We all have our own ideas on when to replace batteries but looking at the Show And Tell Thread got me thinking about when to replace servos. I saw pictures of jets in that thread that had hundreds of flights on them. People stated how many sets of tires they even went through but no mention of the jets servos. So when do you replace a servo? I know we can replace sloppy gears and servos that begin to act erratic but what about the servo that is working fine and has no slop (with or without previously replacing the gears). How long will it last? How many flights do you trust counting on that motor to keep working? I have often thought about planned replacement for critical control surface servos. I was thinking the 200 flight mark for an otherwise perfectly fine running servo. What are your thoughts on this?

Response is very difficult... [&:] