Tail Waggin' Woes...

[P-Diddy]

I have been fighting a nasty tail wag for about 2 months now. It is just a tremor, really. It is a very fast wag that scares the heck out of me. I have never crashed this helicopter, although I have had one contact where the tail hit the ground and the tail rotor blades were damaged. It flew fine after that for several flights before the problems showed up. I have checked all the linkages and even had our local heli guru give it a once over as well. I have tried adjusting the mixture. The faster the rotors go, the worse the wag is.

Here is what I have replaced so far:

tail blades, (replaced with new Align carbons)
belt
one-way bearing
gyro (replaced with new GY401)
servo (replaced with new 9254)
governor (replaced with new Align governor, which seems to work really well BTW)

Oh, and I AM REALLY SORRY for the poor quality of this video. It was shot with a cell phone, and it is best viewed in small screen format, (don't try full screen...).

http://www.youtube.com/watch?v=FKxoilUfwRY

[chosen69]

If it ran fine before (meaning no gyro issues or anything) I am assuming that you might have bent the tailrotor shaft when the tail blades had contact with terra firma. That wouldn't be uncommon. Too bad your video is such bad quality. Maybe it's just me but I can't even see your tail on that...

[fiveoboy01]

I can't see anything in the video either.

You mention nothing about your gain settings. What are they? How about the delay setting?

Where is the gyro mounted, what are you using to mount it? What type of regulator are you using?

You can try a carbon rod for the tail servo(between servo and bellcrank).

[P-Diddy]

Good questions!

-The gain is at 80%. Changing it to a lower setting did nothing but make the nose wander.
-Delay is at 0. Changing it do a higher setting did nothing to fix the problem.
-The gyro is mounted in the traditional location on the gyro plate on the rear top of the fuse. I have tried a few different mounting methods to try and resolve this problem. Currently I'm using two layers of double-sided tape and velcro wrapped around the gyro. It had the nasty wag before when I had just one layer of Futaba's gyro foam tape and no velcro.
-I'm not running a regulator, just straight up 4.8V.

[skovsbo motors]

Hi
I have had similar wag it could suddenly appear in a forward flight without any provocation (gy601)
I did 2 things
First used fine sandpaper(500-800) to make the tailshaft totally smooth and made the slider work without any binding, That helped lets say 30%
Then i remounted my gyro with the CSM gyromount(2 stainless steel plates with 4 pc of soft foam betveen)
since that i havent had any problems

Kim

[fiveoboy01]

Also, you make no mention of whether or not you're sure you're in HH mode.

To me, the 401+wag = a gain issue OR something loose in the tail. That's my experience with my 450. Only time I had issues was when the gain was too high, and another time one of the bolts holding the grips to the hub was backing out.

[sparky]

I would try another set of Tail blades, I have had bad blades straight out of the package.

[rcmarty]

i suggest the dual radial bearings. You can get the quk setup or mod the align set yourself.

Get a 15mm cap or button head bolts and 2 extra bearings

put the bearing in before the thrust set. fit the bolt to bottom out on the hub before it binds up the thrust set.

This gives you 2 raidals and a thrust set. It also gets the thrust bearing out of the grip and therefore not binding up on it.

I do all my heli like that now. Its the same as the quk upgrade just alot less , i think the stock tailgrips are good enough.

Or you could try sanding down the outer race of the thrust bearings , this will help to reduce binding. IT's been a fix on the 600e for a long time now. I dont think its a good fix personally but has worked for many.

Martin :)

i did a better write up with pics a while back , if you search my username you should find it

[nbjeeptj]

my buddy was having trouble with a bad vibration on his tail and after hours of serching gyro / tail / engine tuning he found that the main shaft berring blocks were loose and the vibe in the tail was from that. Just a thought. I wish the video was clearer so i could see what yours was doing.

[erniefritz]

replace the tail rotor hub and thrust bearings

[P-Diddy]

These are great responses. I'll check the bearing blocks and see if they're loose. I'll change out the tail hub and thrust bearings if that doesn't do the trick.

Anything I can try is better than where I'm at now!!

