General Trex 470 Tail Set Up

Harford

Harford

Active Member
I have just completed assembly of my 470 LM. All standard except using a Spirit 2 instead of a MB. This heli flies very well although there is some movement (small amount of movement/wagging) in the tail, with throttle at 73-75%. I have the linkage ball in the second hole in tail servo arm, as specified in the manual (2019 version). I have seen on the internet that there was an amendment stating it should in fact be in the inner most hole, but this was dated 2016. My later manual has not been amended so I am wondering what is correct.

Additionally, on start up, the tail flicks quickly to the right (ie anti clockwise) by about 90 degrees. The throttle curve I was using was 0, 55, 67, 73, 75, 75, 75. I assumed going from 0 to 55% was the cause so reduced to 45%. Better but does not eliminate the problem. I could make further changes to the throttle curve but other helis using a similar curve don’t do this so I am wondering if there is another reason for this happening.

Any suggestions would be much appreciated.

Many thanks
 
RandyDSok

RandyDSok

Well-Known Member
Bumping thread ( since I don't fly helis )... it looks like those in the know may have missed this one ( sorry if they did, I assure you it wasn't on purpose )
 
Blade 400

Blade 400

Active Member
Harford said:
I have just completed assembly of my 470 LM. All standard except using a Spirit 2 instead of a MB. This heli flies very well although there is some movement (small amount of movement/wagging) in the tail, with throttle at 73-75%. I have the linkage ball in the second hole in tail servo arm, as specified in the manual (2019 version). I have seen on the internet that there was an amendment stating it should in fact be in the inner most hole, but this was dated 2016. My later manual has not been amended so I am wondering what is correct.

Additionally, on start up, the tail flicks quickly to the right (ie anti clockwise) by about 90 degrees. The throttle curve I was using was 0, 55, 67, 73, 75, 75, 75. I assumed going from 0 to 55% was the cause so reduced to 45%. Better but does not eliminate the problem. I could make further changes to the throttle curve but other helis using a similar curve don’t do this so I am wondering if there is another reason for this happening.

Any suggestions would be much appreciated.

Many thanks
Click to expand...
I`ve only just started in the FBL realm with a Tarot 450 that had a similar issue.
I was advised to look at gain in the FBL unit to make sure I was in heading hold mode not rate mode, also, to make sure there was no pitch in the tail blades and finally, that you may need to hold some right cyclic in on take-off as she may be rotating because the tail blades don`t come up to a fast enough speed to counter the main rotor head speed until she`s in the air.
I hope this helps :)
 
Geena

Geena

Staff member
Harford said:
I have just completed assembly of my 470 LM. All standard except using a Spirit 2 instead of a MB. This heli flies very well although there is some movement (small amount of movement/wagging) in the tail, with throttle at 73-75%. I have the linkage ball in the second hole in tail servo arm, as specified in the manual (2019 version). I have seen on the internet that there was an amendment stating it should in fact be in the inner most hole, but this was dated 2016. My later manual has not been amended so I am wondering what is correct.

Additionally, on start up, the tail flicks quickly to the right (ie anti clockwise) by about 90 degrees. The throttle curve I was using was 0, 55, 67, 73, 75, 75, 75. I assumed going from 0 to 55% was the cause so reduced to 45%. Better but does not eliminate the problem. I could make further changes to the throttle curve but other helis using a similar curve don’t do this so I am wondering if there is another reason for this happening.

Any suggestions would be much appreciated.

Many thanks
Click to expand...
The wag in the tail. Is it a fast wag, or a slow back and forth movement. Fast wag generally suggests that the tail gyro gain is a little too high, a slow back and forth wag usually suggests that the tail gain is a bit too low.

The tail kick you mentioned is most likely due to the torque of the motor, caused by too fast of a start up. Refer to the manual of the ESC, and see if there is a way to enable soft start. If there is, enable it. Then set the start time you want. I have mine set for a 25 second soft start time. The helicopter will spool up nice and slow, and you won`t get the tail kick.
 
