James Eckman wrote:

White notes that several railroads upgraded their freight cars carrying
capacity through the judicious use of a little paint! So yes some
freight cars in the yard 'evolved'. He also notes that most of them fell
rapidly to pieces under this overloading process. I'm not sure how long
this went on, at least through most of the wooden freight car era at least.

When did the Master Car Builders Association adopt the system whereby the size of the car's truck's axle journals became the basis of the "capacity" of a car? The Association may have been mandated to make the rule by Federal legislation. I could not find any reference to this adoption in White's AMERICAN FREIGHT CAR tome, but this adoption happened formally sometime before 1924-25. Indeed, I suspect the date to be 1911 at the latest.

Prior to 1925, the designated Capacity of a car was recommended based upon the size of the axle journal, but railroads did have the option to stencil almost whatever capacity they desired. Shippers were allowed to load a car with a load of up to 110% of Capacity.

In 1924, the MCB's successor, the Mechanical Division of the American Railroad Association directed the railroads to stencil the Load Limit and Light Weight of the car effective 1/1/1925: - the Load Limit being the difference between the Gross Rolling Load determined by the size of the axle journal and the Light Weight of the car. The 110% limit had been replaced by the Load Limit calculation.

Tim Gilbert