So I receive my P3A about two weeks ago and go flying. No problems. Update all the firmware, no problems. 2km, no problems. But I kept checking for the old phantom 1 and 2 arm end stress crack issue. Didn't see anything. But then today, under good sunlight, I decided to look really hard. Low and behold, stress cracks. DJI never solved the issue. New shell on the P3 but still withnsub standard thickness. Nasty cracks. But since there is a non modular nature with the P3 internals, replacement of any trouble item meaning a new board, I figured enough is enough and glued the final end of each arm. Until DJI truly addresses the cracking on phantom arms near the motors, gluing is the only solution. No, this isn't covered under warranty.

My P2 has those stress cracks only on the motors with black nuts, i posted about it some time ago in the P2 forum. I guess this must be some type of contruction fault becasue only the area around the 4 motor holes with black nuts showed the cracks. Mine never crashed but is from 2013, i hope my P3 will not show those cracks because its always bad when you want to sell it later. I have a bad feeling selling my P2 because the new owner will tell me it has cracks and open a paypal case etc..

Can you post pictures of the cracks? Do the cracks start at the base of the motor screws or some other place?

I never read about body/motor area cracks before, so I'm interested in seeing first hand damage.

By chance, do you use prop guards or not? Follow up question, are or were the motor screws ever removed and were they tight when you discovered the cracks?

I had cracks in my p2,  I went to fly it one day and I noticed a motor was loose,  I was surprised to see it was cracked out around the mounts, I repaired, super glued cracks tight and used graphite fiber strand and epoxy on inside under motor,  has held ever since, actually very hard to find.

I had never crashed it or bumped anything,  It did tip over after landing a time or two on rough terrain,  I didn't think much of it as I figured, to replace a prop once in a while wasn't too serious.  I assumed the shock from the prop strikes were the problem.  I have never allowed that to happen again.

I just inspected my p3p very close with magnifier I see some subsurface stress, in a spot or two  that looks like it could turn into a crack, I have never allowed a prop strike or anything else on the p3,
Not sure I like what I see,  Tightening the bolts to tight or to loose combined with different  materials
heat expansion rates, might be a factor, may require a specific torque value, or liner of some sort around bolts.

Can everybody else confirm if they have stress cracks on their P3?????

gregg1r Posted at 2015-6-25 07:49
Can you post pictures of the cr OKacks? Do the cracks start at the base of the motor screws or some oth ...

No prop guards. I never crash. Props are balanced. But this isn't an isolated case. This was a well known issue on the P2. I had it happen on three out of four of my P2 craft. I was hoping it was solved on the P3 but no. The shell just as ultra thin on the same highly stressed part. The only difference is that on the P2 the cracks began on one of the four motor screw holes and usually spread up to the shell seam. Or around the tiny Phillips screw hole and again spread to the seam. The P2 is different. It starts, usually in a circle, just below the surface of one of the two screw holes before the four motor screw holes. Once cracked there, the seam between top and bottom of the shell starts to open a bit and the torsional integrity of the shell at the arm ends is lost. On the P2 you closes the crack with super glue and wait for another somewhere else cause they would come. The guys that didn't see them on their weren't looking. On the P3, while they aren't so evident if one isn't looking, are far more sacrificial integrity wise. So the only solution, taking into account the non modular nature of the P3 internals, is to super glue the entire ends of the arms, top to bottom, in order to restore the torsional integrity in that area. There is no other way. You could re shell. But if you're already going that route you might as well milk the most out your present one. Frankly, I'm pissed to say the least that DJI never addressed this issue on the P3. It's bullshit and unacceptable on a quad copter of this cost.

Here is the typical P3 crack. It's a design flaw which lends itself to cracking due to too thin of plastic at the most highly stressed part of the shell.

