Location: In the Sahara desert mostly but Michigan sometimes. Not much difference between the two some days.
Posts: 405
Servo case failure
This is a new one on me. Any thoughts as to what caused it to happen appreciated.
I have a 78" Extra setup for 3D which has flown several times without problems. The aileron servos are 8411's.....a little overkill for this sized model I believe but all I had at the time. Today one of the servos locked in the down position and caused it to land hard enough to need some repair. Inspection of the servo showed the case had split open and forced the gear train pins to be offset locking the gears in place. The case had several cracks spread out from the pin bearing and the pin nearest the pot was bent enough to need pliers to remove it from the gear.
Deflection on the ailerons is around 40* no stiff hinges or links. The model wasn't flown at full throttle and then snapped to 3D rates. What do you guys think was the cause?
Using 8711 servos on a 78 just to ensure a strong enough servo case seems silly.
Sounds like stress cracks but that shouldn't have happened that quickly. If it bent the pin then it was definitely stress induced. Maybe lost programming and tried to over travel? Just thinking out loud here.
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Sounds like there may have been a problem with the injection molding process.
Take a close look at the case and see if the breaks were "clean" which would indicate fault lines from the molding process.
In any case JR will most like fix it as an in warranty failure.
To bad it ended up dinging your bird.
That's what I thought at first but the pin was bent and a cracked case wouldn't have caused that. In either case they should warranty it.
__________________ www.vessaero.com
Remember every second of every day there are thousands of men and women giving of their lives to keep you safe. Never forget them for they never forget you!!
Location: In the Sahara desert mostly but Michigan sometimes. Not much difference between the two some days.
Posts: 405
Re: Servo case failure
The push rod was not bent and get this I used a dubro Kwik link to the servo arm and that was fine the pin on it wasnt bent......very strange.
Do you guys know if say Futaba or Hitec servos have a stronger molded case around the pin areas? If so which ones ?
I'm predominantly a JR guy and haven't seen too many insides of other servos for a few years now.
One day I'll buy me a camera but the case is split on both sides of the pin down to the joint where it connects to the motor / electrical section and there's a crack running down the center between the rubber grommets up to the pin bushing in the top mold
Yep Mith I agree with your assessment but there is no other signs of stress on the assy that I can find. I've had a few servos break nylon gears over the years due to bad servo selection or too weak a gear train for their use but a case breakage in flight really lowers the confidence level of what is enough for the job when the cause cant be identified.
hmmmm... the cracked case could be another symptom of what failed rather than a cause....
Exactly and it's near impossible at this point to determine which came first. Either the servo bound up so tight it cracked the case or the case failed, throwing everything out of alignment and caused it to bend. Either guess is as good as the other.
__________________ www.vessaero.com
Remember every second of every day there are thousands of men and women giving of their lives to keep you safe. Never forget them for they never forget you!!
Servo case failure
Linear Mode
