B344

DESIGN: UniCopter ~ Control - Flight - Swishring

An Optional Idea:

Notes:

Higher Harmonic Control 'Humps/Dips' in the Ring to Momentarily Change Pitch so as to Reduce Rotor-Rotor Induces Vibration:

I believe that much of the vibration in an intermeshing helicopter is the result of aerodynamic rotor to rotor interaction. In addition, a twin rotor helicopter with very rigid 3-blade rotors (not 4-blade rotors), such as the Sikorsky ABC and the proposed UniCopter will be subjected to a lateral dissymitry of lift and H-force drag. If the blades were able to make small quick changes to their pitch, much of this vibration could be eliminated.

The idea is that the azimuths and/or the amplitude of these hump/dips be varied with changes in the crafts forward velocity.

Re rotor to rotor interaction; The following 6 lines will require updating to the slower turning (& larger?) rotors.

The circumference at 75%R is 452"

The blade will have a chord of 6" at 75%R and there are three blades per rotor.

That means that 6/452 = 1.3% of the circumference or 4.68º will be the size of each 'hump/dip'

At 700 RRPM, the duration of the 'hump/dip' will be (4.68 / 360) / (700/60 sec) = 0.0011 seconds.

Actually, it may be half of this because the other blade is moving also, in the other direction.

I think that the inertia of the blade will be too high to allow a change of pitch at anywhere near this rate.

See: [Source ~ CC p.267] for a sketch of a typical flight control actuator.

See: DESIGN: UniCopter - Rotor - Disk - Downwash Intersection Azimuths

Consider 'active materials' imbedded in the swash ring to give the 3P humps and dips

Concerns:

The 'cam-follower's contact with the upper and lower rings will probably alternate during rotor rotation. This will cause the cam-follower's direction of rotation to alternate. The current design of cam-follower has point contact with the rings and wear will be problem. This might be reduced by using a cam-follower without a curved outer diameter and having the cam-follower's outer ring mounted on a spherical bearing. Another improvement might be to have the rings wear instead of the cam-follower since they have a greater area.

Last Revised: February 14, 2009