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Coupler Force, kN
2. Slackless Packages
Slackless draft gear packages are sometimes used in bar-coupled wagons or integrated into
shared bogie designs. The design of slackless packages is that the components are arranged to
continually compensate for wear toensure that small connection clearances do not get larger as
the draft gear components wear. Slackless packages have been deployed in North American train
configurations such as the trough train 11 and bulk product unit trains. 12 The advantage of
slackless systems is found in reductions in longitudinal accelerations and impact forces of up to
96 and 86%, respectively as reported in. 11 Disadvantages lie in the inflexibility ofoperating
permanently coupled wagons and the reduced numbers of energy absorbing draft gear units in
the train. When using slackless coupled wagon sets, it is usual that the autocouplers at each end
are equipped with heavier duty energy absorbing draft gear units. The reduced capacity of these
train configurations to absorb impacts can result in accelerated wagon body fatigue or even
impact related failures during shunting impacts. Modelling slackless couplings is simply alinear
spring limited to amaximum stiffness appropriate to the coupling type, wagon body type, and
wagon loading. Alinear damper of very small value should beadded to approximate small levels
of damping available in the connection from friction in pins, movement in bolted or riveted
plates, etc. (Figure 9.24).
3. Drawbars
600
500
400
300
200
100
0
- 100
- 200
- 300
0 20 40 60 80 100
Time, s
2.5
2
1.5
1
0.5
0
- 0.5
- 1
- 1.5
- 2
- 2.5
0 20 40 60 80 100
Time, s
FIGURE 9.23 Simulation results showing “unlocked” draft gear behaviour —flat track.
Drawbars refer to the use of asingle link between draftgear packages in place of two auto couplers.
Drawbars can be used with either slackless or energy absorbing draft gear packages. The most
recent fleet of coal wagons commissioned in Queensland utilises drawbars with energy absorbing
dry friction type draft gear packages. In this case, wagons are arranged in sets of two with
Limiting Stiffness
Wagon Acceleration, m/s/s
Linear Damper
(Very Small Value)
FIGURE 9.24 Wagon connection model —slackless connection.
© 2006 by Taylor & Francis Group, LLC
Handbook of Railway Vehicle Dynamics