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Tricopter wobbles, spins and crashes.

#1
I made myself David's tri a while back. This is the second tri I made. I've had, like around maybe 15-20 odd flights on this one.. HK 2810 750kv motors, blue series 30A escs flashed, 35cm arms, 12 inch props. I'm running it on 4S 2750mAh. Gives me around 12 mins of flight time. Oh yes, KK2.0 v1.6. WP_20130807_026.jpg
Its the one on the left. The other's the first one.
No problems as such so far, very stable. I was out flying it today, just circuits. I was turning, noticed it wobble. It sometimes wobbles, maybe cause my P values are a little high, but not too much. It usually does it only with self level on. What happened today: it wobbled, it got a bit worse. Then it just started yawing. Barely any attitude change, though. It wasn't too high, I just chopped throttle and brought it down. Only the tail motor came off, no other damage. No broken props.
All motors were spinning, receiver test was fine, before I took off. Also, another thing: I'm using a Futaba 8j. I hadn't replaced my batteries, it was reading 5.3V. I was flying within a 15-20 metre radius. Now if the bullet had come off, wouldn't the motor stop spinning? Since it was one of the bullets from the power breakout cable. Immediately after the crash, I took off the tail motor and powered it up; the front two motors were working fine. After a while I noticed the bullet on the black wire of the front left esc had come off. Now, I'm not quite sure when this happened.
Anyone have any ideas as to what might have happened?
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#2
I made myself David's tri a while back. This is the second tri I made. I've had, like around maybe 15-20 odd flights on this one.. HK 2810 750kv motors, blue series 30A escs flashed, 35cm arms, 12 inch props. I'm running it on 4S 2750mAh. Gives me around 12 mins of flight time. Oh yes, KK2.0 v1.6. View attachment 14576
Its the one on the left. The other's the first one.
No problems as such so far, very stable. I was out flying it today, just circuits. I was turning, noticed it wobble. It sometimes wobbles, maybe cause my P values are a little high, but not too much. It usually does it only with self level on. What happened today: it wobbled, it got a bit worse. Then it just started yawing. Barely any attitude change, though. It wasn't too high, I just chopped throttle and brought it down. Only the tail motor came off, no other damage. No broken props.
All motors were spinning, receiver test was fine, before I took off. Also, another thing: I'm using a Futaba 8j. I hadn't replaced my batteries, it was reading 5.3V. I was flying within a 15-20 metre radius. Now if the bullet had come off, wouldn't the motor stop spinning? Since it was one of the bullets from the power breakout cable. Immediately after the crash, I took off the tail motor and powered it up; the front two motors were working fine. After a while I noticed the bullet on the black wire of the front left esc had come off. Now, I'm not quite sure when this happened.
Anyone have any ideas as to what might have happened?
I wonder if the motor wires on the front were failing in flight.

If they were broken but still held together by the insulation, the contact would be intermitiant and the motor might start pulsing -- that kind of behavior would wreak havock with the control board. shoudl have wild occilations while the other motors try to adjust for the sudden uncommanded pitch and roll, and the new imbalance in the torques will cause the servo to swing over to compensate.

That's my guess from the info presented, but what to do before you get back in the air?

Cheack EVERY motor wire and repair any that seem fragile. Re-ballance props and motors as best as you can and try to reduce vibe prior to flight. Double check everything, then take it easy for the first flight or two out.
 

xuzme720

Dedicated foam bender
Mentor
#3
Remember, on the KK2 the motor 1 port powers the board, and the motor ports 2-8 are all joined so an ESC plugged into those can power a servo in another port. If you lost power on the servo side (ports 2-8) the servo may have parked itself and introduced the yaw you had just before the crash. The only problem with this theory is that you should have had a lot more roll if you lost the #2 ESC...
Just speculation at this point unless you can find the black box...
 
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