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Arm falls off in flight & crashed

I could be slightly mistaken, but judging by the image the carbon fiber arm came out of the lock mount. My first guess is the plastic rivet holding the arm to the mount is not there. On the bottom of the lock mount is a small circular plastic piece. This plastic piece is actually a rivet to hold the arm together. Glue alone would not have the durability to with stand up to the stresses of the airframe. View attachment 6524


Watch this and you can see the full flight in HD did you see the close up photo of the are that just fell apart in the shaft
 
We also do a full calibration on each flight while the other person goes back and re-checks things.

imo, this could be the culprit actually. I've watched videos of how people have to handle the H when doing a compass cal, and have done quite a few myself. Just the way we have to hold the arms, spin it and as we switch from set to set with the full weight of the copter and batt doing so.

It just really ups the possibility of damaging an arm structure, and when you do it a lot, maybe this can happen.

2 cents
 
Considering a stress riser is created any place an abrupt angle is present in a structural assembly that could be a good deduction. It might be good cause for those people that choose to calibrate the compass for each day's flying to consider calibrating less frequently to only performing one after traveling long distances.
 
imo, this could be the culprit actually. I've watched videos of how people have to handle the H when doing a compass cal, and have done quite a few myself. Just the way we have to hold the arms, spin it and as we switch from set to set with the full weight of the copter and batt doing so.

It just really ups the possibility of damaging an arm structure, and when you do it a lot, maybe this can happen.

2 cents


This I do also agree on but as you know its not like we are being rough with the H while we are spinning it, Not sure how you gold it but we try to hold our fingers as close the the body as possible. With that said we still never noticed the last few times the arm was even trying to come loose. The bad thing now is I will be pulling some and trying to wiggle each arm from time to time to see if would give any. That may still may not have raised a red flag and keep it from happening. I'm now thinking about adding a drop of glue to each arm but still over time that will crack and break free from the vibrations over time
 
Abcouple drops of thin CA glue may be a good idea. CA and carbon fiber are compatible and it will wick itself into small fractures or open weave in the carbon.

We also just got a new reason to remove the gimbal when doing a compass call. Reduces the weight loading during the spin process.
 
Well yes that is why we put the gimbals guard back on to keep the camera from doing some crazy spins. This H really has been used for little less than 4 months now
 
You calibrate with the gimbal attached and use the gimbal lock to limit a powered up gimbal? Sorry, but that's a double whammy for me,
 
20170712_133931.jpg
You calibrate with the gimbal attached and use the gimbal lock to limit a powered up gimbal? Sorry, but that's a double whammy for me,

I agree. Do not ever power your H with the gimbal lock attached. The gimbal motors are still going to try to move the gimbal and with the cover on, you're just asking for trouble. I simply take my gimbal off when I calibrate my compass. It takes 3 seconds to take it off and 5 seconds to put it back on.
Any thoughts on this? I wrapped some black duct tape between the carbon fiber arm and the attachment point. Does anyone think that this might help reduce the vibrations and possibly keep the arm inside the attachment if the rivet fails?
 
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+1 with Pat and others on the gimbal guard, never leave it on when powering the bird. And I always slip off the cam before doing a comp cal myself, I hate watching that thing go batty every time the bird is inverted, even if it is just for a second or two at a time while rotating it.
 
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Skeets,

The tape might help but it softens with heat. The black color of the aircraft soaks up a lot of BTU's.
 
+2 with PatR on the conditions of doing a compass calibration... no camera mounted,
and absolutely do not power up the H with the gimbal lock in place. You are putting
unnecessary stress on the gimbal motors and making the calibration process more
cumbersome to complete successfully.

This combined with doing calibrations more often than needed is more likely the
root cause of your current issues, not rough handling during the process.
 
Last edited:
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Toss in that the gimbal hates being upside down when under power. The gimbal is outside the stop limits and fights itself.
 

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