Lead Lag Hinges -- Hi Chuck!

curtisscholl

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Dec 5, 2016
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Location
Saline, MI
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Building Gyrobee
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Hi Chuck

I saw a video of a gyro of Chuck Beaty's that had Lead-Lag Hinges on a two blade rotor.

Did you document that particular setup? I am very curious and interested in some details if you would be so kind.

Curtis Scholl

PRA 43249
 
Here’s the link to the drag hinged 2-blade rotor under discussion.


2/rev vibration was so severe as to be dangerous. It was an early attempt at solving vibration problems arising from a rigid rotor pylon. This experiment led to the development of the “slider” mechanism.

Years before, in the early 1970s, I had acquired a set of Hughes 269 rotor blades where the previous owner had sawed a taper in the root ends of the blades to mimic Bensen metal blades and I, not believing there was sufficient in-plane strength remaining to permit the use of a normal seesaw rotor, made up a drag hinged rotor without undersling and had successfully flown this rotor on a gyro that happened to have a very flexible, round tube mast. Worked just fine with minimal 2/rev vibration.

What I didn’t realize at the time was that success was due to the flexible mast.

In the 1970s, it was very difficult to find technical information about underslung see-saw rotors: no high speed internet and only a brief mention in helicopter text books. I bought my first computer in 1997 and struggled with a miserably slow dial-up connection on a rural telephone line for several years.
 
Igor Bensen said in some of his literature that his gyros achieved lead-lag relief by using a flexible mast. He was not always transparent about technical matters but, in this case, he was being straight with us.

I recall scuttlebutt discussions at 1970's flyins about gyro builders who had braced their masts right up to the rotorhead -- and had come to grief. Chuck's right, though. This was all hearsay and hangar flying.
 
Chuck:

I understand. An attempt to fix a problem the result of which was not what you thought it should be. Yes. In my case underslung rotor heads on Huey's are the only thing I am familiar with and I wish I had a Technical Order on it. USAF decided I should work on Huey's rather than the Sikorsky's I wanted to work on.....
 
Chuck

What did you utilize as a damper for the lead-lag hinge? OR was it not necessary? Was the configuration based on a friction "disk" between hub bar and mounting ears? There is very little to indicate a coupling at the rear of the blade at the root for a damper arm.

Curtis Scholl
 
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