Catastrophic design flaw of Phantom 3

[Larry D.]

People with "OCD" shouldn't buy Phantom 3's LOL!
I put these on within a week of buying my P3P - red front for orientation:

Then this 2 piece gimbal/ribbon cable protector:

Then I had to have a gimbal guard - had to modify so there was clearance for camera with new 2 pc protector:

Then:

Ugh! Now "StressCrackGate" I found only one after removing prop guard mounts and inspected thoroughly:

OK I read to much - worry too much - now this:

Somebody stop me!!!! LOL! Maybe I shouldn't fly it and just set it on the mantel to look at...
Nice expensive conversation piece

 

[Larry D.]

Sorry - forgot... These are not stress cracks - correct?

 

[Meta4]

Sorry - forgot... These are not stress cracks - correct?

Correct .. every Phantom has those. Those lines are the joins between the individual moulded parts.

 

[Mako79]

Totally agree, I think many P3s came from DJI overtightened. I slightly loosen screws and just snug them. I check the airframe after each flight, no cracks yet.

I done the same when I first heard about the stress cracks. I had thought it was to do with climate and the expansion of the plastic vs screws so I re-torqued all of them and a few flights later, I got a crack!! I do believe it's the plastic - either poorly quality controlled or just bad plastics that cant handle vibrations.

 

[Mako79]

I would be concerned how the glue handles the heat skippy. Some glue gets soft.

Fairly new P3 here and I have 4 screw hole (not the 2 hole kind) prop guards on - maybe 30 practice flights around home. Reading these treads about stress cracks made me start looking at mine. I haven't unscrewed prop guards to look underneath yet bet I do see one crack in one of the inner screw holes already - UGH! Hopefully not as bad yet as some, but will see after guard removal.

Choices?
Call vender on Monday...
Call DJI om Monday...
I really don't want to send her back but.... Will see...

What type of plastic is this shell made from? Poly?........? Or ?

Question for someone that knows plastics. If I decide to remove top shell and fill (reinforce) the motor mounts and screw hubs where crack is. What would be BEST to use?
Hot glue like above? or some kind of plastic epoxy? If epoxy, what would be the ultimate brand and type to use, to fill the motor mount area up to top of screw hubs. Would this be a bad idea? Fill all 4 the same for weight balance etc...

I would then put prop guard mounts back on as they are the quick removal guards and the guard mounts can stay on.

Opinions please!

Sorry, but my OCD won't let me fly again until I am SURE I did all I can to prevent what has happened to others over stress cracks etc...

It is bad enough, that I am nervous over everything else that could happen to my baby.

Thanks.

Its trial and error. I'll let you know in another 5 - 10hrs of flights. Its spring here so its time to get my wings back. If the crack gets worse or more develops then I will advise first thing.

 

[Mako79]

Just off topic here, because I am curious about your remark here. . You have done about 50hrs on your Ph3 which if on average each flight is 15 min, means you have done 200 flights?. How many batteries do you have?

There is a big thread already on RC Groups DJI owners thread somewhere on this topic and many find the same as I do. We still have a running dispute with DJI that their batteries are not safe after 40 cycles (even if that, we now don't fly them in any built up areas now after 30 to be really safe) where as DJI claim they are good for 200 cycles which in my view is a lie. This are with our 4 Ph2=v2 though. I wonder how well we will go when the Ph3-A/P batteries start getting over 40 cycles?
.

P3 batteries should last longer - they are real 4S batteries. Do an autopsy on a DJI OEM P2 battery and you'll find "6" in a 2 pair cell x 3 config. A 3S should only have 3 cells!! What you get is a terrible balancing act when charging which leads to failure. When in parallel, one of the good battery in the pair masks the health of the other, and its only when you give it some thrust, voltage issues are detected.

 

[Larry D.]

I done the same when I first heard about the stress cracks. I had thought it was to do with climate and the expansion of the plastic vs screws so I re-torqued all of them and a few flights later, I got a crack!! I do believe it's the plastic - either poorly quality controlled or just bad plastics that cant handle vibrations.

Vibrations and/or heat? Combination of both... South Florida here and so far since recently getting my P3 every flight has been in 90+ temps with blazing sun. Everything is pretty hot after a 10-15minute flight - motors - iPad.
Didn't think about possible issues until all of the stress crack talk.

 

[Chris Vedeler]

Here is my Phantom 3 stripped down. Ready for the new shell, motors and Bock gimbal repair kit to arrive.

The hardest part is taking off the top. I was very careful to label everything as there are many tiny screws that are easy to lose and forget where they go.

 

[CallMeMrTibbs]

I used the prop guards from Summitlink purchased at Amazon.com and M3 X12mm Titanium screws to replace the factory set. The prop guards snap on/off. I heard numerous opinions regarding the prop guards adding protection to shell in those specific areas. I installed mine to protect my propellers because I like practice flying in close areas like my backyard.

