Thrall center-beam flatcar - Thrall built 120
of the prototype cars in 1986 for Union Pacific. Prior to this, lumber
was hauled on traditional flatcars. The flatcars were easy to load,
but pagued by the shifting of the load. Bulkheads were added to stabilize
the load, but this also added more weight. Next they attempted to
make the cars lighter by reducing the center sill and adding a tall beam
down the center to make up for the lost strength. The partition also
added strength to the bulkheads so that they could be made lighter.
Thrall made the first such car in 169 following a Candian Naional design.
The final move was to replace the center beam with a truss which would
reduce the weight even further which also resulted in an additional 10
percent capacity.