To Teeter or not to teeter....

[KiteGuy]

I have been having some difficulty wrapping my head around the concept of TEETERING rotor blades and/or hubs:

1. Does teetering fix the problem of having the main rotor blades encounter apparent wind from angles different than the most desired angle? If not what?

2. If I do not desire to do any 3D stuff, might I not be better off going for simpler fixed rotors that are somewhat more flexible so teetering would not be necessary? I understand that some of the more recent military helicopters do that.

A kind person emailed me some documents regarding teetering that were scanned 90 degrees to the right. I developed a crook in my neck when trying to read them. Would someone please tell me what I should know or direct me to text I can read AND UNDERSTAND :o .

Thanks,

Wayne German
WayneLGerman@Yahoo.Com
503-538-4132

[Robert G. Stark]

The teetering of the blades compensates for the difference in lift generated by the advancing blade and the retreating blade. Very early attempts at gyros failed for lack of teetering. When the gyro started forward, it would roll over.

[KiteGuy]

Thanks Robert,

Then reading in between the lines I would guess that during an advance a blade needs less positive pitch than when it is retreating. But how does the hinge help? From what little I can glean it appears to be passive (i.e. not powered). How does it reduce the pitch of the advancing blade or increase the pitch of the retreating blade? Can all of this be done passively? You can see by my face here that I am more than a little mystified. :confused:

[bones]

shoot even i can answer this one,,, the teetering does not change the pitch of either blade, what it does it alows the advancing blade to rise cause of the high air speed than the reteating one, and the retreating one to fall at the same time, basically it alows the rotor to sea-saw as it rotates, thus egualing the lift on both rotors....

[KiteGuy]

Thanks Mark,

It's really neat how a few kind shoves will get you going in the right direction.:) Now to cement this into my cerebrium I would appreciate it if someone would attach a picture of a rotor head with: 1) part names included, or 2) a brief description of what I am looking at. I now know WHAT teetering does. Now I need to know how the hinge works that makes it happen. A drawing could substitute. Thanks for you help.

-- Wayne

[Friendly]

Wayne
I would recommend you purchase Paul Abotts books on Gyro planes. He discusses the theory in a manner that a beginner can understand with lots of illustrations. It will be a good aid when you begin your flight training as well. The books are reasonably priced

[Robert G. Stark]

Where can we get the book??? I know how these things work, being able to explain them is the hard part.

[Robert G. Stark]

Also, read the post on AOA. Angle of Attack.

[Paul Salmon, MD]

The FAA publishes a guide and I believe the title is "Manual of Rotor wing flight?" or something close to that. It explains both helicopters and gyroplanes in great detail. It is probably available on AMAZON.COM books.

[Matthew Parsons]

The rising advancing blade and falling retreating blade is often called "flapping to equality", although I'm sure there are many other terms. Current RW aircraft that don't have teetering hinges aren't routinely rolling over uncommanded, indicating that something is happening to laterally balance lift that doesn't require a teetering hinge.

Teetering hinges prevent mast moments, meaning they don't allow the rotor to bend the mast. In helicopters that require manoeuvrability mast moments are desirable. However, to make the mast strong enough to transmit these moments without snapping, the masts must be significantly stronger. Thus, a mast on a teetering head will be much lighter than an equivalent mast on a non-teetering head. I believe this is one of the most significant advantages.

[mceagle]

How does it reduce the pitch of the advancing blade or increase the pitch of the retreating blade? Wizbang, To try to put it simply, an advancing blade that is rising is effectively decreasing its angle of attack (pitch) to the relative wind, while a retreating blade that is descending is hitting the wind at a greater angle of attack (higher pitch). In practice though, it is not actually that simple.
The teeter hinge allows the pilot to control this pitch variation through changing the angle of the teeter bolt (via the rotor head), thus controlling the gyroplane.

[KiteGuy]

Thanks to all for your kind help.

-- Wayne