View Full Version : Trex 450se + DX7/gyro-tail

05-17-2007, 05:50 PM
Ok, here's my problem (or at least I think it is a problem). I am using a Spektrum DX7 in combination with a Futaba gy401 gyro and 9254 digital servo for tail control. I have the ball link set as close to the servo output shaft as I can get it (drilled a hole next to the servo arm spline). This allows me to set the gyro to the maximum travel for greater resolution. However, no matter what I've tried it only takes about 25-30% of the TX stick travel to max out the throw. Is this normal or do I have something wrong?

**anything past the 25-30% makes no difference. So that leaves me with 70-75% of TX stick movement that doesn't do anything.

Thanks for any help/advice/suggestions.

05-17-2007, 07:56 PM
Reduce your rudder endpoints.Start at 100

05-17-2007, 08:16 PM
Thanks. I did try that and found that if I reduced the endpoints to about 67% I would get full TX stick to tail pitch endthrow. However it made the tail extremely slow on movement unless you slammed the TX stick from side to side. If I leave the endpoints at 100% the servo responds quickly until I reach 25% of the TX stick at which point the tail pitch slider is at the end of its travel.

05-18-2007, 01:10 AM
Checked a hs65,with the pivot point at the horn hub I only get 7mm of linear travel.I guess I don't understand how that small amount of travel is even close to getting you full pitch slider movement.Did you move the ball link on the tail bellcrank in closer to the pivot point than stock?

05-18-2007, 06:09 AM
Nope. Everything is setup the way it came on the tail section. I'm still confused as to why I can't get resolution over 100% of the TX rudder stick instead of only 25%. Thanks for helping.

05-23-2007, 12:55 AM
I have the rudder programmed in my DX7 to 100% and I use the "limit" pot on the 401 to limit it's travel and everything seems to work fine. I am using the 9650 servo and also have drilled a hole as close as possible to the center for my linkage.

05-23-2007, 03:45 AM
PilotDane, I don't have any problems with the setup. Mine is the same as yours using the DX7 set at 100% travel, the GY401 pot to control throw maximums, and the ball link as close to the servo outout shaft as possible. There is no binding and the tail slider reaches it's end travel perfectly. The question or problem is that it only takes 25-30% of the DX7 rudder stick to make the servo repond with 100% of tail slider travel. I would have thought it would have been proportional in that if I move the TX stick 25% the tail slider would move 25% of it max travel, 50% TX rudder = 50% tail slider travel. Does that make sense and does yours work that way?

05-25-2007, 06:58 AM
Finally found an explanation and answer to what I was looking for.

**These days, most gyros have “limit” settings. These allow us to overdrive the servos as far as we want, but tell the gyro where the physical limits are. Thus, when we perform a yaw command on the ground we see that the last 1/3 of the stick motion has no effect. The servo reaches the programmed limit by about 2/3rds stick, and goes no further. But this is not a bad thing. When the heli is flying the entire stick deflection will be used, because our command will be reduced significantly when the heli is yawing. (This information is from Spork on helifreak)