How Coaxial RC Helicopters Work-共轴直升机原理

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原文内容链接：http://www.rctoys.com/pr/2008/04/17/coaxial-rc-helicopters-information-resource/

What is a coaxial RC helicopter?

什么是共轴遥控直升机？

There are several different approaches to coaxial rc helicopter design.There are two main ways that the main rotors of a helicopter can be mounted. In conventional helicopters, one main rotor is mounted on top of the fuselage, and a smaller tail rotor is added to the end of the tail boom. In this system yaw is controlled using the tail rotor, and every other aspect of flight is controlled by altering the pitch of the main rotor blades. It is also important to have a tail rotor so that the torque from the main rotors can be canceled out. Torque is caused by the main rotor spinning in one direction. Because of Newton’s laws of physics (for every action, there is an equal and opposite reaction), the nose turns in the opposite direction.

有几种不同的共轴直升机的设计，主要有2种主旋翼固定方式。传统直升机有一个主旋翼固定在机身顶部，较小的尾旋翼固定在尾管的尾部。这种设计通过尾旋翼控制旋转，其他方向控制通过改变主旋翼的螺距。尾旋翼同样对消除主旋翼的反扭力至关重要。反扭力是主旋翼朝某个方向旋转造成的。由于牛顿物理定律现象的存在(任何作用力都会有相同的反作用力)，机头会朝主旋翼旋转的反方向旋转。

How Coaxial Helicopters Work
共轴直升机原理

Instead of using the tail rotor to control the yaw, two main rotors can be mounted on the helicopter, and spun at different rates. The thrust difference will cause the nose of the helicopter to turn. This dual rotor design is employed in several full scale helicopters, including the CH-47 Chinook, frequently used as a military transport helicopter because of its immense lifting capacity. The same principle applies to remote control helicopters, but most of the time we choose to mount each rotor on the same axial, hence the term “coaxial”.

不同于使用尾旋翼控制旋转，2个主旋翼被固定在直升机上，通过不同的旋转速率控制直升机旋转，反扭力的不同将导致机头转向。这种双主旋翼设计应用于几种全尺寸的直升机，包括CH-47支奴干直升机。频繁地应用到军用运输直升机，因为能够提供巨大的载重力。同样的道理应用到遥控直升机，但是绝大多数情况我们选择同轴固定2个主旋翼，专业术语称作“共轴”。

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Paired rotors spinning in opposite directions
配对的主旋翼反向旋转

The rotors of a coaxial helicopter need to spin in opposite directions to cancel out the gyroscopic force. On some helicopters, both rotors are on top of each other The main axial of a coaxial helicopter actually consists of two separate axils, one mounted inside the other. Each sub axial is connected to a gear at the base of the shaft, and each gear is attached to an electric motor. These two motors operate independently of each other, so varying the speeds of each rotor is possible.

Since the rotors need to spin in opposite directions, the top and bottom rotor blades are curved in opposite directions. This is because each rotor needs to be pointed into the air flow in order to work. The bottom rotor usually rotates in a clockwise direction, while the top rotor rotates in a counterclockwise direction. It is important to note this if you need to replace your helicopters rotor blades. Your helicopter will not fly if they are installed incorrectly.

主旋翼的旋转方向相反抵消反扭力。某些直升机，两个主旋翼在主轴的相应位置上，实际上是两个独立的轴，一个轴在另一个轴的内部。每个轴连接一个齿轮，每个齿轮由1个马达驱动。两个马达相互独立，所以每个主旋翼转速的独立变化成为可能。

因为主旋翼要反向旋转，所以上下两个主旋翼的翼形曲线也是反向的。这是为了每一个主旋翼正确的产生升力。在下方的主旋翼一般顺时针旋转，而上方的主旋翼逆时针旋转。这点在更换直升机主旋翼时要特别注意。如果安装错位，直升机将无法飞行。