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Old Nov 27, 2010, 10:20 AM
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Waynesville, NC
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Gyros - how do they work?

Just got a Helizone Firebird, and am trying to figure out how it achieves that amazing stability. According to the literature it has an internal gyroscope in the electronics.

Can someone explain how it works and relates to the counterweighted flybar above the rotors?

Thanks,
Jack
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Old Nov 27, 2010, 10:38 AM
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The gyro is a MEMS device, and is very sensitive to motion. The gyro is essentially between you and control of the motor speeds. If say a draft tries to rotate the copter, the gyro will sense this. If your control inputs didn't direct that rotation, the gyro will automatically turn the copter back. If it lets it rotate at all, these are getting TIGHT.

So the effect is the nose stays pointed in one direction when you try to fly straight forward. The gyro also compensates for precession, the force that causes non-gyro copters to want to circle instead of flying forwards.

The flybar is independent of the gyro for the most part- what it does is try to keep the Main Shaft below it at right angles to the ground. As the flybar spins, its own gyroscopic forces tend to make it assume a parallel orientation to the forces of gravity (straight down in most places*). Since it is linked to the upper rotor set, it pulls them into that same plane.

When you push "forwards" on the Tx stick, the tail of the heli lifts, and the Main shaft is tilted forward. Since the spinning flybar is also initially tilted, the upper rotors follow, and their airflow directs more to the rear of the copter. The copter flies forwards a short distance, and the flybar progresses back to being parallel to the ground, and the copter slows.

It's a fine balance that allows a coaxial design to continue flying forwards smoothly. In some more crude implementations, the heli "Porpoises", speeding and slowing, dipping and lifting slightly as this process repeats. Even when everything is in harmony, you can still notice the effect visually if you look close.

The bottom line is, skip the non-gyros now for they are unarguably Old School stuff today. The only exception I will point to is Syma's Big S022 Chinook, which being a Tandem, doesn't suffer so bad from being without.

*Certain parts of Santa Cruz, CA are exempt.
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Last edited by killbucket; Nov 27, 2010 at 10:48 AM. Reason: Imagine a Wii controller fighting back, and you have it.
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Old Nov 27, 2010, 03:13 PM
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Thanks - great answer!
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