Patent ID: 7278211
Filing Date: 2007-10-09
Classification: E21B,F16C,Y10T

Abstract:
1. A method of designing a bore hole tool assembly comprising a housing and a mandrel reaching alone an axial direction into the housing and a bearing system for transferring an axial load between the housing and the mandrel and allowing rotation of the housing relative to and about the mandrel, wherein the bearing system comprises at least two bearing stages each arranged to transfer part of the axial load, whereby each bearing stage comprises bearing means and mitigation means for distributing the load substantially proportionally over the respective bearing stages, the method comprising the steps of: a) selecting a first bearing stage stiffness value for one bearing stage; b) calculating, for given stiffness values of the parts of the housing that stretch between the bearing stages and given stiffness values of the parts of the mandrel that stretch between the bearing stages, the value for the second bearing stage stiffness whereby the axial load is distributed substantially proportionally over the respective bearing stages, thereby using the first bearing stage stiffness value as input.