HELP! Align GP780 setup.

[Hummingbird]

Hi folks, I have a new T Rex 550E with the GP780. I'm using a DX8 radio. When I move the rudder stick just slightly I'm getting full movement on the servo and therefore full pitch movement. I've tried adjusting the gyro on the radio (currently set at 70), the travel limit on the radio, dual rates, expo, the lot. But nothing makes any difference. I've done the end adjustment on the gyro using the set button OK, but the pitch of the tail isn't working in proportion to my stick inputs. Also when I spooled up, the tail moved quite rapidly to the left (nose to right). Needless to say I didn't fly it! The gyro does respond correctly when I move the tail - ie, to counteract tail swing, so it is working.

I have a Blade 450 3D which I fly successfully but this 550 is my first attempt at the bigger toys. Any ideas where I'm going wrong? Also can anyone direct me to a good online resource for gyro setup?
Many thanks.

[KevDavies]

you have the gyro sensor reversed.

and the movement of the servo is perfectly normal in heading hold mode

and gyro 101 = Capi's Gyro 101 - HeliFreak

[Hummingbird]

Hi please forgive my ignorance, but what do you mean? The physical position of the gyro unit or an electronic setting. Ta

[KevDavies]

electronic setting. its sensing movement in one direction and putting in a correction. But the correction is opposite to what you need. IE reversed

[Biggles]

Hang on a mo. What you are saying is that if you move the stick slightly the servo moves its entire travel???? If you move the stick slightly does the servo arm move slowly and if you move the stick all the way to one side it moves fast??? If so that means it is in Heading hold and is perfectly normal. If it was in rate mode the servo arm would move in proportion to the stick movement. But on top of that reverse the gyro in the setup procedure!!! It definetly sounds like it is going the wrong way.

http://www.lincsheli.com/page52.html

[Hummingbird]

I'm trying to reduce the travel of the tail rotor so i don't have a crazy over-responsive rudder. Is this right? Or should the tail pitch move the full travel? When I move the stick quickly, the servo moves quick; if I move it slow, it still goes the whole travel but slightly slower. But the tail rotor is moving in the right direction! I can't understand why you are saying to reverse the gyro. I feared this little blighter would cause trouble! Good job it's not flybarless - I have that pleasure still to come. Thanks for your advice though.

[coolice]

Hey.

To me it sounds like you're seeing the symptom of today's heading hold gyro's, basically you are commanding a certain rate of rotation by moving the transmitter stick and the gyro throws in the right amount of tail pitch to achieve that rate. On the ground of course the model does not respond and so the gyro adds more tail pitch to effect a change.

You say you have the tail responding correctly to rudder stick inputs, so a left stick command will initiate a nose left turn? Have you checked the tail gyro is correcting the right way, eg. If you push the models nose left the tail gyro should move the tail to give a right command to compensate.

Going back to your question, you can slow the tail rotor response down, but visually you will not see any change in overall mechanical movement. By lowering the rudder channel ATV (travel adjustment) percentage you will effectively reduce the rate at which the tail can pirouette at in degree's per second. Reduce the transmitter rudder ATV to slow the piro rate, increase it to speed up the piro rate.
.

[Hummingbird]

Thanks coolice, I forgot that the gyro will give false readings with the model on the ground, so that hopefully explains the strange full movement. Yes, the tail rotor does move in the right direction. My final concern is that I had quite severe left tail swing (nose to right) when light on the skids. How can I correct this?
Thanks for your help

[Biggles]

Are you turning the heli on then moving it to a take off point?

[Hummingbird]

Good point - I might have done. And if I did I know why it swings, but I'll try again tomorrow. If I didn't move it after turning on, what else could it be?
Thanks everyone for the help.

[Biggles]

The 780 is notoriously S***. I have 2 sat here. I put a CSM 720 in my 550. With electrics....take it out to a point of take off then connect the battery....never ever connect your battery in the pits.

[coolice]

Hey.

As above I was going to say do you carry it out to the flight line. While doing so the heading hold mode is trying to control the tail.
A trick is to once you have placed the model on the flight line, flick into rate mode which centres the tail blades, then back into heading hold mode and fly. With the tail blades starting off at 0 degrees pitch any swing as the model starts to get light is very minimal.

Another idea is the spoolup on your ESC, is it set to slow spool up? If power is coming in quite quickly this can swing the tail round to.
.

[Hummingbird]

Thanks again, it's a bit of a mine field but I'll get there. I'll apply the advice here and try again.

[Hummingbird]

Thank you. Guess what - my gyro was reversed!!! I couldn't see how it could have been but having read a response to someone with the same trouble, I worked out that it was the gyro, so I reversed its setting and - presto, success. The best news is that I maidened it in the back garden this evening and it hovered so sweetly, very solid and steady. So thanks again to all. I've learned a lot from this and it is only when things are set up bad or wrong that we learn from it.
Happy flying.