Fatigue tests on a compression fork-pin coupling of a front motorbike suspension under fully reversed bending load

The forecarriage of a motorbike allows the driver to turn the vehicle in the desired direction and control its behaviour during the motion. In particular the fork-pin compression coupling of the front suspension is very important for the reliability and the safety of the mean. A failure of this component is very dangerous because it would make the vehicle unmanageable and it could provoke severe injuries to the driver. Therefore it is a very critical component and the designer’s aim is to assure its reliability but at the same time keep the production costs low. One of the most important cause of failure is due to fatigue under fully reversed bending load. In this work, fatigue behaviour of fork-pin couplings, produced by the Paioli Meccanica S.p.a. of Bologna, is analysed and the results of the tests, carried out on an ad-hoc testing system, are summarised.