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HomeScaleAircraftHelicopterScale Model RC Helicopters › Need help with weird tail vibrations
03-03-2017 05:45 PM  16 months agoPost 1
aashu

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scotch plains, NJ

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Please check the short video

Watch at YouTube

I witness this after rpm goes certain level. Tried with main blades on as well and issue is same. Tail blades and whole rear goes in vibrates . Not sure if it is the gain on tail gyro , tail blades or tail rotor. I am using jeti radio with brain hd . Also swapped the db unit with a beasts with same results .

Garden State, NJ

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03-03-2017 06:53 PM  16 months agoPost 2
cap231ex

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Muncie , Indiana , USA

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Almost seems like it is either a bent tail shaft or bent TT.
What ever it is it's hitting a pretty high harmonics to make the camera oscillate like that.

Good luck tracking it down

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03-03-2017 06:59 PM  16 months agoPost 3
ssmith512

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Indianapolis, IN USA

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Gotta start eliminating things.

Try without tail blades first. If same result, then try without tail hub and grips. Work your way to just the mainshaft spinning with no rotor head (if you get that far).

Good luck.

Steve

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03-03-2017 07:23 PM  16 months agoPost 4
bwellmaker

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Long Island

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TGB gears and or bearings also check tail drive shaft couplings.

This a new build?

Have you hit the tail or a hard landing?

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03-03-2017 08:07 PM  16 months agoPost 5
aashu

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scotch plains, NJ

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Thanks
Thanks for taking time to check the video. I did another test with tail blades removed and the vibrations are gone. even at full throttle there is no sign of vibrations. These are 120mm fg blades from Vario . I will unassemble the drive assembly and inspect the drive shaft and bearings etc. could it be that at speed with the large blades, tail servo cant keep them locked ? IT is a new Futaba S3470Sv. It is rated 130 oz-in @7.4 Volts .12 sec/60 degree

And no, the heli has never been flown and I do not think tail ever touched the ground

Garden State, NJ

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03-03-2017 08:12 PM  16 months agoPost 6
ssmith512

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Indianapolis, IN USA

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Servo should be plenty good IMO. Very real possibility the tail blades are out of balance. You need to get them on a balancer and check them. If you have another set of tail blades that you fly on another heli and you know are good (doesnt matter what size), try them on the Allouette to see if they work with no vibration. It is a simple matter of trial and elimination.

Steve

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03-03-2017 11:29 PM  16 months agoPost 7
aashu

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scotch plains, NJ

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thanks
Servo has lots of juice and seems like working as it supposed to. I assembled the tail rotor and put it back but found nothing out of place. Shaft is straight. Checked everything as per diagram below and all is good.
http://variomodels.com/fileadmin/us.../01/1003-10.jpg

I used my old KSJ balancer and they look fine as well . I will buy a set of another tail blades to test. Since it only does it with tail blades on, it could be something to do with them. Another thing I may check is the tail blade centering....

Garden State, NJ

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03-04-2017 03:14 AM  16 months agoPost 8
Mojave

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Palos Verdes, Ca. USA

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First order of business, swap in another set of tail blades and run it up to speed. If the problem goes away, you know it's the blades. If the problem persists, look somewhere else... Tail gremlins, my favorite kind...
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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03-04-2017 03:23 AM  16 months agoPost 9
coptercptn

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Mesa AZ. USA

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I know this is "basic"... but make sure the tail blades are on in the correct direction....

Home of the "Sea Cobra".....

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03-04-2017 04:05 AM  16 months agoPost 10
BeltFedBrowning

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Kansas City

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Once you eliminate the tail blades, it could be tail hub bent or machined off center, tail grip to tail hub bolts bent or different lengths, bent tail shaft, or less likely bad tail shaft bearings.
I had one do the exact same thing once and it was a out of round tail pitch slider, it was assembled incorrectly.

