View Full Version : Rotor Angle of Attack
Can you tell me what the Maximum AOA you can get when setting on the ground in three point position, and what the minimum AOA you can get in the same position.
Also what size of tubing did you you use on your pylon for the rotor?
07-01-2007, 10:39 AM
TLAR, that looks about right. This Tlargyroplane is an altered example of a tractor gyro. It is meant to show some of the essential points of concern early on in the design mission.
1. Find the center of gravity of AUW, all up weight of gyro. Position very near the thrust line.
2. Postion landing gear. Ideal for tractor gyro is 15 to 17 degrees for good handling. The angle of 16.7 is very near ideal.
ATAN(15/50)180/PI() = 16.7 degrees. opposite is 15, adjacent is 50, = 16.7 degrees
3. Position the rotor head behind the CG 9 to 12 degrees. This was set in the middle at 10.5 degees. This is for the control to have full authority for tilting the rotor.
ATAN(13/70)180/PI() = 10.5 degrees. opposite is 13, adjacent is 70, = 10.5 degrees
4. Set height on the mast so rotor will miss the tail. This rotor will contact the tail rudder, set at 68.1 degrees, if any inadvertent flapping occurs, unless a device is used to hold
the blade up during spin up. Ideal angle of 50 to 53.3 degrees is necessary. This example..........
ATAN(137/55)180/PI() = 68.1 degrees. opposite is 137, adjacent is 55, = 68.1 degrees, way too much.
5. Postion the tail wheel. This allows proper angle of rotor for the start up run. Trikes are about 5 degrees and tractors are 7 to 9 degrees.
ATAN(19/154)180/PI() = 7 degrees. opposite is 19, adjacent is 154, = 7 degrees.
07-01-2007, 12:29 PM
I guess I didn't see this thread when you first posted it; sorry.
I use a single 2x2 aluminum piece for the main mast, but it has a flying wire on each side for lateral support, and the fore/aft mast support that attaches to the top of the roll bar.
With the stick locked all the way forward the rotor head is tilted about 1 degree back.
I've never measured the angle in the rear-most position, but it's a RFD rotor head and I think it has about 28 degrees of travel.
The fuselage sits at about a 10 degree angle when on all 3 gear.
07-02-2007, 12:58 AM
Where did you get the figures for the ideal placement of wheels, mast, etc? I mean, who originated the numbers?
I liked the drawing, but am confused as to the line you drew for center of pressure. Was that line just a notional center of pressure, or what? How do you figure the CoP (how is it drawn and depicted?)
How about center of drag?
Where did you get all of this excellent info??
07-03-2007, 03:55 PM
Originally Posted by magilla
Can you send me more info on where you got thse numbers for "ideal" placement?
Spencer, I have no credentials. I am a name dropper and a plagiarist. How about Arlis Riggs, Pazmany, Ed Alderfer, pbool, John Voor Husesen, Barnaby Wainfain, Beaujon, Dennis Fetters, Clyde Beaty, Raghu A.. Herron, P. Abbott, J. Eich, Hollmann, Cierva, J. Tervamaki, Stiles, and of course ole what's his name, Bensen.
I would like to "judge" my Jungle Gym tractor against the design criteria.
Also, how do you figure Center of Pressure and Center of Drag? (how are they drawn??)
This from Abbott, make a cut out of the side or top with the pilot in the seat and balance it on a knife blade, cop should be behind teeter bolt, 3 to 12 inches. The Vancraft was right on the teeter bolt. Most are farther back than that. It measures the windvane effect. Do a top view and see if your horizontal is effective.
07-03-2007, 04:00 PM
Here are two sites or pictures of Ken Rehler accident where he was killed in a yaw down draft.
Shows too little wind vane stabilty.
See if they come through.
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