Re: Question about shafts, rods, and broken parts.

One point I'd like to make, is that before I got into live steam, I had heard of equalizers on steamers but I never took the next step in undestanding. Equalization allows the drivers to move up and down a little to stay in contact with the rails.
The implication is that the distance between the crank pins is changing slightly on uneven track. So not only is piston rod going back and forth and the side rods round and round, but also the drive axles are going up and down and the wheel sets going sidways (especially around curves). With all of this movement, fatigue failures due to repetative motion are very possible.
I am sure that this is simplistic. If anyone else has comments, I'd love to have them.
Doug vV