For the past 20 years Murray Motorsport have specialised in sales and servicing Proflex dampers for race, rallycross and rally cars. In recent years they have expanded the range of damper brands available and now offer a range of products to cater for all levels of the market from clubman to professional. Murray Motorsport has invested in a new damper dyno which now enables them offer an additional service the first of its kind in Ireland. Most dampers serviced will be tested afterwards and a graph will be available for customers. Some of the basic advantages for getting your dampers tested are: • Check they are performing correctly • Check the position for optimum range of adjustment settings • Match the settings of each shock (equalise the left vs. right) How the Dyno Works: A shock dynamometer (dyno) is a piece of equipment used to display how the damping force of a damper changes with shaft velocity. The shock is fixed at one end, and attached to a vertical shaft on its opposing end. The vertical shaft is connected to a motor in such a way that as the motor turns, the shaft displaces vertically for a set distance. A load cell at the shock’s fixed end is used to sense the amount of load on the shock and this is translated to a computer program. The motor runs through a set list of velocities, plotting how much force is being recorded at each velocity. This PSD Dyno can measure in various stroke lengths, speeds and the load cell can measure up to 16000 Newton’s. Reading Dyno Results: Force vs. Velocity - Low speed shaft velocities contribute to driver feel and the car’s body movements (sprung mass). Mid speeds shaft velocities affect the car under braking, during fast changes of direction and ride harshness. High speed shaft velocities are concerned with absorbing energy from bumps and controlling energy from the vehicle’s unsprung mass. When a shock is compressed due to a bump, the damping force is called compression damping (or bump damping). When the shock extends due to the energy from the spring, this is called rebound damping. In this example of a Force vs. Velocity Curve, the compression damping is displayed in the top portion of the graph and the rebound damping in the bottom portion. Force vs. Velocity Graph: Force vs. Displacement- The dyno can also be used to output a Force vs. Displacement graph. This graph shows the force a shock generates as it travels through its motion in both the compression damping and rebound damping phases. Force is shown on the vertical axis, and is measured in lbf or N, and displacement is shown on the horizontal axis, measured in mm or inches. Quadrant A displays the shock’s force as it is accelerated in bump, quadrant B as it is decelerated in bump, C as it is accelerated in rebound and D as it is decelerated in rebound. This plot can be used to troubleshoot a shock you are having issues with, or to ensure hysteresis levels are at an acceptable level. Hysteresis occurs when the damping forces are higher as the damper is decelerating compared to when it is accelerating, and will decrease the effectiveness of the shock. This effect can be seen in the next graph, where the damping forces in quadrant B are higher than in quadrant A. Hysteresis is the primary reason that a shock should be valved to be used in the middle of its adjustment range, as hysteresis is significant when you use the stiffest adjustment settings. Force vs. Displacement Graph: The Force vs. Displacement plot can also be used to find a fault with your shocks. For example if the shock is damaged in a crash, bending the shaft slightly, then the plot will show a spike as it will take larger amounts of force to move the shock through the bent region of the shaft. The graph below shows a significant amount of resistance in the accelerating bump phase of the plot, indicating a significant problem with the shock. If a car is run with this shock it will experience grip issues on bumpy tracks in minor cases, and loss of vehicle control in major cases. Force vs. Displacement Graph Showing Faults