Gyro Drift - is this normal?

[Caduceus]

I recently purchased a Twister 3D Storm and have an issue about the gyro set-up. It comes with a Twister branded HL400 dual rate tail lock gyro. I've done the usual routine and set the tail rotor servo to neutral, servo arm at 90 degrees and brought it to a hover in standard/rate mode. I've then done a mechanical adjustment to servo position along the tail boom to get it to hover straight at neutral trim. So far so good.

The problem starts when I switch to Heading Hold mode or even switch off and re-initialise in HH mode. The servo will not remain centered and drifts quite quickly to the end of it's range. It always goes the same way. When I spool up in this position, the tail rotor remains at max pitch until it gets light on the skids and the tail starts to move. Only then does the gyro start to do what it's supposed to do, quickly correcting the movement and coming back to the hover pitch position. It's quite annoying to have to spool up with the tail rotor at max pitch - it doesn't do this in rate mode - it spools up at hover pitch.

Now I can get rid of the servo drift while it is sitting on the ground by adjusting the rudder trim or sub-trim but when I do that, it won't hold heading in a hover - it just rotates in the direction of the trim change as you would expect.

My question is whether the servo drift at rest is normal?

[ZipZap]

Can you raise and lower the gain?

[astroflyer]

servo drift in heading hold is normal.

when spooling up, before lifting off, move the rudder left and right a bit and the gyro should set the servo where it needs to be allowing the tail to hold.

[Pinecone]

If that gyro is based on the Telebee/Align/Eflite gyro, you need to adjust subtrim to eliminate the creep. That gyro does not sense center pulse length, so you have to adjust the delivered pulse length to match te gyro.

Finless has a video on setting it up. It is in the HDX300 video build thread.

[evolusia]

Hi. Your setting your gyro up in the wrong sequence, it`s Headlock first then Rate mode, but personally I`d set it to Headlock mode and leave the Rate mode alone.
Heres what I would do assuming you have your servo and gyro directions correct to start with
Disconnect the tail linkage from the servo
Zero rudder trim and sub trim.
Set rudder ATV to 100%
Set the gain channel to give 50%. ( depending on the TX this can actually be a value of 50 on the display for both switch positions or depending on the set up 25 for one switch position and 75 for the other. A value of 50 in this second type of set up is null neither Rate nor HL)
Use a 4.8v pack to power the RX or unmesh the motor
Switch on the RX.
Select the switch position that gives Rate mode ( one position will leave the servo more or less where you put it and is HL mode, the other will allow the servo to come back to neutral when you let go of the stick and is Rate mode. )
Let it all settle for two or three minutes.
Flick into HL mode and then go into rudder sub trim and adjust as appropriate to get the minimum drift.
Flick into rate mode to find servo centre again and leave it there for the time being.
Adjust the arm to get as close to the 90 degree position as possible. This can only be done by moving the arm on its splines or adjusting the internal pot. ( Not recommended if you are heavy handed
Adjust the servo position on the boom and/or linkage rod to give zero pitch on the tailblades
Now using the TX, move the servo to it`s extremes both ways and select a hole position on the arm which does not allow the linkage to bind up at either end of these extremes.
Once you have this position reduce the rudder ATV to about 65%, recheck your gain value and test hover.
The gyro will send the servo to the correct hovering position and you will still have full servo deflection in both directions.
Adjust the rudder sub trim to eliminate any drift one way or the other, and the heli stays put. You may need a click or two on the external trim every now and then because this type of gyro is renowned for drifting due to internal and external temperature changes unless it has drift cancellation built in, and this can be variable.
Aim to set the gain to lock the tail without any wag. The gain may well need to be a lower value when you go into FFF. If your TX supports it, select the gain rates from the Flight Mode switch ie Normal, Idle up1 etc.
Pirouette rate is determined by the Rudder ATV so increase it slowly until you get the rate you want without any bounce from the stops although it`s probably never going to be brilliant
This should get you going.

For what it`s worth:
Forget about using both modes together with this type of gyro because its a pain and the end result is not worth it This is because you cannot set the end stops of the servo travel independently, and so the initial tail rotor offset required to get the heli to hover in rate mode gives unequal travel to the pitch slider. You then end up with a heli that will spin one way and not the other or more likely has a very sluggish pirouette rate which is not good.

Hope this helps :thumbup:

The man who never made a mistake never made Owt