I have recently run across a number of references to the 1500s as being "T-54 class". I do not think I have ever seen such a designation on any Frisco reference unless it is supposed to be shorthand for Tonnage Class 54. And were not they Tonnage Class 56?. Did the Frisco ever use such a designation internally, or is it picked up from an assumption about the way the Frisco worked? I know many other railroads used such designations, the Missouri Pacific (MP) being an example near to home, as in BK-63 for their 63" driver Berkshires. But, I have not run across such usage in or on anything Frisco.
The designation appeared as “sub lettering”, which appeared below the Frisco lettering on the cab. As built, the 1500s were T-54. The Frisco also tended to include the booster engine tractive effort (TE) in the tonnage rating. Take a look at the diagrams and early ETT’s.
Changes to boiler pressure (BP) and driver wheel diameter altered the 1500s tractive effort (TE). Delivered with a BP of 200, which the Frisco later boosted to 210. Driver diameter was increased to 69.5". MEP = mean effective pressure. Using Cole, here are the differences: BP----Stroke---Cylinder Diameter---Driver Diameter---MEP---TE 200---28"------28"---------------------69.0"----------------0.85---54084.64 210---28"-------28"---------------------69.0"----------------0.85---56788.87 210---28"-------28"---------------------69.5"----------------0.85---56380.32 I have been in both T54s.
Don, That was the impression that I have always gotten from talking to people and reading. At least until recently when these T-54 references started popping up. It seems to be that people unfamiliar with the railroad confused the Tonnage Class designation with the class designations used by other roads, such as the Missouri Pacific. Karl's chart neatly shows why some of the diagrams show T-56 class. If anyone has Frisco documents, other than the diagrams, referring to the engines by their tonnage classes, I would be interested in seeing them. Karl refers to ETTs, but I am unfamiliar with that reference.
The Employee Timetables (ETT's) include a Locomotives By Tonnage table in the Special Instructions section. I do not believe that this "classification" was ever used to identify a locomotive or the "class" to which it belonged, per se. That was done with the series number, as in, 4000-class, 4200-class, etc. I do not believe that one can equate the Frisco's T-number to other railroad' systems, as in, K-4, L1, M1, Y-6, Ja, etc. Soon after the Memphis Road merger, an attempt was made to develop a standard locomotive taxonomy, which would be displayed on the coonskin number plate. It was known as the Hancock system. Will have to post that system later. Search the site for the string, "hancock".
