Experimental study of wheel-rail adhesion characteristics and law of influence in wet condition. During the 19th century, it was widely believed that coupling the drive wheels would compromise performance and was avoided on engines intended for express passenger service. Properly dried sand can be dropped on to the rail to improve traction under slippery conditions. Copyright © 2020 Elsevier B.V. or its licensors or contributors. Mech. The term adhesion railway or adhesion traction describes the most common type of railway, where power is applied by driving some or all of the wheels of the locomotive. It is present in a single wheelset and will accommodate the slight kinematic incompatibility introduced by coupling wheelsets together, without causing gross slippage, as was once feared.
The phenomenon of hunting was known by the end of the 19th Century, although the cause was not fully understood until the 1920s and measures to eliminate it were not taken until the late 1960s. Note that steam locomotives of old were driven only by 'drivers' that were connected to the 'side rods' of the locomotive. In this process, adhesion coefficient was measured by measuring the value of torque sensors that are installed in the axis of the driving motor and the axis of the braking motor.
For steel on steel, the coefficient of friction can be as high as 0.78, under the best of conditions (= utopic laboratory condition, on railway realty: 0.35 -0.5 [2]), whilst under extreme conditions it can fall to as low as 0.05. "The Dynamics of Railway Vehicles on Straight Track: Fundamental Considerations of Lateral Stability". 1 Numerical analysis model of wheel/rail Fig. When an engine slips, particularly when starting a heavy train, sand applied at the front of the driving wheels greatly aids in tractive effort causing the train to 'lift', or to commence the motion intended by the engine driver.
Provided the radius of turn is sufficiently great (as should be expected for express passenger services), two or three linked wheelsets should not present a problem. Published by Elsevier B.V. https://doi.org/10.1016/j.prostr.2020.02.060. It is measured using a number called the coefficient of friction [: when adhesion is low, the surfaces are slippery – for a plate on a kitchen worktop the adhesion is less than 0.1; This may result in loss of adhesion - causing the train to slow, preventing toppling. Alternatively, the inertia may be sufficient to cause the train to continue to move at speed causing the vehicle to topple completely. The present work aims to better understand the phenomenon of adhesion under degraded conditions during railway braking maneuvers with the aim of optimizing the anti-slip algorithms in order to reduce damage to the profiles of wheels and rails and to minimize the braking distance. With perfect rolling contact between the wheel and rail, this coning behaviour manifests itself as a swaying of the train from side to side. The definition of creep in this context is: In analysing the dynamics of wheelsets and complete rail vehicles, the contact forces are treated as linearly dependent on the creep. In practice, the swaying is damped out below a critical speed, but is amplified by the forward motion of the train above the critical speed. Typically, the area of contact is elliptical, of the order of 15 mm across.