Below are some altered tandem helicopter that I had intended to be for my patent HIR concept as well, but tweaked to depict a tandem gyroplane. A buddy of mine has been working on a small scale proto of this concept. Like me, he's crashed a few models working through the issues. In conjunction with rotor thrust lines, I had been curious if the geared free wheeling hubs may have a disturbance of air flow with regard to the relative wind. Perhaps the blade tip vortexes disrupt everything...think that's the right term for it. Any way... those little circular flows of air at the tips of the rotor blades. I've seen them when we've popped smoke and the blackhawks flew in to pick all of us grunts up. I'm not an expert, just trying to help a friend trouble shoot.
Ungeared tandem gyroplane. Blades tips have clearence. Relative wind/air columns do not overlap.
Geared, free wheeling tandem rotor gyroplane. Blades pass between one another. Synched, but relative wind columns overlap.
Below was the powered tandem helicopter that I had intended to utlize with the HIR concept. The coaxial works and the single mast almost works.
Below, a couple of pics of Joe Nelson's tandem gyro rigid tethered test jig. The second pic he finally got stable hover. He has had issues with the free flying model with inconsistent rpms between hubs and other issues. He's getting closer to his goal.
5 comments:
I read somewhere about an experimental gyroplane with dual counter-rotating blades. It didn't work, because the lower blade blocked airflow to the upper, causing an unbalanced distribution of lift.
I've been playing with the idea of a tandem rotor gyroplane, and I think the front rotor might block airflow to the rear rotor in a similar fashion. This would certainly account for stability issues you're seeing. I think the solution is to have the rear rotor on a much higher mast, so both rotors can get clear airflow.
I've mocked up a quick visual in paint: http://img132.imageshack.us/img13
Whoops, wrong address for the picture.
http://img132.imageshack.us/img132/6881/tandemrotorgyroplane.png
Seth,
Joe has done a few configurations similar to your drawing. They did not do well in the "garage wind tunnel" test that provides good relative wind for testing his concept. The columns of air would disrupt one another preventing good even flow up through both rotor discs at the same time. That's not to say you cannot find a way to make your version work. The gratification is the process of finding it out.
Joe finally found a stable configuration with the blades not inter-meshing between one another.
I would expect that the only way to insure a stable air flow for both rotors would be to have them mounted outboard (left and right)from the fuselage. I would also think that having the blades pitched so that they counter rotated would also add stability. Just some musings from a dumb old country boy
Yeah we discussed that given the dual rotor gyro that I've seen fly were outweighed. There's no such thing as a dumb country boy. Some of the most creative mechanical thinkers/problem solvers were and are country boys. Usually out of it being necessity or obsession/ hobby. Some of them I knew and learned from. Dave
Post a Comment