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
Ok, as way of an update...check out my new mount!
Due to a "senior moment" by me, I managed to only order 1 instead of 4 (remaining three onroute), but not before time...I did a check over of the "trainer" quad tonight as it had now done 1 hour of flight time since the crash. And...worryingly the mounts were loose on 2 motors!
So it's officially grounded until this is resolved. This first one looks promising - blue lactite in all the threads, and the new mount with the "X" bracket as well. It *should* do better. It will also cut down on the vibes too, but TBH I'm only exceed +/-5 briefly when doing full sticks anyway.
Wait till you lose a prop at 400 feet over the river and get to only hear the loud boom of your lipo exploding as it hits the water. with your $500 dollar go pro on board all never to be seen again =)
Yes it happened to me and i rebuilt and learned from my mistakes if you are good only mech failure gets you proper pre flight inspection and maintenance can avoid that.
Multi rotors are not reliable craft and anything below x8 is a lead balloon in the air once something goes wrong. aggressive 3d flying should mean regular replacement of parts that flex such as props and those boons.
@ RD - yeah - motor is a write off. threads pulled off 2 of the holes, wiring snapped, and part of it was "ingested" into the motor base, jamming it solid. I can only imagine the damage to the bottom of the poles. I think the shaft is ok, and the prop is fine, as is the prop mount. But...for safety sake, I've written it off, and am getting a replacement. What I can save will go in the spare bin (the shaft would be especailly useful).
I may try and repair it one rainy afternoon when I'm feeling experimentally brave.
The motors are 2216-11's (900kv). To be honest, they are slightly underpowered for the weight I've got on. A bump to 700kv (hopefully without needing to go to 4S) would probably be good, but as this is my "trainer" quad, I'm not throwing money at it, unless it really needs it. Even the use of t-motors and CF props was a bit overkill.
Ouch! And to make matter worse the wiring was jerked out of the motor. It is probably repairable...probably.
What motors are those? They look quite beefy.
Regarding logging... (short story) I had enabled logging on one of my MRI systems trying to catch a problem. I forgot about it until the service call came in (weeks later) regarding sloooow system performance. Yep. The hard drive was nearly full of logging events. Lesson learned.
-=Doug
That's interesting Nano - funnily enough coming from an IT background I know the impact of logging too verbosely, but it is standard practise when deploying a new service - so I had i all the interesting bits turned on. I was hoping to turn it back to defaults after 2-3 flights and the airframe/PID's were fully optimised.
In the few flights I've done, I can't say I've noticed any performance issues. I do clear down the logs after every flight, as I know filling up the memory with logs can have consequences (just like IT system actually!)
Mr Euan Ramsay,
Did you always enable RAW and MOTOR log on during your flight?
If yes, please disable it. Maybe it will make you crash again.
See this: link
the star adaptors are good because typically they bend before the motor breaks... just make sure to Loctite all the screws when you install them...
I know that it feels like I keep plugging the jDrones anti vibration mounts; but they're perfect for this, a little pricey, but much more resilient; and will save shafts somewhat in Crispin's case.
I may be wrong, but I think that brass still has a slightly higher tensile strength than aluminium (motor base) and as such would pull the threads out of the motor first... but brass is brittle and wouldn't tolerate being bent back and forth very much...
Consider drilling out the holes in your mounts and inserting a rubber grommet in them and putting washers on the bolt as well, it'll take some of the vibrations out in much the same way as the JD anti-vibe mounts...
Better do the same for the big quad too!
You live and learn...:-)
-
1
-
2
of 2 Next