Re: Superheated side valves (NNG)

Rich, that is an interesting thought on the steam pressure. Allow me to share something regarding the Red River and Gulf, Crowell and Spencer Lumber Co. locomotives, that may (or may not) shed some light on this.
The two companies operated a common carrier (RR&G) railroad, and also hauled log trains up to 45 miles over the same RR using the lumber co. engines. Grades were up to 2%, and train length was limited to 18-20 cars. Between 1915 and 1923 the companies bought 6 new 4-6-0's from Baldwin for their operations. The first two were class 10-30-D (18 X 26 cylinders) and the last 4 were class 10-32 D (19 X 26 cylinders). All had 52" drivers, walschaerts valve gear, 180# BP and weighed virtually the same. As each engine was built, there were modifications and "improvements".

Here they are in order built with their "improvements"

RR&G #102, 10-30-D, 1915, Wood burner, saturated, balanced slide valves, alligator crosshead, single 9.5" air pump, diamond stack

RR&G #103, 10-30-D, 1918, wood burner, superheated, piston valves, alligator crosshead, single 9.5' air pump, Rushton stack.

C&SL #400, 10-32-D, 1919, wood burner, superheated, piston valves, alligator crosshead, single 9.5' air pump, Rushton stack

C&SL #300, 10-32-D, 1920, coal burner, superheated, piston valves, alligator crosshead, twin 9.5" air pumps

RR&G #105, 10-32-D, 1922, oil burner, saturated, balanced slide valves, multiple bearing cross head, 9.5" cross compound air pump

RR&G #106, 10-32-D, 1923, oil burner, superheated, piston valves, multiple bearing cross head, 9.5" cross compound air pump

I find the various mix on what they did on the engines, an when they did it most interesting. All non oil burners were converted to oil between 1923 an 1924, an all engines with only an single air pump were given an additional 9.5" or 11" pump at that time also.

#102 left early in the 1930s, and the 103 at the end of the decade.

#105 was retired in 1945, and the 300 in 1948. #400 and #106 were retained until the end of common carrier operations in 1953.

I have asked numerous "steam people" as to why that the 105 was built late in the series and was not superheated but have never gotten an answer.

The only things that I can glean from all of this is that as traffic dwindled, the smaller engines went first in the 1930's, then when the operations were cut back from 65 miles to less than 20 miles, the saturated engine was scrapped and only the superheated ones were retained until the end.

It is an interesting story, and I have often thought about writing some of it up for a magazine, but I surely would like to have more in the way of answers. Your comment about superheat not being of much value in engines with less than 200# BP may explain some of their thinking.

As a side note with all of this, all of the engines that I am familiar with on the Texas State RR are less than 200# pressure but even on a 20 mph railroad of only 25 miles, the single saturated engine boils up a significantly greater volume of water on every trip.