[SOLVED] Broken one of the arms

Discussions and questions about the Crazyflie Nano Quadcopter
tobias
Bitcraze
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Location: Sweden

Re: [SOLVED] Broken one of the arms

Post by tobias »

Great that it is holding up!
One thought is to design a 3D printable part that would strengthen the arm or could be used to repair it. The Shapeways strong and flexible material is pretty good as we used it for our previous motor mounts.
The current arms are pretty strong and elastic which protects the sensors for high g force as well as the soldering. Making it to stiff and we will just move the problem else where. That's why making the motor mount the weak part I think is the way to go. It could be as simple as cutting the PCB arms 10mm shorter and having the motor mount hanging a bit. Another idea to make it stronger is to tie a fishing line between the arms. That would make the construction strong, flexible and light.

As soon as I have time a will do some experimenting. I have some old prototypes I can use as crash dummies. :)
mrb0y
Beginner
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Joined: Thu Mar 07, 2013 1:18 am

Re: Broken one of the arms

Post by mrb0y »

san84 wrote:I managed to repair the arm. I did some careful flights with some small crashes and it holds. I still have to see if it also holds in a bigger crash. I used "Bison Kombi Snel" a 2 component epoxy glue and aluminium household foil. I cut a strip of foil and applied glue to the not shiny side and wrapped it as tight as possible around the fracture to strengthen it. I had to shorten the motor mount and glue it because it was not really press fit anymore.
Fixed arm.jpg
What are you using on your motors as shock absorber? The purple things? Thanks!
san84
Beginner
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Location: Netherlands

Re: [SOLVED] Broken one of the arms

Post by san84 »

The purple things I use as shock absorbers I salvaged a long time ago from a broken CD-ROM player. They are hollow and there is a hole in the middle where a screw went through. In the CD-ROM player it was also some kind of shock/vibration absorber. They work great but sometimes my Crazyflie will bounce up and land on it's back.
tobias
Bitcraze
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Joined: Mon Jan 28, 2013 7:17 pm
Location: Sweden

Re: [SOLVED] Broken one of the arms

Post by tobias »

I just quickly wanted to explain my theory. Still a lot of testing left to be done. The pictures should be pretty self explanatory but the idea is to make the motor mount the weak/flexible part by moving the motor mount out a bit.
Attachments
Motor mount flex up.png
Motor mount flex up.png (377.78 KiB) Viewed 7140 times
Motor mount flex side.png
Motor mount flex side.png (314.49 KiB) Viewed 7140 times
Motor mount flex down.png
Motor mount flex down.png (376.6 KiB) Viewed 7140 times
Motor mount flex attachment.png
Motor mount flex attachment.png (326.01 KiB) Viewed 7140 times
bstott
Beginner
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Re: [SOLVED] Broken one of the arms

Post by bstott »

Hmmm. Interesting idea Tobias. One could then wrap that arm end with the fishing line, you mentioned above, to strengthen the member so that the flex is not too soft. The combination of flexible motor mount and wrapped fishing line would add dampening from vibrations and absorb the shock on impacts.
alexkwolfe
Beginner
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Joined: Fri Jun 07, 2013 6:47 pm

Re: [SOLVED] Broken one of the arms

Post by alexkwolfe »

My crazyflie broke in the exact same way after falling about 10 feet. I'll try your fix too.
tobias
Bitcraze
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Joined: Mon Jan 28, 2013 7:17 pm
Location: Sweden

Re: [SOLVED] Broken one of the arms

Post by tobias »

You can fix it like this which works pretty well.
toastbrot
Beginner
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Joined: Fri Jun 14, 2013 7:27 am

Re: [SOLVED] Broken one of the arms

Post by toastbrot »

mine broke also the second flight test exactly the same spot. all in all this is clearly the weakest spot. actually i exepected a better product and honestly i would not buy it, if i knew. and support from bitcraze to fix this or provide a solution is inexistent. also refund does not seem to be an option. so, actually i dont recommend buying a crazyflie at current state, as its simply not worth the money.
foosel
Expert
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Location: Obertshausen, Germany
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Re: [SOLVED] Broken one of the arms

Post by foosel »

toastbrot wrote:and support from bitcraze to fix this or provide a solution is inexistent
tobias wrote:You can fix it like this which works pretty well.
Image
Also: AR.Drone 2.0 (RC-enabled thanks to self-soldered MiruMod) and Hubsan X4 H107
smiler
Member
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Joined: Wed May 08, 2013 2:51 pm
Location: Uppsala, Sweden

Re: [SOLVED] Broken one of the arms

Post by smiler »

toastbrot wrote:and support from bitcraze to fix this or provide a solution is inexistent.
I wont bite to the rest of the trolly stuff in your post but I wouldn't say that it's inexistent. This was linked in the post above yours and there's some other stuff in this thread aswell.
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