Item 0954

OTHER: Miscellaneous - Thoughtless Idea - Coaxial Transmission w/ Yaw Control

Objective:

This design provides for yaw control in all flight realms, without the requirement to reverse the pedal linkages when transitioning to autorotation. Yaw is achieved by varying the relative rotor rpm between the two rotors instead of applying differential collective.

Drawing:

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Description:

The large outer pinion drives the upper and lower outer crown gears in opposite directions. This gear set would have a ratio of approximately 4:1

Inside and attached to each of the above two outer crown gears are inner crown gears. These inner crow gears intermesh with their own set of 3 or 4 inner pinions and these two pinion sets have their own holder, similar to the planet gear holder in a planetary gear drive. Between the two inner pinion gear holders is a 'control' gear with back to back teeth.

Each pinion gear holder is attached to its own mast. If the control gear remains stationary then there is a 2:1 reduction between the outer crown gears and the masts, and this give a total reduction of 8:1.

The control gear does not want to rotate since the CW torque on it matches the CCW torque. If this crown gear is friction driven from one or the other of the outer crown gears then one rotor will turn faster than the other. I.e. yaw. In other words, what is done to the control gear determines the rpm of each rotor and/or where the rotors blades cross each other.

 Notes:

I think that a specific azimuth of the control gear will give a specific location for blade crossings. In other words; there is a single home position, in rotation, of the control gear which results in the rotor blades of the two rotors always crossing at the same rotor azimuths. 

 Yaw:

Method A;

The central back-to-back crown gear has two indents on its outside circumference. They are located at 180 degrees to each other. Two spring-loaded cam-followers have the ability to ride into or out of the two indents. When in the indents they hold the orientation of the rotation of the rotors in respect to each other.

Each of the pinion planetary gear holders has its own brake device that can make contact with its outer circumference.

As one of the pedals is depressed, braking is applied to the appropriate pinion ring gear and at the same time the spring loaded force on the cam-followers is decreased. Yawing is enacted by the reduction of rotation speed in the appropriate pinion gear holder and that decrease in rotational speed being transferred via the crown gear to the other pinion ring gear, and its mast.

Method B:

The central back-to-back crown gear is rotated in either direction and at any speed, by some device, depending on the direction and amount of yaw required.

This 'some device' could be by locating a worm wheel between the crown gears of the central back-to-back crown gear and then driving this central 'sandwich' by a worm. The driving of the worm could be done by an electric motor. If the ratio of the worm & wheel is 10:1 or greater friction will hold this 'sandwich in position and the motor would only be used during yaw or to adjust the blade crossing azimuth. Concern: This motor may have to be quite large

 Miscellaneous:

An additional outer pinion can be added if there is the desire for two engines.

 Potential Concern:

Aligning all the gears.

The overrunning clutch may have to be located on the outer pinion and this means that the complete gear box is on the rotor side of the overrunning clutch.

The synchronizing of two engines may present difficulties.

 

Publication:

Date:

 

Homebuilt Rotorcraft

Nov 2001

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Initially displayed: November 5, 2001 ~ Last revision: October 8, 2007