work, you need a fixed opening for entrainment that holds the nozzle centered at the right distance inside the petticoat. As the bogie steers from left to right this tilts slightly but that will matter little to the flow of combustion gas.
Problem #1 is providing the flexible connection of the exhaust stand. Theoretically there are a number of options here, including a ball joint and various 'flex' tube types. Exhaust steam pressure is probably in the low to middle twenties peak value in steady state, but drifting might get weird; this is also where cinders not ejected from the smoke box gather by gravity to become a caustic abrasive paste in any steam leakage...
Meanwhile up above the entrainment zone you have need of another flexible joint that also has to expand or st life slightly to accommodate movement. This might be done with a tapered bellows or a hollow ball joint, as there is no pressure; the problem is that cinder cutting is likely to cause the same problems as in ATSF 'hinged boilers' in the wacky-articulated years.
Much of the accelerated wear in Mason's version is limited to regions of what is drawn as a simple conical petticoat, easily formed and riveted or seamed using a mandrel. The rest of the stack could be hung appropriately to carry the assumed moment of a filled spark arrester outside the smokebox; that might be high and at a long lever arm to the internal locating supports.
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