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HomeAircraftHelicopterFuel-Helicopters New or Limited ActivityNext D › [ENV] Tail Hub Failures
04-19-2011 09:30 AM  7 years agoPost 1
cyr

rrNovice

france

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Hello guys,

I have already encountered two tail hub failures on my nitro FBL Rave. Each time it happened after 40/50 flights, and the hub broke exactly the same way: at the point where the hub goes from 5mm to 4mm.

First time, I was 99,99% sure that is was properly assembled. However I thought "OK, I could have put the thrust bearing in the wrong way with smaller diameter toward the hub, or maybe a nylstop nut could have become loose giving it some runout... let's give it a new try".

I put all my attention making a perfect rebuild.

- I screwed both nuts with a little amount of locktite, being sure not to overthight it at all.
- I swaped NextD tail blades which are extremely stiff with Edge 105. Indeed, Edge are a little bit more flexible, and I thought it would contribute to reduce stress onto the hub.
- I lowered stop gain in my Vbar, making tail stops even smoother
- I lowered main rotor RPM from 2000 to 1950

40 flights after... same scenario: tail hub broke, remaining tail blade went apart hurting the boom, tail shat bent and umbrella gears immediately stripped.
Fornunately both times I was a lucky guy and land the heli without any other dammage.

By now, I don't want to give up with the Rave. Indeed, exept this two tail hub failures, I had not have any problem, the heli hold extremely well. And even if it is a little bit heavier than the Trex700, I won't go back for it because Align quality is just a pity compared to the Rave.

However, I am disapointed and a little frustrated that CYJ staff do not answer my PMs.

I have asked to a small machining company to make me hardened hubs.

Cyril

http://www.hostingpics.net/viewer.p...694909photo.jpg
http://www.hostingpics.net/viewer.p...8529IMG0499.jpg

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04-19-2011 12:55 PM  7 years agoPost 2
Pulento

rrVeteran

CHILE

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There have been some reports from others pilots of similar failure. Hope this isn´t common.

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04-19-2011 02:40 PM  7 years agoPost 3
Chris Bergen

rrElite Veteran

cassopolis, MI USA

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A HARDENED hub is not the answer. It'll only make it brittle.

Chris D. Bergen

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04-19-2011 03:26 PM  7 years agoPost 4
cyr

rrNovice

france

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@ Pulento: do you have a link ? How does the concerned guys solved the problem ?
This morning, another pilot reported the same issue on a french forum.

@ Chris Bergen
I totaly agree with you, I misspoke. I meant something STRONGER, redisigning it with a more "conical shape" instead of the sharp one on stock ENV hub, at the point it goes from 5mm to 4mm (sorry for the poor vocabulary )

I think it would have been much better to build the tail rotor around a 5mm diameter hub.
On my previous JR helis, tail hub was still 4mm and bent on almost every crash ... but I have to say I prefer a hub that bend hitting the ground than something harder that break inflight...

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04-20-2011 01:09 AM  7 years agoPost 5
Pulento

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CHILE

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Cannot find them But I do remember it was on this same forum or over the Freaks forum.

On the other hand Vibe 90 tail hub has the same dimensions just about 0.2mm shorter which means you can't bolt all the way or you'll bind the bearings I unscrewed about a quarter of turn, also it has less metal on center. And the Vibe 90 was Curtis design

That hub is used on the Vibe 50 also so it is easy to find.

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04-20-2011 03:09 PM  7 years agoPost 6
mainshaft

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Bangkok Thailand

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Are you running YS engine?

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04-20-2011 03:40 PM  7 years agoPost 7
cyr

rrNovice

france

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Hi,

I am running an Os Hz with SB-20, without vibrating issue.

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04-20-2011 04:08 PM  7 years agoPost 8
Buzzin Brian

rrProfessor

College Station, Texas

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This has happened a couple of times. It is not wide spread, but regardless we are changing the part to address this issue. We do not have the new ones just yet, but rest assured we are maikng a change to keep this from happening.

cyr I just sent you a PM. I will get you taken care of.

FYI me and Curtis have been working on a project, so I have been away from my computer. So I appologize for my delayed response.

Brian

Build it, fly it, crash it. Repeat as often as needed.