I will say that someone suggested I check to make sure that the tail rotor grips were screwed in all the way, and I found that one of them actually had a little bit of in/out play. I tightened the screw and it went away. I don't know if that could cause this problem, but that was also a good suggestion.

You guys are really helping me a lot, thank you!

-Pat

[P-Diddy]

my buddy was having trouble with a bad vibration on his tail and after hours of serching gyro / tail / engine tuning he found that the main shaft berring blocks were loose and the vibe in the tail was from that. Just a thought. I wish the video was clearer so i could see what yours was doing.

replace the tail rotor hub and thrust bearings

i suggest the dual radial bearings. You can get the quk setup or mod the align set yourself.

Get a 15mm cap or button head bolts and 2 extra bearings

put the bearing in before the thrust set. fit the bolt to bottom out on the hub before it binds up the thrust set.

This gives you 2 raidals and a thrust set. It also gets the thrust bearing out of the grip and therefore not binding up on it.

I do all my heli like that now. Its the same as the quk upgrade just alot less , i think the stock tailgrips are good enough.

Or you could try sanding down the outer race of the thrust bearings , this will help to reduce binding. IT's been a fix on the 600e for a long time now. I dont think its a good fix personally but has worked for many.

Martin :)

i did a better write up with pics a while back , if you search my username you should find it

I replied to this before but apparently it got lost. Marty, I think this is a very good idea and well thought out! I don't know if it will fix this problem, but I'm going to do this upgrade. It just makes sense.

-Pat

[P-Diddy]

Also, you make no mention of whether or not you're sure you're in HH mode.

To me, the 401+wag = a gain issue OR something loose in the tail. That's my experience with my 450. Only time I had issues was when the gain was too high, and another time one of the bolts holding the grips to the hub was backing out.


Sorry, the 401 is in HH mode, and changing to different gain settings did not get rid of the problem. Thanks for trying to help, though.

-Pat

[rcmarty]

my 600E would wag a good 3-4 inches back and forth ! made for a very short maiden flight

after i modded the tail grips , with the same settings it was perfectly still.

i don't have the abilty to really wring it out though.

Its the same as the quk stuff , just when i had the problem the quk was just out and shipping to canada waas going to be a long wait IF i could find one that is. Took me all afternoon to get it figured the first time , not it's a 20min or less mod i do on every build.

MArtin :)

[chimaera]

Is there a thread for this mod?

[rcmarty]

Yes , i posted a while back in the E section.

600E thrusted upgrade is the same as the 600n thrusted setup

http://www.helifreak.com/showthread.php?t=38182&highlight=tail

Martin :)

[P-Diddy]

I'm still fighting the tail wag, unfortunately.

I dialed down the 401 to about 60% and put in a delay, and it at least flies, but the tail can kick out of hard maneuvers, making it a little iffy.

This week I took it all apart and replaced the drive bearings and main shaft bearings. I also installed a metal fan. If it was vibration-induced, I think I have now covered my bases.

[sparky]

on my 450, my gain is only 45. try lowering your gain below 50.

[P-Diddy]

Gain on the smaller 450 is going to be a different setting regardless. I have the gain on my 450 at about 45 as well. The 600 used to fly very, very well with the gain set at 85.

An update: A couple weeks ago, after tearing the entire helicopter apart and putting it back together again with a lot of new bearings on the main shaft and drive, the problem was still present. Then, it got worse when the heli made a sudden, uncommanded piro to the right, just long enough to confuse the pilot. I tried to set it down thinking everything had started to come apart in the air and it tipped over.

Guess what? A slow, no-throttle tip-over cost me about $100 in repairs. =/ That, of course, does not include replacing the $80 set of blades.

One last try and then this chopper is off to ebay. I'm going to go back to having fun one way or another.

[rcmarty]

Give the tail mod a try , my 600e wasn't even flyable either. After the mod (same settings on radio) it was perfect.

Martin :)

[P-Diddy]

Hi Marty. I think you're referring to the mod to make it two radial bearings and one thrust bearing per tail grip. That was my latest effort, and I tried it out today. Unfortunately, it didn't help.

I've tried everything that's been suggested now and I've spent enough money on the problem to have replaced the entire kit by now. This isn't fun anymore, it's just damn frustrating.

