Trex 450 v2 tail problem - RCCanada - Canada Radio Controlled Hobby Forum
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Old 09-02-2010, 12:18 AM   #1
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Trex 450 v2 tail problem

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Hey guys, i can't seem to get my tail working properly since i got a new radio and tail servo. When I am hovering and doing some very light flying, the gyro holds fine, however when i give it a decent amount of throttle, the nose pulls left about 90 degrees almost instantaneously. I tried playing around with the gain however regardless of what i set it, it still does that same thing.

sorry if the description isn't so detailed, i'm still kind of new to this.

trex 450 V2
Spektrum DX7
Futaba GY401
Futaba 9257 for tail servo

if anyone has some advice for me, that would be great!

Last edited by revos5; 09-02-2010 at 12:20 AM.
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Old 09-02-2010, 12:40 AM   #2
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Re: Trex 450 v2 tail problem

Make sure your revo mixing in the transmitter is off or inhibited. I have this same setup and can check in the morning what my settings are.

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Old 09-02-2010, 03:58 AM   #3
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Re: Trex 450 v2 tail problem

Sounds like it's not in heading hold mode. The radio is the place to start looking for problems with settings. Stupid question but is your gyro sensativity plugged in or is is possibly loose in it's place
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Old 09-02-2010, 07:40 AM   #4
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Re: Trex 450 v2 tail problem

Make sure that your tail slider has lots of travel in both directions. This can happen if the tail cant get enough pitch to counteract the torque from the blades. Also make sure that your motor is not bogging down. Reduced rpm on the tail can also have this effect.
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Old 09-02-2010, 08:03 AM   #5
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Re: Trex 450 v2 tail problem

Your gyro is not reacting fast enough to counter the torque that is being generated when you jam the throttle.

Everyone who posted above gave some great advice.

I suggest you approach it methodically to get it sorted out.

You don't tell us what gyro you have so I will give a generic process that is based on the most popular type of gyro, the GY401 and its clones:
EDIT: Sorry, I see you say you have a GY401. That is great. Disregard my comments on clones...Max
  1. Make sure you have no revo mix turned on. This is usually a no-brainer becuase it is always inhibited as a default setting on all radios I have seen. Nobody ever uses it, and setting it up is a pain, so I doubt you have it on. Nevertheless, you should check your radio just in case someone else set if up for you
  2. Check that the ball ink on the servo arm is the correct distance from the center. 12.5mm seems to work best for me.
  3. I am making an assumption based on the fact that I don't know what gyro you have , but you do know that some gyros have a "Headlock" mode and a "Rate" mode, right? I am assuming you know which is which. If not, figure it out and let us know.
  4. Next Check your travel adjustment. It is best to do this in "rate" mode (Non-Heading Hold): First, on the radio, make sure your TA is 100% in both directions, then:
    Move your rudder stick to max and watch the tail pitch slider. Using a screwdriver, Adjust the "LIMIT" settings potentiometer on the gyro so that your slider has maximum throw for both left and right stick deflection. Some pilots prefer a bit of over-travel to get a crisper response from the rudder. That is OK- it is personal preference. What you are looking for here is that you get the MAXIMUM throw or a pinch more (but not less). IF one side bottoms out before the other, go with the one that needs more (a bit of overtravel is OK)
  5. Now you have to set the Gyro sensitivity on the radio. The greater the sensitivity, the less likely it will turn when you jam the throttle. Too much sensitivity will cause tail wag. Too little will case the heli to turn when you jam the throttle, just as you described.

    Fly the heli. Depending on how you have your switches set on your particular radio, you need to go to either the travel adjustment screen (if it is set on your GEAR switch) or your GYRO screen (if you enabled the gyro feature)

    In both cases, you need to adjust the gyro sensitivity (GAIN) on your computer radio UP until the tail starts to wag, and then dial it down a bit at a time until the wagging stops. That is your maximum head locking setting. If you continue to dial down the gain, the heli will begin to drift just as you described. You need to set this up separately for both heading modes on your gyro (ie, you set up the gain for the gyro in "rate" mode, then again for "Heading Lock" mode)

That should work

Last edited by Max; 09-02-2010 at 08:16 AM.
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Old 09-02-2010, 10:15 AM   #6
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Re: Trex 450 v2 tail problem

I think Max hit the nail on the head. Most times I've seen this it's because the servo can't get over quick enough to counter the sudden torque. The solution is to move the ball on your tail servo horn a little further out than it currently is, then readjust limits and gain.

It could also be low gain, low headspeed or you're pulling too much collective.

As for overdriving the tail servo, I can't say I agree with max. Binding is always bad. Given you probably won't hit the limits often in flight, but if you do, binding stalls out the tail servo which puts unnecessary wear on it. There's really no reason to overdrive it at all. You won't get any crisper response by binding things up.
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