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I have read about some helicopters now using a mechanism referred to as a "bearingless rotor". From what I've seen online, the system involves a flapping hinge.

What I struggle to get my head around is how the rotor spins without a bearing. How is this achieved?

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There are still bearings for the spinning part of the rotor mast coming out of the transmission, and for blade pitch in the hub itself. The bearingless part is that the blade flapping and lead/lag functions are accommodated by "elastomeric" hinges, basically, rubber-type compliant bushings. It's very similar to the control arm attachments on modern cars where the control arm is attached to the frame with a large rubber bushing, bonded into a sleeve that is bolted to the structure, that accommodates the arm's rotation while isolating the control arm from the car.

Some helicopters also achieve this function by making the root section of the blade into a flexible shaft that is free bend in the flapping and lead/lag direction.

Hingeless rotors have been around since at least the late 70s.

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  • $\begingroup$ Are you saying that "hingeless" and "bearingless" rotors are the same thing? $\endgroup$ – FreeMan Jun 30 '20 at 16:01
  • $\begingroup$ I would say so. The motions at issue are the lead/lag flapping movements, which if they are mechanical, are hinges with bearings, or if using elastomeric bushings, don't and you wouldn't consider an elastomeric mounting a "hinge" in the mechanical sense. When I first read about this innovation in the late 70s the term was "hingeless rotor", as opposed to "rigid rotor" like the Cheyenne had. Another term for them was "semi-rigid" rotors. $\endgroup$ – John K Jun 30 '20 at 21:55
  • $\begingroup$ Just wanted to clarify since the question is about a "bearingless rotor" and you referenced "hingeless rotors" in your last sentence. $\endgroup$ – FreeMan Jun 30 '20 at 22:07

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