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and rollingstock gauges are clearly influenced by the British railway practice, as are braking
systems. Wagon couplings on freight trains are predominately autocouplers with friction wedge
type draft gear packages showing the North American influence. Privately owned railways on iron
ore mines in the Australia’s North West show even moreNorth American influence with American
style braking and larger structure and rollingstock gauges. Australia is also characterised bythree
track gauges,alegacy of colonial and state governments before federation. The presence of narrow
gauges of 1067 mm results in alarge fleet of rollingstock with adesign differing from standard
gauge rollingstock in North America, Britain, and the southern states of Australia.
This chapter is arranged to firstly give an overview of longitudinal train dynamics. The second
section goes into considerable detail on approaches tomodelling longitudinal train dynamics. The
mostspace is giventothe modellingofthe wagon connection model. Subsections are also devoted
to modelling traction and dynamic braking systems, rolling resistance, air resistance, curving
resistance, the effect of grades, and pneumatic braking. The subsection on pneumatic braking only
provides an explanationofthe effect of pneumatic braking on train dynamics. Modelling pneumatic
braking systems would require achapter in itself. Further more brief chapter sections are included
on the interaction of longitudinal train dynamics with lateral/vertical wagon dynamics, crashworthiness,
comfort and train management, and driving practices.
A . A N O VERVIEW o F L ONGITUDINAL T RAIN D YNAMICS
Handbook of Railway Vehicle Dynamics
Longitudinal train dynamicsisdefined as the motions of rollingstock vehicles in the direction of the
track. It therefore includes the motion ofthe train as awhole and any relative motions between
vehicles allowed due to the loosenessofthe connections between vehicles. In the railway industry,
the relative motion between vehicles is known as“slack action” due to the correct understanding
that thesemotions are primarily allowed by the free slack in wagon connections, coupling freeslack
beingdefined as the free movement allowed by the sum of the clearances in the wagon connection.
These clearances consist of clearances in the autocoupler knuckles and draft gear assembly pins.
Cases of slack action are further classified in the Australian industry vernacular as run-ins and runouts.
The case of arun-in describes the situation where vehicles are progressively impacting each
otherasthe train compresses. The case of arun-out describes the opposite situation where vehicles
are reaching the extended extremeofconnection free slack as the train stretches.Longitudinal train
dynamics therefore has implications for passenger comfort, vehicle stability, rollingstock design,
and rollingstock metal fatigue.
The study and understanding of longitudinal train dynamics was probably firstly motivated by
the desire to reducelongitudinal oscillationsinpassenger trains and in so doing improve the general
comfort of passengers. The practice of power braking, that being keeping power applied with
minimum air braking, is still practiced widely in Australia on passenger trains. Power braking is
also used on partly loaded mixed freight trains to keep the train stretched during braking and when
operating on undulating track. In the Australian context,the studyoflongitudinal train dynamics is
evidenced in technical papers coinciding with the development of heavy haul unit trains for the
transport ofcoal and iron ore. Measurement and simulation of in-train forces on such trains in the
Queensland coal haulage was reported by Duncan and Webb. 1 Moving to trains of double existing
length was reported at the same time in New South Wales in apaper by Jolly and Sismey. 2 Interest
was also evident in South Africa with the publication of apaper focused on train handling
techniques on the Richards Bay Line. 3 The research was driven primarily by the occurrences of
fatigue cracking and tensile failures in autocouplers. From these studies 1–3 an understanding of
the force magnitudes and an awareness of the need to limit these forces with appropriate driving
strategies was developed. During these developments, the first measurement of in-train forces in
long trains utilising distributed locomotive placement were completed. An important outcome
was that athird type of in-train force behaviour was identified. Prior to these studies in-forces
were divided into two types, namely, steady forces and impact forces. Steady in-train forces are
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