scope:

It is well known in the offshore industry that rack and pinion for jack up application are exceeding the permissible contact stresses by factors of 3 - 6 according to AGMA and ISO gear calculation methods. However, in reality, these applications are working without any failure for more than 20 years. This paper outlines the general design requirements of rack and pinion for lift boat or jack up rig applications. The typical load spectrum will be discussed and operation conditions will be explained for a better understanding of these applications. Furthermore, it will be shown how to get started with the analytical evaluation of such design. The analytical process will be in compliance with the requirements of certification body's like the American Bureau of Shipping (ABS). It will start with the basic root bending stress calculation per AGMA or ISO with a specified load spectrum. As stated the contact stress will be evaluated separately in more detail. Overall two methods will be discussed to approach this problem. The numerical method as a linear- or nonlinear- Finite Element Analyses (FEA). And the second method an analytical approach based on the brinell theory. The linear FEA analyses will help to get a better understanding what influence is contributing to the high stresses in the rack as well as the pinion. It will show how the contact stress is behaving in comparison to the surface depth of the rack. And if there are any other stresses, impacting or contributing to the high stresses in the rack and pinion.