Boooo...
After a good day out yesterday, I took my small quad out for some full stick action tonight.
And it was all going well until...I think I sheared off a motor. At 20m. So this happened:
Reason I think the bolt sheared, is the fine thread left in the bottom of the motor (I tried to show it in the pic). And the way it just tumbled out the sky. I think you can see it in the logs from the motor logs (crash event starts at 20 with impact at 20.4).
Up until then it was flying well - but if anything a little under powered; feels more "Nissan Micra" than "Nissan GTR". Though it would appear the mounts can't handle it if you drive the Micra like a GTR...
It appears the legs took the brunt - all props and unsheared motors are ok, as is rx/telem, battery GPS and APM. Motors were pretty hot when I picked it up - they'd been working hard.
Vibes until then were good - +/-5 to 6 when doing full sticks, and +/-2 when hovering:
I've attached the flight log, just in case anyone wants to prove my "sheared motor" theory wrong.
Comments
PS: You say sheared, but sheared means that the bolt end would still be in the bolt hole. if you mean the thread had stripped, that would be much more likely with a brass bolt than a steel bolt. This could even just be due to over-tightening. With a steel bolt you are more likely to strip the aluminium bolt hole, but the brass bolt it would be the aluminium bolt hole. From the picture bolt hole threads look ok, which is good news, as tapping them to a larger size can be a pain. You should be up and running with some soldering and new bolts in no time.
A good tip is that don't check a bolt is tight by tightening it a little bit, as eventually it will be over tightened. Place a dob of nail varnish (hard wearing paint) on the bolt and joint, if it cracks (i.e moves) remove, reapply loctite, then reinsert.
As Jesse says you need blue Loctite on the threads. And use steel screws not brass. Brass is much softer and is good for use in wood applications where you don't want it to mark the wood.
@Euan; I sincerely doubt that you sheered a bolt, there's not enough load on that small quad and one motor to do that. it's more likely that you had 3 bolts progressively come lose and the vibrations of the motor just worked the last one back and forth until it gave up as well.
loctite the bolts when you replace them and balance your props again just to be sure...
How many screws do you use to attach the motor to the mount?
I always use all 4.. not sure why an event like this would happen if all four screws are used to attach the motor.
What are you using to mount the motors? I too had a crash last week for the same reason. :(
I use nylon screws to hold the motors on for the simple reason that during a crash the screws will snap thereby saving the motors from bent shafts. I suspect fatigue set in after a while and during some rather violent flying one of the screws let go. It all ended in tears but I sheared off 3 more motors (failed plastic screws) and no real damage.
Oh well...a good excuse to strip, improve and rebuild? I like it the way it is - its a good trainer setup - nice easy controls, with not too much power. Will maybe just tweak ans tidy the wiring a little.
Wow! That is a shame. Sorry for such a bad crash. On the bright side... quite a bit can be learned from a crash. The more of these experiences we have the better we get at avoiding them in the future.
Sorry for your loss. I can almost spell "Mayday" with the white stickers on the arm :-)
-
1
-
2
of 2 Next