all of a sudden I Have a very bad Tail Vib??

[concept1]

Guys, i have been flying my Hurricane now for 3 months and this bird has been supper smooth. I went out this weekend and the tail now has a very very bad, acctually violent vib on spool up and spool down, so bad once the pitch slider came off the arm. it gives a loud flutter then it's gone. I did a seach since I remember others having a similiar issue, and didn't really find a fix.

now also since my last flight, I did knock the heli off my bench and bust the tail fin. the Heli never really hit the ground but i did catch the tail fin and bust it off. I did loosen the tail case to replace the fin and possibly change the belt tension. on one of the past posts someone had suspected the 2 piece pulley caused interference from tightening the case? nothing is bent and the tail blades have not changed, nor has anything else on the heli since it's last smooth flight, except the tail fin. it only vibs at a certain rpm and once above that point or below it is ok.

[dutch_anykey]

Same here,

Last saturday, i spooled it up and it really vibes at a certain rpm...until its full speed. Then in the air i heard a short loud screeching sound....nothing wrong with the control but i landed anyway. Took a short look but couldnt find anything...No gear striping, belt tension is o.k. as well. Decided to fly the 450 for the rest of the day. Havent had the time yet to find out what is causing this.

I had bad vibes before, but that was to blame on a cracked tail case. Right now I don't have a clue yet where to start. It might be the stock plastic frame. I fly the Z30 1100. Maybe it's too much for the frame. It feels like the frame is getting more and more flex lately. No cracks or anything discovbered yet though.

And i'm more concerned about that short screeching sound i had. I'm going to replace the oneway bearing see if that helps.(check for hair line cracks) Also check if the front main gear is not loose, check the bearing in the tailcase. loctite them in, maybe they spin in their socket,

Anyway, keep us posted. I will report when i applied my changes :)

Maurice

[concept1]

well here is some more info, I did fly it 2 flights, it flew fine once over a certain rpm, but on the second flight, i was getting a funny gear noise and turns out i lost 3 or 4 teeth on the rear main gear? my guess is this happened do to the extreme vibration I had on spool up.

[ianjh123]

If you can find the cause of this it would be great. I has the same problem and changed every part of the tail with no result. I ended up with a Trex cnc tail and it is the first time I could fly without the tail vibration.

[concept1]

did you have your problem from new, or after several flights? I believe it was your post some time back I was looking at. it seems like at just over 1/4 throttle it gives out a resonance so bad the tail vibrates back and forth about 1.5 inches and the tail blades flutter badly. if you don't get past this point quickly the pitch slider ball comes out of the socket, and you can't get it back on without removeing the arm.

[dutch_anykey]

Concept,

I had the same as you once.. It popped the link of the tail.....But that really was a problem of my tailcase..... And it wasnt a tailwag at that time....it was a violent scary "my heli is going to explode" kinda thing. :YeaBaby:


http://www.helifreak.com/showthread.php?p=416668#post416668

Maurice

[concept1]

it is really hard to describe, it is a violent wag/ loud Flutter for a breif second as the heli comes to a rpm and passes. if you watch the tail it becomes a real blurr as it flutters and probalby wags about 1.5 inch side to side, up and down, can't really tell because it really becomes a blurr and in less then a second it's gone and normal again. when you reduce the rpm it does it again at or about the same rpm just over 3/8 stick on the throttle, (about your second point on your throttle curve) if you hold the throttle their I swear the heli will explode. while watching the rest of the heli you don't see anything abnormal. I have never seen anything like this in my 10 years of heli's

[Merlin.swe]

I would check the belt tension again. I had a funny noise also on spool up so i tensed the belt just 1mm and now the noise is gone.
Remember that the tail is aluminium so if you are flying in cold weather the tail shrink and the belt tension changes.

[concept1]

I can't beleive it. I looked at it again last night, for the 3rd time and the tail case is cracked! You can't tell by looking at it but if you grab the tail rotor and put pressure on it then you can see it is cracked. So I assume this is the problem, but now my concern it how did it get cracked? It did fall off my bench and the tail hit a bottom shelf and busted the tail fin, but this was not a hard knock or fall, the tail just swung off the bench and down 2 feet to a shelf, it could have hit just the right angle to crack it I guess. I will have to order a new case and see if the vibration goes away? i just hope the case is not failing in flight?

[dutch_anykey]

Hi Concept,

Was it cracked in the exact same spot as i showed in my picture?...Because i think that the material in that spot is waay too thin..

Still not sure about the cause...i didnt crack mine on the bench or anything...it was in flight that i noticed strange rudder behavier...i landed and spooled up and down a few times...that's when the violent shaking got worse...After that i discovered the crack...

Still not sure what caused it.............

Maurice

[concept1]

mine broke right where your secondary small crack is, behind the arm. not in front of the arm like yours, but I do see you have a very small crack right were mine broke. yours looks real jaged as well mine is a real clean fine brake, you can't tell at all by looking at it, you have to put pressure in it so it seperates to even see the brake.

[dutch_anykey]

Mine wasnt vissible either...on the picture i was forcing it open by hand. Anyway...Weather is bad and it's dark early again...winter time has started...no time to test.

Mauirce

[concept1]

got my new tail case today and went out for a quick flight, the violent shake is gone! but i do beleive their is some vibrations in the tail at certain rpms, i am really wondering it this did indeed bust in fight? I also noticed my new case is more rigid then the old one? the half that is not busted I can easily flex back and forth, the new part can not. now is this new material or does the plastic just get soft over time (short time--3 months)

[AdrianM]

The tail case was loose on my boom no matter how I tightend it . I placed a piece of card stock between the case and the boom...no more vibes.

[tungym]

You must ground your Hurricane and have a bench test to look for the cause of vibration. Mine has 2 crashes due the vibration. That is caused by resonance due to some imbalance of grips, worn bearing, flexy tail gear box....... It is really odd as all of us has the problem after months of flight.

In my case, the vibration persist despite new gear box, longer boom support (using Align one) , new tail gear box and grip bearings, new tail shaft ...... The vibration still persists.

Finally, the problem "cured" after I changed a complete set of Align tail. I guess multiple factors contribute to the vibration/ resonance. So you may not be able to "cure" completely by replacing just a part or 2.

[concept1]

i loosened my tail belt and it help alot, but still some vibs?

[AussieJester]

The tail case was loose on my boom no matter how I tightend it . I placed a piece of card stock between the case and the boom...no more vibes.


You sure the boom was in its little slot on the tail casing? If so I cant see how it could possibly be loose.

[AdrianM]

You sure the boom was in its little slot on the tail casing? If so I cant see how it could possibly be loose.


Yes it was but the peg that went into the hole has some play and for some reason the tail case just could not get tight enough to grip the OD of the boom tightly. I piece pf paper solved it though.