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Old 04-09-2017, 07:22 PM   #1 (permalink)
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Default Never had this happen in over 15 years in the hobby.

Well I total my Exo 500 today and the neo not sure on servos yet.
I been flying and building for over 15 years and never had this happen to me.

I was hovering about 100 feet up and it exploded in the air with 30% left on the battery. all the frames broke, neo broke, battery gone all blades gone, one cycle servo gone, canopy gone, this just the start.

Looks like the screw that holds the main grip where its threaded sheer off as you can see in the picture.

Took me well over 3 months to build it and take my time building it and gathering whet I call top notch electronic for this helicopter for it to explode in 3 minute.

Most likely this was/will be my first and last compass I will build.
the metal main grip flew out and could not fine it on the tall grass
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Last edited by Luis Murillo; 04-10-2017 at 11:30 PM..
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Old 04-10-2017, 03:03 AM   #2 (permalink)
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I think it's a bad accident. I'm sorry this happened. In other helicopters I've seen the grip to spindle bolts come out but I've never seen the bolt shear. I would expect wear on the bolt if you were doing a lot of overspeeds. The screw breaking inside the spindle shaft is strange.

I've seen helicopters explode in flight but that was due to the main shaft bending in flight. In one of the pictures, I can see wear on the spindle shaft where the thrust bearing would be.

Luis, I hate to ask you this because I know you're upset, I would be upset, too--but if you can find that blade/grip? It would be really helpful because hopefully the other end of the screw that sheared is inside the grip.

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Last edited by dunkonu23; 04-10-2017 at 03:37 AM..
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Old 04-10-2017, 05:49 AM   #3 (permalink)
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Luis,

that's nasty, sorry to hear about your rotten luck.

is the screw sheared or has it unscrewed?.. It's probably just the way I'm looking at the photos but I seem to be seeing a threaded hole, not the end of a sheared screw?
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Old 04-10-2017, 06:20 AM   #4 (permalink)
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I'm seeing some threads in one picture but no threads at the end of the spindle shaft. I think some clarification of this would be in order.

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Old 04-10-2017, 06:48 AM   #5 (permalink)
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Sorry to hear about your crash Luis. Anytime a main blade flies off from any heli in flight it usually causes bad things to happen. I would also be interested whether this was a result of a spindle shaft bolt getting unscrewed, the head of the bold getting sheared off, or something else.

The classic Gaui X3 had issues with the bolt getting unscrewed from the spindle typically with bad results. You had to really tighten the bolts with lot of force in addition to putting thread lock... Quite a few even used red loctite on the bolts to prevent them getting unscrewed.
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Old 04-10-2017, 07:06 AM   #6 (permalink)
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I used blue and my bolts were coming out after 20 flights. Now I have RED and the they haven't moved after the same amount of flights.

Sorry for the crash.
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Old 04-10-2017, 07:33 AM   #7 (permalink)
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Quote:
Originally Posted by Lighty View Post
I used blue and my bolts were coming out after 20 flights. Now I have RED and the they haven't moved after the same amount of flights.

Sorry for the crash.

Seriously?
I never use anything but blue on my helis.
*I shall check my screws*
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Old 04-10-2017, 07:53 AM   #8 (permalink)
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Quote:
Originally Posted by Thoemse View Post

Seriously?
I never use anything but blue on my helis.
*I shall check my screws*
It was the BLUE stick loctite.
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Old 04-10-2017, 08:27 AM   #9 (permalink)
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Quote:
Originally Posted by Lighty View Post
I used blue and my bolts were coming out after 20 flights. Now I have RED and the they haven't moved after the same amount of flights.

Sorry for the crash.
Was this on an EXO?

Scott
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Old 04-10-2017, 08:28 AM   #10 (permalink)
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I've never had a blue (liquid) Loctited screw come out.. Having said that, for piece of mind, for some things that are especially critical and that I expect never to remove (swash balls being an example) I use red. Red still can be removed but to avoid stripping or shearing it's best to heat with a soldering iron first.

