More of those indirect-Walsch-in-forward-gear engines than I thought. How about a Toledo, Angola and Western 0-6-0? Other switchers too-- L&NE and CNJ 0-8-0, NH 3-cyl 0-8-0, C&O 0-10-0.
The PRR 2-8+8-0 and 2-8+8-2 were indirect; PRR’s CC2 0-8+8-0 had indirect on the rear eng only, as did the first order of C&O 2-8+8-2s.
One of the best coverages of valve gear design was in the Bulletins of the Railway & Locomotive Historical Society back in the days when it was housed in the Baker Library. There were a lot of issues of the bulletin before that subject was exhausted. All steam engines of any application (not just railroads) resulted in serious interest in valve gear.
Nobullchitbids wrote:
“2. No one so far has mentioned the effect that superheating had on the problem. I’ve always been told that Stephenson only could be used with slide valves, which could not be used once superheating became the standard practice. This explains why Walschaerts took over at the turn of the last century even though it was invented half a century earlier.”
With reference to point 2, I would suggest that there were additional issues, other than those already mentioned, which lead to the demise of the Stephenson valve gear for locomotives.
1- The Stephenson valve had relatively large sealing faces, and were generally designed for outside admission of steam which results in the steam acting on the outside of the valve, forcing the valve against the sealing faces of the cylinder block. Thus, as locomotives grew in size, so did the size of the valve and the area of the sealing / wear faces. Since these valves were normally operating in a horizontal direction on top of the cylinder block, the weight of the valve (which in the larger sizes can be considerable) is added to the downward force of the pressure of the steam acting on the back of the valve, thereby increasing the friction forces between valve and block. As the boiler working pressure is increased so too does the aforementioned friction forces, which further increases the wear rates and reduction in engine efficiency.
2- With all outside admission steam valves, there is the issue of being able to seal the valve rod against live steam loss through the gland as steam pressure increases.
3- Superheating reduces the lubricity of the steam significantly. The resulting dry steam can no longer provide lubrication of those large sealing faces of the Stephenson valve, which again increases energy losses due to fr
C&O used Unaflow engines in its last carferries. In addition to the efficiencies mentioned above, the low back pressure allowed for quick responses to reversals, an important factor while maneuvering into and out of the dock areas.
I’m gonna guess that railfan admiration of valve gear in motion might not have been a design consideration. [%-)]
Actually, I am in complete awe of those engineers who could dream up such complex “monkey motion” in the first place. In fact, I have nothing but admiration for anyone who seems to understand valve gear workings as you do. If I study steam locomotives for another 50 years, I might begin to follow it.
Yet another simple question that turns out to be more complicated than we think!
I don’t know, but he may have been born before 1863–the patent was granted to him in 1912–perhaps he was born when “Cump” Sherman was President of what became LSU, and his parents admired the man then?
The engineering is to this layman incomprehensible. As a what if, would this valve system be of any value to enhancing the performance of a reciprocating steam locomotive?