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Home✈️Aircraft🚁HelicopterFuel-Helicopters New or Limited ActivityAvant › Mainshaft Shearing in flight because of mod w/ fix
04-28-2011 02:31 AM  10 years ago
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haq0901

rrVeteran - Miami, FL USA MyPosts All  Forum  Topic

Mainshaft Shearing in flight because of FBL w/ fix
Setup: Avant e-Aurora FBL using stock Avant flybared head converted to FBL.
Futaba BLS252 x3 Cyclic servos 6v
Futaba BLS251 Tail Servo
Kontronik Jive 120HV Esc
Xera 4030/2.5y 560KV
Futaba Cgy750
Futaba R6108SB
Edge 693FBL
Edge 105mm
TP 4400mah 45c 6s x2
13/-13 pitch
8 cyclic
2100rpm on head

Cause of Crash: Mainshaft Shearing mid-flight

Was flying a few packs today nothing different from the many times i've flown this heli, and on the second flight of the day while doing some piro flips my heli exploded in mid-air. Blades flew one way(100ft away), boom another(50ft away) and main frame fell like a rock straight down. Upon gathering all the parts and inspecting all parts looking for cause of explosion, I came to realize that my mainshaft that was recently replaced(20 flights old) sheared in mid flight. Still has the rest of the mainshaft stuck in headblock. The shaft sheared right at the top jesus bolt as you see in the pictures below. Upon shearing it cut the boom clean off. Then when it hit the ground it cracked the V1 frames which are impossible to find again. Took out one of my BLS252 cases as you see below, and took out the BLS251 tail servo gear train. Even the R6108SB receiver case cracked open. Batteries luckily made it through, atleast I think so(voltage on each lipo checked out fine, and no puff).

Main shaft was received from carbon xtreme 2 weeks ago.

List of damages:
1.Endless

Total: $704.75 w/Edge Mains and tail
$554.75 w/out mains and tail

----->This could've been worse believe it or not! Lets say i'm flying at an event and the crowd is give or take 30-50ft behind me and i'm flying on the deck 20ft in front of me. And todays events were to repeat themselves and those blades which landed about 100ft away hit any poor soul(God forbid a child worse case) I wouldn't be able to forgive myself! To all of you who own this Heli PLEASE be careful.<------



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04-28-2011 03:07 AM  10 years ago
Gernejr

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Miami, Fl

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Damn that's just not right. All the Cheapo Align's 700n & 700E I've smashed into the ground and I have never broken a Main Shaft. Can you say "Quality Control"?
Herman you know I'm Looking for new 90E but a $13.oo shaft just cost $700 bucks . I think I will keep looking and wait on few more of the new 90E that are done out this year.
Sponsored by Visa
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04-28-2011 04:34 AM  10 years ago
Justin Stuart (RIP)

rrMaster

Plano, Texas

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I am sorry for your loss.Avant RC
Scorpion Power Systems
Thunder Power RC
Kontronik Drives
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04-28-2011 04:56 AM  10 years ago
haq0901

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Miami, FL USA

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It is a great flying bird, really caught me by surprise. Never thought something like this could happen to an Avant.... of all birds. One of the reasons I chose this brand is b/c of great quality. I'm really bummed out to say the least. Dont even know where to start to put her back in the air. Not to mention nobody has frames in stock.
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04-28-2011 05:02 AM  10 years ago
merlin3

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dayton, ohio

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i would msg augusto and just see what he has to say. i know they have a stronger main shaft coming out for fbl but that is to prevent bending, theres no way it should have broke. something is definitely wrong.Justin - Team Horizon, Team Byron
2-700x, Trex 700n, small helis
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04-28-2011 05:03 AM  10 years ago
haq0901

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Miami, FL USA

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I dont have any contact info for Augusto..... but if he could help I'd really appreciate this.
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04-28-2011 05:05 AM  10 years ago
OICU812

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Grande Prairie, Alberta, Canada

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Holy shabizzle! Question was this heli outside for awhile after the crash, or near a bunch of water, OR... you have a ton of humidty there??? How long "after crash" till you took these pictures? I ask as it seems odd the amount of visible corrosion in the core of the shaft! Not sure of hearing any other Avants snapping shafts in flight, but on a heli that size it certainly is not good! ...Once upon a time there were Nitros, flybars and frequency pins...
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04-28-2011 05:07 AM  10 years ago
haq0901

rrVeteran

Miami, FL USA

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Not Corrosion its DIRT.... when it fell like a rock mainshaft dug into dirt at field. Pictures were taken minutes after crash, I was at field.
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04-28-2011 06:43 AM  10 years ago
OICU812

rrMaster

Grande Prairie, Alberta, Canada

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Ahh ok sorry could not tell is all, hope you get some answers on this for certain! ...Once upon a time there were Nitros, flybars and frequency pins...
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04-28-2011 07:27 AM  10 years ago
Tradhunt

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Fairfield, Ca. USA

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Wow Haq... Sorry to see something like that happen. Thats the first time I've seen that happen.I don't crash... I land with style
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04-28-2011 07:36 AM  10 years ago
Jason Bell

rrElite Veteran

California

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WOW sorry that happened to you.
First time I saw the Ridigdcore head I asked Augusto why the yoke was longer and why it had those two screws that clamped the shaft. He said that when designing the head the simulations for testing these instances showed that the much larger force from a flybarless head would stress and fatigue the top area of the shaft where the screws are and make it break. The design of the Rigidcore is not only sexy but functional in this manner and that's why the clamp is there.

