Simon Iwnicki (Editor)_ Maksym Spiryagin (Editor)_ Colin Cole (Editor)_ Tim McSweeney (Editor) - Handbook of Railway Vehicle Dynamics, Second Edition-CRC Press (2019)

A History of Railway Vehicle Dynamics
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on the sharp curves typical of railways in mountainous regions became acute. This stimulated the
development of various kinds of articulated locomotives, as has been described by Wiener [30].
Many of these designs were highly ingenious such as the Klose locomotive [31], in which the problem
of altering the length of the driving motion on each side in order to accommodate radial axles
was solved.
According to Liechty [26, p. 29], a three-axle vehicle in which the lateral displacement of the central
axle steered the outer axles through a linkage was also tried out on the Linz-Budweis railway in
1826. It was argued that three axles, connected by suitable linkages, would assume a radial position
on curves and then re-align themselves correctly on straight track. Other examples of inventions in
which wheelsets are connected to achieve radial steering are the three-axle vehicles of Germain
(1837), Themor (1844) and Fidler (1868), Figure 2.4b. In these schemes, the outer wheelsets were
pivoted to the car body. More refined arrangements due to Robinson (1889) and Faye (1898) were
much used in trams on account of the very sharp curves involved in street railways [32].
As an alternative to the use of the bogie, in 1837, W. B. Adams proposed an articulated two-axle
carriage. Adams invented a form of radial axle in 1863, which had no controlling force, with the
result that, on straight track, there was considerable lateral oscillation of the axle. Phipps suggested
the idea of a controlling force, which was subsequently applied by Webb and others [33].
Another form of steering exploited the angle between the bogie and the car body in order to
steer the wheelsets relative to the bogie frame, using a linkage, Figure 2.4c. A similar objective
is achieved by mounting the outer wheelset on an arm pivoted on the car body and actuated by a
steering beam, Figure 2.4d. An alternative approach was to steer the wheelsets by using the angle
between adjacent car bodies, Figure 2.4e.
All these developments were based on very simple ideas about the mechanics of vehicles in
curves and depended on systems of rigid linkages and pivots. Though the aim of designers was usually
radial steering, very often, the design involved a compromise in which only partial steering was
achieved. Not surprisingly, in the light of modern knowledge, there is considerable evidence that,
when such schemes were built, they exhibited an even wider spectrum of various hunting instabilities
than the more conventional mainstream designs. This is probably why many of these inventions
failed to achieve widespread adoption. On the other hand, following the publication of his book in
1934, Liechty’s designs were applied in the next few years on a number of railways, and the experience
gained with these over a period of 40 years was reviewed by Schwanck in 1974 [34], who
concluded that wheelset steering is ‘one of the most effective means against flange and track wear,
and that the expenses resulting from its application will be written off by the resultant savings’.
2.6 CARTER
As already mentioned previously, Le Chatelier made the first attempt to understand the hunting
oscillation in the late 1840s, but the first recognition that hunting was the result of an oscillation
with growing amplitude seems to have been made by Boedecker in his book of 1887 [35]. Boedecker
extended his curving analysis to consider the case of a two-axle vehicle with rigid primary suspension
and coned wheels. The wheel-rail forces were represented by Coulomb’s law. Using a numerical
solution, Boedecker showed that ‘each displacement, however small, of the middle of the axle
from the centre of the track results in a wavy course of the vehicle of which the amplitude increases
with each swing of the axle until limited by the flangeway clearance’.
The model chosen for the wheel-rail forces limited this approach. Carter made the decisive step
forward in 1916.
By the end of the nineteenth century, experience had shown that the standard locomotive
configuration with a leading guiding bogie was usually safe. Bogie hunting, if occurred on a
locomotive or bogie vehicle, usually involved the relatively small mass of the bogie, so that the
forces were not dangerous. On the other hand, symmetric configurations, such as the 0–6–0,
were used only at low speeds, as at higher speeds, they were subject to riding problems, lateral