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HelicopterMain Discussion › A question on servo life?
09-30-2017 12:23 AM  7 months agoPost 1
InvertedDude

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USA

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Now, I am aware that this can be a controversial topic. I feel like it is warranted to add to the benefit of RR database.

Okay, how do you know if your servos are on the way out? Would like an answer, thanks RR. All electronics have a MTF (Means to Failure) lifespan.

Frankly, I just test them for holding power and pre-flight wriggle.

Brushed motor

Brushless motor

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09-30-2017 12:37 AM  7 months agoPost 2
EEngineer

rrProfessor

TX

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Hard to answer. So many variables. Brushed vs brushless servo motor. ND the quality of the motors which might not always correlate with the price. Mechanical hookup used......is it being strained at the endpoints, etc. Voltage used

Lol

Logo 600SXs, 800XX, TDR IIs

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09-30-2017 12:42 AM  7 months agoPost 3
InvertedDude

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USA

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EEngineer

Yeah....but can you give a wild guess?

For example my JR 8311...when do I replace them? 1, 2 or 5 years?

3 flights daily x 7 = 21 flights per week.

Something?

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09-30-2017 12:53 AM  7 months agoPost 4
jackp332

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Claremont, Nh USA

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I use the same basic test as the O.P. I dont do any formal load testing or holding power etc. If i notice chatter while on the bench or a lack of centering i take them out of service immediately even if i cant duplicate the problem twice. I have had cheap $12 dollar servos last for years with hundreds of flights on some of my old planes while i had a $140 cyclic fail while hovering my gasser directly in front of me with drastic consequences. At post mortem examination the servo was stuck at full deflection in one direction. After talking with the manufacturer i determined it was most likely the result of heat from the engine and too high a voltage. I lowered my voltage and have never had one (i replaced it and still use the same servos) fail since. I probably have 200+ flights on this particular machine now and it is as smooth as the day i put her into service. For what its worth, i just fly easy sport and scale style with no 3d or hard aerobatics what so ever.

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09-30-2017 01:05 AM  7 months agoPost 5
EEngineer

rrProfessor

TX

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Applying mech. resistance while moving the TX stick can ID gears going bad.....servo making odd sounds....that'll all work.....in general, i don't use "used" servos as I don't know how they've been abused......everybody has their own method that has worked for them over the years.

Logo 600SXs, 800XX, TDR IIs

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09-30-2017 02:13 AM  7 months agoPost 6
grimthenoble

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Ketchikan, Alaska

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I would buy all new servos after 2 flights, don't want to take chances! On a serious note, I take mine apart every 25-30 flights (or once a year), inspect gears and re lube them. Better quality servos will be made with tighter clearances and will technically last longer. But theres always the exception of crashes, miss use etc.. Brushless servos seem to last forever.

Never go Full Retard!

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09-30-2017 02:32 AM  7 months agoPost 7
Pistol Pete

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Seffner, FL

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The only person to my knowledge that has kept track and posted such here in RR is Raj aka "rbort".

Dont recall the exact Futaba servo number but if not mistaken, might be around 300 hours on a gasser when he replaces them before failure.

I trust his numbers.

Search "servo life" using "rbort" for name.

Usually the first thing to go in a servo is the potentiometer.

YMMV

~~Enjoying the hobby one flight at a time~~

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09-30-2017 02:41 AM  7 months agoPost 8
jackp332

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Claremont, Nh USA

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I agree with EEngineer- I remember once i had a servo that had a chipped tooth on a gear internally but when you just moved the sticks it operated and sounded fine. Using a finger on the linkage to apply slight pressure (i did this by accident) revealed the problem.

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09-30-2017 03:23 AM  7 months agoPost 9
EEngineer

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TX

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I hate
to open the servo case. Don't know why, but I think it's because I fear fubarring the gear train alignment with a finger fumble.

Logo 600SXs, 800XX, TDR IIs

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09-30-2017 03:54 AM  7 months agoPost 10
dkshema

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Cedar Rapids, IA

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There is no magic gear train alignment inside a servo. There is nothing to fear inside a servo.

The small number of electronic parts inside a servo would probably give you am MTBF in the neighborhood of tens of thousands of hours. Unless you'really abusing them voltage or thermal-wise, you won't "wear out" the electronics.

