Thursday, October 29, 2015

Repairing a Broken Motor Pod

Repairing a Broken Motor Pod for the Hubsan X4 Quadcopter

Hubsan X4 (H107C) 4 Channel 2.4GHz RC Quad Copter

After crashing my Hubsan X4 quadcopter probably close to 50 times, one of the motor pods finally decided to snap off.  I was disappointed at first, but then realized that it could possibly be fixed.  That, and I could write a post about it.
To repair things, I first used some GorillaGlue (Amazon) and a cheap clamp that I bought a while ago to secure things while it was drying.
The wiring was hanging outside of the plastic piece, so I stuffed it back into it’s indention beside the structural socket part on the bottom of the arm as best I could.  A tiny flathead screwdriver can help with this.  You may also have to stuff the wiring back in at the bottom of the pod if it’s been pulled out.  Once this is done, you can align the socket and snap the leg back into place.
As an aside, if you think this quadrotor breaks easily, here’s a guy crashing his Hubsan X4 (Availablefrom Amazon).  It takes this minor abuse quite easily, but I’ve crashed it much harder, so eventually it does break.  I don’t think a large ‘copter would survive nearly as much abuse.
Once the arm is set into place, I applied some Gorilla Glue where the fracture actually happened.  This method worked OK, and survived a crash or two, but after some thought I finally came up with an attachment method that held up quite well: small zip ties.  As seen in the photo, you can add a zip tie as close to the base of the pod arm as possible.  My method was to apply Gorilla Glue to the crack, then securely zip tie the base up.  The glue seems to secure the zip tie, and the tie keeps the arm in place.

Before being repaired
Clamping for glue only
dried glue

It worked so well, that I had to put it on the other front arm after another violent crash.  It might not be a terrible idea to reinforce the front arms preemptively like this.  Or you could just be more careful than I was.
On an engineering note, it doesn’t seem like the best idea to mount the “eyes” where they did from a structural point of view.  The slots for the eyes are placed near or possibly on where the arms are subjected to the most stress during a hard landing or impact.

I’ll admit, the eye holes do look pretty cool where they are, but come on guys.  I haven’t done any analysis of it, but I’m sure moving the eye position in just a little bit would have improved the strength greatly.
Be sure to check out my initial review of this little quadrotor here.