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Major stress cracks on Phantom 4 Pro/P4P
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9883 56 2018-2-26
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Eric13
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luciens Posted at 2018-6-30 09:59
Resurrecting this thread, as my P4P has these same stress cracks on all 4 arms now after maybe 30 flights. The problem, though, is obviously faulty design - the motors are hard mounted to the airframe with no shock mounting. Compounding it is the super stiff and inflexible shell and arms. Anything that spins a prop has to have some form of "give" in the mount; vibration and Coriolis force, etc., has to go somewhere if there isn't something to absorb it in the installation. All you folks familiar with full scale aircraft design know what I mean.

The cracks are a kind of "built-in" shock mounting that sort of developed by themselves, I guess you might say.

Did all these cracks appear after one specific flight or over time?
I keep thinking there are some bad batches out there.
Some people report major cracks, others nothing.

It would make sense if most people report cracks after a certain mileage. But that's not the case.
Some people treat their drone like a raw egg and get these. I have abused my P4P a lot and still after more than 1000km: Nothing.
I'm wondering if there is only one production facility for these drones - in China - or if they get produced worldwide at different facilities.


2018-6-30
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luciens
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Eric13 Posted at 2018-6-30 10:32
Did all these cracks appear after one specific flight or over time?
I keep thinking there are some bad batches out there.
Some people report major cracks, others nothing.

In my case, after about 30 or so flights. No crashes, no abuse, always very carefully hand caught, careful attention to prop tracking.

Probably the machines that don't crack are, ironically, less well made than the ones that do. The problem is the extreme stiffness of the arms and complete lack of shock mount on the motors. If a poorer, more flexible plastic is used, or the assembly is a little shoddier on a particular batch, that probably helps the situation and those machines stay together longer.

I don't see any fix other than some shock mounting of some kind or other under the motors.

Or just simply leaving the machine as-is. Once the bottom shell is cracked, you can wiggle the motor and see that that's probably what the motor/prop installation "wants". 3 of my arms are cracked completely through and the 4th is just starting to crack. On mine, if the upper shell was going to start breaking it probably would have by now.

Obviously not worth the risk so mine will go in the bin, I guess. Or I might remove the innards and use the motors/ESCs/flight controller on an F450 or something like that.

I could exchange it but the new one will just crack too...
2018-6-30
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dronybaloney
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I still think its the latest fw , which causes heavy wobbling of motor arms upon take of and landing( when shutting down engines) and landing geat touches ground. In had stress cracks in armvents. Sent it to dji and got a replacement with this latest fw. Downgraded back to .602 which caused less wobbling.did sent soooooo many posts to dji. And they never came with a sollution or feedback and no new fw update.i gave up at they , hoping no cracks occur. I check p4p after every flight for cracks
2018-6-30
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luciens
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dronybaloney Posted at 2018-6-30 14:19
I still think its the latest fw , which causes heavy wobbling of motor arms upon take of and landing( when shutting down engines) and landing geat touches ground. In had stress cracks in armvents. Sent it to dji and got a replacement with this latest fw. Downgraded back to .602 which caused less wobbling.did sent soooooo many posts to dji. And they never came with a sollution or feedback and no new fw update.i gave up at they , hoping no cracks occur. I check p4p after every flight for cracks

Heh, no, firmware updates won't fix or un-fix bad airframe design. I'm running a much older firmware, in the .500's I think, and the behavior of the motors is fine.

The arms are just far too rigid and stiff and so the motor/props eventually just break them loose.

I'm going to patch mine with silicone glue and see how that comes out. My hope being that hat'll hold it together at least somewhat but hopefully will retain some of the flexibility so it wont tear itself up again or do more damage. This is out in the country and no where near people type flying of course....
2018-6-30
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Mark The Droner
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I don't know.  You might consider rubber mounts such as what is found here:  https://www.ebay.com/sch/i.html? ... er+mounting+washers

You'd have to use the right length screws and then experiment to see how the AC flies.  

The problem with things like this is, at least in my experience, when you think you've found a solution to a particular problem that you believe is smarter than DJI, you later realize your solution was actually dumb, and DJI chose not to do it long ago for some good reason which isn't apparent right away.  

Good luck.
2018-6-30
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luciens
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Mark The Droner Posted at 2018-6-30 16:32
I don't know.  You might consider rubber mounts such as what is found here:  https://www.ebay.com/sch/i.html? ... er+mounting+washers

You'd have to use the right length screws and then experiment to see how the AC flies.  

True in many cases, but clearly not well thought out and tested was this one, as the failure rate with the Phantom shell demonstrates. Even apart from that, anyone who's worked with installations of anything that flies through the air by cranking a prop knows that hard mounting the engine/motor/prop onto a rigid mount and airframe is a formula for disaster.  I suppose I should have known, but I bought it anyway

The grommets might work, but as you say, getting the whole thing to work isn't easy. And it's probably a redesign DJI should be doing and not us. As for mine, I'm going to glue it back together and see what happens.

2018-6-30
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djiuser_PEp4mLwh74c7
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Sorry to hear about that. It makes me worry about my P4P+ two, coz I just updated my FW recently.
Change the shell is cheap and easy.

The reasons the crack are unknown. It is not like a tiresome broke. Heavy vibrations may result in plastic stress, and the tip of the arm is the weak point.
2018-6-30
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luciens
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djiuser_PEp4mLwh74c7 Posted at 2018-6-30 20:49
Sorry to hear about that. It makes me worry about my P4P+ two, coz I just updated my FW recently.
Change the shell is cheap and easy.

