on_your_six

My Feedback: (11)

I am having trouble with tail wag using the GP780 gyro. I have increased the head speed and played endlessly with the gain. It is a slow wag. The aircraft is brand new and the tail drive does not seem to be bound up anywhere. I am to the point of sticking a 401 on the tail just to see if it is the gyro or the mechanics. I have had this problem before on a 450 ended up changing out the gyro. Not a seasoned pro, but I have built around 20 helis to this point.

Using a Dx6i Radio and the Stock Trex500 super combo kit.

on_your_six

My Feedback: (11)

OK guys... having a bit of trouble here with an Align GP780 Gyro ($180). The heli has a slow tail wag that cannot be dialed out with gain settings.
We played with a lot of the settings without success, then we finally put a cheep $12 Gyro on the tail and guess what; NO WAG.
We plan to test the other two brand new gyros to see if they work... if not, we are going to send them in for replacement.

I did a web search and talked to a couple of guys about the issue... tail wag can be caused by vibration, slow head speed, fast head speed and a number of other things.
I came up with a list of possible causes. (this list is gold)

1.) mounting tape - some gyros are fine with the gray 3M double sided mounting tape, other gyros prefer the green jelly Zeal or Align brand of vibration mounting.
2.) If you think that it is a gain issue; start by cranking the gain all the way down and start moving up, testing as you go. A good hover gain setting may not be a good value for forward flight.
3.) Make sure the guides for the control rod from the servo to the tail are not moving. The rod needs a firm path to deliver all the power to the tail.
4.) Some guys recommend changing the throttle end point from 100% to 110%. This is the servo travel adjustment.
5.) Make sure Rudder travel end points are both 100%. The gyro actually sets the movement.
6.) Out of balance main blades or blades that are not tracking can introduce vibration that makes the tail wag. Check the tail blade balance while you are at it.
7.) Some guys recommend tightening the tail blades in the grips.
9.) Take of the control rod off from the tail. How smooth is the tail slider movement? If it is sticky at all, find out why. Locktite in the wrong place can cause the tail to wag.
10). Change the tail mechanics with a tail that is working, if you have a spare one laying around.
11.) Make sure that the tail slider is not hitting the right or left stops. make sure that there is a bit of gap between the bearing on one side and the blade holder on the other.
12.) Hover the heli for a bit... a brand new heli is tight and it may require a bit of wearing in.
13.) Torque Tube Tails: Make sure the torque tube operation is smooth, you might have to take the tail off the heli to check this. Check for missing umbrella teeth.
14.) Belt Drive Tails: .. check the belt for tightness and missing teeth. I have had the front plastic gear heat up and start slipping on the shaft. Try turning the tail blades holding the mains against turning. If you have some slop, change the piece causing the tail to slip.
15.) What gyro voltage are you using...try changing it within the allowable parameters.
16.) Make sure you are using a digital servo if the gyro is set for that. An analog servo will burn up after a while using the digital setting.
17.) Try another gyro, The Futaba GY401 is an industry standard. You can eliminate most mechanical problems and concentrate on electrical issues by seeing if this gyro works. If it does not, then you can concentrate on the mechanical side of things.
added 2/21/2013
18.) If you are using Spektrum gyro sense menu, try turning it off and using travel end point adjustment values.
19.) Check the radios channel monitor function to see what the radio is doing as you move the rudder stick. What is the gyro switch or flight mode switch doing to the rudder gain channel?

The order of the list is not sequential... maybe you have other items to add to the list??

Solman

If you have a belt drive, you should be able to press in about half way with moderate force. Also since you are using a DX6I, are you using the gyro menu or travel adjustment end points?

on_your_six

My Feedback: (11)

I do need to tighten the belt on my machine... thanks for reminder..
The machine in question... we were using the gyro sense menu... as soon as we changed to the travel adjustment method the tail wag went away.

What are the proper settings for the gyro sense? I was using 20.5 and 20.5 to start. So as I understand... that should have been 50+20.5= 70.5 value the gyro saw.
The manual is rather skimpy talking about this.

We also have had a radio rudder channel failure, so it could have been the radio all along.

WJK

Solman

That was going to be my next point. Don't ever worry about what the number is on the gyro gain. the number itself is meaningless. What is important is to find a number that works for you. Also mechanically center it in rate mode. Do not use trim in the transmitter. depending on your model, either move the servo back and forth or adjust the link length. It should hover in rate mode with little or no rudder adjustment. Once you do that, adjust your pitch slider endpoints so you get max throw and not bind.

on_your_six

My Feedback: (11)

OK, but there should be a starting point around which you can start... agree with your rate mode manual adjustment.

Talking to some guys on line yesterday... seemed to be experienced, yet they had both seen helis that could not be made right (tail wag) after a crash. Now that just confounds me. Grimlins... it has to be vibration, bearings, alignment... just finding it is the problem.

Thanks

Solman

From my experience and talking to other people with their issues over the years, Align gyros have always been weak with tail gyros. So I stay away from Align gyros all together. My best advice is go with something else. Believe it or not, the best tail gyro that I have ever used cost less than $30. I had the Assan GA250 which is a clone gyro of the Spartan. I used it on a 450 and 600 with great success until I went FBL. I would do tail slides and never had a washout.