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Prop Guards & Stress Cracks...
2150 30 2015-9-10
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SpunOne69
lvl.4

United States
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I check my P3P regularly after every flight to see if there are any stress cracks ever since it was brought up on this forum...30 something flights, no cracks.  As soon as I put those PhantomGuard quick release prop guards on it...BAM!! Both rear arms got the stress cracks around two of the screw holes!! WTF??  I was careful not to over-tighten the screws, I followed the instructiions, even used a drop or two of blue thread-locker.  I think those stupid guards may have something to do with the cracks...

2015-9-10
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SpunOne69
lvl.4

United States
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Since I bought these "authorized" DJI prop guards from a DJI authorized service center (Drones Plus in Santa Clara) is it possibly a warranty issue?? I would really like a new shell...
2015-9-10
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fwickeha
Second Officer
Flight distance : 173455 ft

United States
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What kind of "blue thread lock" did you use?  Some of that stuff is toxic to DJI plastic.
2015-9-10
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rayrokni
Captain
Flight distance : 8139875 ft
United States
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read the blue thread locker and you may see that it says not for use on plastic.!!
2015-9-10
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Willie Wonka
First Officer

United States
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rayrokni Posted at 2015-9-10 22:52
read the blue thread locker and you may see that it says not for use on plastic.!!

ANY thread locker weather its red or blue is never to touch plastic as i know from experience
2015-9-10
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fwickeha
Second Officer
Flight distance : 173455 ft

United States
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This has been discussed on this forum previously.  
http://forum.dji.com/thread-1125-1-1.html
You might contact DJI and ask if they will replace your shell.  Suggest you send them good pictures and request an RMA.
2015-9-10
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rayrokni
Captain
Flight distance : 8139875 ft
United States
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Willie Wonka Posted at 2015-9-11 10:58
ANY thread locker weather its red or blue is never to touch plastic as i know from experience

i use a thread lock specially for plastic
2015-9-10
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DJI-Tim
DJI team

Hong Kong
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Hello, SpoonOne69, sorry for your cracks, i wish you was more careful using thread locker. thread lock.PNG
You can purchase new shell from dealer

2015-9-10
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nayajin
lvl.2
Flight distance : 71368 ft
South Korea
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DJI-Tim Posted at 2015-9-11 12:17
Hello, SpoonOne69, sorry for your cracks, i wish you was more careful using thread locker.
You can p ...

I use thread-lock from Tamiya.  It seems to be safe on my phantom.  Or you can also try Loctite 425 if you prefer this brand more. ;)

2015-9-11
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SpunOne69
lvl.4

United States
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I used the standard "blue" lock-tite threadlocker...it wasn't those holes that cracked.  The prop guard holders mount to the two outer-most motor screws (you remove the two motor screws and replace them with longer ones to hold the prop guard locks) The holes that show the stress cracks are the ones before the four motor mounting holes, they are the ones that hold the top and bottom of the shell together. So no lock-tite was used on the holes that cracked.  Besides, who would be dumb enough to put so much thread locker on that it over flows onto the holes.  Not trying to sound like a dick, but I repair $50,000 color copiers for a living, I know the difference between M-tight screws, M-collared screws, regular screws, machine screws, etc...believe me, if I wanted to dis-assemble my P3P, it would NOT be a problem for me.
2015-9-11
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SpunOne69
lvl.4

United States
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I was only posting this thread to see if other people that have the stress cracks were using prop guards or not.  I find it strange that for 30 or so flights, I showed no signs of the cracks at all (believe me, I checked regularly) but after only 2 flights with the prop guards, all of a sudden there are cracks??  It seems too coincidental...
2015-9-11
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SpunOne69
lvl.4

United States
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Besides, when you apply lock-tite to ANY screw, you put a small dab on the threads (not the tip) and then you wipe off the excess liquid so that it only fills in the grooves of the screw...you don't just blob it on and then put the screw back!!
2015-9-11
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rayrokni
Captain
Flight distance : 8139875 ft
United States
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SpunOne69 Posted at 2015-9-11 10:32
I was only posting this thread to see if other people that have the stress cracks were using prop gu ...

it is not coincidental when the screw wells have been eaten away by the loctite
2015-9-11
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jaronpv
lvl.4
Flight distance : 723776 ft
United States
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Mine has stress cracks too on the rear arms.  Never used prop guards.  My theory is the rear arms receive the most stress due to those motors working harder during forward flight, which, lets be honest, is the most common flight direction!  I had mine looked at by a DJI dealer.  Their recommendation: Fly the bird.  Install a good strong arm kit.   and dont worry about it.    I purchased the strong arm kit from uavbits.net
2015-9-11
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SpunOne69
lvl.4

United States
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I did the temporary "cable ties" fix to each arm, I am going to look into both the strong arm kit and buying a new shell...I plan on calling or visiting the DJI dealer that sold me the prop guards...
2015-9-11
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SpunOne69
lvl.4