[rcmarty]

stock align carbon tailbaldes ?

MArtin :)

[P-Diddy]

They're not stock, mine is the sport version. It came with plastic blades. I'm now using Align CF tail blades, but I've also tried the old ones and a set of plastic Raptor tail blades. They all produce the same result.

[rcmarty]

I also have the sport version.

dx7 , 9451 , ar7000 , 401/9254 , gv1 -2100 , 2 in 1 , hyper/mp5 , mah 600's.
dual radial mod ,

gyro : 0 delay , 100 limit , ball 13.5mm out on 9254 , dx7 -> 70% on travel adjust menu.

Before the gyrp plate was available (or just) people were sticking the 401 to the servo sides. Some servo's caused issues with the 401. Like wise on the tail if the gyro was too close to the belt drive bearing (on the boomblock) it would also cause issues.

I didn't want it getting all slimed up out back. I servo taped a aluminum plate onto the side of my servo's then stuck the 401 with futaba tape on it. I also put some velcro on the gyro (narrow strip) and a strap that goes across the gyro. Very loosely fitted i cut a small slit in the velcro and tywraped it into the gyro mounting holes. Worth noting the velcro isn't tight in any way , just kinda hovers over where they are toughing (locked in though) , if the tape let go it would catch the gyro.

After reading about some of the 611 problems with the sensor above the servo's (with or without the gyro mount) the 611 comes with 2 types of gyrp tape , 1 has a thin layer of metal in it.

The plate offered up some stiffness in the servo's and a noise shield to boot.

That's all i can think of.

How about a high freq vibe not that visible -

motor ? % nitro ? head shimmed ? pipe ? headspeed ? blades ?

New tailshaft after that crash ? and tipover ?

On the boomblock , the drive pulley for the belt . Is the plastic gear on there straight ? Both my kits had the gear molded on off center. I'm a slow builder , like to roll and watch things alot , as a result i tend to finds some oddities.

Tail slider -> metal or stock plastic ? If the metal one is locktited and tightened up even a hair to tight , they get notchy. I found this part (metal for my build) to be the pickiest part to get right.

When you sipn the head with the tail grips at center , do the tips of the tail blades follow the same line ?

A bit of thinking out loud and afew things you may have tried all into one here. Sometimes a second look is the charm.

MArtin :)

[P-Diddy]

Martin,

Thank you very much for all your help. I went out and purchased the front gyro plate after the recent tip-over. I replaced the boom, spindle, main shaft, and a bunch of other pieces. The tail shaft is straight as can be. It has the metal gears. This is a new tail shaft and slider that I purchased before to see if that was the problem. I'm not finding any pieces of the belt on the frame or any indication in the air that it was slipping at all.

In fact, today my test was very flawed, one of the reasons being the belt was very, very loose as I discovered when I got home and took another look at things. I also had a small amount of delay in the gyro after trying to use that to tone down the problem on previous tests.

I have added a shim to the motor and that hasn't made a difference, nor did replacing the bearings, (although the engine certainly runs better now). I replaced the plastic fan with a metal one, just in case.

I've examined the tail drive a LOT and it is smooth as can be. The motor is the trusty old .50 Hyper with a generic muffler on it. I'm running 30% Cool Power Heli fuel. I've tried different headspeeds to see if that changes anything. If I bring the HS up really high, (no tach, sorry) then the tail just shimmies more consistently instead of only at times with a normal HS.

The tail blades track perfectly. They have a lot less play in them now with the mod. I was looking at the tail on two Sceadu .50's today, and I was amazed at how much play there was compared to mine with the mod.

Tail slider is the metal fork version, (upgraded it when I replaced the slider and tail shaft). It moves very smoothly. I replaced that after finding that it was binding at the extremes. It does not bind at all anymore and I've greased it before each flight, just to rule that out.

I agree, a second look is definitely worthwhile, and I've done a second, third, fourth, and more, and I still can't seem to figure this out!

I don't think it's a gyro issue. I've replaced the 401 with a brand new one and a brand new 9254.

*SIGH*

Like I said, this isn't fun and I'm strongly considering just scrapping the whole heli and selling it on ebay.