Emilio Cabezas

Hi,

Remember my two-bladed, .25 engined pusher? I posted some photos and comments a couple of months ago under the subject "Promising two-bladed pusher design". I´ve been flying this model for some time using a two-blade rotor; blades individually hinged. The model flew but was rather difficult to handle; one must be alert in order to make corrections due to frequent unwanted pitch and roll motions. Recently I have fitted a teetering head (single central hinge, like the full sized gyrocopters) and, much to my surprise, the model flies now much better than it did with the individually hinged blades. I used the same blades in both cases; only they are slightly heavier now (5 more gramms for each blade). The flight photo is an old one (individually hinged blades) for I was alone at the field when I flew the teetering variant. The other photos show some details of the modified model. With these results and those obtained by Jochenk (I recently posted a link to his video) with his electric, teetering head pusher, I´m led to think that, contrary to the previous beliefs of many of us, teetering heads are a good option for two-bladed Bensen type RC autogyros.

Emilio

mnowell129

Congratulations.
How much blade weighting is used?
Are they CG corrected?
mickey

billf

Very interesting result! Thanks for your report, Emilio.
One question: Do you employ any delta-3 in the pivot? As I recall,
John Kallend used delta-3 for his Whistler...The idea being that
he could get smoother teetering.

Bill

floridagyro

Very good Emilio

If you remember Hal debolt, he built a large tractor type gyro and used a teetering head. It also had a single central hinge. His plan was to just lift off the ground and bring it back down for the first flight. Unfortunately it lifted off much sooner than expected and it was flying very good but he chopped the throttle anyway and it crashed into a fence, never to be tested again.[]

You have a pusher but do you think the teetering head would work as well with a tractor type?

Emilio Cabezas

Mickey, Bill, Phil,

Many thanks for your kind words. I´m very happy that I finally got good results with a Bensen type, teetering head autogyro. I was really amazed that the model flew in a so sedate manner.

Mickey, I use 20 grams (0.71 oz) of lead near the tip of each blade, close to the hardwood leading edge so as to bring the C.G. at 33-34% (from the leading edge); this is also the blade bolt location. The blades are rather heavy (2.42 oz each for a rotor diameter of 50.4 "); I thought it was necessary for a teetering rotor without a flybar.

Bill, I don´t employ any delta-3 in the pivot. I also recall John Kallend used delta-3 for his Whistler. It might be worth trying; I think the main advantage would be an easier rotor spin-up, specially for take-offs from the ground.

Phil, I think the teetering head would work as well with a tractor type; these tend to be more stable than short fuselage pushers so the results could be even better. However I don´t think that teetering heads are better than hinged or flexible heads and 3 or 4-blade rotors; these work very well with tractor types.

Emilio

floridagyro

Hi Emilo,

I like the simplicity of the teetering head and it's one less rotor blade. My Wallis gyro has a swashplate and also a teetering head. It's the most stable gyro that I have ever flown. Do you think less torque is required by the servos with a teetering head vs. the flapping blades?

What's the weather like in Spain now?

Phil

Emilio Cabezas

Hi Phil,

I´ve been several days away from Madrid; saw your note today. Well, as far as I know, teetering heads require the least torque by the servos. Moment (force times distance) is zero at the single hinge location, while there is some moment to overcome when tilting an articulated (flapping blades) or a flexible head, due to a combination of blade centrifugal force, blade tip path plane and "hinge offset" (distance from hinge to rotor axis; usually measured in full size rotorcraft as a percentage of rotor radius). This moment is quite low for low values of "hinge offset".

The weather in most parts of Spain is warm and sunny now.

Emilio

ottogiro58

Hi Emilio, Congratulations, It is great that you are having such success with your two-bladed teeter head model. I have always felt that two-bladers are the way to go !!! Eager to see more...... Any video of it yet ?? Thanx !!! Charlie Anderson

Emilio Cabezas

Charlie,

Thanks for your kind note. If I ever get a good video, I´ll try to post it. Perhaps, in the near future, I will undertake the building of a slightly scaled-up version, suitable for a .46 engine. Emilio