Here's a snip from an old thread (Feb 2006) from a C. Beaty post:
It’s a long story, Mike, but I’ll try to repeat it as succinctly as I can.
I traded some stuff for a set of run out Hughes-269 rotorblades.
I made up a hub that incorporated a door hinge style joint at its center and used outboard drag hinges because the previous owner had tapered the root ends of two of the Hughes blades to make them resemble Bensen blades.
They flew beautifully after the usual amount of tinkering but I had the misfortune to be flying over the Gulf of Mexico about 100 yards offshore at Birdy’s altitude when a wire running my electric fuel pump came loose. Mustering dolphins, of course.
Needless to say, I did a water landing in about 12’ of water.
Someone was kind enough to give me a ride back to the airport where we picked up my trailer and a pair of ski ropes. Since I was already cold and wet, -it was around Christmas-, I swam out to the spot, dove down and tied a rope to the gyro.
Got the thing home, pulled the spark plugs on the engine, hosed everything down with fresh water and after a couple of days of drying, the trusty Mac lit right up.
I still had the urge to fly but had only one good rotorblade left. The obvious solution seemed to be a one-blade rotor.
I had seen pictures of the one-blade helicopter by one of the predecessor companies of MBB, so thought, with insufficient thought, why not?
My first attempt wouldn’t autorotate; I had been in too much of a hurry so had used a length of 1½” steel rod for a counterweight but it was too draggy.
Dragged everything back to the shop and made up a proper counterweight; a teardrop shape welded up from 1/8” steel sheet with enough lead poured in for balance.
The rotor autorotated just fine and was glass smooth as long as the stick wasn’t moved. Rapid stick movement caused a violent vertical hopping about like a dirt-tamping machine.
I think I might have gotten daylight under the wheels but decided then and there one-blade rotors weren’t my piece of cake.
My friend Gary, younger and far braver than I, wanted to have a go at it. Gary was just then growing new skin after a bout with an overhead stick.
I said; “Gary, be careful, move the stick very slowly or it will start hopping pretty violently.”
Well, Gary wasn’t careful; the machine started hopping and he stirred it around rapidly trying relocate the sweet spot and it hopped over with the rotor at full speed.
Gary lost more skin and it was back to the drawing board for me.
I suppose the MBB helicopter worked because of the use of a Hiller style servo rotor which can be adjusted for very slow rotor following. I have no idea how they compensated for the unbalanced torque.