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How difficult is it to replace Mavic rear arm?

subcanis

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I tangled with some branches and had a minor crash a few weeks ago. At the time I didn't notice any damage, but subsequently I realized that there was an increased amount of vertical play in the right rear arm. Turns out I cracked the over-extension stop tab (it's directly above the joint). I epoxied it, and it broke again...re-epoxied it and it's holding for now, but that's only because I've been VERY gentle with it. Apparently, the only way to replace the tab is to replace the whole rear arm, motor and all. Has anyone done this? The arm assembly is inexpensive enough, I'm just wondering how involved the repair process is...level of disassembly, soldering, etc????
 
BTW I have done many many and the most important thing is have have a soldering iron that can get to 750-800°f. If you use a crappy iron, you can damage the main board waiting for the solder to break which it never will. A good soldering iron will break the solder in 2 seconds flat.
 
BTW I have done many many and the most important thing is have have a soldering iron that can get to 750-800°f. If you use a crappy iron, you can damage the main board waiting for the solder to break which it never will. A good soldering iron will break the solder in 2 seconds flat.

Thanks. That's just what I need! The mechanical stuff is no problem, but I'm not much of an electronics guy, I don't solder much. I'll have to see if I can get my hands on a decent iron. It's just the power connection to the motor that needs soldering? How involved is the rest, just a few screws and such?
 
Thanks. That's just what I need! The mechanical stuff is no problem, but I'm not much of an electronics guy, I don't solder much. I'll have to see if I can get my hands on a decent iron. It's just the power connection to the motor that needs soldering? How involved is the rest, just a few screws and such?

Yes just the 3 motor wires. Youll need a 1.5mm hex and a phillips.
 
Hi thunderdrones I have no experience with repairing electronics and I was wandering if I could repair it and how simple it is to repair.
 
Hi, I need to order this support piece for the rear left arm. Still $29?

Do I need to unsolder/resolder the whole arm just to replace the support piece?

How much is the full rear left arm?

What do you think about leaving this unrepaired? I did a quick test flight over soft grass and it seemed to lift off OK, but I didn't fly it far. The arm stops in the same location and the good arm doesn't always touch the support piece unless I push it up against it. This leads me to believe the stop is just there so you fold out the arms to the correct spot each time.

What are you thoughts?
 
Hi, I need to order this support piece for the rear left arm. Still $29?

Do I need to unsolder/resolder the whole arm just to replace the support piece?

How much is the full rear left arm?

What do you think about leaving this unrepaired? I did a quick test flight over soft grass and it seemed to lift off OK, but I didn't fly it far. The arm stops in the same location and the good arm doesn't always touch the support piece unless I push it up against it. This leads me to believe the stop is just there so you fold out the arms to the correct spot each time.

What are you thoughts?

I actually have the same kind of stress crack on my left rear shoulder. It does seem to have a bit more play in the left leg, but everything works alright. As a temporary stop gap I've used an elastic hair tie as illustrated in the photos below to add additional support to the shoulders. Arranged as I have it, it doesn't interfere with the visual positioning system or the ultrasonic sensor.


ec9ff03391e965b8c70cc575194198fc.jpg
2ac4f9d9d704cbe1ad16e52a184afb34.jpg
 
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I just realized my photos don't really illustrate it, they were meant to document the stress fissure. I'll take some later on.
 
I finally replaced my right rear arm last week after the support tab being broken for a couple of months. It was glued 4 times, but continually re-broke and I probably made 30 or so flights with it broken. Honestly, it didn't affect the flight quality or "feel" noticeably. I did however notice it visually as that arm moved substantially more than the other 3, especially in windy conditions. I ultimately decided to replace the arm because I didn't want to see what might happen if all that extra movement eventually caused further failure.
I am no electronics expert either, but with some good advice from Thunderdrones about the proper soldering iron temperature, the repair was fairly simple. I replaced the entire arm assembly, motor and all. It was less work that way and only cost an extra $15. And I have a spare motor just in case now!
 
FYI, The thread where we discussed the repair is called "Lead free solder" I can't figure out how to link it here, but there are some pics of my repair there if you are interested.
 
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I just noticed my rear left should tab is also cracked. It must have been after a crash which happened over a month ago. I fly in sport mode all the time and just noticed the back leg overextending when I tried moving the Mavic around while it was hovering.
I'm not going to replace it since I don't have a soldering iron which is hot enough. I might make a DIY clamp of some sort at some point though but it's been fine for over a month so I don't really worry about it too much.

How far does the back leg extend without the tab? Can it flip around all the way to the front?
 
Thanks for all the feedback. That bungee is interesting, but the support tab has come completely off and I can rotate the arm all the way around ;)

Again, I flew it cautiously over some grass and it went up fine, hovered fine, and moved around (slowly) fine so it seems that the tab is there as secondary support only, with the spring loaded hinge in the arm itself as primary.

I won't do any fast movements as I think that's where the arm could unintentionally rotate up and there would be zero chance of recovering.

I'm debating replacing the arm myself or sending it in. Not due to repair skills, but more so concerned that there is some internal latent damage from the crash that hasn't manifested yet and does so when I am 100m up. Is this a risk? PCBAs, mechanical, vision system, etc.

The vision system needed recalibration for after the crash and it went through successfully; no more errors. Is this good enough indication that it is good to go?

Sorry for the tangent.
 
the support tab has come completely off and I can rotate the arm all the way around ;)

Hmm, that doesn't sound too good, thanks for the info. In that case I need to do something about mine before it breaks off. I'll see what I can come up with in the coming weeks.
 
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Hmm, that doesn't sound too good, thanks for the info. In that case I need to do something about mine before it breaks off. I'll see what I can come up with in the coming weeks.

Quick update:

I've been flying with the support tab broken off for the past week, going up to 120m, sport mode with quick direction changes, etc. and it's held up just fine. No issues with the arm rotating out of place during flight and stability doesn't seem too compromised. I'll still fix it, but I think my hypothesis is correct: the support tab is meant as a guide to ensure the arm is folded out to the correct position, more so than providing real support in flight.

YMMV: Fly with a broken/cracked support tab at your own risk!
 
@Thunderdrones it is possible to break this tap by frequently doing hard braking in high sped or will this break only in the event of a crash ?
 
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