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Servo failure

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Old 04-17-2013, 07:30 PM
  #1
t-max97
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Default Servo failure

I was flying my big stik .40 today and on the second flight of the day, after a stall turn when I pulled out of it the right wing kept dropping, not really quick but I new something was wrong, I couldn't think of anything that could have shifted enough to make it do that so my next thought was servo failure, well I was right and luckily it was in a fairly neutral position when it failed "stripped" and I was able to easily land it. The servo's are hitec hs-311, I have about 15 flights on these servo's with no problems what so ever until today, now I don't know if I trust the other's, what do you guys think? I could always just use them as throttle servo's and get futaba's for everywhere else.
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Old 04-18-2013, 03:05 AM
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Default RE: Servo failure

This is a really low end servo with 42 ozs. of torque, maybe it was flutter that caused your problem, maybe not, you did not state what surface this was on or just how fast you fly your Stick, I have seen a few Sticks that were very fast up on the pipe and would surly induce flutter with less than perfect linkage or POS servos installed. Maybe you should consider getting yourself a little better grade of servos for your own piece of mind. Just food for thought.

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Old 04-18-2013, 06:08 AM
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Default RE: Servo failure


Quote:
ORIGINAL: sensei

This is a really low end servo with 42 ozs. of torque, maybe it was flutter that caused your problem, maybe not, you did not state what surface this was on or just how fast you fly your Stick, I have seen a few Sticks that were very fast up on the pipe and would surly induce flutter with less than perfect linkage or POS servos installed. Maybe you should consider getting yourself a little better grade of servos for your own piece of mind. Just food for thought.

Bob
Lol sorry, it was the left aileron. I had been flying at a decent speed, not full throttle all the time or anything but I was doing alot of rolls, stall turns and inverted flight. I bought this plane at the perry swap meet as a newly assembled arf and it already had these servo's on it, I guess I'll change them and Ill also check the linkages for any play. Thanks
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Old 04-18-2013, 07:20 AM
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Default RE: Servo failure

Gear trains just don't strip, there is a reason for it to happen. Flutter is the usual cause but I had two aileron servo gear trains strip and break on me from getting slammed by RF. That was my fault for a bad set up. 42 in. oz. is all I ever used in 40 size planes but there are a lot better choices today. I would guess it is more a set up problem then a servo problem. Slop in the control linkage perhaps. I'm not brand loyal but I do use hitec servos most the time. Other then the one bad set up I have never broken a set of gears.
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Old 04-18-2013, 11:07 AM
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Default RE: Servo failure

I believe a lot of my servo failures are due to the servo train being "hit" during transit to and from the field. The other day I lost the rudder servo when a sudden wind knocked my plane off a table at the flying field. That was very visible. The "knock" during transit are not as visible. I keep extra servos on hand and will replace one if in doubt.
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Old 04-18-2013, 11:17 AM
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Default RE: Servo failure

Like Villa I have seen the HT servos with the carbon fiber gears break when used on large control surfaces on hard landings. Just the snapping motion can break them. CF gear trains are not one of Hitecs better ideas. I still and have a few sets but I haven't bought a new servo with the CF gears in a very long time. Carbonite must mean crap in some language?
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Old 04-18-2013, 11:29 AM
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Default RE: Servo failure

Those 311's are pretty fragile servos, but reliable if they are used in the right application. It's entirely possible that the seller sold you a new ARF with old servos in it. Since you're asking for suggestions, I'm going to say use a 311 on the throttle, then get HS-425BB's for all of the control surfaces. They have more torque which you probably don't need, but they also are considerably tougher with the ball bearing supports.
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Old 04-18-2013, 12:47 PM
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Default RE: Servo failure

Thanks for the input guys, I took the servo apart and It's actually not stripped "felt like it was", everything looked fine except some light corrosion on the circuit board so I sprayed some electrical cleaner on it and it works fine now, Im still not going to use this one and all i'll use the others for is the throttle.
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Old 04-18-2013, 05:18 PM
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Default RE: Servo failure

Well that's worse.  Now you have an unknown failure.

Were you using a Futaba arm on a HiTec servo?  They slip.

One wing dropping can be your trims got moved and you didn't notice or wing warp.
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Old 04-18-2013, 07:26 PM
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Default RE: Servo failure


Quote:
ORIGINAL: Charlie P.

Well that's worse. Now you have an unknown failure.

Were you using a Futaba arm on a HiTec servo? They slip.

One wing dropping can be your trims got moved and you didn't notice or wing warp.
It was a hitec arm, the futaba's slipped, It wasn't the trim as that was the first thing I checked during flight and the servo would not move when I landed.
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Old 04-19-2013, 06:44 AM
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Default RE: Servo failure

I'd toss that servo. It's not expensive enough to try and save.
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Old 04-19-2013, 07:03 AM
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Default RE: Servo failure

+1

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Old 04-19-2013, 09:47 AM
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Default RE: Servo failure

I'll keep it for the spare gears but I wont use it.
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