It would be good to get clarity on if the failed bolt on the OP's EXO unscrewed or if it actually sheared. The photos look like it's simply unscrewed, but maybe I'm missing something?
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Old 04-10-2017, 08:36 AM   #11 (permalink)
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Hmm, really looks like it got unscrewed quite far and then ripped out the last few threads that couldnīt handle the load anymore.
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Old 04-10-2017, 08:39 AM   #12 (permalink)
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Sorry for your losses I know exactly how it feel had my main woodies seperate at the grip bc the builder never epoxy the woodie grip support to blade

From the looks and you can do search. Looks as if you over tightened the bolts and it didn't break on tightening but the grip flexed enough to finish it off in flight. These bolts don't need to be excessively torqued down the lock tite will hold. When rebuild torque to spec n lock tite
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Old 04-10-2017, 08:47 AM   #13 (permalink)
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So is what's being described stripped threads, not a sheared bolt? (two very different things)

Looking at the two or three 'missing' threads.. I thought at first that was an intentional 'counter bore' and that they all looked that way. If that's not the case then is would seam either the bolt was far too short thus not giving enough engagement into the (relatively soft) alloy, or the bolt partially unscrewed itself before stripping.
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Old 04-10-2017, 09:05 AM   #14 (permalink)
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Look to me sheer thread. I was at my bank 2, 2300 on the head hovering since i only had 30% left on the battery. I was pushing it hard but nothing like what i seen people do on video. I always use blue lock tite on all my metal to metal.

Finding the other main grip on the grass where i fly goin to be very hard. Took me 10 minute to find my heli after it exploded and went down
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Old 04-10-2017, 09:36 AM   #15 (permalink)
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There are only two or three threads missing, that means not enough thread engagement. How much thread engagement is there on the opposite side?

A bolt into alloy should have something like '2 x bolt diameter' of thread engagement.
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Old 04-10-2017, 11:03 AM   #16 (permalink)
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The screw has plenty of engagement. Please refer to the build thread and look at the size of the screw and how the system works.

I'm believing the screw simply came out then ripped the rest of the way out. Had it broke in the threads, the other portion of the screw would have to be there.
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Last edited by dunkonu23; 04-10-2017 at 11:19 AM..
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Old 04-10-2017, 11:18 AM   #17 (permalink)
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I aways use locktite and never has this happen to any of the heli i have own....gues aways a first for everything.
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Old 04-10-2017, 11:22 AM   #18 (permalink)
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Quote:
Originally Posted by Luis Murillo View Post
I aways use locktite and never has this happen to any of the heli i have own....gues aways a first for everything.
Yes, there is a first time for everything. If you can find the other grip and blade, it would prove the back out the rip out theory conclusively. It would be greatly appreciated.

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Old 04-10-2017, 12:59 PM   #19 (permalink)
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Quote:
Originally Posted by dunkonu23 View Post
I'm believing the screw simply came out then ripped the rest of the way out. Had it broke in the threads, the other portion of the screw would have to be there.
Scott
If it's a definite that the bolt has plenty of engagement then this^^^ is the most likely explanation that's constant with the damage.

The screw only took two or three threads when it went, so that must be all that was engaged at the moment of failure. If more than this is engaged when the screw is fully tightened during the build (easy to prove) then either the screw was never fully engaged (unlikely), or it's come loose in flight and worked most of the way out before finally ripping out the last couple of threads.

The possible fretting marks on the outside of the spindle shaft also may indicate that the grip was loose.
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Old 04-10-2017, 01:28 PM   #20 (permalink)
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Quote:
Originally Posted by Grumpy_Old_Man View Post
If it's a definite that the bolt has plenty of engagement then this^^^ is the most likely explanation that's constant with the damage.
It's definite. The screw when properly tightened is tightened with the end of the spindle shaft as the stop.

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