That little crack spreads all around the hole thereby rendering that screw useless. It's no mystery why DJI added clips between top and bottom shell on the P3. But its not enough. The shell is still too thin in that area and with the twisting forces at play here, cracks can happen quite quickly. Never mind the fact that I only have 24 flights on log and hand catch every landing. For those who are considering chiming in saying a dab of super glue there, keep in mind that I fixed cracks on 4 P2 craft I've just owned and I assure you that in this case and location its simply not sufficient. The only solution to hopefully provide longevity in the repair is to glue the seam or shell joint on the ends from screw hole on one side to the other. For others who are considering suggesting send to DJI, been there, done that with a cracked P2 shell with no crash. After a long wait the new one cracked as well. What we must do here is inspect our craft because this is bullshit and unacceptable.

SULTAN Posted at 2015-6-25 08:08
This is a well known issue, strange DJI didn't solve it in the new P3!!!

You can See this google  ...

Thank you.

After a quick review, I'm going to go out on a limb and say that the removable prop guard mounting plates using the motor mounting holes may  be just the ticket to keep the cracks from starting. I'll also SWAG that the P3 cracking is going to be worse than the P2 due to greater engine braking.

As for the other screw holes cracking, I'd say that the installation torque of the fastener was probably too high taking into account the thickness of the plastic.

Would there be enough interest in a set of repair plates if I were to offer them up? They would be both screwed as well as bonded into place.

I've got close to 30 years of aerospace composite repair and design experience, and this doesn't appear to be a difficult task.

edbighi@gmail.c Posted at 2015-6-25 10:03
That little crack spreads all around the hole thereby rendering that screw useless. It's no mystery  ...

Wow, That really sucks, What next?  You described the p2 cracking perfectly,  After I took a couple of my motors out,  that had cracking I super glued cracks , scuffed plastic around the plastic ferrells and under motor with dremel , mixed up epoxy and carbon fiber, like a fiberglass mix applied around ferrells and under motors , watch clearance.  Another tip if you have an open gaped crack, or small piece missing, rub baking soda into it and then apply thin super glue, very strong repair, try not to be messy, grind, sand , polish, and it will be stronger than before, You wont have to glue shells together, I didn't have to anyway, I have had no problems since. Its irritating to see it manifesting in the p3.

I just replaced the lower shell of my travel copter (Phantom 1) for this very reason; though mine was cracking at the tips of the front arms. Lower shell only.

Fortunately replacement full shell for a P1 is like $70 and I got about 250 flights out of it before it really needed replacing. Still, troubling to see that given it's a well known issue DJI hasn't refined the design a little bit.

On believe me DJI reads these stress crack threads. But for this issue in particular you will never read one single word from them. After all, the typical "are you on the latest firmware" question does not apply. It's a clear design flaw issue with carries down every generation like genes from an alcoholic grandfather. The retaining clips on the new shell are a clear example of their awareness of the issue but it now somehow transfers all the loads to the two screw holes between the lights and the motor screws. In my case I've got 24 flights in before I noticed. But they probably were there even earlier had I known what to look for. A couple of my my cracks only became visible when I lightly put a little twisting force on the motors. About as much force as one would apply when installing or removing the propellers. Do this on yours and you might see a crack that you didn't know was there. On the P2 it was different. Those were easier to see as they propagated from usually on of the motor screw holes out to the seam between top and bottom. Sometimes all the way to the seam, sometimes not. Or on the tiny Phillips hole towards, again, the seam. On the P3mwhat is more prevalent is a circular crack just below the surface of one of those two screw holes between the lights and motor screws. If you look, you find so be ready for disappointment. On all my P2 craft that cracked, four, there was usually one arm cracked. On my P3, four of the eight screw holes had cracks. I am convinced this isn't a manufacturing defect but more of a design defect (too thin of plastic in the area) which lends itself to a very small screw tightening tolerances. But then again, when one factors in the far superior torque of the new motors, it's not so much the overtightened screws that will bring up the ghosts. The motors themselves will transfer all their loads to those two screws in a twisting motion on the arms. Add in active braking and a little wind turbulence nto the mix and, bam, you have cracks. As it stands, with the power of P3 motors, thickness or lack thereof in that area of the fuselage, two screws handling that load, necessity nfor an entire board change for any P3 system fault short of burned out motors, the only solution I see is to glue the top of the shell to the bottom along the seam in order to provide strength in that area. I accept an extra 80-100 buck new shell cost to any board/motor replacement in order to gain that extra strength piece of mind on a flying device since a glued shell would be destroyed when opening. And since any work to rectify this issue by DJI would include a new shell anyway, it is the only solution I see unless DJI would get off it's ass and finally fix this three generation old issue which has nothing to do with software or electronics. Believe me, you will not hear one peep or read one word on these threads from DJI because they KNOW the issue is there and there is no fix short of glue or shell change with no guarantee of the new shell not cracking. They might say "what flying do you do" but there might be an answer like "the type of flying shown in your marketing videos" which is different from the 50 meters away, tree filmimg, tree colliding, gimbal destroying folks that DJI is far better prepared to deal with.

