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The bogie mass isasignificant percentage of empty wagon mass, typically, , 20% (per bogie)
and therefore having significant inertia. Acceleration and deceleration is applied to the bogie at
the centre bowl connection, some distance above the bogie centre of mass. The result being
that significant wheel unloading, 50%, due to bogie pitch can be both measured and simulated, 5
Figure9.38.Even worse wheel unloading could be expected for an empty wagon placed in aloaded
train where impact conditions can be more severe. The case of an empty wagon in aloaded train
combines low wagon mass with larger in-train forces — more severe longitudinal wagon
accelerations.
IV. LONGITUDINAL TRAIN CRASHWORTHINESS
Crashworthiness is a longitudinal dynamics issue associated with passenger trains. Design
requirements of crashworthinessare focused on improving the chances of survival of car occupants.
There are two areas of car design related to longitudinal dynamics that require attention and will be
mandated by safety authorities in most countries. Passenger cars require:
† Vertical collision posts.
† End car crumple zones.
A . V ERTICAL C OLLISION P OSTS
The requirement is based on the scenarioofawagon becoming uncoupled or brokenaway and then
climbing the next car. The chassis of the raised wagon, being much stronger than the passenger car
upper structure, can easily slice through the car causing fatalities and horrific injuries, Figure 9.39.
Design requirements to improve occupant survival include the provision of vertical collision posts
that must extend from the chassis or underframe to the passenger car roof, Figure 9.40. Standards
will differ depending on the expected running speeds and country of operation. The specification in
Australia for operation on the Defined Interstate Rail Network 16 requires the following forces to be
withstood without the ultimate material strength being exceeded.
At total longitudinal force of1100 kN distributed evenly across the collision posts. The force
applied 1.65 mabove the rail level.
Ahorizontal shear force of 1300 kN applied to each individual post fitted at alevel just above
the chassis or underframe.
FIGURE 9.39 Collision illustrating wagon climb. Source: From McClanachan M., Cole C., Roach D., and
Scown B., The Dynamics of Vehicles on Roads and on Tracks-Vehicle Systems Dynamics Supplement 33,
Swets &Zeitlinger, Amsterdam, pp. 374–385, 1999. With permission.
FIGURE 9.40 Passenger car showing placement of vertical collision posts.
© 2006 by Taylor & Francis Group, LLC
Handbook of Railway Vehicle Dynamics