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03-04-2017 02:52 PM  16 months agoPost 11
aashu

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scotch plains, NJ

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thanks
Very strange since these were brand new. I will go over everything you folks mentioned

Garden State, NJ

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03-04-2017 03:36 PM  16 months agoPost 12
Peter Wales

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Orlando Fl

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Also check the trust bearings are both the right way round

Peter Wales
http://scalehelicopters.org

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03-04-2017 05:50 PM  16 months agoPost 13
Mojave

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Palos Verdes, Ca. USA

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"Very strange since these were brand new. I will go over everything you folks mentioned"

I know, it defies logic. But new parts are sometimes "off". This is why I always roll main intermediate and tail shafts (actually any shaft) on my granite counter to see if they are out of round before installing them. It eliminates any nagging questions when I find a problem down the road.
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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03-04-2017 10:21 PM  16 months agoPost 14
aashu

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scotch plains, NJ

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thank you
Agree 100%

let me see what I find.

Bearings look ok. Just to confirm, do the wider race of thrust go in towards tail or outward towards blades?

Garden State, NJ

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03-05-2017 02:39 AM  16 months agoPost 15
aashu

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scotch plains, NJ

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Hi
First of all thanks to all who suggested all the things.
I think I found the issue.

The solder that joins tail housing to lattice fuse , the two small bars are not even soldered (they look like they are).

While the top of the tail housing is soldered solid, as soon there is some load on tail, due to lack of support it starts this vibration.

Barry, your observation was dead on, the whole tail housing was twisting back at forth.

Now, big question is how do I solder it. I recently bought a set of these
silver soldering rods to build a lama style landing gear (Still waiting on delivery).
http://www.ebay.com/itm/Harris-Safe...n0AAOSwQYZWvPfY

Do you think this could be used with a propane torch to tach the join ?

Garden State, NJ

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03-05-2017 02:43 AM  16 months agoPost 16
BeltFedBrowning

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Kansas City

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A high frequency vibration could easily have caused this. I would still check everything.

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03-05-2017 02:58 AM  16 months agoPost 17
aashu

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scotch plains, NJ

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yep
Very possible.

I have only attached battery for 4 times all together and very first time I started the tail was acting up. Rest of the joins on fuse are very solid. I pretty much checked everything else except for trying a set of blades. Once If fix it, i may decide to get a set. BTW, to showthe crack, I had to use some force. Otherwise you cant tell they are cracked and look to be soldered well

Garden State, NJ

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03-05-2017 04:24 AM  16 months agoPost 18
Mojave

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Palos Verdes, Ca. USA

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Yeah, I guess these old eyes are still working...LOL. Practice silver soldering on some scrap stainless tubing, you'll get the hang of it after a few tries. Just clean the joint well with sandpaper, followed by alcohol wipe and silver solder it using a MAP gas torch (good heat). Use a high quality paste flux and you'll be fine.
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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04-04-2017 02:21 AM  15 months agoPost 19
aashu

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scotch plains, NJ

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I am back
At this point, I am really frustrated.

I soldered the crack. It is rock solid. I opened the tail again inspected the shaft. from roll test to visual inspection , I found no sign of any bends. Yet, I ordered another shaft andset of blades.
First I tried the blades, same issue. Then I replaced the shaft with new and with new blades, no good .

I also checked all bearings in the grips and made sure the thrust was proerly installed and lubed with vario recommended grease. Nothing has helped so far. Only thing which I have not done is replaced the two main bearings inside tail rotor. They seem to be healthy.

It is a GRP housing http://www.vario-helicopter.biz/us1...ing::31446.html

I did not se any sighns of bearing runouts either. Any other pointers ?

Garden State, NJ

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04-04-2017 12:14 PM  15 months agoPost 20
Notar

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Taxachussetts

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What is the actual head speed when this happens?

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HomeScaleAircraftHelicopterScale Model RC Helicopters › Need help with weird tail vibrations
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