Abstract: A manufacturing system that manufactures a downhole tool string, which includes a model that describes relationship between properties of the downhole tool string, properties of a borehole, properties of a formation, and properties of a mud cake formed on a surface of the borehole and a design device that iteratively determines contact parameters that describe one or more contact points expected between the downhole tool string and the mud cake based at least in part on the model, in which the contact parameters comprise contact force expected at each of the contact points, adjusts the properties of the downhole tool string to add a spacer at one of the contact points associated with highest contact force, and indicates location, type, or both of the spacer to enable the manufacturing system to attach the spacer to the downhole tool string before deployment of the downhole tool string in the borehole.

Abstract: A number of fan assemblies are shown. Configurations are shown that include one or more diffusers. Diffuser locations and specific diffuser configurations are described that improve one or more fan assembly characteristics, including, but not limited to fan efficiency.