Sorry Russ, I did not include 3751 because that class was not born out of the experimental Madam Queen.
As first delivered, the 3751 class was built with 73" drivers (not 72"). They alone with the 3450 4-6-4s and the 4101 2-8-4s were built in 1927. They were the extention of the 3400 4-6-2s, 4000 2-8-2s and the 3700 4-8-2s. They were Santa Fe's first expanded use of a 4 wheel truck since the experimental 3829. Santa Fe saw that they could make a modest increase in the fire box and improve power and effencency in the process. Infact the 3450s and the 4101s shared the boiler and frame dimensions. The 3751s were the first 4-8-4s designed and as such were called "Heavy Mountains". After three major rebuilds, 3751 and 3759 (Kingman) very closely resemble 3768 (Wichita).
Though Santa Fe was pleased with the improvements of their three new designs, they wanted more improvements but with the stock market crash of 1929, they were afraid to do much but did order a lone locomotive in 1930 to test out other ideas. The main purpose for 5000 was to test these ideas including being used in passenger service on Raton. She also was used in freight and helper service too. The information from these runs and the experiments with 3752 directly lead to the development of the "Big Three" which was ordered in 1936 and is what the 3460, 3765 and 5001 classes were called. Another key was that after the three class order in 1927, Santa Fe learned too, that they really liked having as many similarities in their classes as possible because it made maintenance easier.
Another aside is that 3765 was to be streamlined just like 3460 and both locomotive's were to be protection for the new Super Chief. After 3460 was completed much heavier than planed, the streamlining for 3765 was canceled but not before the Stainless Steel handrails and break wheel were completed along with the solid pilot. These were applied rather than scrapped.
Sorry but I thought you might like to know.
Phil
