The following is a part of a response to RW-1 and describes the design philosophy used by Bell in their latest soft in-plane rotor heads that also incorporate elastomeric bearings for pitch change.
“The yoke that you referred to is also a part of the structure of the rotorhead. The elastomeric bearing is mounted inside of it and it most likely absorbs centrifugal loading while allowing pitch change. Leading and lagging pivots about the elastomeric bearing and is most likely absorbed by the soft inplane elastomeric dampers at the root of the yoke assembly”.
The A star and Twin Star rotorheads are different and this difference causes a high rate of degradation of the elastomeric elements and increases the maintenance and operational costs.
On these types of rotorheads the outboard elastomeric element instead of being the pitch bearing that accommodates leading and lagging it is the lead and lag bearing which only accommodates lateral displacement. This causes the lead lag bearing to be the pivot point for lead and lag. The tail end of the blade is being restrained by a bearing that allows pitch change and absorbs centrifugal loads but is now being subjected to very high lateral loads which it is not designed to react.
In other words like many French mechanical devices it is built backwards.
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The Cat