If you are able put some 425 on an inconspicuous area of the phantom shell and watch what it does. Should be ok if applied sparingly to the threads only and screws installed carefully but it definitely reacts badly with the "plastic".
Inspect your P3 before flight!
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I agree. Although DJI did improve the shell design with the second series motors and that helped, but if the bolts are over-torqued, it creates severe pressure on the thinnest part of the moulding which results in stress cracks. As you said, if there's been an issue with the plastic flow in the mould, which is generally caused by temperature fluctuations, it can cause microscopic bubbling which weakens the material.
I think it's likely it's badly engineered and too cheap (materials and process). I have replaced several shells with no crashes or toy style drone racing. New style motors also.
Yep, I've only used a tiny amount of the product and the bolts are totally secure.
Me too.... it dissolves the plastic if you get it on it.
I think the quality of the plastic is actually pretty good so I think its really down to assembly issues. When you've replaced the shells, have you found any common points of failure?
Hmmmm. Well, I stand corrected so thanks to you and HCWM too. I may do a test on some of the various bits of scrap poly I have, including some from the 70's when I worked at Airfix.
Always the motor mounting bosses to the extent of the lower shell. Same place they all seem to fail. It is probably polystyrene- low cost, light (advantages) but unfortunately very brittle compared to alternatives. If it was good quality and nice suited to purpose we wouldn't have so many failures.
Right, so always round the motor boss, where its affixed by the bolt? The problem is one of rigidity I guess, as that's the last place you want the material to flex as it'd affect the position of the prop blades, which wouldn't be good. Is the material on the top shell the same as the bottom?
Seems to be yes... only had one crack in the top shell (shroud area around the motor armature). Still flying that AC but keeping an eye on it.
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My cracks, as most ,have happened while not being flown. Mine was in a case for about a month and cracked while in the case. Read my post. Or any of this thread and you will understand.
Correct. I have balanced props and no weight. Still cracks. It is simply bad plastic.
...yesss...because the main cause is the excessive clamping of the screws that creates a compression stress on the plastic seat, the secondary causes are the bad plastic compound, vibration and dynamic stresses.
All fractures start from the screw hole.
The engineer's design is good, construction and assembly are not optimal....
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Cheers HWCM. However, the P3 shell is polystyrene, not ABS or Polycarbonate, but I understand where you're coming from, but they tested Loctite 222MS and 242. Further down on that thread they point out that Loctite 425 is safe with plastics....
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All right... but its still weird
I am using a photographic bag for my drone, carrying it ony my back still no cracks But the truth is that I inspect all the rotor screws with allen wrench before every flight...I see, but many arms crack about midway, no where near the screws or screw holes. Like mine did....yesss...because the main cause is the excessive clamping of the screws that creates a compression stress on the plastic seat, the secondary causes are the bad plastic compound, vibration and dynamic stresses.
All fractures start from the screw hole.
The engineer's design is good, construction and assembly are not optimal....
It seems to just be brittle plastic.
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