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Tail wag gone!, but at what price?

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Tail wag gone!, but at what price?

Old 12-26-2006, 10:42 PM
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Default Tail wag gone!, but at what price?

Short story long, I bought this rex about 3 months ago, did some serious sim time before flight then really worked this baby, twice a day for 30 days, to the point of nose in hovers by flight 63. Then I got bold one day and tried a nose in landing. First one went fine than disaster ! my first crash. After a feathering shaft, blade gripes, tail servo gear set and a boom strike, I was back in the air. Rotor head wobble was still there during spool up and down, I'm contributing that to a loose, HDE, grey frame, elevator linkage design; mainly cause I can make it go away with a little fwd cyclic in the rough spots. Anyway no tail wag on this puppy since day one, now, a constant rythmic wag apparrent only after take off speed is achieved and there after during all realms of flight. After exhausting every tip and trick on this topic found on RR, I came upon the last one of the day, "Hey, try this it worked for me, reverse your tail blade grips to trailing edge input instead of leading" So I said "what the hell" I was completely frustrated at this point having tried: new blades,old blades reversed, new input rod, freed up every linkage I could, swapped the entire tail gearbox/rotor head assy to the old one that shipped with the heli, replaced the drive shaft in the black new gearbox, messed with the gain on my GY240, could not mask it with with my radio, being only a Futaba 6XA, replaced the MRH shaft, moved the tail servo arm closer to the middle. Man I tried all the tricks aside from buying a new ESC( reprogrammed that )and Gyro. I felt like Kevin Costner in tin cup trying to get rid of the "Chile peppers" ! I was desperate. Then I reversed my blade gipes on my tail and the wags were gone. ***! Now tell me how the heck does that hold water, anyone!! enligten me please. And above all is this wag free state of mechanics safe for FFF?? Iv'e seen some different setups on the net with the pitch horn on the trailing edge, is this safe for the Trex?
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Old 12-27-2006, 03:00 AM
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Default RE: Tail wag gone!, but at what price?

If you had a boom strike you probably need to replace the main shaft. To check pull it & roll it on a piece of flat glass & look for movement. Just about anytime you bend the feathering shaft you will bend the main. I always replace both - they're cheap!
Old 12-27-2006, 10:24 AM
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Default RE: Tail wag gone!, but at what price?

Did that after the crash, any comments about the tail, anyone?? anyone , Bueller?[sm=71_71.gif]
Old 12-27-2006, 10:47 AM
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Default RE: Tail wag gone!, but at what price?

OMG! HAVEN'T YOU GUYS NOTICED IT YET?! i have a question, are teh tail blades in those pictures already put on backward? if so, you have a build problem, i'm not sure if it'll cure your tail wag, but ur tail is mechanically wrong. twist your belt 180 so that your tail blades are spinning in THE OTHER direction. so that the blade nearest the canopy is spinning TOWARD the main rotor blades. then flip your tail blades back and undo whatever you've changed so that you have the leading edge in front. i'll bet this will cure your problem.
Old 12-27-2006, 02:13 PM
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Default RE: Tail wag gone!, but at what price?

I know the blade grips are backwards, the blades turn the same way they have always turned and any other heli Iv'e seen including here http://www.trextuning.com/buildccpm4.php Mains go clockwise, tail go counter.

"The tail rotor can then be installed onto the tail rotor shaft and secured in place with the supplied grub screw. Again use blue loctite (243) to secure the grub screw. The tail hub should be flush with the end of the tail rotor shaft. Clip the ball links onto the blade grips, again with ball links leading the blades as shown. Tail rotor rotation should be anti-clockwise."

I've looked at the pics I posted last night and I believe they are just like the Trextuning site shows.

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Old 12-27-2006, 02:51 PM
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Default RE: Tail wag gone!, but at what price?

So in the pics you just posted with the yellow tail blade, looking at it from this side, the heli's right side, the rotor rotates counterclockwise, yes? And you are showing the current configuration of the tail blades, yes?
Well, this looks correct to me, the thick LE is going forward, the rotor is rotating up thru the main wash, this is correct, yes?
So are you saying that you had it incorrect before when it was wagging?
I am confused, yet again.


