In an attempt to design a purely hydrodynamic slider bearing that carries its own weight while in motion, the Rayleigh step bearing was chosen to accomplish this task. The Rayleigh step bearing in concept is a bearing which consists of two horizontal parallel planes separated by a shoulder height. While the step bearing is in motion, the pressure of the fluid film in between the bearing and the track on which it will be sliding should create a lift force which will support the bearing’s weight. This in theory would leave only the drag force of the fluid on the bearing to slow the bearing down. This bearing was designed to carry the maximum weight possible for a step bearing by calculating the design parameters of the velocity of the bearing U, the inlet film thickness hi, the outlet film thickness ho, and the step length n. The maximum velocity U that the bearing could achieve was determined by using an energy balance. In a simplified equation where all the energy is assumed to be transferred from the pendulum to the bearing with a mass m, the maximum possible velocity U of the bearing was found to be 1.45 meters per second. By differentiating equation (7.50) from Engineering Tribology by J. A. Williams given the velocity U and the dimensions and weight provided in the drawing of the bearing design, this made it possible to find the optimum film thickness ratio H and land ratio P. It is from these ratios that the shoulder height and the step size were calculated that were incorporated into the design. Another important design factor that went into this design was striking height of the pendulum on the bearing. In an attempt to ease the transition of energy from the pendulum to the bearing, it was decided that this striking point should be at the bearing’s center of gravity in the x-axis. By doing so, no moment is created by the striking force that would induce a rotation of the bearing that would prohibit the natural lift created by the fluid film. As stated earlier, theoretically, the only retarding force on the bearing should be the drag from the fluid film. In reality, some friction between the bearing and track contact is to be expected as well. With this in mind, the material Teflon was chosen for its ultra low coefficient of friction with most materials including the track material of aluminum. With a bearing made out of entirely Teflon having a density of 2.2 grams per cubic centimeter, and a dimensions of 8.5cm long, 6.35cm tall, and 5.0cm wide, the overall mass of the bearing is 594 grams.
