RC Helicopter Gyro Explained

RC Helicopter Gyro Explained - Part 2

Now that we know what a gyro is (from the previous post) lets see how it applies to RC helicopters.

Why does a helicopter need a gyro? The answer is - for stability.

As you might know, in a helicopter the main rotor generates both the lift and the trust. Therefore the engine (or the main motor) has to provide a lot of torque to the rotor. Unfortunately, this torque not only spins the rotor but also spins the fuselage of the helicopter in the opposite direction. That's why a helicopter needs a Tail Rotor or a similar 'anti-torque' mechanism to cancel out the torque on the fuselage.

To keep the helicopter stable the anti-torque mechanism must respond quickly to any changes in torque. But the problem is, the torque is always changing. Changes in the engine or motor speed, changing the pitch of the rotor or even gusts of wind change the torque and will try to spin the helicopter out of control. In a RC helicopter, manually adjusting the tail rotor for these constant changes would be next to impossible. The helicopter gyro takes care of this by detecting any yaw movement (swinging movement) and sending the commands to the tail rotor (or any other anti-torque mechanism) to compensate for it.

What are RC gyros made of?

In the early days, RC helicopters also used mechanical type gyros. These consist of two flywheels spun by a small motor. This setup was mounted on a pivot and a magnetic sensor detects any movement of the wheels happen because of the movements of the helicopter.

A mechanical gyro used in old RC helicopters

The newer RC models use piezoelectric gyros, which has several advantages over the mechanical ones. Reduced size, weight and battery consumption and improved accuracy have made the piezo-gyro the choice for the newer models.

A piezoelectric gyro used in newer RC models

Gyros are also divided in to two categories by how they respond to yaw movements - Yaw Rate Gyros and Heading Hold Gyros. I'll talk about them in the next post.

References
http://en.wikipedia.org/wiki/Helicopter
http://en.wikipedia.org/wiki/Radio-controlled_helicopter
http://en.wikipedia.org/wiki/Tail_rotor

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