On my MX400Pro, the stock tail grips had the link balls rigged on the trailing edge. On the TRex SE tail rotor that I replaced it with, the links are on the leading edge. I have tried it both ways, the difference is in the direction that the pitch slider must move to produce a yaw in a given direction. With it rigged the "wrong" way, you run out of rudder authority in one direction or the other, I can't recall which, but other than that I didn't notice any difference in tail wag.
Old 12-27-2006, 02:59 PM
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Default RE: Tail wag gone!, but at what price?

Yes to all Q's except the last one.
"So are you asying that you had it incorrect before when it was wagging? "No, "chopperdudes" commented on the builup indicated in my pics. He said my blades were turning the wrong way, I posted back, I never changed the direction of rotation, just the grip ball location, leading edge to trailing. Than I tried to compare my present build config is the same as the Trextuning site displays(yellow blades).
Old 12-27-2006, 03:38 PM
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Default RE: Tail wag gone!, but at what price?

Oh, ok now i understand.
I've been trying to help someone on another thread with a similar problem, we are stumped, I'll point him over here it might help him.

If you changed the grip link location, did you not also have to reverse the rudder servo and the gyro?
Old 12-27-2006, 04:16 PM
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Default RE: Tail wag gone!, but at what price?

Nope, just re rigged my tail control rod with AFSC off then check the throw on my ATV and flew it. I'm sorry to say though, this might not be fixed. I flew twice today out front , and it's still waggin a little. I think my HS-50 servo mmight be on it way out.
I thought your friends tail problem was a twitch of sorts right? mine is a definate wag, osscilation.
Old 12-27-2006, 04:26 PM
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Default RE: Tail wag gone!, but at what price?

opps. my bad, i now i see what you mean, switch the blade grips, not the blades, that's why i was confused. what tail servo are you running now? you might want to try the S9650.
Old 12-27-2006, 04:29 PM
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Default RE: Tail wag gone!, but at what price?

ORIGINAL: texmech

Nope, just re rigged my tail control rod with AFSC off then check the throw on my ATV and flew it. I'm sorry to say though, this might not be fixed. I flew twice today out front , and it's still waggin a little. I think my HS-50 servo mmight be on it way out.
I thought your friends tail problem was a twitch of sorts right? mine is a definate wag, osscilation.
Now I am really confused. With the grips on one side, a push on the rudder pushrod will pitch the blades in one direction. With the grips reversed, and no other changes, a push on the rudder pushrod will now pitch the blades in the _opposite_ direction, will it not?

What gives?

Old 12-27-2006, 04:46 PM
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Default RE: Tail wag gone!, but at what price?

Hi, Jellyson

You are right the rudder servo would need to be reversed. Just tried it. The wag did not stop however

Paul
Old 12-27-2006, 04:58 PM
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Default RE: Tail wag gone!, but at what price?

Both the gyro and the rudder servo must be reversed together. So there are 4 possibilities, only one of which is correct...
rudder backwards, gyro backwards--not works.
rudder correct, gyro backwards--not works.
rudder backwards, gyro correct--not works.
rudder correct, gyro correct--maybe works.

Old 12-27-2006, 05:20 PM
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Default RE: Tail wag gone!, but at what price?

Sorry to confuse yall, I was'nt pretending to know what a I'm talking about, I'm still a noob. I also have my 3 yr old asking me a million questions as I type. Now That I think back I did move my servo the other way. I was trying every combination known to man that day it's hard to regurgitate it all.
Old 12-27-2006, 05:22 PM
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Default RE: Tail wag gone!, but at what price?

OK if you reversed your servo you also have to reverse your gyro.
Old 12-27-2006, 05:36 PM
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Default RE: Tail wag gone!, but at what price?

OK here is how to tell if your directions are correct, without actually flying.
THe nose will move in the direction that the trailing edge of the tail blades moves.
Looking at the helicopter from the rear, like you were sitting in it--if the TE of the tail blades moves to the left, the nose of the helicopter will try to yaw to the left. If the TE of the tailblades moves to the right, the nose of the heli will try to move to the right.
So hook everything up, gyro disconnected, rudderservo connected to the radio. Motor unplugged. Power on.
Right rudder stick deflection should produce TE moving to the right.

Now plug up the gyro and set the gain to about half. Do the same stick test, the result should be the same, travel may be different but direction the same.
Now manually swivel the heli nose to the right. The TE of the tail blades should move to the _left_, as the gyro wants to neutralize your right yaw by yawing back to the left.