Harford

Harford

Active Member
Many thanks for your responses. The wag is slow and it it not doing it consistently. I am sure I have read somewhere on these helicopters this can happen when the battery is lower on power, near the end of flight. I will be a little more observant about this next time I fly (not much chance right now due to dismal winter weather), and do more research on gain adjustment through the Spirit 2.

The tail kick has been fixed. My fault, I had not carried out throttle calibration on the ESC. Did this and all is fine. However, good to know about the soft start time setting.

Thank you again.
 
Tony

Tony

Staff member
I would like to comment on the ball placement for the tail linkage. Back in the day when Digital servos were pretty new and there were still some analog servos out there, servo centering was, lets say, less than ideal. It was great for the time, but nothing like we are seeing now.

The further from center you place the ball, the faster you can move the tail blades a given amount, however the Accuracy of the movement was not as good as it is with it in the center hole, or towards the center.

If your tail servo is fairly new, use the middle hole for quicker movement for the same degree of movement. If your servo is older, use the inner most hole on the arm to make it less twitchy.

And don't be afraid to play with the tail gain. You want to raise the gain up until you get oscillations (fast wag) then back it down about 5%. You always want to be in heading hold mode (HH).

With you saying the wag is slow, then the tail is "Hunting" and the settings may be making the tail lethargic. For this, make sure you are on the correct tail channel, and raise the tail gain up until you get what I posted above.
 
Admiral

Admiral

Well-Known Member
Reading through the thread one thing that I haven't seen mentioned is head speed, which is particularly noticeable near the end of the flight, when the lower head speed reduces tail authority and can cause a slow wag. Worth mentioning, but I normally find it's a gain problem.
 
Harford

Harford

Active Member
Thank you for your responses.

The heli is new and I have left the rudder servo ball placement in the centre hole, as specified in the manual which came with the heli. I have read various posts on this subject and yet to see anyone supporting a move to the inner hole as suggested in Align's dated (2016) amendment.

I have the gain set at 50% in the Tx which I understood to be a recommended default setting. I am familiar with the process Tony outlines and will go through this process.

The point raised by Admiral is what I was referring to in my last post - you have done a better job of articulating than me. Thank you.
 
Tony

Tony

Staff member
If your gyro gain goes from -100 to +100, I have always started at +65 for my tail gain settings and went from there. Center hole will allow higher gains, and outside holes will require lower gains. For max stability, you can move to the inside hole and raise your gain as the servo will have higher resolution in the inside hole vs outside hole.
 
Harford

Harford

Active Member
Thank you for this advice. I used to have slow wag issues with my older Trexs which used GP780 gyros. This issue largely disappeared after moving on the FBL units. Good to know about the +65 starting point - I have never been up that high, but as you suggest, don't be afraid to try.
 
Tony

Tony

Staff member
Yep, but also be ready with that throttle hold to auto it down from a low hover as well. If the tail starts to wag, and the gain is too high, it can scare the bejesus out of you lol. I have had this happen more times than I would like think think, mainly on the 3GX though haha.

And I think I have been out of working on these things too long. For 0-100 I use 65% (breaks down to 30% gain), but for -100 to +100, I start at 45. My sincerest apologies. So 50 should be just fine. My bad! Man, I need to get back into this hobby lol.
 
Smoggie

Smoggie

Well-Known Member
What ESC are you using? If it's the standard Align one dont use the ESC governor, it's rubbish and causes a wag that cant be tuned out.

Otherwise if the wag is slow then i'd try cranking up the gain. If you get to the point where you just start seeing a fast shake of the tail on hard pitch pumps or fast flight then you have found the limit, back down 5% or so from there.
 
Harford

Harford

Active Member
This is a standard Align Super Combo kit which means the ESC is a RCE-BL50X ESC (Align brand but perhaps sourced from HW ?). I will adjust the gain upwards as suggested - than you.
 
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