The Swashplate

Here you see a picture of a four-bladed rotor system with a swashplate. You can download it here . If you have never seen a swashplate before this probably looks completely alien. At least that's how I felt when I first saw one. But don't worry. I will explain very carefully how it works and how to build it.The swashplate works by changing the angle of attack of the blades as they go around. This causes more lift to be produced on one side of the rotor and less lift to be produced on the other side. As a result the helicopter is able to move around.The swashplate consists of two parts: a lower and an upper swashplate. The lower swashplate, is stationary and consists of four pistons moving around an inert block. Note that since pistons are used, the controls are RTC (return-to-center). The lower swashplate transmits movements to the upper swashplate, which is spinning together with the rotor. The upper swashplate then pushes on the pitch hinges, which causes the blades to change angle of attack. Control inputs made through the swashplate are called cyclic pitch or cyclic for short.A helicopter also needs a way to increase and decrease the thrust. It does this by changing the angle of attack of all blades simultaneously. That is the purpose of the last mechanism, which is called the collective pitch. It works by moving the entire swashplate up or down, thereby causing all the pitch hinges to be pushed in the same direction. The piston just under the rotor, highlighted in yellow, is simply there to act as a suspension so the swashplate is able to freely move up and down.By using steering hinges for the collective pitch mechanism, you can find just the level of thrust you want. Most people use steering wheels attached directly to the pitch hinges and that works fine as well. But by using steering hinges, you can limit the range of motion of the collective, insuring a more precise fine-tuning of the helicopter. My method is also how the mechanism works in a real life helicopter.In this video I show how to build a swashplate and demonstrate how it all works. Please note that the swashplate is tethered to the ground so it doesn't spin around because of the torque. You will be better able to understand how it works if you try building it yourself.