Happy , to see that you, delivered the goods.

Hopefully there will be meeting, indepth discussion, and eventually a plan of attack..

Unfortunately , this may take several long months of R&D.
But so, get it started...

RedHotPoker

edbighi@gmail.c Posted at 2015-6-25 17:31
On believe me DJI reads these stress crack threads. But for this issue in particular you will never  ...

This looks like a possibly worse problem on the p3 than it was on the p2,   Do you suppose they will have it figured out for the phantom 4.  I believe that my fix is a viable alternative, the carbon fiber coating around the plastic ferrel , encapsulating it, is very strong, stronger than the original plastic.  They will not crack out again if repaired properly, guaranteed.  Glueing the arms shells together messes with my OCD.  If you have to open the body again after glued you are screwed,  screwed and glued.  I will remove the upper shell on my p2 and take a couple of pictures, of the repair if anyone is interested.

gregg1r Posted at 2015-6-25 10:32
Thank you.

After a quick review, I'm going to go out on a limb and say that the removable prop g ...

I agree gregg that this can be fixed , but disagree with the prop guard reasoning
This problem can be fixed, I have successfully repaired with carbon fiber mat hair, mixed with epoxy, cut the carbon hair to 1/4" or less length and mix with epoxy, and coat around the ferells, after you super glue.  I think a repair package would be a viable product. I diasagree that the prop guards will prevent this, as the matter of fact I think they could make the problem worse. You have added weight and a leveraging factor, when bumped, will amplify and transfer stress to main frame adding to the stress on the shell half connecting ferells.

Prop guards can accelerate the cracking. Maybe not on a phantom 2 but on a phantom 3 yes. This is because the cracking on the phantom 3 cracks on the 2 screw holes that sit just between the lights and the motor screws. Mostly from torsional twisting forces. Just look at a crack, slightly apply twisting pressure on that arm and one can see the crack spread. But regardless, some of us don't crash if ever and have no need for additional drag on a phantom. Much less weight. Frankly, this is bullshit that three generations into the phantom and we still deal with stress cracks. I've flown all sorts of radio controlled craft and never experienced such stress cracks in such a short period of time. And if the cracks and failures occurred, companies far smaller than DJI, with far less resources, always recognized the issue, admitted it and offered a fix with heavier duty parts and the like. But DJI? Nah. They operate like soviet era Mikoyan design bureau where a bunch of pilots would say, look, this part here is delaminating. Then Mikoyan would say, no, we design the best. It's the pilot's fault. Besides, don't you know more pilots are lined up to fly MIGs? Yeah, DJI is operating not much different than soviet era aircraft manufacturers. Peak of technology and arguably the best craft, but soviet era trouble area rectification and customer service.

And again I ask, where are the DJI folks to come in here to chime in? I think they see stress crack threads and go, oh crap, no, don't go there. Where is that unintended CSC thread. Yeah, that one is safe.

mtnmaddman Posted at 2015-6-25 20:07
I agree gregg that this can be fixed , but disagree with the prop guard reasoning
This problem can  ...

I believe I've seen pictures of your repair in the google link provided above.




