Left Rudder Vibration Issue

[dtil817]

Hey guys,

I just built my first quadcopter. Its the X525 kit from Amazon. I'm using a multiwii 2.5 flight controller v2.3 and an Orange Micro 6 channel receiver bound to a DX6i. The copter will pitch, roll, rudder to the right, and hover without any issue. The problem I'm having is with left rudder. When initial left rudder input is given through the DX6i, it starts to turn slowly then it begins to vibrate quite bad. This seems to be resulting in confusing the sensors, and I have to land it before losing control. I've balanced the motors and props and those seem fine. I verified the sub trims and exponential settings are at "zero". Any ideas are greatly appreciated!

Dan

 

[Hugh Hemington]

When you apply rudder (yaw), one diagonal pair of motors is slowed while the other is sped up. That maintains altitude while letting the torque of one pair spinning the same direction exceed the other diagonally opposing pair, turning the quad on its axis. If you can yaw right but yawing left causes issues, the first thing I would check is the props on the clockwise-rotating motors. Make sure neither is mounted upside down.

A prop should have a lateral crown looking from tip to hub, so that the air is scooped downward when rotating. If one is mounted upside down, it will not provide the expected thrust and this will be most impactful when that pair of motors is tasked with keeping the quad at altitude.

 

[dtil817]

Hello Hugh,

Thank you for your reply. I verified that he propellers are mounted correctly. I used two regular props and two pusher props. And thank you for the note regarding how the copter will try to maintain altitude by spinning two props faster while yawing. I was wondering about that and was thinking I need to add mixing. Since my initial post, I installed 4 new carbon fiber props and the issue is cleared! I think the old props were just too darn heavy. I don't know the brand, but they were the gray plastic ones all hobby shops sell. Probably not the best for a quad.

Thanks again!
Dan

 

[Hugh Hemington]

Glad you got it sorted. Yes, pusher and puller props are not necessarily mirror images as you need on a quad to turn CW & CCW. Now with four PROPer props, things work better.