Blade grip screw breaks, blades fly off!

[BlackTitanium]

Blade grip screw breaks, blades fly off!

All I could do now, is watch the rest of the Heli fall to the ground.

One blade stuck in the ground on the field, about 50 yards away, the other in the parking lot near my truck.
I found the head of the socket screw still inside the blade grip.

Damage was amazingly minor:
A few paint chips, on the blade that landed in the gravel parking lot
Broken tail boom
Bent torque tube
Canopy destroyed
Lost one Quick UK canopy magnet
Two bent skids
Broke the tail boom support strut mount on the frame
Broke one skid mount screw, bent the other three
Bent both DFC rotor grip arm integrated control link mount screws

[theailer]

I had a similar issue with my Fusion 50 but I used some cheap wooden blades and the blade roots themself literally exploded in the air. This happened in may and I still haven't found the blades

[NRPY]

This is most unfortunate. Sorry to hear about this. Probably a fatigue failure in the blade grip bolt.

[Tristin]

Eish, bad one! How many times have you had to tightened and loosen that set of screw before this crash? I can only think that the screw has been made weak by a good deal of working or maybe over tightening? Remember the forces on the head and feathering shaft are huge, and it’s all held together by one hex screw on either side. Eish ! Sorry about the other damage. I also like making my screw very tight on my feathering shaft and my screws have been torqued and loosened at least three times now…??? When one replaces a T-rex feathering shaft do the shafts get supplied with a fresh set of screws?

[Tristin]

Thank the good Lord you were not hovering at eye level when she came apart, can you imagine the damage that could cause to one!!!

[BlackTitanium]

Originally Posted by Tristin

Eish, bad one! How many times have you had to tightened and loosen that set of screw before this crash? I can only think that the screw has been made weak by a good deal of working or maybe over tightening? Remember the forces on the head and feathering shaft are huge, and it’s all held together by one hex screw on either side. Eish ! Sorry about the other damage. I also like making my screw very tight on my feathering shaft and my screws have been torqued and loosened at least three times now…??? When one replaces a T-rex feathering shaft do the shafts get supplied with a fresh set of screws?

I usually only torque the screws finger tight, with an ample amount of thread lock applied.
I think the screws may have been reused after one or two previous crashes.
I know I didn't install new screws, the last time I replaced a spindle shaft,
because they were still in the bag. Only one set of screws comes in the bag with two
spindle shafts.

Originally Posted by NRPY

This is most unfortunate. Sorry to hear about this. Probably a fatigue failure in the blade grip bolt.

From now on, I will replace those screws when the head is involved in a crash or if I have to remove them.

[rcflyerheli]

Originally Posted by Tristin

Thank the good Lord you were not hovering at eye level when she came apart, can you imagine the damage that could cause to one!!!

+1000. I had a similar event happen on a Blade 400, except the spindle bolt just let go. It was my first heli, and I didn't know to undo everything and re loctite it. I was about 25-30 feet from my heli when it threw the blade, just as I was applying collective to lift off, and that blade hit me right in the kneecap. It was a wooden blade, but it still put a baseball sized knot on my knee and I limped around for a week.

This is one of the reasons I don't even try to do all the hard 3d stuff close in with a 700 sized heli. Maybe even with a 600 size at the insane HS everyone seems to be running. Someone is gonna get seriously hurt one day.

[HFMan]

Originally Posted by BlackTitanium

I usually only torque the screws finger tight, with an ample amount of thread lock applied.

I've never heard this is the proper technique. You're relying solely on thread lock... could well have been your problem. Perhaps the bolt wasn't tight enough, and it was "rocking" just a wee bit back and forth (but would not back out due to the thread lock). Over time, it may have weakened and stressed the bolt.

I think you need to reconsider how you install feathering shaft bolts.

[levpardede]

looks like metal fatique to me
could be cause it after crash, i personally would not reuse spindle bolt after crash on a big heli.
no problem for over thigten the spindle bolt on 3mm hexa, otherwise your hexa screw driver will twist.
just don't install the after crash spindle bolt on a fresh bird.
hope this help.
i feel sorry about your crash sir..

[BuckAye]

sorry to hear it man...but glad you're ok and no frame damage. Good lesson on the reuse of bolts - I will definitely be careful about that in the future!

[certaut]

it's quite easy to over torque small bolts. If you over torque a bolt it stretches the bolt and the stretching destroys the integrity of the steel and makes it weak. we always just replaced the small bolts and carefully checked the big ones for stretching when I did that stuff a (long) time ago

[Wkessler76]

Replace with KDE's Screws.


SHCS M4 x 0.7 x 10mm

$4.95 for 20 screws

Better class hardware. I confirmed this with Patrick @ KDE.


http://www.kdedirect.com/BearingsandFasteners.html

[BlackTitanium]

Originally Posted by HFMan

I've never heard this is the proper technique. You're relying solely on thread lock... could well have been your problem. Perhaps the bolt wasn't tight enough, and it was "rocking" just a wee bit back and forth (but would not back out due to the thread lock). Over time, it may have weakened and stressed the bolt.

I think you need to reconsider how you install feathering shaft bolts.

I torque the screw, firm enough, to ensure that it is well seated.
I don't gorilla grip the driver and over torque the screw, which would stress the metal.

I'm pretty sure it was fatigue from a previous crash, not being in the habit of replacing
screws and a bad habit reusing bent screws.

This crash was a lesson learned!

[Stevin]

I posted a thread this past week about the exact same thing happening to me. In my case I never found the blades or grips. About 4 of us searched for about 20 minutes and couldnt come up with them. I was flying over the higher grass so I know there is a good chance that my rail blades could be in usable condition. I will def take another look this weekend. Just like you I had minor damage, the tail boom was slightly bent and could have probably just been straightened out but with the new dfc head coming I didnt want to take any chances so I changed it. Besides that the only other part that was really toast was my new fusuno canopy. The heli fell like a brick out of the sky. Oh yeah also one skid was cracked

[Dan E]

I'm still amazed at the amount of force those tiny little bolts can withstand. You're looking at easily over 500kg being put onto them. Can you imagine a small car being lifted by nothing but two spindle bolts?

[davehour]

Originally Posted by Dan E

I'm still amazed at the amount of force those tiny little bolts can withstand. You're looking at easily over 500kg being put onto them. Can you imagine a small car being lifted by nothing but two spindle bolts?

Pretty impressive if one think about it...