Shay Truck Pivot and
Nelson Riedel Nelson@NelsonsLocomotive.com
Initial: 4/28/03 Last Revised: 06/05/2004
Note: The truck pivots were initially grouped
with the truck brakes. Later I decided to split the pivot and rollers and
group with the trucks. The brakes were then grouped with the other
parts of the brake system.
The pivots and rollers are the interface between the
trucks and the frames.
|The photos at
right show the pivot and rollers installed on the upper spring
plank of a truck. A brass pivot pin connects between the
bolster on the frame and the hole in the pivot block on the
truck. The brass pin allows rotation of the truck and
maintains alignment in the horizontal plane.
The pin is a loose fit in the vertical direction.
The weight of the frame rests on the rollers on each side of the
pivot block as shown in enlarged photo on lower right.
This arrangement is different from at least some of the full sized
shays I've examined; they depended on the pivot pin to carry the
weight of the frame. These full sized shays used pads rather than
rollers to supplement the pivot pin if the frame leans too far to
one side as shown in photo below.
| The set of six rollers is shown
on the right. The roller holders were machined from
rectangular bars stock. The first step was saw out the notches
on the ends and to use a drill to rough cut the slot. The mill
was then used to finish the holder to the correct dimensions.
Kenneth suggested a 10-32 screw for the roller axel. I
didn't have any 10-32 screws long enough to have an unthreaded part
near the top. Instead, I used a 3/16" rod as an axel.
Each axel is held in position by a 1/16" expansion pin.
The holes for these pins were drilled through the holders so
that the pins can be punched out to remove the axel and roller.