 

[dlbyers]

Here is my Phantom 3 stripped down. Ready for the new shell, motors and Bock gimbal repair kit to arrive.

The hardest part is taking off the top. I was very careful to label everything as there are many tiny screws that are easy to lose and forget where they go.

Just a thought, not a criticism... Not sure if I'd be putting the electronic parts in a ziplock bag. Electrostatic discharge can destroy those components.

 

[Mako79]

Vibrations and/or heat? Combination of both... South Florida here and so far since recently getting my P3 every flight has been in 90+ temps with blazing sun. Everything is pretty hot after a 10-15minute flight - motors - iPad.
Didn't think about possible issues until all of the stress crack talk.

I'm no plastic expert.
Just logically thinking - the screws act as heatsinks and transpires to the plastic. Cool - hot - cool x 50 on plastics will cause it to become more brittle. I've seen this on Asian plastic bowls used in microwaves over a long period. Now add high intensity micro vibrations to brittle material and this will increase the chances of cracking.

 

[Mako79]

Here is my Phantom 3 stripped down. Ready for the new shell, motors and Bock gimbal repair kit to arrive.

The hardest part is taking off the top. I was very careful to label everything as there are many tiny screws that are easy to lose and forget where they go.

View attachment 30682

Would a strong arm kit work as a repair kit in your scenario?? Just glue back the broken plastic of the motor (to keep the correct camber/cant) and use the strong arm as a brace.

And can you let us know if the new shell is a revised/redesigned shell or is it the same craplastic.
Thanks.

 

[Tashier]

Just a thought, not a criticism... Not sure if I'd be putting the electronic parts in a ziplock bag. Electrostatic discharge can destroy those components.

Good call on the ESD. I wouldn't risk it either. Usually it's more of a problem with IC's not actually soldered into boards yet but can still be a problem.

 

[Chris Vedeler]

Would a strong arm kit work as a repair kit in your scenario?? Just glue back the broken plastic of the motor (to keep the correct camber/cant) and use the strong arm as a brace.

And can you let us know if the new shell is a revised/redesigned shell or is it the same craplastic.
Thanks.

I thought about that. I wouldn't trust it for many reasons. Primarily because the motor wouldn't be properly positioned. The plastic tore free. The edges don't fit well.

I fly hard and far. Last thing I would want is the repair to fail with my bird 2 miles away on the summit of some inaccessible mountain. Air worthiness is critical for me and I'm not going to mess around.

 

[Chris Vedeler]

Good call on the ESD. I wouldn't risk it either. Usually it's more of a problem with IC's not actually soldered into boards yet but can still be a problem.

I should have known better. I used to work in IT. Well too late now. I won't touch it until it is ready to be installed. Hopefully the electronics are rebust enough.

 

[Tashier]

I should have known better. I used to work in IT. Well too late now. I won't touch it until it is ready to be installed. Hopefully the electronics are rebust enough.

I used to work in Silicon Valley on IC's for years. Hated all the ESD shoes, clothes, smocks and wrist straps we had to wear. Better than a fab at Intel though...

 

[Tashier]

Question to the OP and anyone else if it hasn't already been discussed. Do you balance your props? Looking at your original pic and how the prop is mounted on the opposite end of the motor mounts, any vibration would work that motor mount to failure with the leverage applied to it. Just wondering if that's a contributor. I have yet to balance my props but have ordered the stuff to do so.

 

[Chris Vedeler]

Question to the OP and anyone else if it hasn't already been discussed. Do you balance your props? Looking at your original pic and how the prop is mounted on the opposite end of the motor mounts, any vibration would work that motor mount to failure with the leverage applied to it. Just wondering if that's a contributor. I have yet to balance my props but have ordered the stuff to do so.

While balanced props are clearly better than unbalanced props, I highly doubt that could have been the cause of my failure. I was using stock DJI props as do most others. I never noticed any unusual vibration. Even perfectly balanced props will cause vibration as they speed up and slow down. The motor mounts need to be robust enough to handle these vibrations and the vibration caused by stock DJI props.

I'll probably never know for sure what happened, but my theory is that the fact that I routinely fly in temps up to 100F the plastic fatigued to the point of failure. I probably had cracks that I hadn't noticed for weeks.

In any event, I recognize the fact that I fly my P3 pretty hard to be doing the types of video I do (flying over mountains). The P3 does a remarkable job but clearly had a design limitation that I run straight into. Instead of buying a $3000 quad, I can simple be aware of this limitation and reinforce it using the Strong Arms.

 

[Tashier]

I don't doubt it's a design problem. Just thinking balanced props would help. Were your props balanced?

 

[notelpats]

Totally believe in the prop guards to reinforce motors. Longer screws and pulls both thin arm plastic and thicker guard plastic together as 1. No stress cracks yet here either (knock on wood),my remedy is to snug all screws like a spark plug than give 1/8 more turn in a x pattern on each arm.