General Trex 450 - tail needs too much 'right rudder' input

[mooserider]

Hey all, I made a new thread, as the old one is off topic now. I have learned a lot since then as well.

Now that I have rate and HH mode set up now in my Tx and understand them better, my problem is that I need way too much right rudder input to keep the thing flying straight. The tall blows out easily on pitch bumps. To demonstrate this, I made some videos earlier. Maybe someone can catch something that I've been missing.

Setup info: It's an old kit I got about 5 years ago. Standard setup following Tony's videos (+10). I setup the tail in rate mode, with the servo at 90 and giving some sub trim to make it perfect. Reset the rudder end points. Then tested in rate mode (before this video). It spins nose left. So I extend the linkage to give it more (nose) right input from the tail. I continue this until I have as much 'right' in the tail as you see in the videos, resting the end points each time on the 3gx. I also have some right rudder trim in the Tx too... as the linkages are getting short on thread.

Video 1 - showing tail, correction direction and the right rudder it needs by default: https://www.youtube.com/watch?v=1lb2vcBRj-Y
Video 2 - during flight: https://www.youtube.com/watch?v=rfcmxQNzjRQ
You can see the tail still needs constant correction. I switch to HH mid flight, and it helps a little, but not much. I also do some pitch bumps to show the tail blow out, but it's quick, as the camera (my phone) is stationary. Sorry for the length, I didn't have editing software.

 

[Tony]

Video 2 is private, but no worries on that. With the 3GX, you shouldn't try to fly in Rate mode. Flip that thing into HH mode and see how it does there. It sounds like it's close, so I would give it a shot.

 

[mooserider]

Thanks Tony. Not sure why it was private but I fixed it.

I use HH in the video as well. It helps a little, but not a lot. Isn't it abnormal though to have to have so much right rudder built in by default? There's only another third of the slider for it to move. I'm sure this is all related to the tail blow out as well. The gains are also fairly high for the tail to keep it like centered.

 

[Tony]

If you are running a somewhat linear throttle curve, this is why your tail is blowing out. Most all of them do it. Try running a 0 45 70 70 70 curve and see what that does above mid stick. Should tame it down.

Just watched the second video. Can you post screen shots of your parameter menu's?

 

[holtneil]

Hi mate on the 3gx you adjust the sub trims so all read zero on the set up , 3gx does not like trim , I used Tonys videos too , and the set up is good , if the heli is the old style the servo will be on the tail boom , if it is do this , set up rod length to the manual with the servo arm at 90 degs slide the servo up or down the boom till the tail pitch is zero , now set up end points on the 3gx , test fly in rate if the tail drifts and it will then slide the servo up or down the boom till the drift has stopped ( dont adjust rod unless you have a pro and the servo is hard fixed to the frame) Now that the drift is zero , pop it into HH and it will be locked rock solid

 

[mooserider]

Ok, I got it fixed pretty well I think now. I set the throttle curve like Tony mentioned and it killed the tail blow out. But it was also very sluggish on pitch increases, so I bumped up the last two values to 75%, like 0, 45, 70, 75, 75. And now it takes off like a bat out of hell and holds the tail stable!

The rudder servo is fixed, on the tail boom. I only used a little right rudder trim because the linkage was getting too long to unscrew the ball join connectors any further. There's still plenty of throw left both ways, and I reset up the 3gx each time. I think (not positive though) that the swash trims are the ones the 3gx doesn't like you messing with... I don't think it's as crucial for the rudder is it?

The next thing I want to tweak is the pitch curve I think, to flatten out the middle just a tiny bit. When I'm hovering, there's only one click on the throttle between moving slowly up and it dropping down. I read that you can set the pitch curve to help this be less sensitive at mid stick.

Thanks of all the help you guys! It's flying how I've been looking forward to now, and you guys are definitely the ones to thank for that!

 

[Tony]

If you are using a ratchet type of throttle, get rid of it! That is for airplanes. Helicopters need more precise control of the collective. Forgive me, but I can't remember what Tx you are using. If 6i, take the case apart and I think you just flip the metal bar over. On the 8 and up, you just take a rubber plug out of the rear, loosen the ratchet strap, and tighten down the smooth strap.

And the 3GX doesn't like any trim on anything. You should only use sub trim, and even then, only in DIR mode. What I would do is take the trim out (if this is what you used) and set it back in sub trim.

 

[mooserider]

Got it! I'll fix the rudder trim tonight, thanks Tony!

The Tx is an older DX7 (not s). I use it for my airplanes too, but I can still try and remove the ticks in it. I'll check it out!

 

[Tony]

I will almost bet (I remember seeing that in teh video now lol), you will have to take the case apart. You will find it's much more controllable after you flip that strap over or what ever you have to do to that one.

 

[holtneil]

HI tony your spot on the DX7 will need to come apart he can use the DX6i custom videos you did on how to take the case apart

 

[murankar]

So if you have a boom mounted servo then slide it up and down the boom to fix your tail drift. One way to center the tail slider is to fold the tail blades in the same direction. Rotate the tail rotor so you get a good look at the blade tip alignment. If they are equal or even then your good, if not then slide the servo to correct it.

Sent from my LG-E980 using Forum Runner

 

[Tony]

Right on Neil. Thanks for the confirmation.