"yaw'll" got that?

(I'm from San Antonio)
Old 12-27-2006, 06:22 PM
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Default RE: Tail wag gone!, but at what price?

Got it, nice explaination thank you! really .. Down to the root though, I'm still waggin. It's funny though, I even flew it twice last night with no wag. My guess is, it's the HS-50 servo. It must be going slowly. or something . I'm masking the problem with the grips reversed I think. But I flew today regardless 4 packs! Man it felt good to fly outside again, it's gonna be a long winter.
Old 12-27-2006, 06:38 PM
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Default RE: Tail wag gone!, but at what price?

OK tex it is possible that it is working better now and that you had binding or play that was preventing you from seeing the tailwag before your repairs.
I ask you this: are you using the very shortest possible servo arm geometry? That is, rudder pushrod in the hole in the arm that is closest to the servo axis?
If you are using a longer arm it can be difficult to get rid of wag at any gain that is useful, but binding or play may prevent the wag from being visible--am I making any sense?
So tell me the length of your servo arm--mine is 7.5 mm and that is actually too long for me, I still get a bit of wag too.
What I am saying is maybe your arm is too long so it is wagging at low gain, but before your crash there was too much binding or play for you to be able to see the wag. So try shortening the arm and re-setting the gain.
Old 12-27-2006, 07:40 PM
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Default RE: Tail wag gone!, but at what price?

I saw the post about the servo arm geometry last night and tried that actually. I split the difference on my arm, I was at about 10mm or so with the only arm hole I had. I made a new hole at 5mm give or take a mm. As for the play or binding thing, I'd have to say I was pretty loose considering I was using a z bend on the servo arm and a ball on the pitch horn. Now I'm using a ball on both sides. Very smooth operation not too tight not too loose, not in the hanger bracket.
My gain has been 100% on my 240 since day one of my short heli experience. My Fut 6xA does not have gyro settings.

8 years in Houston and Corpus tagged me the name Texmech
Old 12-27-2006, 07:45 PM
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Default RE: Tail wag gone!, but at what price?

texmech, are you using govenor mode on your esc? If so, try turning it off and see how the tail reacts. Sometimes the gov will fight the gyro and the result can be a pesky tail wag. Just one of many causes...
Old 12-27-2006, 09:05 PM
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Default RE: Tail wag gone!, but at what price?

Nope no gov mode on my align 25a, just a bare bone rex here nothing fancy. I'm only now getting in to FFF with figure 8's and nose in hovers.
This thing was wag free for 87 flights! Something got tweaked just don't know what.

Trex 450XL aluminium boom plastic grey frame
Hacker B20-15l 3700kv
Electron 6
Hitec 56's and the 50 on the tail
GY240
Align 25a ESC
Dnpower 2150's 43 cycles on each 10-11min above 32 deg, 8min below 32 deg
cellpro charger ( awsome!)
Futaba 6XA TX Sucks but got me this far! waiting for my buddy to upgrade tee heee
Carbon 325 Main blades
stock tail blades
80 metal head ( blade grips and spindle plastic - the sacrificial lambs )
Old 12-27-2006, 10:13 PM
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Default RE: Tail wag gone!, but at what price?

Well, now that things are smoother can you reduce the gain and still get adequate performance?
100 precent seems like a lot...on my MX400Pro/Trex hodgepodge, I am using an align rce500x with a hs65 servo, it holds like it was on a rail, no twitch, gain is 87 percent out of 150 (dx6) so that is actually just over 60 percent.
I can induce a mean twitch, divergent if that means anything to you, if I go much over 90 out of 150.
Old 12-27-2006, 10:29 PM
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Default RE: Tail wag gone!, but at what price?

Have you tried switching from LE grip to TE grip on your tail rotor yet? Sorry if its been posted but looks like from you pics you have TE grip on you Tail not LE like a stock trex.
Old 12-27-2006, 10:33 PM
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Default RE: Tail wag gone!, but at what price?

And so we come full circle....
g'nite all, more tomorrow
--John
Old 12-27-2006, 11:01 PM
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Default RE: Tail wag gone!, but at what price?

Scott,
read post number 1 and post me in the morning, I'm done.

Good night John, Thanks for the input!

Steve

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