Discussion relating to the Penn Central, up until its 1976 inclusion in Conrail. Visit the Penn Central Railroad Historical Society for more information.

Moderator: JJMDiMunno

  by Allen Hazen
The experimental steam turbine locomotive, Class S-2, number 6200, was a 6-8-6. Various writers say it was originally planned as a 4-8-4, but because of the war-time unavailability of light-weight metal (nickel steel for boiler? aluminum for cab and boiler cladding?) the design got too heavy and it had to be built as a 6-8-6.
It was a huge locomotive: 120 sq ft grate (a size typical of large 2-10-4 types), 120 inch combustion chamber... Total weight is quoted as 589,000 pounds (engine alone: engine+tender was over a million pounds). Would a 4-8-4 of this size have been practical even with lighter-weight ingredients?
For comparison, the heaviest U.S. 4-8-4 were the Santa Fe 2900 class, at something like 510,000 pounds (engine alone). They were based on the design of the 494,000 pound 3776 class: the weight increase of 16,000 pounds was because the lighter weight materials used in the pre-war 3776 weren't available during WW II when the 2900 were ordered.

So how much would the S-2 have weighed if "strategic" materials had been available? Comparison with 3776 versus 2900 suggests that maybe ?? 20,000 ?? pounds could have been saved: this would still have left it significantly heavier than the heaviest 4-8-4.

Is there any surviving documentation on the evolution of the S-2 design?
  by Allen Hazen
Oops! I meant to post this to the PRR forum, and just noticed that it is in PC.
Can the moderator move it? I suspect people who go to the PRR forum would be more likely to be interested in steam than people who go to the PC forum!
(I've been thinking about the S-2, trying to look up some things, and might eventually post a follow-up.)