Wheel/rail adhesion is affected by the contamination that is present on the railhead. This can be broadly divided into three categories oil, water and solid debris. The frictional phenomena associated with each of these groups were examined on a variety of laboratory simulation rigs. The interactions between each group were then explored so that a comprehensive description of wheel/rail adhesion could be established. Concepts of boundary lubrication can be used to describe the low friction of surfaces contaminated by oil and/or water. However these concepts are shown to have their limitations when solid debris is trapped in the contact area and either significantly lowers adhesion when mixed with small quantities of water under dynamic conditions, or increases the coefficient of friction by adsorbing the oil. There is insufficient oil on most track to cause low adhesion even when the rails are wet. Under some specific circumstances debris helps form thin layers that cover the wear band and are weak enough in shear to reduce adhesion and cause wheel slip. Leaves readily form such films although the most common constituents are rust and water. Laboratory experiments have shown that low adhesion can be caused by mixtures of rust and water, and a theoretical explanation for this has been developed based on their rheological properties. It is concluded that low wheel/rail adhesion is usually caused by a viscous paste formed of solid debris and small quantities of water. It is because Britain has such a cold, damp climate that wheel/rail adhesion on BR is such a problem.

This thesis presents an analysis of the kinematics of a mobile rubber tyred gantry crane (RTG Crane), as typically used for container handling operations, for the ultimate purposes of research into automation. Dynamical models are proposed for the crane based on a simplification of the structure into the gantry frame, the overhead trolley, and the cable mounted spreader slung below the trolley. The underlying trolley/spreader cabling geometry for commonly encountered designs has been analyzed, and novel mathematical relationships have been established for the first time. Full three dimensional motion is encompassed in the dynamical equations of motion, and various movement scenarios are examined. As an adjunct to the geometrical modelling a new phenomenon, described herein as geometrical extension, is defined in its role as an inherent anti-sway property in multi-cabled spreader suspension systems. The phenomenon is explained and investigated using pure geometry and a numerical method to assess its effect in practise. The final section of the thesis uses the single and multi-cable dynamics to evolve an accurate, and generic, fuzzy logic control and simulation for the RTG machine. Various performance scenarios are highlighted for typical freight manoeuvres. This work is now ready for experimental testing and evaluation in an allied project, thus the remit for the theoretical work of this thesis has been completed.

Life, limb and money continues to be lost in agriculture world-wide as a result of vehicles overturning on sloping land. It appears that vehicle operators lack the information required to prevent this. Studies of overturning accidents on hillsides have suggested that overturning is often the result of dynamic vehicle behaviour and in particular the result of striking discrete terrain obstacles. Currently, the only standard measure of the stability of vehicles for hillside use is the static stability limit. Several researchers have studied the response of vehicles striking discrete obstacles and have computed reductions in safe slope with increases in speed or obstacle height. However, there are many variables influencing the vehicle response; and no 'dynamic stability' test has been proposed and adequately backed up with theoretical analysis. This thesis describes work to provide more insight into the complex problem of vehicle dynamic stability, leading to a proposal for a dynamic stability test. A DADS computer model has been developed and validated by comparison with a farm trailer constrained on a test rig, with test variables speed, slope, tyre pressure, moment of inertia, static wheel load, static stability limit and obstacle length. It was found in both empirical and simulated cases that the trailer response reached a maximum at a certain speed, dependent on the natural frequency of the system, and that the overturning slope was at a minimum at that speed. The completed model predicted the slope on which the trailer overturned to within 27% of the slope in 95% of cases. Attaining this level of accuracy involved a detailed study of tyre properties, especially radial stiffness. It was found, unexpectedly, that this decreased by around 50% during large amplitude dynamic compression such as occurs when striking an obstacle. The relationship between the proposed index and the vehicle parameters was studied and it was found that static wheel load and tyre stiffness affected it most significantly. The index appeared to increase with the square root of the tyre stiffness and decrease with the square root of the static wheel load. The index could be used in conjunction with the static stability limit to compute a slope below which it would be theoretically safer to use the more dynamically stable vehicle.

To achieve high speeds with legs, a hybrid leg mechanism, which has been named Buraq, is designed. Buraq is actuated by a motor driven crank in longitudinal direction, and by a hydraulic ram in vertical direction. The crank radius and the phase can be adjusted during operation to allow legs driven by the same shaft to change phase and longitudinal stroke, so that gait shift and steering can take place. Also a force analysis of the leg mechanism has shown that, when the vehicle is running, the Buraq legs can act like the spring of a bouncing mass-spring model. Using the method of energy storage and retrieval, it should be possible to travel at high speeds by saving considerable energy.

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