Always Check Your Props Before Take Off!

[AaronB]

Looking at another post from one of our members trying to bend and or break the prop and could not I decided to take one of my older damaged props and try and break it. There was no way I could fold it over and have it break at the fold.

A single fold is not an indicator of durability, most cheap plastics will not break on a single fold. A better test is how often can you bend the prop backwards and forwards before it separates - this would be more representative of the stress the props can undergo from constant vibration. A nick in the side of the prop could develop very quickly (like a crack in a windscreen) to full separation when up and flying.

 

[Cipta]

Hello,
a little suggestion which maybe could help to reduce the problem with broken props. I wrapped a fitting (very small) piece of "Tesa" (or some similar Tape with the same thickness) around the bolts to reduce the clearance. Now the props are not so loose on the bolts. Before the takeoff I have to unfold the props. I have perceptible less vibration on the arms of Anafi. The vibration on the loose original propellers could also be a reason for the cracks (I never had after nearly 100 Flights). In my opinion the dent from the bump of opposite bolt is not the main cause. I don't use any Loctite ore something to lock the bolts.
I have seen that the case from Anafi extendet can also squeeze the propellers - if they are not wobbling at the bolt the chance for squeezing during transportation is reduced also if I place them in the right way.
Maybe it's a little try and error to find the right balance between loose and too strong - the props should align even with start from hand. For me one layer of "Tesa" around the bolt was the right thickness.
One final word to the Case of Anafi extended - in my opinion a magnet shouldn't be so close to the Anafi. I removed it and use velcro.

Greetings from Germany

 

[Liger 1956]

Which type of "Tesa" tape did you use?

 

[Cipta]

Which type of "Tesa" tape did you use?

The transparent ClearType auf Tesa - but you can use any type of tape which is fitting. The most important is that the propeller allign itself when the Motors starts with low rpm like they do at hand start.

 

[Jagerbomb52]

Trying to understand what you want to do here? From what I can tell you want to stop the props from free movement of rotation is that correct? I would have thought they would need to rotate freely or am I missing something here?
The after market props I have bought fit tighter and rotation is some what restricted. I found those to sound differently but seem to work just fine.
I do wonder about the tighter fit if that is a good thing or a bad thing.

 

[Cipta]

In my opinion it's not the best if the prop is too loose on the bolts because too much clearance in most mechanical dynamic parts leads to undefined behavior and stress of bearings. Any change of rpm cause a misalignment and unbalance - stress.
As far as I know most serious fold-props aren't loose on the bolts.

 

[Moonfly]

[QUOTE = "Cipta, post: 17080, member: 1845"]
Secondo me non è il massimo se il puntello è troppo largo sui bulloni perché troppo spazio nella maggior parte delle parti meccaniche dinamiche porta a comportamento indefinito e sollecitazioni dei cuscinetti. Qualsiasi cambiamento di rpm causa un disallineamento e uno squilibrio - stress.
Per quanto ne so, i puntelli pieghevoli più seri non sono allentati sui bulloni.
[/CITAZIONE]
very interesting. I ask if you can show a picture of your Anafi to understand how you put the "tesa" . Thank you.

 

[Dirk_ANAFI]

...
I do wonder about the tighter fit if that is a good thing or a bad thing.

I think a tighter fit is a good thing, if the fit is in the correct unfolded prop position and a bad thing if in a wrong prop position.
So I would leave them turning freely.

 

[Cipta]

[QUOTE = "Cipta, post: 17080, member: 1845"]
Secondo me non è il massimo se il puntello è troppo largo sui bulloni perché troppo spazio nella maggior parte delle parti meccaniche dinamiche porta a comportamento indefinito e sollecitazioni dei cuscinetti. Qualsiasi cambiamento di rpm causa un disallineamento e uno squilibrio - stress.
Per quanto ne so, i puntelli pieghevoli più seri non sono allentati sui bulloni.
[/CITAZIONE]
very interesting. I ask if you can show a picture of your Anafi to understand how you put the "tesa" . Thank you.

Hello,
you would see nothing at a picture with transparent Tape
The dimension of tape are ~ 5mm x 6mm so it doesn't overlap when warped around the shaft. I also have tried a aluminium tape but it was a little too thick and the props didn't align in the low rpm during handstart which I prefer.
At the moment I cant find any disadvantages except to have roughly unfold the props before start. So for me the advantages are more dominant and I don't have any dent from the bump because the tighter fit they will not reach the opposite screw.

 

[Dirk_ANAFI]

Hello,
you would see nothing at a picture with transparent Tape
The dimension of tape are ~ 5mm x 6mm so it doesn't overlap when warped around the shaft. I also have tried a aluminium tape but it was a little too thick and the props didn't align in the low rpm during handstart which I prefer.
At the moment I cant find any disadvantages except to have roughly unfold the props before start. So for me the advantages are more dominant and I don't have any dent from the bump because the tighter fit they will not reach the opposite screw.

Main thing is, that the props unfold by centrifugal force and reach the unfolded position easily. Nothing else is important.

 

[Vegasrobbi]

Well I guess it was bound to happen. Threw a prop for the first time in 275 flights. It let go at the hub, Anafi did the Flip-O-Death and it fell to the ground. The motors shut down as soon as it was inverted so no Solo like dance on the ground.

