Item 1444

DESIGN: Electrotor-Plus ~ MRGA - Gyro - General


    1. The hub spring or offset teetering hinges provides additional cyclic control; at the expense of adding vibration.
    2. The gyro reduces this additional by 1.41 - 1 = 59%.



I think that the offset and the hub spring will assist the blade's out-of-plane moment as the blades move toward 0 teeter (flap) and resist the blade's out-of-plane moment as the blades move away from 0 teeter.

Concerns for Consideration:

Phase Angle:

Spring - About Y-axis: See last note.

Damper - In X-axis Moment Rods:

Cyclical Coriolis Due to the Hooke's Joint:

Lower Hooke's Joint on Rotorhub:

Control Moment Gyroscope:

Direct Torque Control Moment Gyroscope:

Related Pages:

Found this question and answer on It is the same as I was asking on Eng-Tips:

Subject: What happens if the gyro cannot precess?

Question: If you apply a couple to the gyroscope but stop it from precessing what happens?
For example I hang a weight on the gyroscope, but it cannot precess about a vertical axis because of a stop.
Does it move downwards instead of precessing, if so how fast?

The applied couple with horizontal axis should generate angular momentum parallel to this axis. How
does this show up if the gyro cannot precess? Is there another couple which cancels it? If so where?


Answer: A gyro is a flywheel with freedom to move at right angles to the spin axis. Remove this freedom to move and it is no longer a gyro.

Where Precession occurs it is always at right angles to the applied torque.
In the case you have given, there are two torques applied at the same time.
There is the torque due to gravity and the torque from the stop.

Torque is a vector quantity and therefore the sum of these two forces will produce a resultant torque. The Gyroscope will precess at right angles to and at a speed determined by the vector sum of the applied torques.

<< How does this show up if the gyro cannot precess? >>
If a gyro is restrained so that it cannot precess it ceases to be a gyro.
However any angular motion of a flywheel IS precession, if a gyro is forced into angular motion, in whatever direction, then the gyroscopic couple accompanying it is at a right angle to that motion.


Now to consider the ramifications. In my requirement the 'torque due to gravity' is the flapping of the blades and the 'stop' is the large moment of inertia of the total rotorcraft.

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Last Revised: January 26, 2009