Jason Bell
AMain.com
Mikado "V Team"
Xnova Motors
Optipower USA
RCProPlus
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04-28-2011 07:44 AM  10 years ago
Tradhunt

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Fairfield, Ca. USA

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Great job Augusto thinking of that and thanks for the info on the head design Jason.

I can't wait for them to come in stock I need 2.

I've been tempted to pick up another Aurora nitro or electric.
I don't crash... I land with style
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04-28-2011 07:55 AM  10 years ago
Blax1

rrVeteran

Sydney Australia

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Yes excellent info Jason, but gee there a quite a few guys that have given up waiting on the Rigidcore head and have converted from FB to FBL................So guys if you know anyone that has done this conversion, let them know straight away.

Very sorry for your EXPENSIVE loss mate, gee that's a real bummer!
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04-28-2011 08:11 AM  10 years ago
The man

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at home

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I am curious, why is there much larger force from a flybarless head. You can make the same manuever with flybar head and a light set of paddle and it will break at the same place.
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04-28-2011 01:11 PM  10 years ago
haq0901

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Miami, FL USA

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Relaying those test results that were supposedly found on simulation software a little earlier would've helped! Thanks for the timely input. Wish I wouldve known this before I went and threw around this 90 size bird care free! So if it's not the mainshaft being defective it's just design flaw really, and the incident could in fact repeat itself being a converted FBL or STOCK. Electric heli's simply put out more torque so the stock head design might not be good for electric power. Not to mention DANGEROUS.

Ps. I wonder why I can't find this thread under new posts anymore, I can only find it under The Avant tab.
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04-28-2011 01:48 PM  10 years ago
merlin3

rrKey Veteran

dayton, ohio

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you can contact augusto on the avantrc.com websiteJustin - Team Horizon, Team Byron
2-700x, Trex 700n, small helis
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04-28-2011 01:49 PM  10 years ago
haq0901

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Miami, FL USA

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Anyone have or can get their hands on V1 frames, I'm not interested in changing to v2?
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04-28-2011 02:27 PM  10 years ago
stang281472

rrApprentice

Commack, NY

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Sorry for your loss. I wouldnt go as far saying its a design flaw really. The stock head wasnt designed to be FBL and because people convert it (just did myself also) to something outside of its intended use and then put a very powerful motor like yours which should be same as 4035-560 scorpion (I am running 4035-560 in my flybarred e aurora and it has data logged as high as 8400 watts which is 11.24 HP) you can see where this could happen. FBL does put alot more load on the head and clearly the rigid core head was designed around that fact being the added support the headblock has. On machine I did convert to FBL I am running the 500 KV motor and even while doing conversion of stock head I was questioning it being a good idea. With all these big electric its way too easy to make ridiculous power levels on machines that really were designed using parts from 3HP nitro use.

Nonetheless it sucks to have that happen. I am sure if you contact Augusto he will help you in any way he can.

Tom
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04-28-2011 02:32 PM  10 years ago
Gernejr

rrKey Veteran

Miami, Fl

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How does FBL head put more force than FB head? I would think that on fbl you have less less mechanical mass without fb assembly/flybar and paddles. JMO I think having sinlge thearded bolt on 10mm shaft without clamping the head to shaft is asking for trouble. Look at the amount if metal left from inside thearded hole to outside of shaft . Thats weak point , then if then shaft hardness is to high now you have brittled area more likey to broken. This maybe why most 90 size heli have 12mm main shafts. Im shocked this hasnt show its ugly head sooner. Haq maybe your just flying to hard for the avant 90e ..Sponsored by Visa
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04-28-2011 02:44 PM  10 years ago
stang281472

rrApprentice

Commack, NY

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Actually its quite easy for a FBL system to put more load on it being how much cyclic you can run and how fast you can dial up that change to happen. Thats why Avant designed new shafts in the first place. They were fine flybarred and when they went to FBL they were able to bend them in flight. Think that pretty much shows there is more force from FBL. I have had pro pilots fly mine with the 11.24 HP flybarred and I have flown it since it came out very hard and havent managed to snap or bend a shaft. Hardly him flying to hard for the machine. Just think that converting stock head to FBL is not a good idea (and again I just did this myself so not flaming) There is a reason the rigid core was designed the way it is.
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