Design of radial circular run-out tolerances on crankshafts considering bearings' lubrication performance

Influencing mechanism of radial circular run-out deviation of main journals on the lubrication performance of main bearings was studied. A design method of radial run-out tolerance on crank main journals was established considering the lubrication properties. The run-out tolerances on main journals were calculated using the crank bearing models. The tolerance values of different solutions were analyzed. It is clear that the radial circular run-out deviation has great effect on the lubrication characteristics not only by affecting the bearing's load space but also changing the actual rotation axis of the whole crankshaft as well. Solution using the midline of the maximum and minimal values of run-out deviation as the rotation axis is optimal. The design method of crank run-out tolerance can explain the practical tolerance precision of radial run-out.