United States
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Just ordered the "strong arm" kit from uavbits...we'll see how that works   Thanks for the advice...
2015-9-11
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SpunOne69
lvl.4

United States
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Took my P3P to Drones Plus (DJI Authorized service center near me) and showed the guy the stress cracks and explained that the prop guards he sold me were probably the cause...he agreed   Says they'll send photos and flight logs to DJI and replace the shell...
2015-9-11
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SpunOne69
lvl.4

United States
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Well...its in the shop
2015-9-11
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rodger
Captain
Flight distance : 15812070 ft
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United States
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Very interesting Post. I think that you would be better off using a dab of RTV. as mentioned above it may have some thing to do with the Loc-Tite. Try a dab of what you used on an old prop from DJI and see if it has any effect on the Plastic? If it does, please let the Community know.
2015-9-12
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rodger
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Flight distance : 15812070 ft
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nayajin Posted at 2015-9-11 07:56
I use thread-lock from Tamiya.  It seems to be safe on my phantom.  Or you can also try Loctite 425 ...

The Taniya Thread Loc is definitely safe on Plastics. I use it on RC Tanks and have never had an issue with any cracking. The Tanks take a heck of a beating and keep on ticking. The other thing is that it is made for Plastic and Metal.
2015-9-12
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rodger
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Flight distance : 15812070 ft
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SpunOne69 Posted at 2015-9-11 10:32
I was only posting this thread to see if other people that have the stress cracks were using prop gu ...

I would have to agree with you on that one Spun. That would make me a bit concerned also.
2015-9-12
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SpunOne69
lvl.4

United States
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The holes that cracked had NO threadlocker on them...I used threadlock on the two outermost motor mounting holes (where the quick release brackets are installed) the holes that cracked were the ones that hold the shell together, NOT the motor mount holes...so using threadlocker or not is a moot point.  My point is that installing/using the quick release prop guards may be causing the stress cracks.  I noticed a definite "wobble" in my P3P when descending straight down, it never did that when I had NO prop guards...that "wobble" may have been enough "stress" to crack the screw holes. I'll know more when I get my P3P back next week...
2015-9-12
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Joe Blow
lvl.4
Flight distance : 417149 ft

United States
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I commented in other threads about stress and prop guards.  When you install prop guards you are inducing a huge amount of extra drag to your DJI3 airframe and drag can produce more stress on the airframe especially during high vertical speed descents.  My believe is that additional drag and stress from the prop guards caused cracks at the weakest points, the screw holes.  
Yes, I am not a fan of prop guards........have you ever seen a real helicopter with prop guards on the main rotor>


2015-9-12
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sdavis1974
lvl.2
Flight distance : 219170 ft
United States
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Exact same thing happened to me spun, except I got one flight and the rear arm cracked. Also I believe that warning on the loctite info is for plastic screws into plastic materials because it swells
2015-9-24
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toddf.perkins
lvl.4

United States
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over 100 flights with removable prop guards. No stress cracks here. Had the removable guards put on b4 my first flight. If anything, I bel rive the removable guards add extra stiffness to the arms.
2015-9-24
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Dioden
Second Officer
Sweden
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I haven't seen any cracks on my P3P yet, but many says they seen it. I wonder why the don´t build it in composite material instead, I think it would be stronger then.
2015-11-12
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Chuck1906
lvl.3
Flight distance : 1037425 ft
United States
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Is it true that stress cracks are the result of props that are not balanced correctly?
2015-11-12
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SpunOne69
lvl.4

United States
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I'm no aeronautic engineer, but I would have to say no...I think it's more caused by the flexing of the arms when the Phantom turns at higher speeds.  I have read that over-tightening of the body and motor screws can be part of the cause as well...
2015-11-12
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toddf.perkins
lvl.4

United States
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Too many people are having this issue. I think it's a fundamental flaw with the design. I am willing to bet that over time most phantoms will develop stress cracks at some point
2015-11-12
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SpunOne69
lvl.4

United States
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DJI already released an "updated" shell design, which in a way, admits there were problems with it.  But they never actually "admitted" that stress cracks are an issue.  If they did that, they would have to replace anyone's shell that had the cracks.
2015-11-12
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gustofusion
lvl.4
United States
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Most of the time thread lock is simply not needed. People seem to fall into the mindset that it is needed because someone mentioned it. Did you think that something that is simply stickey would serve as a  "Thread Lock" after all what does thread lock do??? It keeps a screw or bolt from loosening due to force or vibration. Now ask yourself, what can prevent a screw or bolt from vibrating loose, may be something as simple as a micro drop of elmers glue, or maybe a tiny touch of silicone. Please start considering common sense approaches to the types of remedy's available to you rather than simply jumping on the band wagon.
2015-11-16
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