Reciprocal feathering? Don't know what to call this...

piolenc

Joined 6/2007
Joined
Jun 27, 2007
Messages
113
Location
Iligan City, Philippines
Aircraft
none
Total Flight Time
13 (student)
This is about an alternative to flapping as a means of cyclically varying the incidence of the rotor blades. In this scheme, the two opposing blades are rigidly linked to each other, but are held to the hub by a bearing that allows them to feather - that is, to change their incidence. A decrease in incidence of one blade produces a corresponding increase for the opposite blade. The position of the feathering axis with respect to the blade chord lines is chosen so that the blades oppose each other, each one trying to reduce its own angle of attack to the local stream, forcing the opposite one to a higher angle. Naturally the advancing blade, seeing higher dynamic pressure, is able to feather itself to a degree, forcing its retreating mate to a higher angle, thus balancing the aerodynamic forces on the two blades.

Years ago I thought I had "invented" this, only to find instances where others had used it. Now I'm searching for it again, but I can't find it, which means that I'm using incorrect search terms. Can somebody help me with the correct teminology?
 

karlbamforth

Newbie
Joined
Nov 2, 2005
Messages
1,336
Location
Langkawi, Malaysia
Aircraft
Fixed wing/ rotary
Total Flight Time
500+
Wilford rotor ??

Wilford rotor ??

Marc,

That sounds like the Wilford rotor system.

Send me your email I have a couple of pics/drawings.
 

piolenc

Joined 6/2007
Joined
Jun 27, 2007
Messages
113
Location
Iligan City, Philippines
Aircraft
none
Total Flight Time
13 (student)
Marc,

We discussed the Wilford system here.

http://www.rotaryforum.com/forum/showthread.php?t=9582&highlight=Wilford

I may have some other documents not posted here, if so I will send to you by email.

I have a lousy memory. I had seen that thread and downloaded your pictures, then visited the NASA site to get the two NACA reports cited...then gotten submerged by some incoming translation job and forgotten the whole thing.

Yes, yes, yes. Anything you come up with that is not already available online would be most welcome!
 

piolenc

Joined 6/2007
Joined
Jun 27, 2007
Messages
113
Location
Iligan City, Philippines
Aircraft
none
Total Flight Time
13 (student)
The earlier discussion of the Wilford rotor system seems to be gone. Too bad, because I think that Irv Culver's early work for Lockheed (which eventually led to the Cheyenne, among other things) may have offered a solution to the over-rotation problem of the Wilford rotor. See US Patent number 3,080,001. It is for a helicopter rotor, but it seems to offer an easy way of varying the moment of inertia of the rotor around the feathering axis. It also seems to be trying to change the "flapping" properties of the rotor, even though it is not hinged to flap.
 
Top