File:UP Big Boy T-Truck Rocker Arr.jpg

Attached is a portion of the trailer truck arrangement drawing for a UP Big Boy. You can see the way the prototype rocker, rocker seat and bearing, and the rocker plate (which is mounted on the bottom of the frame cradle) were designed. Notice the "teeth" (or "toes") at the bottom of the rocker plate. From http://www.chaski.org/homemachinist/viewtopic.php?t=76521