Strange problem with JR8411 servo
09-29-2015, 12:05 AM
#1
Strange problem with JR8411 servo
Hello guys,
I bought a Built but never flown Ultra Flash with all electronics on RCU a while ago, put my tubine (P-160SX) inside, set everything up and went to fly.
The bird flys amazing, and came with JR 8411 servos on elevator and ailerons.
I fly very aggressively, and very high speed with lots of rolls, small example:
https://www.youtube.com/watch?v=YEh8uO_k12I on flight #8 or so, on the exit of a right side slow roll (fast speed, exactly like the one in the video above) the jet wanted to keep rolling after i released the sticks for about 1/4 roll, it then stopped and resumed full control and i immidiately landed.
after an inspection on the ground, everything seemed to work well, and i started thinking maybe it was a dumb thumb, and went up for another cautious flight. this time, right after takeoff, in a right turn to crosswind, the jet dipped left (i believe) and returned back to level, i immidiately cut the engine and landed tail wind - again all smooth.
upon ground inspection today, i found that the right aileron servo seems to have been messed with, as the sealing O-ring on the servo is out of its place in the servo case, and when i put the 2 aileron servos (JR 8411) on a servo tester i found the left one behaved normally, and the right one, on the end of the right roll side travel (left side as seen in the video) has a dead zone, in which it jumps to max mechanical travel and binds. mind you in flight the servo never gets there so this is not what happend in flight, but this is proof that the servo is faulty at least some what.
Here is a video (Please excuse the Hebrew commentary):
https://www.youtube.com/watch?v=r0OQf-v41sA Obviously this servo will be replaced and while being highly suspicious with a good percentage that it caused the Roll problem, im sttill not 100% calm to fly again after replacing the servo.
So what i would like to know is - does anyone have any good tips on how to try and reconstruct the "jump" i felt in flight, on the ground, before i take her up again?
i tried to wiggle all wire connectors from the aileron servo to the receiever, that didnt come up with any results. so far what we see in the video is all i have.
thanks for reading.
I bought a Built but never flown Ultra Flash with all electronics on RCU a while ago, put my tubine (P-160SX) inside, set everything up and went to fly.
The bird flys amazing, and came with JR 8411 servos on elevator and ailerons.
I fly very aggressively, and very high speed with lots of rolls, small example:
https://www.youtube.com/watch?v=YEh8uO_k12I on flight #8 or so, on the exit of a right side slow roll (fast speed, exactly like the one in the video above) the jet wanted to keep rolling after i released the sticks for about 1/4 roll, it then stopped and resumed full control and i immidiately landed.
after an inspection on the ground, everything seemed to work well, and i started thinking maybe it was a dumb thumb, and went up for another cautious flight. this time, right after takeoff, in a right turn to crosswind, the jet dipped left (i believe) and returned back to level, i immidiately cut the engine and landed tail wind - again all smooth.
upon ground inspection today, i found that the right aileron servo seems to have been messed with, as the sealing O-ring on the servo is out of its place in the servo case, and when i put the 2 aileron servos (JR 8411) on a servo tester i found the left one behaved normally, and the right one, on the end of the right roll side travel (left side as seen in the video) has a dead zone, in which it jumps to max mechanical travel and binds. mind you in flight the servo never gets there so this is not what happend in flight, but this is proof that the servo is faulty at least some what.
Here is a video (Please excuse the Hebrew commentary):
https://www.youtube.com/watch?v=r0OQf-v41sA Obviously this servo will be replaced and while being highly suspicious with a good percentage that it caused the Roll problem, im sttill not 100% calm to fly again after replacing the servo.
So what i would like to know is - does anyone have any good tips on how to try and reconstruct the "jump" i felt in flight, on the ground, before i take her up again?
i tried to wiggle all wire connectors from the aileron servo to the receiever, that didnt come up with any results. so far what we see in the video is all i have.
thanks for reading.
Last edited by i3dm; 09-29-2015 at 12:10 AM.
09-29-2015, 12:06 AM
#2
Here is a picture of the suspect servo next to 2 other 8411's i got with the jet (suspect is on the left).
the one on the left seems to have a different motor / wiring inside.
can anyone who has seen a 8411 from the inside confirm the 2 right ones are original and left one is modified?
here is another video, this time on the bench:
https://www.youtube.com/watch?v=FZdX2fMB4ew i cant get the servo to fail in any other way other than whats seen in the video, which obviously cant happen in flight, as the servo never gets to max travel.
the one on the left seems to have a different motor / wiring inside.
can anyone who has seen a 8411 from the inside confirm the 2 right ones are original and left one is modified?
here is another video, this time on the bench:
https://www.youtube.com/watch?v=FZdX2fMB4ew i cant get the servo to fail in any other way other than whats seen in the video, which obviously cant happen in flight, as the servo never gets to max travel.
Last edited by i3dm; 09-29-2015 at 12:10 AM.
