Hi,
I have a new Trex 500x which is driving me insane, it has a constant tail wag ( 50 - 75mm ) at anything above 60% throttle
At 60% throttle the tail gain is at 65% but if I go above 60% throttle even dropping the gain by 20% makes no difference

I have double checked everything mechanical , tail is perfectly smooth, no play in the mainshaft, motor mesh has a small amount of backlash, main blades are perfectly balanced, the only thing I can see is the main gear is not perfectly flat and has around 0.5mm vertical deflection

The one thing that I have found is that on the Y axis (aileron) vibration analysis it shows main rotor off the scale but I can't see anything that could cause this and everything appears to be running true . Could this cause tail issues as vibrations in the yaw axis are perfect

I originally set the heli up using the Trex 500 preset but have dropped rudder delay to 2 (DS535 servo)
Is there anything else I should change

Any advice appreciated

Regards
Andy

Hi,

if the tail holding/working well at 60% throttle, then I think it could be:
- caused by a governor settings - try to decrease Governor Gain (if possible)
- caused by some mechanical resonance that makes the movement very hard

If you increase the throttle above 60% do you see any additional noise from the model?

Sometimes tail shaft (if it is loose) can start to oscillate very rapidly at higher RPM. This will be visible on the Spectrum Analysis plot.

Please make the measurement with tail blades on (carefully) and send me the plot, if possible.
Then will be able to find where is the problem.

Vibration is usually not a problem for unit, but for the model itself where a movement can become uneasy. then such oscillations can occur.

_________________
Spirit System developer

Hi Tomas

On the bench there is no visible vibration at any speed on any part of the heli but I did notice some strange hesitation from the motor when moving the throttle down then back up again .
There is no change in sound just the tail wag as throttle increases . The wag does not increase gradually, it is either there or not especially when changing from normal to idle up where the tail kicks with the rapid change in headspeed

I have turned the governor off in the esc and will try a flight this afternoon
The tail is belt driven

With tail blades on which axis plot would you need to see ( tail I would assume )

Regards
Andy

Thanks again Tomas

I would never have thought that the Governor could affect the tail like that but it flies fine with governor mode off
The only other change I made was dropping rudder delay to 0

I haven't checked the vibes again but am not worried about that now as it flies ok ( for an Align )

Regards
Andy