The motor and pot are the least reliable and most prone to failure. Dirty pots are very rare these days. I don't believe I've run into a dirty pot in decades. Motors are more likely to die due to vibration than wear-out.

As noted, damaged gears are relatively easy to diagnose and to replace.
Odds are that you would replace a servo due to damage resulting from a massive crash before you would wear it out .

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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09-30-2017 01:08 PM  7 months agoPost 11
ICUR1-2

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Ottawa, Ontario

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I have had newer servo's fail for no apparent reason. it just stopped working. and I was using the correct voltage.

spending time, paying attention

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09-30-2017 01:13 PM  7 months agoPost 12
Dr.Ben

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Richmond, VA, USA

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I know that Nick Maxwell documented over 500 less-than-gentle flights on a set of bls252's with a think one gearset change. I agree that the pot may be the limiting component since motor bearings aside, brushless motors last a heck of a ling time.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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09-30-2017 03:43 PM  7 months agoPost 13
EEngineer

rrProfessor

TX

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brushless motors
Less moving parts......no mechanical commutation......I use them exclusively to the extent I can......

Logo 600SXs, 800XX, TDR IIs

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10-01-2017 12:00 AM  7 months agoPost 14
Four Stroker

rrElite Veteran

Atlanta

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Wayne Mann reported to me a lifetime of 9202 servos of 500 flights.

The AS5600 Hall Effect chip CLAIMS to be immune to stray magnetic fields and mentions RC servos in the spec. sheet ?

Dr.Ben may recall that around 1975 Proline (as reported by Jim Oddino in RC Modeler and rumors were around) made some prototype servos with this technology:

https://www.nidec-copal-electronics...ometer/jt30.pdf

A ball bearing brushless servo with a contactless pot would last forever baring crashes.

BUT the precision of contactless pots is still in question. Some day we will have them in servos - ones that work. I have a JR MPH83GWV tail servo that works fine BECAUSE the reference is actually the gyro sensor and not the pot. It is not immune to stray magnetic fields -refrigerator magnet.

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10-01-2017 12:31 AM  7 months agoPost 15
ICUR1-2

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Ottawa, Ontario

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Maybe using a laser optics for referencing center would work but servo size would certainly increase due to the amount of electronic circuitry required .
A stupid potentiometer provides an easy solution.
Perhaps making the servo more service oriented would be a better solution

spending time, paying attention

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10-01-2017 01:41 AM  7 months agoPost 16
JuanRodriguez

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The Villages, Florida

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And servo price would certainly put it out of reach for most !

Been there, done that and old enough to know better.....

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10-01-2017 01:49 AM  7 months agoPost 17
EEngineer

rrProfessor

TX

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Hehe. 1975 Proline......Jim Oddino.....RCM......there's a blast from the past

Logo 600SXs, 800XX, TDR IIs

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10-01-2017 08:03 PM  7 months agoPost 18
Heli_Splatter

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USA

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I don't hesitate to pull servos apart and replace gears. It is very simple and saves a lot of money. Pull it apart and take a picture. Clean out all of the silicon grease. Put the new gear/gears in place and apply new grease.

Test the servo for centering and strength. If there is problem with either, you should likely toss the servo in a bad servo container. Save parts because you might have a broken case sometime.

As you are using servos never yank the arm around. Be gentle with them.

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10-02-2017 02:18 PM  7 months agoPost 19
Richardmid1

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Leeds, England

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Frankly, I just test them for holding power and pre-flight wriggle.
Yep, pretty much all you can do. Although you could also check they aren't getting excessively warm after a flight or that your RX battery isn't running down faster than normal. Also it wouldn't hurt to check and clean the connections into your RX or FBL unit.

I guess you could increase the life of a servo by running it on lower voltages and refresh rates so it wasn't working as hard. For example running a HV 333Hz tail servo on 6v and 200-270Hz.

60% of the time, it works every time!

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11-16-2017 09:59 AM  6 months agoPost 20
aerotony

rrNewbie

Sydney, NSW, AUSTRALIA

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Discussion of contactless position sensoring is all new to me. Does anyone have anything to add to the final paragraph in posting #14?

Any information gratefully received.

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HelicopterMain Discussion › A question on servo life?
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