Articulated correction bit
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What is the difference between a semi-articulated and a semi-rigid rotorheadif any?? Those labels are confusing and only semi-useful! If the rotors are mounted to a plate that is hinged at the mast, articulated correction bit the whole disk teeters around that hinge, and no bending forces are imposed on the mast during those teeterings, it is a articulated correction bit rotor, sometimes called a semi-rigid rotor.
This is a classic first-generation rotor head, invented by Art Young in the mid 's It is easy to make, easy to maintain, and relatively articulated correction bit. It is also a very marginal design for the high-end work helicopters have to do, mostly because it has a relatively small maneuver envelope, and does not provide consistent control in low g or sideslipping flight.
For very light training helicopters and home builts, it is a very nice rotorhead, as long as its limitations are respected. As an aside, the rotors on the V Osprey are basically teetering rotors, with the 3-bladed rotor head gimbal-ring being articulated correction bit to the mast by bearings.
A semi-articulated rotor is again a bit of a stretch, but the Robinson design could be said to be one, where the blades flap from a hinge that is a bit away from the mast, but the whole rotor head also tilts.
It has most of the limitations of the teetering rotor above, but the head can be lighter because the flapping of each blade prevents the bending articulated correction bit being carried by the rotor head, thus it can be lighter.
Also, the blades move more freely, so the controls should feel quicker and more responsive than a true teetering rotor. At the risk of correcting the master I was told that the 'flapping' hinges on the R22 head are not flapping hinges, but are actually coning hinges. This came from someone way up there in the lofty heights of Robinson management.
Vaqueroaero, Thanks for the correction, has anyone got a pointer to a Robbie rotorhead sketch so I can more fully understand that?
I believe the difference is that the MR blades are prevented from moving below their 'resting' attitude by the droop stops on their hinges, yet are not prevented from rising and thus coning. If I'm wrong please correct me I'm here to learn from you guys!
Sikorsky, "A semi-rigid main rotor is always a 2 bladed rotor system. It gets its name from the fact that it does not have a lead-lag hinge. The following articulated correction bit an interesting story articulated correction bit a semi-articulated rotor, which had three blades. The following two web pages may be of value. Pictures of rotor hubs; including four of the Robinson hubs. An articulated head has a flapping hinge, A feathering hinge, and a hinge that allows lead and lag.
A semi-articulated head eg: A semi rigid head eg: A fully rigid head will have no hinges whatsover and all movement is absorbed by rigid extension arms to the head. As an aside - there is articulated correction bit such thing a coning hinge as the only thing that cones is the blade which would do so with or without a flapping hinge as Mr Cierva discovered in the 30s or didn't as articulated correction bit case articulated correction bit be IMHO of course: Letsby Avenue, I'm not sure if you're definitions are on the money.
I was under the impression that a articulated correction bit rigid rotorhead e. BO was perfectly entitled to have a feathering hinge without running the risk of losing its 'fully rigid' description. And also if you maintain that there is no such thing as a coning hinge, then could you explain what is the design purpose of the two offset hinges on the R22? Just from a semantic point of view I don't think there are any fully rigid rotor heads.
Is it not a bit of a misnomer as all rotor systems hingeless or otherwise have elasticity to varying degrees? Not being an avid R22 fan I can't comment on their 'offset hinges' but they sound like Delta3 hinges which act as flapping hinges but due to their offset cut across the blade reduce flap to a manageable degree.
Most helicopters achieve this D3 by offsetting the control arm instead. There is a delta 3 angle designed into R22 rotor head 18 degrees - see Dave Jackson's link but there is no Delta 3 articulated correction bit per se unlike the tail rotor. They are in fact principally coning hinges although whether or not there is a small element articulated correction bit flapping to back up the teetering hinge as I think Nick is suggesting I articulated correction bit not venture an opinion.
My brain cells only do so much work on a sunday morning articulated correction bit they go on strike! D As an aside, if the changing of a blade's pitch angle due to flapping is called 'pitch-flap coupling' because of Delta articulated correction bit anglewhat do you call the changing of a blade's AOA due to flapping?
Brain cells on strike! Yep - I can confirm I was talking tosh - since the R22 has a two blade teetering head there is no need for flapping hinges. It articulated correction bit always my understanding that the rs "coning hinges" whatever u want to call them they are still there served mainly to lighten the rotor system.
The logic being that the blades didn't need to be as heavy because they didnt need to take all the coning loads, the same went for the head.
Articulated correction bit these things being lighter allowed for lighter transmission and associated systems. One quick question, in that link that Dave Jackson posted i noticed what looked like some electrical connections on the top of the Mi-2 head.
Are articulated correction bit for an anti-ice system articulated correction bit something? There aren't any absolutely rigid rotors; but the guys in this picture http: Would you have a direct link to the article? It explained how Uncle Frank got to 18 deg, something being 17 deg the other 19, so to split he put it to That was exactly it! Here a place with some nice pics and explanations but nothing like the details on the report on your site: