billf

Back when we first started getting together (PHARTS I,II, III) Ralph Kalb, who was a physicist with a company in Milwaukee proposed an autogyro design with two rotors outboard and more or less in line with the thrust line of the engine. At PHARTS III, a couple of fellows from Worthington MN showed up with an autogyro that had side-by-side rotors attached to separate outrigger shafts that could be individually rototated. The shafts however, were mounted high on the fuselage. The plane flew very well and was responsive in roll. So with some spare time this Fall I decided to combine the comcepts. (See attached photos).

I have been delaying publishing these picts until I was able to claim that the "durned thing flys." Well, today, with the temp around 35 I was able to have the first successful flight. Previous attempts had resulted in the plane pitching up vertically on lift off. So after moving the attachment point of the outrigger shafts so the center of lift was moved back and moving the batteries as far forward as possible, the plane now took off smoothly. Roll control was smooth with the rotatable outrigger shafts. One of the problems with dual side-by-side rotors can be solved by adjusting the 'aileron' trim so that the slower speeding up rotor is given a bit more angle of attack, while the other rotor gets a bit less AOA. Since each outrigger shaft is controlled separately, a computer radio allows 'flaperon' operation. Thus both rotors can be tilted back simultaneously to assist spin up. Then the 'flap' control is neutralized and the rotors assume their -5 degree tilt back.

With winter threatening to arrive (finally) around here, I'm not sure of many more test flights...so I'll bring the plane to the March Spring Hill get-together.

BillF

rcflyerfl

My Feedback: (1)

Bill,
You certainly have a very interesting looking Autogyro there.. Glad to see you have been exercising your brain on a regular schedule..
If I can make the fly-in at the cow field I would like to look it over.
Good luck with it..

Jim

floridagyro

Hi Bill,

I really like your design. Do you remember when I tried that. I used aluminum tubing with one large servo in the center that would rotate one forward and one back. My best design was the servos mounted on the end of each boom which would rotate the rotors, very similar to your design. I didn't have the coning angle in the blades, like your design, rather I had the rotor booms coming from the fuselage at a 10 degree up angle, sort of like dihedral in a wing.

If you remember, it would fly great but it would like to flat spin sometimes during a turn and it would flat spin all the way to the ground.

What did you use for rotor blades?

Good luck,

Phil

billf

Hi Phil..
Happy New Year!!

I had forgotten that you had built a plane with tilting outriggers. Forgive me for not mentioning your pioneering effort. While I mentioned that the plane flys smoothly, my piloting skills probably are not up to demonstrating the full menu of maneuvers that this plane probably can do. You will have to give it a try in March!! <G>

I used my usual balsa cored, fiberglass covered SG6042 airfoil blades. I started the design by weighing everything and then calculating the rotor area needed to get to less than 5 oz/sq.ft. (I should reweigh now and see just where the number is now.) One problem that comes up with the rotors so close to the thrust line is that it is difficult to measure a hang angle and adjust it by moving the batteries here and there. Thus my first two flight attempts resulted in vertical pitch up immediately after lift off. Maybe there can be some formula figured out that relates the center of the lift point with the position of the CG. Or, the relation of the tilting outriggers to the CG???

Regarding the coning angle, that is the result of the TLAR discipline (That Looks About Right).

If we get any more unseasonable warm weather here, I'll try another flight.

Bill

floridagyro

Hi Bill,

I was just looking at your gyro and it doesn't look like you have much down thrust for the motor. I've found, for whatever reason, that I have to put 5 to 8 degrees of down in these motors to get them to handle right. On the duel rotors I hold the gyro by the two rotor shafts and check down angle. About 10 to 15 degrees works for me. I always start with more nose down and more down thrust in the motor and if it gets off the ground I can adjust later. I've lost too many of them when they pitch up and then roll over into the ground. I also, have about 10 to 12 degrees pitch up in the rotor shafts.

DC gyros are the worst culprits, if they pitch up on takeoff, without the conventional elevator, you can't get that tail up.

Hope this helps.

Phil

billf

Hi Phil...
Ah, you are so perceptive!! I had about 3 deg down on the motor and have now added another two. You may have noticed that the fuselage actually is a profile PT. So with the outrigger shafts located just about on the thrust line, it's tough to get anything like a reasonable "hang angle" like when the rotors are mounted higher. Anyway, I think I'm close now with the CG location in relation to the outrigger shafts. As you noted, I do have both rudder and elevator controls as well as the flaperon function for the rotors. On the few flights so far, I have used the 'flaps up" position of the rotors just to get the rotors spinning during taxiing. When they begin to spin up, I'll flip them back down to about 5 degrees tilt-back.

Bill

rcflyerfl

My Feedback: (1)

Bill,
I noticed the PT Profile but wasn't going to say anything.
When you talk about the 5oz per sq. foot are you using the same formula that was used for the Clark Y airfoil.. I have found that the SC 6042 will lift a lot more that the Clark Y.. Just my thougts..

You still have a neat Autogyro..

Jim

boberos

Nice work, Bill,

Hope to see you & it at SpringHill in March.

About coning on dual rotor gyros. Some say it is important; others say not.
Everyone seems to agree that a little dihedral is a good thing.
Comments?

Bob G

floridagyro

Hi,

I found that on a dual rotor, you have two choices. If the booms come straight out from the fuselage you have to have coning to control with the rudder or you can bring the booms out and up about 10 degrees, like dihedral in a wing, you don't need coning in the rotor. I usually bring the booms up about 15 degrees and then tilt the rotor shafts out about 5 degrees and that helps to prevent the blades from striking the boom.

Phil