Passin' Thru
Newbie
No, not in pitch to any degree although his pneumatic trim system may mask any anomalies.
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hhuummm! Now THAT is ..... "interesting!"
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No, not in pitch to any degree although his pneumatic trim system may mask any anomalies.
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Still, has some difficulties,hope you can help me.
Is the main Rotor used to turn the gyrocoptrt(tilting) or it's only there to define height of the gyrocopter?
Hi Terry.
You've made me curious, Does this type of rotorhead eliminate under sling? If so, doesn't under sling help balance center of mass changes when one blade is higher in the plane of rotation than the other. Or have I got things wrong again?[/
Dennis, you are correct, but the necessary undersling can still be achieved.
One interesting example of this type rotor head is the one built by Dick DeGraw for his wife's gyro, "DeBird" I think he calls it. He went this route in order to facilitate some other features like continous partial power and jump takeoff. All design involves trade-off, and there are always some "down-sides", or negatives. In rotor heads of this type stability can be a problem. "Neutral" trim centering and control sense feed-back must be artificialy augmented. Absents of control pressure graduant may sound good on paper, but it is very unpleasant to fly. Without a very stable airframe, it is suicide!:sad:
Back in the 60's Jerrie Barnett designed and built a simular arrangement for the JB-4. He coupled the prerotator drive universal directly to the spindle. After a bit of experimental experience, he realized the positive stability advantages of the offset and moved the pitch axis forward of the spindle. Eventualy he went full-circle back to his earlier-later "offset yoke" design with a few revisions. :yo:
Hi Terry.
You've made me curious, Does this type of rotorhead eliminate under sling? If so, doesn't under sling help balance center of mass changes when one blade is higher in the plane of rotation than the other. Or have I got things wrong again?
Terry, NONE of the photos yo show are Karrol DeGraw's "DeBird"!
The "Gyrino" is Dick's original jump takeoff machine he built about 20 years ago.
If you look past the drive and the "wooblin' rod" cyclic / collective, up there in the black short cylinder you'll find what you're talking about. At least as best I can interpet what you are talking about.
I don't know what the red machine is, except it is just another way of increasing the undersling without raising the head. I've used that method in a couple of my experiments.
Terry, here is a video you may or may not have seen.
The first gyro visible is the "Gyrino"; the second one that looks somewhat like a 2-place Dominator is Karrol DeGraw in "DeBird".
It ain't what you're looking for, but I thought it may interest you.
http://www.youtube.com/watch?v=9gfBYARn-T8
I basically have gone through the same thoughts as you Terry….and semi-ended up with a semi-rigid head, which has its own problems. It did fix the pre-rotation "control-torque" problem though. I always came back to my rigid-head because it "fixed" the stuff I didn't like and most of what you're talking about….although it does add some of its own peculiarities….like a swashplate and servo-tabs, but these I can live with. If you want simple, go with the standard run-of-the-mill teetering head.....and learn to live with it .
The Bell H-13 and I believe the Hiller have those axis on the same gimbal plane...the "problem" is that the shaft/mast must have enough clearances from this head hole for antiquate teeter in all axis. The head must therefore be larger and stronger due to that center hole. Sigh....I know....clear as mud.
Here’s a rotorhead with coincident teeter hinge and roll/pitch pivots using a Shafer A-8 spherical roller bearing.
Its only usefulness was as a learning tool. It taught me the essential roll played by rotor thrust feedback in making unstable gyros flyable.
It appears that some helicopters get by without roll and pitch or offset spindle feedback.