# How to swivel a quad?

Well, we are building our own quadcopter(without any diy kits).. Any ideas on how to swivel(rotate it horizontally)?

P.S. We are noobs.

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### Replies to This Discussion

Do you mean yaw? If so, you do it by speeding up the counter rotating props while you slow down the forward rotating ones, or vice versa.

Hi,

Thanks for the quick response! Would you care to elaborate on that? I really don't understand the dynamics of what you're saying

Ajit, in the above diagram you can see that two of the props turn clockwise, two of them turn counter-clockwise. In order to spin the quadrotor flat against the plane that it's on (yaw) , the two pairs of same-spinning motors are sped up, while the opposite pair is sped down. To reverse the spin all you do is reverse the order.

Oh! It's like that! I get it now! Thanks a lot man, seriously!!

Take note that accelerating the motors has a greater effect than simply setting the pairs at different speeds, so the quad will turn faster while the motors are changing their speeds, and will turn slower when the motors have a constant speed.

...At least that's what my knowledge of physics tells me.

oh okay, thanks for the information!

Yes Allen, you are right, but the conservation of angular momentum effects are small compared to the constant torque from the motors pushing the props though the air. How do you explain the fact that a quad can rotate indefinitely if you want it to.

That comes from setting the motor pairs at a different speeds, like having the CCW motors moving faster than the CW motors.

The reason this works is because of the fact that the motors are still applying work to the propeller to keep it spinning. If the motors did not, the propeller and motor would eventually slow down due to air drag.

Finally, because the motors are continually working on the prop's, they continually apply a torque on the frame, which allows us to rotate the quad indefinitely (Thank Newton).

For aggressive maneuvers, the angular momentum effects may have more of an impact on the flight dynamics than the steady state torque... although I haven't gotten to verify that with my own testing just yet.

so are you guys done with it?

No man, not yet! Lots of work to do!

Hope your not trying to build everything from scratch, that'll take forever. Lol.

No, not really. We bought the frame, and one of the things we want to do from scratch is build our own autopilot system, and image processing algorithms. Any idea how much time that will take? What do you suggest we do? I mean, we want to gain as much experience from this project as we can.

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