The removable prop guards, use a fixed plate that references into the holes used by the motor mounting screws. This spreads the load over a larger area as additional material to bed the screws against.



All too aware of torque applying tools and issues associated with their use.

We had an outfit that came in monthly to calibrate the torque limits.

With a plastic body you need to be using a coarse thread forming screw. This screw alternates
between a high and lowthread to reduce the stresses on the plastic componenet.



The cracking around the body attachment screws are probably a mix of too small of a starter
hole and the fastener being tightened too much.

gregg1r Posted at 2015-6-25 21:49
I believe I've seen pictures of your repair in the google link provided above.

That"s not my fix, That fix is using what appears to be epoxy steel, probably works, not as strong as mine and would be heavier. The bottom plates may help, especially on the p2, The cracking of the shell halves ferells is the result of the transfer,  The arm halves when assembled form an open  parabolic torsion box, It gets its strength from the form itself.

In order to maintain that form it is screwed together of course relying on the the attachment system to maintain the structural integrity, The fitting together tolerance, and placement of screws, are determining factors,  Also in maintaining the "compression factor"  (another factor) , that the two halves have to have to maintain functional integrity.
Thats why super glueing would work so good.

All of these forces play out on the bottom shell of course, right at that point of the ferell attachment to the shell.  The screw and post on the top shell is absolutely structurally solid. nothing to worry there.

This is an easy fix, That we should"nt have to do.

These cracks are most likely due to over tightening the screws.  My P3 does NOT have any stress cracks yet.  

I plan to remove the screws and use a drop of thread lock on each screw and gently screw them back in taking care NOT to over tighten them.

Fulgerite Posted at 2015-6-25 23:29
These cracks are most likely due to over tightening the screws.  My P3 does NOT have any stress crac ...

Thread lock into plastic? With rc cars I've used drops of CA glue on the threads, then screw in quickly to desired torque. I'm curious if DJI has torque specs for this?

Fulgerite Posted at 2015-6-25 23:29
These cracks are most likely due to over tightening the screws.  My P3 does NOT have any stress crac ...

If you plan on using a thread locking type of product, you would be better off using a torque stripe lacquer instead of an anaerobic Loctite material.

I've got access to many different grades of thread lockers, but find that nail polish works best for small screws.

Another cause of this cracking could be insufficient additive in plastic that protects it from UV rays. Might be that cracks happen faster in sunny countries.
On the other hand if DJI would say a word regarding torque of these small screws - if such a fix is possible - that would be really nice. I'm not really sure that all this unscrewing-adding-thread-locker-screwing-back will do any reasonable good impact instead of making things worse. If cracking did not happen yet. i.e. as a preventive action.
...Or may be placing some thin rubber ring below the screw? Nano-silentblock.

sns Posted at 2015-6-26 00:03
Another cause of this cracking could be insufficient additive in plastic that protects it from UV ra ...

It's really sunny here in Austria. Almost as much as Scotland. Joking aside, the only thing that can provide additional torsional strength for the two screw holes on the phantom 3 is better grade plastic or just some added thickness on those screws holes. Completely gluing the seam on the last two inches of the arm looks like it will do the job and relieve the stress on the two screw holes. As for prop guard mounts, all they do is help out the four motor mount screw locations. They still do nothing for the two screw hole locations and in fact, with the guards themselves mounted, make for even further torsional stresses on the two side by side screws.

I just finished seam gluing the last couple of inches of all four arms on my P3A. I  layed the beast on its side and spread a good head of crazy glue along the seam in order for it to seep in there. After about five seconds I swiped the extra glue away. Whatever marks were left when it was all dry I scuffed away with a Mr Clean dry erase pad since they aren't that aggressive and conform very well to the curves in that area. I'm pretty happy with the result. Not as happy as I would be had DJI addressed this third generation issue but oh well. I'm not opening the case cause if the esc fails, chances are the bird will crash. Besides, if one replaces a P3 main board, what's an extra few bucks for a new shell anyway. Here is the result.

