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Transportation - haulage and hoisting
Published in Ratan Raj Tatiya, Surface and Underground Excavations, 2013
Drawbar pull: This is the force exerted on the coupled load by a locomotive through its drawbar, or coupling, and is the sum of the tractive resistance of the coupled load. The drawbar pull that a locomotive is capable of developing is determined by subtracting the tractive effort, from the sum of the tractive resistance of the locomotive. This resistance is offered by several sources: rolling resistance, which the entire train offers is equal to weight of the train in tons. (i.e. weight of locomotive + weight of mine cars with pay load) multiplied by a frictional coefficient ^, which could be 10-15 kg/ton (20-30 lb/ton); Curve resistance which can be ignored, gradient resistance and the force required to provide acceleration to the motion (as given in the formulae specified below). Drawbar pull=R0WTRunning resistance/tR0=μ+/-{(1/n)×1000)+/-(a/g)
Curving resistance from wheel-rail interface
Published in Vehicle System Dynamics, 2022
Qing Wu, Bo Wang, Maksym Spiryagin, Colin Cole
Comparatively, results in Figures 6–8 and the figures in Appendix show that the corresponding speed of minimum resistance moves from 80 km/h in the 200 m radius case to 50 km/h in the 400 m radius case and then has the tendency of moving to higher speeds again when curve radii are larger. These observations indicate that curving resistance is influenced by both vehicle speeds and curve radii. Meanwhile, with the same curve radius and vehicle speed, Figures 6–8 show that resistance forces are also different when superelevation is different. This again confirms the influence of superelevation to curving resistance. Table 3 summarises the variations of resistance forces due the changes of vehicle speeds and track superelevation. It can be seen that curve radii are still the main influencing factor to curve resistance; the variations due to vehicle speeds and superelevation changes are smaller than those due to curve radii changes. Comparing vehicle speeds and track superelevation, the former seems to have stronger influence, especially in tight curve cases (200 and 300 m curve radii). The variation ratio has an average value of 16%. Interestingly, the variation ratio in Table 3 is constantly decreasing from 49% at the 200 m curve radius to −2% at the 600 m curve radius, and then increasing to 15% at the 800 m curve radius. This changing pattern resembles those observed in Figures 6–8. The connections between these observed changing patterns are interesting, but are not instantly clear.
Running safety analysis of a freight train passing through a single crossover during braking
Published in Vehicle System Dynamics, 2022
Yichang Zhou, Yunguang Ye, Markus Hecht
In the studies mentioned above, only a single vehicle with an allowable speed passing through a turnout was investigated, and the longitudinal interaction between adjacent wagons was ignored. In fact, the brake force generally is produced on the vehicle before it enters the switch panel from the tangent track so that the vehicle can pass safely through the turnout at an allowable speed. However, this operation causes residual longitudinal forces between adjacent wagons on the turnout section. A more serious situation is that the continuous braking operation is essential to execute in the turnout when the track is located on the downgrade line, inducing considerable longitudinal in-train forces. To investigate the influence of longitudinal forces on the vehicle-track performance on a turnout, Zhang et al. [19] studied the behaviours of a heavy haul locomotive with an electric braking system running through Chinese 12# turnout and simplified the turnout model as an S-shape curve without considering the continuous change of rail profiles. The results showed that the dynamic braking on the turnout could significantly deteriorate the running safety of the locomotive, and the larger the braking force, the higher the derailment coefficient. Ge et al. [20] investigated the derailment behaviour of an empty wagon influenced by the longitudinal force, wheel-rail friction coefficient and running speed when negotiating the turnout on the through route. Compared to the through route, trains on the diverge route face more derailment risk due to the curve resistance. In addition, the central buffer models are used for Chinese railway vehicles in both studies.