Multi-body model of a bobsleigh: comparison with experimental data

Bobsleigh is a winter sport in which teams make timed runs down narrow, twisting, banked, iced tracks in gravity-powered sleds. To win the race it is of great importance to have a sled that is optimized from both the sliding and the aerodynamic point of view. However, also typical vehicle parameters, such as the weight distribution and the inclination of the steering axis, play an important role. In fact, being the friction coefficient between skates and ice very small (approx. 0.04), an change in the weight acting on the front skates may significantly modify the steering feedback of the driver thus highlighting his/her driving ability. Better trajectories imply less corrections on the steering axis and thus better performances. The inclination of the steering axis, instead, generates a torque similar to the self-aligning torque produced by road vehicle tires thus stabilizing the front skates and requiring less control ac-tions to the sled driver. Up to now, bobsleigh design has been carried out mainly on the basis of the feedback of ath-letes. The drawback of this approach is that it leads to small modifications in the bobsleigh design and it does not allow to objectively identify the influence of the applied modifica-tions/innovative solutions on the bobsleigh overall performance. To be able to quantify the influence of certain design changes on the performance of bob-sleighs, it was decided to set up a multi-body model of a two-men sled. To validate the nu-merical model an experimental campaign with an instrumented bobsleigh was carried out at Cesana Pariol Olympic Park. During the tests, the bobsleigh was instrumented with two iner-tial gyroscopic platforms to measure the dynamics of the two frames constituting the bob-sleigh body, sixteen strain gauge channels to measure the ice-skates contact forces, one optical sensor to measure the bobsleigh speed and one potentiometer to measure the steer an-gle imposed by the driver. Numerical results have shown a good agreement with the experi-mental data.