prescribed ways using required materials. Vehicles are normally driven
aboard flatcars over ramps on hand at the site either already constructed or
fabricated on the spot using field expedient methods and materials. When
several vehicles must be loaded on more than one car, the circus method is
used. Vehicles are driven forward from one flatcar to another over
spanners, or bridges, until the first car in the train and then successive
cars are occupied. The position of each vehicle will have been determined
in advance.
Items must be blocked and braced on rail cars to keep them from moving
in transit and being damaged or from damaging other items. Several forces
act upon the unsecured load from the motion of the flatcar. Longitudinal
force moves it lengthwise, transverse or centrifugal force pushes it
sideways as the car rounds a curve, and vertical force bounces it up and
down. Chocks nailed at the front and back of wheels keep trucks, trailers,
etc., from moving lengthwise on the flatcar. Cleats, or boards, nailed
along the outside of outer wheels prevent centrifugal force from flinging
vehicles off the car on curves. And wire connecting the vehicle wheels and
the stake pockets cuts down on some of the bouncing.
Although different bracing techniques take care of design differences
between vehicles, all wheeled vehicles are blocked and braced in essentially
similar ways. All use chocks of one pattern or another to keep vehicles
immobile; and all use wire or cable, in varying combinations, to help
vehicle bodies resist longitudinal, transverse, and vertical forces.
Equipment too long or too wide to fit on a flatcar may be carried if
special provisions are made. If truck wheels or tank treads extend over the
edge of the side sill, the car floor can be extended by nailing a plank over
the stake pockets for the wheel or tread to rest on. And an idler car can
be used ahead of or behind the car that actually carries the equipment so
that the extended portion, such as a boom, may be protected in transit.
Rules issued by the AAR specify how long and how wide the protruding part
may be to make use of an idler car.
Section II applies the loading, blocking, and bracing principles set
forth in section I to various examples of military shipments.
38
Previous Page
