P4P Stress Cracks

[Notchiro]

Hello everyone, just today I noticed a stress crack on the back arm of the drone. Is this normal for this drone, I have 44 flights on it so it’s weird that I already have one. But can anyone tell me if this is normal for this drone?

 

[Fly Dawg]

Stress cracks are never "Normal", this is the first Iv'e seen with a P4. There are tons of threads on the P3 stress cracks. Never a good thing.

 

[Notchiro]

Stress cracks are never "Normal", this is the first Iv'e seen with a P4. There are tons of threads on the P3 stress cracks. Never a good thing.

Here is a picture of it it’s on the vent

It’s worse in person but this is the best pic I can get.

 

[Fly Dawg]

Iv'e seen very few on the arms themselves. Usually they are on and around the motor mount screws, for that one for now, being that it is not on the motor mounts, just keep a close eye on it and see if it starts to expand. It may or may not.

 

[blade strike]

Please contact support for a replacement shell

 

[johnccha]

I used to get loads of these cracks on my phantom 1 , I used to solve problem by putting supper glue in crack . Fixed permanent.

 

[Notchiro]

So just an update it started to expand and became really noticeable so I am exchanging this one for another P4P because I only have this drone for like a week

 

[dronie326]

I had the exact same cracks happen on two P4P's that were about a month old. They expand pretty quick so it should definitely be replaced. What case are you using? My best guess is that the cases I am using exerted too much force right on that area of the arm. I'm not 100% that's the issue yet but I had the shells replaced and modified the case so we'll see if it happens again.

 

[Bakersfield Quad]

I still think the crack is related to braking and prop balance issues. The stress on the airframe, doing high speed maneuvers, would be right where the cracks appear. I would wonder if high speed flight and flight maneuvers might not be real factors here.

Usually it is only the rear two motor arms that crack. This is no likely for no reason, but do to some factor yet determined.

Does anyone know enough about how the 4 motors work when braking, to know whether the rear two motor arms are going to be put under more stress than the front two, when braking?

 

[dronie326]

I can tell you that in my case it was not from any high speed flight or braking. They were used very lightly for mapping and all four arms showed cracks.

 

[Bakersfield Quad]

I can tell you that in my case it was not from any high speed flight or braking. They were used very lightly for mapping and all four arms showed cracks.

Cool, then that puts this into question. Do you fly your drone at over 35 mph? Have you adjusted the braking action, to lessen it by chance?

I am only trying to figure out the reason for the cracks, no everyone gets them apparently. I am new at the drones, so I research as much as I can to understand them better.

I do not fly hard either, but I observed that if you are moving at 30+ mph and let the stick return to neutral, the drone stops very fast, make a hell of a lot of noise and the props race at very high speed. Now if the drone would have been 200 yards away, I would not have been aware of what it was doing, but this happened right over my head. So, it would be really easy to cause a hard load on the frame, unintentional of course.

I am going through all my props, the balance is not that good on any of them. They also weigh as much as .6 grams. 5.5% difference is weight is significant and may or may not have any influence on the air frame, still waiting for someone with more knowledge to explain whether a difference of 5.5% in weight would cause issues in the motor controls, but probably not.

However, out of balance dynamically, is another story. Vibration will crack plastics fairly quickly, compared to say aluminum. Any vibration with a plastic frame, is not good. So I will not fly without balancing and weight matching the propeller sets.

 

[John Locke]

They also weigh as much as .6 grams.

Is this a typo?

 

[Bakersfield Quad]

Is this a typo?

No. I weighed 12 blades so far, lightest is 11.0 grams, heaviest is 11.59 grams.. I was stating they weigh as much as .6 grams different, the weights are all over the place.

 

[John Locke]

No. I weighed 12 blades so far, lightest is 11.0 grams, heaviest is 11.59 grams.. I was stating they weigh as much as .6 grams different, the weights are all over the place.

Actually it is a typo. It should have said "They also weigh as much as 11.59 grams" or "They also have as much as .6 gram delta" Sorry to be so picky. I thought that's what you were talking about, but I doubt if total weight between different props makes that much difference, as long as they're balanced. It's likely one corner of the quad has a much larger weight delta than 1 gram over the other 3 corners. That would be an interesting measurement, to see just how off-balance the Phantom is. I'm sure it's close, I'm guessing within 15 grams per corner. Can you measure that with your scale?

 

[KingDad1985]

Maybe the supplied grey strafoam case might be causing the cracks on the underarm vents. Check it out

 

[KingDad1985]

The reason I say that is mine had the same cracks. I have a new one now. The case seems to push down on the motors, while also pushing on the vents.

 

[Bakersfield Quad]

The reason I say that is mine had the same cracks. I have a new one now. The case seems to push down on the motors, while also pushing on the vents.

Well, now that is certainly something to consider. So, you use the foam case that came with the P4P?
I have a hard case, back pack that I use, the foam case I put away. But that is some thing that I did not check out, I put the bird in the new case as soon as I got it,

This could be interesting information, how many that have had cracks, keep it the gear in the DJI foan case?

 

[Bakersfield Quad]

Is this a typo?

yes, period instead of comma, old eyes and small things.

 

[John Locke]

I think this kind of plastic has flaws by random chance, some shells may be weaker than others. My P4 was 362 days old and I found a serious crack in the corner of the battery hole, identical to another forum member who posted their battery hole crack. DJI replaced the craft with a new one. My craft had a wrap on it, so the crack wasn't visible until I took off the wrap on day 362. Lucky I was prompted to check the craft closely without the wrap.

If the crack isn't serious enough that would affect flight integrity, I'd recommend to fly the craft till it's 11mos old and keep a close eye on it. Then send it in for replacement. This delays the wear and tear on your new craft, waiting until just before the warranty is up on the first craft.

 

[Bakersfield Quad]

Yeah, I will keep a good eye on the shell. I am also going to see how the craft feels with the balanced props, I checked it last flight, touching each motor arm, below the motor to judge the vibration. It was not bad, but I could feel a difference between motors, I suspect Prop Balance.
Now that I have balanced the props, I will check it again and see how it feels.
Not only am I a pilot, but I was once an aircraft mechanic, overhauling jets most. So I know how insidious vibrations can be.