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Truck Warp: Causes and Cures (Part
1 of 2)
By Gary P. Wolf • September
22, 2004
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Whether you are primarily interested in
the track or the vehicle side of the
wheel/rail interface, the effects of "truck warp" should be of interest
to you. This two-part article examines the impact of warp in the overall operating
environment. Part 1 examines what truck warp is; Part 2 (coming next issue)
will address
the
effects
of truck warp and the measures that can be taken to prevent it.
Webster defines "warp" as "to turn or twist out of shape." This
is exactly what happens to a rail truck, or bogie, when it warps: it twists out
of shape. The term "truck warp" came into vogue in the late 1980s,
when the new 125-ton doublestack cars entered rail service, and a significant
number of rail rollover derailments occurred. At first, these derailments were
largely unexplained, but through dedicated research it was found that the trucks
on these cars were parallelogramming, or getting twisted out of square. More
simply put, a rail bogie should operate with the bolster and sideframe oriented
90 degrees, or square, to one another. If they don’t maintain this square
orientation, or if the bolster and sideframe twist as much as one or two degrees
out of square, the truck becomes "warped." (This was pointed out
in a previous Interface Journal article on the "Effects
of Rail Cant on
Wheel/Rail Forces and Derailment Potential.")
Figure 1 shows a top-down
view of a normal truck; Figure 2 shows the same view of a warped truck. While
they may not appear strikingly different, only a few degrees of warp can produce
severe consequences for both the wheels and truck components, and the track infrastructure.
It's no wonder then that warped trucks are also known as "bad actors."
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AUGUST 2004
"Effects of
Rail Cant on Wheel/Rail Forces and Derailment
Potential"
READ
ARTICLE
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