Well the "smoking gun" is that they all break in the same place and in the same manner. These are definitely stress cracks from a bad installation design, meaning no shock mounting for the motor/prop and a far too stiff arm with stress risers at those vents on the bottom. When a mount is too stiff, the repeated stresses find their way to the weakest part and work it until it finally fatigues and breaks.  I've seen this a million times in both full-scale and model installations that weren't done properly.

A patch-around might be to get rid of the vents on the bottom, or just do it the right way and get it overwith by shock mounting the motors.

Anyway, just resurrected this thread so folks were aware this is still a problem with the Phantom in general.
2018-7-1
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jfc
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Just had mine replaced. 11 days from sending in to receiving the replacement. Cracked in the exact same area on the lower shell. Seems to be a common problem not sure why a fix hasn't come out as yet. When it does will DJI stand by their product and correct the problem for all current owners? I hope so.
2018-7-1
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Bashy
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They break in the same place because thats the weakest point closest to the motors, i wonder if UV is breaking it down, not enough for use to notice it going brittle or anything but deffo enough for the arms to crack under stress., anyhoo, this is deffo a manufacturing defect, there are far too many for it not to be and as such there should be a product recall and refit no mater the age
2018-7-1
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thunderbyrd
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Bashy Posted at 2018-7-1 20:50
They break in the same place because thats the weakest point closest to the motors, i wonder if UV is breaking it down, not enough for use to notice it going brittle or anything but deffo enough for the arms to crack under stress., anyhoo, this is deffo a manufacturing defect, there are far too many for it not to be and as such there should be a product recall and refit no mater the age

This may be an older thread but my P4P has the same stress cracks in the same places but only on the forward arms and one small one next to the battery.   I think I'd rather replace the bottom shell myself as opposed to sending it in the DJI for repairs because it will take weeks.  Funny thing is my stress cracks are only on the bottom shell.
2018-8-12
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Stach Rogalski
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I have again noticed stress cracks forming under my 8 month old P4 Advanced, three weeks ago... after having a P4 Pro that was two months old with bad cracks... DJI... Please address the arms cracking issue!

I also just waited three weeks to have mine assessed and or repaired.. but alas it came back with them stating there's no structural quality issues!?.... A crack in the arm is a quality control and manufacturing issue!
2018-12-11
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maven4336
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gyrex Posted at 2018-2-26 04:53
It's around 4 months old. I know European support are pretty quick because I've had some kit serviced there before and they really try hard to get it back to you ASAP especially if you need it for work. Australia on the other hand have been pretty bad so I'm loathed to send it in. I'm tempted to use some duct tape until we finish our trip. I can't be without the bird for too long - it's an essential part of my work kit while travelling.

Hello saw your post, bought My p4p + a little over year ago started seeing cracks like yours so bought new shell it’s been about 5 months and again I’m seeing the first crack around motor, do you have any idea on why and what is the best route to getting it fixed and not happening again, please any information would help ty. My email is bda4336@gmail.com
2019-2-27
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gyrex
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maven4336 Posted at 2-27 17:03
Hello saw your post, bought My p4p + a little over year ago started seeing cracks like yours so bought new shell it’s been about 5 months and again I’m seeing the first crack around motor, do you have any idea on why and what is the best route to getting it fixed and not happening again, please any information would help ty. My email is bda4336@gmail.com

You'll just have to keep replacing the shell because the plastic obviously hasn't been designed to tolerate the flexing.
2019-2-28
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Manxmann
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luciens Posted at 2018-6-30 09:59
Resurrecting this thread, as my P4P has these same stress cracks on all 4 arms now after maybe 30 flights. The problem, though, is obviously faulty design - the motors are hard mounted to the airframe with no shock mounting. Compounding it is the super stiff and inflexible shell and arms. Anything that spins a prop has to have some form of "give" in the mount; vibration and Coriolis force, etc., has to go somewhere if there isn't something to absorb it in the installation. All you folks familiar with full scale aircraft design know what I mean.

The cracks are a kind of "built-in" shock mounting that sort of developed by themselves, I guess you might say.

I think DJI should be the ones that come up with a rectification ....... it should be free & initiated where necessary as a re-call.  
My P4P+ developed cracks on 1 leg,  it has been 4 weeks since I left it with the dealer for repair & no advice as to what is going on.  
As usual,  DJI are keeping their collective heads down !!!!
2019-3-1
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Tree
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due to this thread I checked my p4p and found several stress cracks on Feb-11-2019, filed a claim, followed the DJI routine, uploading records, and received my replacement drone on the 21st feb
2019-3-1
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maven4336
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luciens Posted at 2018-6-30 18:23
True in many cases, but clearly not well thought out and tested was this one, as the failure rate with the Phantom shell demonstrates. Even apart from that, anyone who's worked with installations of anything that flies through the air by cranking a prop knows that hard mounting the engine/motor/prop onto a rigid mount and airframe is a formula for disaster.  I suppose I should have known, but I bought it anyway

The grommets might work, but as you say, getting the whole thing to work isn't easy. And it's probably a redesign DJI should be doing and not us. As for mine, I'm going to glue it back together and see what happens.

I’m on my 4th shell, even went with obsidian just to see if it would hold up better but Iv just noticed a new crack, all shells have cracked on the back legs, and yes will be glueing from here out, it’s a waste to buy any more shells,  poor plastic DJI
2020-4-12
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