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04-20-2011 05:29 PM  7 years agoPost 9
cyr

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france

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@Brian: no problem I have just seen on Curtis' blog that he gave you a huge sanding work on the fuse prototype, so you'll have to think about switching your pseudonym into "Busy Brian" for some days

It is nice to know that NextD has already started to work out a stronger hub, to definitively make the Rave THE bird to fly with.

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04-20-2011 09:51 PM  7 years agoPost 10
Pulento

rrVeteran

CHILE

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Nice to hear about the new hub. I´m enjoying mine.

And one of the things I like most about it. It´s a dependable .90 I beat it with confidence. I´ve fly it at 2100 RPM without any trouble

But I prefer it at 2000 RPM.

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05-06-2011 06:01 AM  7 years agoPost 11
uk135

rrNovice

Thailand

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Same thing also happend to mine, I already encountered twice of the tail hub failure. First time was about after 20 flights, and the second time after only 7 flights.

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05-06-2011 08:51 AM  7 years agoPost 12
cyr

rrNovice

france

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Hi guys

So far, I am still waiting for Brian send me the parts I dammaged ... I hope he will not forgot me.

Meanwhile, I have reddened my hub with a blowtorch during 2 minutes and then let it cooling down slowly, in order to soften the metal. I have about 40 flights with it, but I still cannot fly the bird with confidence

I hope this will help a little

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05-06-2011 07:38 PM  7 years agoPost 13
Buzzin Brian

rrProfessor

College Station, Texas

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I have not forgotten you. I am waiting on the new hubs before I send you anything.

Brian

Build it, fly it, crash it. Repeat as often as needed.

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05-09-2011 12:21 PM  7 years agoPost 14
tfagermoen

rrNovice

Norway

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This weekend the tail hub broke in the air resulting in a big crash with lots of broken parts on my Rave ENV flybarless.
This was on the 48 flight on my 2months old machine. I'm realy frustratet and don't know what I should do about it. I don't feel like rebuilding it for almost the price of a new kit plus a new Hatori SB20, Canomod canopy and some servo gears. I don't know if I could trust the tail hub and feel relaxed when flying this machine.

Terje

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05-09-2011 02:46 PM  7 years agoPost 15
scott s.

rrElite Veteran

Orange, Ca.

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Tail Hub
i just bought a tail hub about a month ago, does this mean i shouldn`t fly it.

i`ve assembled it but haven`t flown it yet.

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05-10-2011 02:52 PM  7 years agoPost 16
paverpilot

rrNovice

Corona Ca. USA

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you guys are making me nervous, i am not a good enough pilot to recover from tail hub breakage. I just bought my rave two weeks ago after seeing it fly in Las vegas i decided to try a flybarless nitro version. now I don't know if I should build it or try to return it.

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05-10-2011 03:52 PM  7 years agoPost 17
kawaznic

rrApprentice

Bréval, FRANCE

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Hi,

For me, I change the hub each 30 flights... until a new part from CYE comes out.
May be not the right solution but still no crash for now...

Nicolas

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05-10-2011 04:44 PM  7 years agoPost 18
Futura SE

rrKey Veteran

Fayetteville, Arkansas

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Something is wrong there was no mention of this problem up until now and this machine has been out a while.

Bad batch of hubs? Almost has to be. The part looks to simply be a JR part anyway.

Norman Ross Jr.

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05-12-2011 11:17 AM  7 years agoPost 19
gotnoclue

rrApprentice

sydney

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definately thinking a bad batch must have gotten through as i know someone who has well over 100 flights with no breakages.
mine has around 30 with no issues, both kits were from the first batch of kits to go out.

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05-13-2011 06:31 AM  7 years agoPost 20
scott s.

rrElite Veteran

Orange, Ca.

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Last Sunday
A guy at my field lost his tail today.
He was not beating on it, just doing easy piro flips when we heard a bang. I though it was torque tube or stripped gears but it turned out the shaft on the hub snapped off with the grip and tail blade flying off.
We never did find it.

He was lucky in that he was high enough he was able to hit hold and get it down without wrecking.

I wonder if this is a jinxed bird? He is the second owner and the previous owner also had a tail hub break in the same place.

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