Broke an arm so I guess I'll try some CA and lightweight fiberglass cloth to repair.

 

[Rocky the FS]

Replace props after how many flights? Post #13.
Wow, you are WAY beyond that!!! I'm going to use 150 as maximum, along with minute inspection with a loupe at all hubs every 10 flights or so.
I REALLY don't want to lose a prop in flight! They are cheap compared to a broken Anafi.

 

[AnafiPilot1]

Why don't you pick up the mechnical kit and replace the arm? might be better in the long run, plus you have 3 spare legs

Amazon.com : Parrot - Mechanical Kit for Anafi Drone - Drone Body + 2 Front Arms + 2 Rear Arms + Hinge and Mount + LED + Coaxial Cable Front and Rear + Screws and Assembly Tool - Anafi Drone Repair Kit : Gateway

Amazon.com : Parrot - Mechanical Kit for Anafi Drone - Drone Body + 2 Front Arms + 2 Rear Arms + Hinge and Mount + LED + Coaxial Cable Front and Rear + Screws and Assembly Tool - Anafi Drone Repair Kit : Gateway

www.amazon.com

If you do intend to repair - can I suggest - remove the leg, and remove all the cabling, etc - use small amount of superglue to glue the leg back together so it mates properly - then I would use good quality quickset one shot style epoxy resin - and apply that around the crack from the inside of the leg, make sure to apply plenty of epoxy away from each side of the crack - at this point you can also add in some small strips of the fibreglass cloth. With epoxy I find plastic needs to be keyed using sandpaper, as it binds much better while curing.

Do not just use superglue (CA) for the repair itself as it becomes brittle and will just snap causing more damage!!

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Well I guess it was bound to happen. Threw a prop for the first time in 275 flights. It let go at the hub, Anafi did the Flip-O-Death and it fell to the ground. The motors shut down as soon as it was inverted so no Solo like dance on the ground.

Broke an arm so I guess I'll try some CA and lightweight fiberglass cloth to repair.

 

[Vegasrobbi]

Replace props after how many flights? Post #13.
Wow, you are WAY beyond that!!! I'm going to use 150 as maximum, along with minute inspection with a loupe at all hubs every 10 flights or so.
I REALLY don't want to lose a prop in flight! They are cheap compared to a broken Anafi.

I replaced these props with new Parrot props not even 25 flights ago; so I don't know what to conclude other than "check your props before every flight". I do look at the props before each flight and these props were not crashed prior to the failure. This may have been a defective prop, it failed at the hub which is rarely where I see damage. I mostly look at the thin "leaf" blade that tends to crack.

Oddly enough the old props were beat up pretty good from tree landings and I thought it would be a good time to replace them all. The old props never had a hub failure, I broke blades off the hub and the hub stayed on the screw making me think this was a defective prop.

 

[Rocky the FS]

I replaced these props with new Parrot props not even 25 flights ago; ...

Sorry, I thought you meant that they had 275 flights on them. It does sound like a defective prop, for sure.

 

[AaronB]

The Anafi is an amazing piece of technology but every time I fly it feels like Russian roulette.

I understand Parrot are shaving off every ounce to extend the flight time - but shortcutting the structural strength of the props just seems like madness. You only need to compare the Anafi hub to a more conventional prop to see how far they have gone...

 

[Liger 1956]

You are not comparing like with like. Without knowing the forces on the Anafi blade during flight and the strength of the material it is impossible to say what factor of safety Parrot has built in. They would also have to take fatigue loadings into account which can accelerate growth of any small cracks in the blade. If the fracture face is available then it may, under a microscope, be possible to determine whether it was a fatigue failure or not. As you say they have to make it as light as possible, as with all flying things but it may be close to the limit.

 

[AnafiPilot1]

I think the Anafi props are well thought out - I like that they are thin and flexible, which makes then tough, also the flexibility must help with vibration redution and noise.

If I had any concerns it would be the interface between blade and hub, and hub / hub screw itself.

Did notice when I changed the props on mine, the black passivated finish on the hub screws had worn on some areas on some of the screws and the pattern was different between them - could this be due to poor tolerances on the inside finish of the hub.

I was really surprised to see that, I did not think the probs moved around much on the hub screws after they spun-up. While the Anafi is flying there must be some sort of twitching/movement between hub screw and prop causing this wear! maybe that movement is what absorbs vibrations and noises.

Here are my screws after around 45 flights and around 2 hours of total flight time.



The blade section is so flexible that cannot imagine

You are not comparing like with like. Without knowing the forces on the Anafi blade during flight and the strength of the material it is impossible to say what factor of safety Parrot has built in. They would also have to take fatigue loadings into account which can accelerate growth of any small cracks in the blade. If the fracture face is available then it may, under a microscope, be possible to determine whether it was a fatigue failure or not. As you say they have to make it as light as possible, as with all flying things but it may be close to the limit.

 

[AaronB]

If I had any concerns it would be the interface between blade and hub, and hub / hub screw itself.

If the blades are not perfectly balanced then the strain on the hub section is significantly increased through vibration, and this is particularly relevant for the Anafi since the hub is far away from the centre of rotation.

 

[Rocky the FS]

no one has emailed parrot and asked them about the blue substance yet?

It is a locking compound similar to LockTite.