The Phantom 2 was famous for those hairline stress cracks around the 4 motor screw holes but only the motors with black hubs, silver hubed motor never showed stress cracks around the srew holes

edbighi@gmail.c Posted at 2015-6-26 00:16
It's really sunny here in Austria. Almost as much as Scotland. Joking aside, the only thing that ca ...

I totally agree with this, I really cant bring myself though ,to glue the halves together, until I have explored other options, Thanks for your idea's.

gregg1r Posted at 2015-6-25 21:49
I believe I've seen pictures of your repair in the google link provided above.

This repair actually looks terrible I believe the shaft would be rubbing on the epoxy steel and would likely have to be ground before the motor would bolt back in,  the reinforcing is not really in the right place.

Just got done with a flight. Not much wind, about 1.2 km distance, 120 meters high. No problems with the repair and seam gluing. So far it's holding together.

sns Posted at 2015-6-26 00:03
Another cause of this cracking could be insufficient additive in plastic that protects it from UV ra ...

Considering these drones spend 99% of the time inside a storage case or indoors I seriously doubt that UV is a significant factor.  And these crack are happening on the bottom side that is shaded from direct sun.  If UV were the issue the cracks would be on top of the drone... Not the underside.

I believe the plastic used is polycarbonate.  Polycarbonate is about the toughest plastic availlable but even Polycarbonate does crack when placed under sufficient stress for long periods of time.  Most plastics will crack if put under sufficient stress for too long.  If the screws are over tightened stress cracking would be expected.

Wide temperature swings can also induce stress cracks in plastics.  So excessive motor heating cold also be a cause.  

The plastic itself is quite strong. One would have to struggle in order to crack any other part of a phantom. But the thinnest part is around the motor area. It's the equivalent of mounting the two turbines on a Learjet or Gulfstream on the thinnest part of the fuselage. A little thicker material in that section of the phantom would not only go a very long way to stopping cracks, but would aid in the integrity of repairs. For the life of me I cannot understand why DJI didn't do it this time around when they spent so much effort redesigning the shell with clips and new light area. Weight? The motors are not only far more powerful but in the past there were folks adding all sorts of payloads to phantoms. And those were less powerful motors. I understand the reasoning in weight reduction for longer flight times, but at what cost?

New video posted. The cracks keep coming.



http://www.phantompilots.com/thr ... page-10#post-434838

edbighi@gmail.c Posted at 2015-7-1 15:53
New video posted. The cracks keep coming.

https://youtu.be/SlQNtU0N2Q0

Mine was so bad that on decent the motor mount broke from the shaking and the motor /prop flew off ... It was at 6-7 feet elevation. I sent it in to them 2 weeks ago. I have delivery proof that they accepted it from UPS. No word at all from them. I can only imagine this will drag into a 3-4 month 'fix'.... God only knows what they will charge me. Or if I'll ever see it again.

35 flights so far, no cracks fortunately. I've never really seen inside a Phantom - is there any re-enforcement? What happens when the shell does crack like this? Can it bring down the aircraft?

Oliver Posted at 2015-7-2 08:38
35 flights so far, no cracks fortunately. I've never really seen inside a Phantom - is there any re- ...

If the motor breaks free from the arm, then yes it can cause a crash as quads won't fly on three motors.

gregg1r Posted at 2015-7-2 08:45
If the motor breaks free from the arm, then yes it can cause a crash as quads won't fly on three m ...

Well, I wouldn't expect it to be able to fly on 3 motors but can such hairline cracks really lead to complete destruction and detachment of the arm/motor?

Oliver Posted at 2015-7-2 09:53
Well, I wouldn't expect it to be able to fly on 3 motors but can such hairline cracks really lead  ...

Provided you keep an eye on things and stop flying or repair the cracks when they appear you shouldn't have a problem.

However if you continue to fly after the screw area shows multiple cracks, all bets are off.

I have the same cracks

DJI really has to face up to the fact that the the phantom 3 cracks even worse than the phantom 2 did. They really have to get on the ball here.