Saturday, April 12, 2008

Shay truck brakes

Last week, Keith and I paid the brake rigging out in the yard. Keith wanted to accomplish two things. First, he had to count the number of brake pins for the machine shop. The parts are set up for the rear truck. Alberto is currently machining new pins out of tool steel. Keith also needed to see that we still had all the parts.

Although I've seen the rods and levers around the engine house, this was the first time I saw the rigging parts laid out in a diagram. It helped me to see how the system works. Use this colored diagram to see how the linkage parts interact:

  • Blue -- stationery rod; anchors the system to the bolster
  • Red -- brake levers; the main lever (largest of the three) is bolted to the truck frame at the bottom; the remaining two levers are bolted to the brake beams in the center of the lever
  • Black -- movable brake rods; two pieces make the bottom rod; they're joined by a turnbuckle
  • Gold -- the brake beans with brake shoes; there's one bean per wheel set
  • Yellow -- brake hangers or dog bones; there are two per wheel set or four per truck
When you're viewing the front truck from the engineer's side of the locomotive, a rod pulls the top of the main levers to the read (not pictured). That motion actuates the joined brake rods and pulls both brake beans to the center. The brake system for the rear truck is set up as a mirror image of the front truck (pictured in the Lima shop drawing).

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