Here's a little more information on trucks, extracted from messages on the MFCL. Some of it it may be beyon the practical limits of S modelling, but it's still good to know. -- Tom Hawley -- Lansing MI
Truck sizes Wheel Journal Nominal Size Bearing Size Wheel Diameter Wheelbase 40 ton 5" X 9" 33" 5' 6" 50 ton 5½" X 10" 33" 5' 6" 70 ton 6" X 11" 33"* 5' 8" 100 ton 6½ X 12" 36" 5' 10" 125 ton 7" X 12" 38 6' * An exception to this wheel size is a 28" diameter wheel for a special 70 ton low height truck used with the piggyback and autorack flat cars. According to Jim Eager 13 Nov 04 ETTX and KTTX/TTKX trilevels were the ones with 28in wheels, and AFAIK, ETTXs still have them. BTTX/TTBX and TTGX bilevels have always had 33in wheels. Jim also said 29 Jan 2006 The size of bearing also increases with each step, and there are more springs in a different configuration. As the truck sideframe gets longer it also gets heftier, and to keep the bolster at the correct height the top of the sideframe is slightly swayback on a 100t truck, and much more so on a 125t truck. On 30 Jan 2006 Eric Neubauer wrote Heavier trucks require heavier spring groups so you'll also find a small increase in wheelbase to accommodate this and the larger wheels. The center plate size also increases. Your best bet is to check out the Car builders Cyclopedias which give standard dimensions. Freight car diagrams also show some of the information. Obviously, heavier trucks require stronger truck parts as well. Trucks represent 25% or more of a cars light weight, so they are cut to bone to minimize weight. Also, there are changes in nominal capacities circa 1964 and in the 1990s. Pre 1964... 30, 35, 40, 50, 70, 90-ton were standard 1964-1990s... 55, 77, 100 and 125-ton were standard 1990s on... 286 GRL replaces 263 GRL (since capacities are no longer stencilled on cars the concept of a nominal capacity has little use)
