View Full Version : Do I need to adjust my gyro gain?

Ray K.
05-06-2009, 05:32 AM
Hey everyone!

This last weekend, I finally got to really fly for the first time this season. I was running through some simple circuits and everything looked okay, so I went to fly a couple loops and rolls. Everything looked and felt good there, so I popped a few backflips. I noticed that when I'm transitioning to the inverted part of the maneuver (maybe 140 into the rotation), I get a mean little shimmy in the head. It stops as soon as the disc loads up again.

It's my understanding that stiff dampers can cause this to happen (I'm using the Trueblood reds), but this seems like a lot- more than it shimmied last year, at least. I just got done rebuilding the bird and I'm confident that everything is right, mechanically speaking. The only thing that I changed was the tail servo horn, and extended the length by another couple of millimeters.

I'm hoping that it's just improper gyro gain that's causing this shake, because I haven't yet changed the gyro gain since I changed the horn.

I'm using a Futaba GY401 with a Futaba S9650, remotely adjusted from a DX7 with the HH gain set to 73%. I'm using the wheel that came with the servo, and the furthest hole out on it... looks like 8 or 9 mm. Servo specs are ~45 oz/in @ ~.11 sec/60.

I just want to be sure that I've isolated the problem, and if anyone knows or has suggestions about what's really going on here, I'll be happy to hear from you!


05-06-2009, 12:08 PM
If it's in the head, it has nothing to do with your tail gyro.

Does your RPM drop during this part of the maneuver? If the headspeed is dropping below where the dampers are happy, it'll do weird stuff like this.