Hub Springs

[PaulPounds]

Greetings all,

I recently ran across the section on hub springs at the Synchrolite page:

http://www.synchrolite.com/1230.html

I too looked into hub springs for my four rotor helicopter (though I didn't know anyone else was working on them at the time). I was using the springs to give my teetering rotors the behaviour of a hinge-offset which I could adjust by changing the springs.

The torques involved don't map to a full-scale heli, but I wondered if people are still looking into them.

Thoughts?

-Paul

 

[Intermesher]

Paul,

The use of a hub spring is not appropriate for a 2-blade rotor. The rotor will experience the same 2/rev vibration that a 2-blade articulated rotor would.

Basically, a teetering rotor pulls the top of the mast to reorient the craft. An articulated rotor also pulls the top of the mast, but in addition, it pries the mast over due to the centrifugal force operating at the offset hinge.

A hub spring rotor or articulated rotor with two blades would experience both forces when the blades are aligned with the tipping of the plane and only the 'pulling' force when they are normal to the tipping.

Three or more blades per rotor will eliminate this problem.

If you are willing to have three blades per rotor, you might want to consider;

http://www.synchrolite.com/1377.html

Hope this helps.

Dave Jackson

 

[PaulPounds]

Thanks for the tip about the vibration - that might go some way to explaining some control problems we'd been having that went away when we removed the springs. As it turns out, I don't think we will use the springs at all because our stability model shows we don't need them.