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Servo Life

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Old 08-28-2003, 12:54 AM
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S Atkinson
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I had a Fut 148 servo fail last week ,unfortunately it was a critical function & I wiped out. This servo was probably 8 years old but obviously I have no real idea of its operational time . At what point should we consider a servo as time expired & change it to a non critical function.
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Old 08-28-2003, 01:36 AM
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How's 8 years sound Try 5. Depending on how much and hard you use them, you should adjust that number a bit.
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Old 08-28-2003, 03:53 AM
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The electronic components can last up to 40 years, just might have to replace 40 gear sets over its life time...
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Old 08-28-2003, 04:48 AM
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The motors will last NO where near that amount of time.
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Old 08-29-2003, 07:44 PM
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JohnW
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That's a hard question and I have struggled with it ever since I started flying. Many failure modes are all but impossible to detect or predict before the failure, so there just is no way of knowing. So, I have taken the approach that prevention is best.

I fly a lot and easily put over 300 flights a year on just my primary plane. I have planes under two years of age with over 500 flights. Servos still work fine, but the question of when to replace nags me sometimes. For me, that is an expensive proposition as all new servos for my two primary planes will run me close to $2000. Since they still seem to work, I probably won't replace them until I either crash the planes or sell them.

As for minimizing your risk, there are several things that can be done to help reduce collateral damage (i.e. plane loss) and to circumvent the problems in the first place due to failed servos.

Try using dual servos on critical controls when ever possible, i.e. dual elev/ail servos, even it this means cutting the elevator. Obviously, you wouldn't cut the elevator on a scale plane, but most sport types this is feasible. The idea being if a servo fails, hopefully you will still have enough control to land. I have had total servo failures on dual setups and have landed without incident.

Softmount engines. Electrics have basically no vibration, but glow/gas planes can shake hard. Even a small .40LA shakes. Soft mounts can easily extend the life of onboard electronics by a factor of two or three.

Buy more servo than you need. The idea being that the servo typically sees loads much less than its rated design, therefore, it should last longer than a servo that is operating at it limits.

A servo can fail at any time, but most failures I have experienced are due to trauma. Typically from rough ground handling and/or transportation. Be extra careful when transporting/storing planes and that should help.

Cheers
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Old 08-30-2003, 02:09 PM
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Rodney
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I had 148's on the ailerons of a big bipe (Lazy Ace) and after about 6 years of heavy use, the ailerons started to be jumpy. I removed the servos and took them apart. The wipers on the pots had literally worn away the conductive material. This was after literally thousands of flights so I could not complain, in fact think it is a good testimonial for the Futaba 148's.
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Old 08-30-2003, 05:57 PM
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If you just replaced the pots it'd probably be fine for a bit longer as long as the coil's in the motor were still good.
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Old 08-31-2003, 12:50 AM
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S Atkinson
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The post by Rodney prompted me to take a good look at the failed 148.
Visual & continuity checks on the board show no faults . All gears & the mech structure seem to be fine.The connector is good .
The pot shows no excessive wear & it is tracking ( elect) nicely .
The tant capacitors test o.k
Not having a schematic or info on the I/C's -that ends the looksee!
I'm going to buy 2 new servos . Which to get is up for grabs.
I must admit that these 148's look very nicely made
Handsome is as ------------------ does.
Thanks for the posts.
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