The Shaft does not just (for the purposes of our discussion) refer to the shaft that the propeller is mounted on, as some installations may have 3 or 4 shaft segments, perhaps between vee drives, thrust bearings, universal joints or such devices.

We need to know three things;

• the total number of gearboxes and vee drives or reduction boxes between engine and propeller.
• the total number of bearings between engine and propeller, including cutlass and P bracket bearings, but not including any bearings already accounted for as part of a gearbox, vee drive or reduction box as an internal component.
• Shaft diameter in inches.

Again, for the purposes of the propeller calculations we do not need any other data or any specific data relating to makes and models, this is because the data that is required is sufficient to calculate the power lost in the shaft to overcome friction in these devices, and calculating this power loss is all we are concerned with.