Investigation of Long Bow Vibrations

Abstract

The work was about mapping which vibrations occur in bows and how they could affect accuracy. The work was carried out during the Corona pandemic, which meant limited resources for experimental measurement and the experiments were done in an office environment and not in the field. If possible, it was important to find applicable theory behind all experimental results. One goal was to measure with simple means and really understand what was to be measured and how. All experiments and measurements were done on a recurve bow. The measurements therefore began with recording sound using a microphone. Accelerometers were used for further measurements. To increase the understanding of these, a known source of vibration was needed. Thereby, a loudspeaker was modified with the possibility of attaching accelerometers in the middle of the diaphragm. The loudspeaker was powered by a signal generator via a power amplifier. A PC oscilloscope was used to record and interpret signals from the accelerometers. Three different oscillations were recorded, one elemental transverse oscillation of the string, the bending oscillation of the limbs and the third was transverse oscillation laterally with the string and arrow together. All three had a period that was much longer than the shooting. It was then considered important to be able to measure to describe the movement of the handle during the shooting process, which is specific to each combination archer and bow. Experiments on this were done with available equipment that was not sufficient due to too slow serial communication. After creating a theoretical model of the frame, ”cushioning pads” could be shown to have a positive but rather small effect.