when servos should retired
 

hey guys..

after a similar post about airframes must put aside cose of over use...

i was wondering when i servo should come out from a jet ?

servos on my prop planes work overtimes way harder but also my jet servos are with me many years in airframes doing there job!


so any expirience on that? ...how much servo motors lust ? anyone expirience die of a servo becouse of age?and lets stick with jr and hitec flagships[8D]

RE: when servos should retired
 

:Dwell...

one option is after you crash your plane :D
the other is up to you

RE: when servos should retired
 

If a servo is working well & has no slop in the geartrain, I would leave it in place. You can buy a new servo & it can die in minutes. Better the devil you know;).

RE: when servos should retired
 

This is a subject which has always interested me, so here goes.

I have some , quite a few, JR servos which are over 24 years old they still work perfectly.

My high operating time servos are JR 9411s. These are on the rudders of my original Bobcat (7 years old) which are gyro controlled so are always working. It is a demanding function and the servos originally spec' ed for the BobCat rudders by BVM, JR3421s , burned out quite quickly and JR recommend they NOT be used for gyro applications. After 250 flights the 9411s are still working absolutely perfectly so they stay in place till (if) they fail to so I can get SOME info. on servo lifetime.

I also remember reading comment on servo life by Curtis Youngblood. His opinion is that good servos last until the model crashes from some other cause. !

I have only ever had 3 servo failures on jet models, 1 4721 and 2 8411s all caused by prolonged stalling on ground test/set up. All 3 servos locked absolutely solid.

Might be worth adding that I always use powerful servos, which some might regard as overkill, to give the servos an easy life. always use a Hangar 9 digital load meter during set up to minimise current draw and always use voltage regulation at around 5.7 volts !

Coffee finished, over to you .

Regards,

David Gladwin.

RE: when servos should retired
 

Hi David,

What is the biggest current you have ever monitored with a stalled servo, say DS8411 @ 5.7V regulated ?
I have a very nice dual DVM module and need to select a suitable shunt resistor for current monitoring. 5A or 10A ?
Would make a good project for Friday afternoon !

http://www.martelmeters.com/pdf/datasheets/DPM702S.pdf

Thanks.

RE: when servos should retired
 

:DLOL:D

RE: when servos should retired
 

I BELIEVE if I remember correctly from a JR article that a stalled 8411 can easily pull 5 amps. I have never actually monitored the current when stalled. (too busy unstalling it !) I use the Hangar 9 device for fine adjustment, essential when adjusting servos on controls with mechanical stops, eg flaps, gear doors etc. Its amazing how even tiny adjustments can have a very significant affect on current draw.

My Weatronics receivers give the numbers on my Air world Hawks, (both have numerous 84s, 85s and 4 8711s. ): 1.5 amps static, 3-5 amps in flight rising to 7 amps with fullflap running down, and spikes of around 10 amps.

The new Weatronics 2.4 receivers allow servo adjustment in 4096 steps, using the up/down key on the PC, THATS accuracy !

I am convinced that minimising current loading is very helpful in improving servo life.

Regards, David.

RE: when servos should retired
 

Most definately, and minimising risk of voltage drops and Rx brown outs in flight.
I shall build up my little meter for a 10Amp range.


Thanks.

RE: when servos should retired
 

George,

Got to admit that after being in Rc off and on from the late 60's I have never seen a burned out motor to one. The biggest failure I'v seen is the gears. For that reason I check the gear slop after every 40/50 flights. Like you said, "it depends on the app". I was amazed at how little the jets servo's are abused as compaied to the big 3D machines. Most of our jet surfaces or sealed and I think that puts longed life into the servo. the only exception being what David said about the extra wear done with gyros or crashes. All my 605's have came back full circle. I would not use them in a mid sized 3D but have some smaller jets that this servo is ok for. I do look for and buy the metal conversion gears for them when I can find them and run them on 6 volts. Mabey Red can fall in here and give us his taste on this!!

RE: when servos should retired
 

the lack of vibration is what gives turbine powered jets longer servo life, pretty much the only abuse they see is from taxing and landings. a gassers vibrations on large surfaces constantly work a servo just like a gyro. the only motors I've ever burnt out were on high revving glow engines where the vibration resonance of the pushrod would burn out the pot and/or motor to the throttle servo.

RE: when servos should retired
 

Here's one I made earlier......
Servo tester needs charging up and then I can calibrate the meters properly.

RE: when servos should retired
 

I run-in my servos before installing and check before installation that the servo moves smoothly without any hick-ups. Like this I have gone past 500 flights and have never changed a Jet servo through failure. I always use JR servos and check that the surfaces are free and smooth, this is the critical thing for servo life. As stated servos get an easy life in turbine models, my Bandit with two TP Li-Po packs only use 150 mAh per pack per 10min flight.

Dave W