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Really angry now ... again tail mounts snapping.


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solentlife
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Joined: 30 Dec 2010
Posts: 914
Location: Latvia / UK

PostPosted: Sat Sep 03, 2011 9:52 pm
PostPost subject: Really angry now ... again tail mounts snapping.
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I've been flying the 450 for days now without any problems ... tail fine ... all as should be.

Today - I go out and then vibration, sounds .. starboard boom strut comes of tail fitting,



then tail rotor assembly twists to right (looking at back end as flying).



I down the 450 ... back to bench and check her over ... I find thread stripped in boom fitting for strut - so I find a small suitable self-tapper to sort it.
All straight ... tightened up ... fine.

Go out and again strange noise which is deeper tone than normal sounds ... and tail twists to LEFT this time !! Boom / struts OK.

Back to bench and check it over ... find canopy rod on one side is loose ... so that's loctited up and fixed. tail assembly is put back straight and this time a drop of loctite dropped in joint to boom before tightening.

Out again and she spins up fine ... then strange deeper tone noise again and tail mount snaps ...



So what is happening ?? Could it be that I'm tightening belt too much ? Seems unlikely as it's way I've done it since getting the 450 ages ago.
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T-R-E-V
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Joined: 20 Jan 2009
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Location: United Kingdom

PostPosted: Sat Sep 03, 2011 10:26 pm
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How ironic is that, Shocked

We have just finished discussing the importance of tail booms, Rolling Eyes

And you prove firsthand the devastation that can be coursed without them. Crying or Very sad

Sorry found out this the hard way. Nice photos. Wink

Trev.
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pjdog
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Joined: 12 Jan 2010
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Location: Hudson, Florida, USA

PostPosted: Sat Sep 03, 2011 10:39 pm
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I've had plastic tail assemblies come apart like that but not a metal one?

I've had carbon Fiber tail booms fracture at the tail assembly like that but not a metal boom?

I bent a metal boom with a hard landing.

I'm thinking maybe a defective tail assembly. It does happen. I had a tail assembly on a brand new heli fracture right away. So has Tombo242. Very first spin up. These things are not perfect.

jack
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tombo242
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Joined: 04 Nov 2008
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Location: Santo Estêvão, East Algarve, Portugal. Now 82, but still feels 22.

PostPosted: Sat Sep 03, 2011 11:30 pm
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Well this one sheared and it had the knighthead bars (tail boom supports) fitted and secured.



Tom.
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solentlife
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Joined: 30 Dec 2010
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Location: Latvia / UK

PostPosted: Sun Sep 04, 2011 12:14 am
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I can accept 1 maybe 2 going with hard knocks etc. ---- but to actually see one just sheer off and not even airborne ?

I am totally lost on this now ...
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nick_onelove
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Joined: 01 May 2011
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Location: Mendocino County, CA, United States 21 years old

PostPosted: Sun Sep 04, 2011 2:28 am
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Yeahhh, this is way over my head, I just wanted to grab an email notification for this thread. Good luck!
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Skyepuncher
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Joined: 29 Aug 2011
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Location: south-central Ohio

PostPosted: Sun Sep 04, 2011 2:49 am
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You mentioned a strange noise before this happened. Makes Me
wonder if You had a bearing fail, & then seize in the tail rotor.
Have you had a chance to check that?
Scott
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solentlife
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PostPosted: Sun Sep 04, 2011 3:06 am
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Skyepuncher wrote:
You mentioned a strange noise before this happened. Makes Me
wonder if You had a bearing fail, & then seize in the tail rotor.
Have you had a chance to check that?
Scott


Did cross my mind ... first of all I put the noise down to similar when the struts come loose and you get that resonance sound. Then the canopy rod loose ...

Will be checking it out tomorrow ... but tail rotor and all appeared to be free when I brought back to bench.

Edit : Thinking back to last when it sheared ... I am fairly sure that motor speed was higher than normal ... I seem to remember needing a lot more throttle than usual.

mmmmmmmmmm bearing .... mmmmmmmmmm
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tombo242
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Location: Santo Estêvão, East Algarve, Portugal. Now 82, but still feels 22.

PostPosted: Sun Sep 04, 2011 3:39 pm
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Nothing wrong with the bearings in mine Skyepuncher, smooth, free and in my spares box. The metal on the break lines showed crystalised fracture over some 75% of the break. It is possible that a very slight imbalance in the tail rotor assembly could cause this. I now balance my whole tail rotor assembly instead of just the blades and haven't had the fracture problem again. . . . (yet)!

Tom.
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solentlife
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PostPosted: Sun Sep 04, 2011 11:19 pm
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Andrejs at flying today pointed me to this :



an all-in-one Tarot integrated tail unit .........

Now that looks a lot better than the bolt together jobbie ...

Anyone used one ? Any ideas / thoughts on it ?
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solentlife
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PostPosted: Tue Sep 13, 2011 12:53 pm
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New standard tail mount arrived - the two piece job, while waiting all-in-one.

Fitted ... flew ... fine ... no strange noises ...

BUT I did run with a belt slacker than usual and that appears to help.
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nick_onelove
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Location: Mendocino County, CA, United States 21 years old

PostPosted: Tue Sep 13, 2011 3:55 pm
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Well at the very least it's good to hear you're back in the air.
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lightning
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PostPosted: Tue Sep 13, 2011 6:30 pm
PostPost subject: tail rotor
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very interesting problem....but no doubt frustrating not to mention expensive.shear direction ....is it always the same index?as in the same direction.drawing on knowledge of much larger machinery i would like to guess [yeah just a guess] a combination of belt tension and rotor balance.in this instance over tensioning could possibly cause the rotor to become unbalanced and compound the problem, however this seems to be in the opposite direction to the twist in the belt ;not in the direction one would assume.did you have any bearing falure?do you know any mechanical engineers? good luck with this one .dont you just love the challenge!!
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solentlife
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PostPosted: Tue Sep 13, 2011 6:48 pm
PostPost subject: Re: tail rotor
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lightning wrote:
very interesting problem....but no doubt frustrating not to mention expensive.shear direction ....is it always the same index?as in the same direction.


Appears to be same direction for break each time but to be honest - I don't like being THAT close to the 450 when spun up. The twist of tail mount - that was always to right looking at 450 with tail towards you as in take-off, but last instance was to to left !

Quote:
drawing on knowledge of much larger machinery i would like to guess [yeah just a guess] a combination of belt tension and rotor balance.in this instance over tensioning could possibly cause the rotor to become unbalanced and compound the problem, however this seems to be in the opposite direction to the twist in the belt ;not in the direction one would assume.


Frustrating isn't it !!

Quote:
did you have any bearing falure?


No - none whatsoever ... but I did clean out everything before flying again in case grass or other had got in.

Quote:
do you know any mechanical engineers?


Yes but his spanners are too big for this !! Rolling Eyes More used to working on Soviet Tractors !

Quote:
good luck with this one .dont you just love the challenge!!


Can do without this challenge !!
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lightning
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PostPosted: Tue Sep 13, 2011 7:42 pm
PostPost subject: tail rotor
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i know the soviet tractors you refer to.....all too well .they are as twitchy as a Razz nervous cat.and just as unpredictable....not to say i dont like cats.both directions eh ?this is a wonderful problem you have or have had.im mean that literally .....cos its got me wondering.you see , i love a mental challenge .....not to say im mental.hehe....but solving engineering problems is my job and i get a kind of warm fuzzy satisfaction when one is sorted.....sick isnt it.twist to the left twist to the right....you know the rest of the song lol.hope you find the cause mate!!
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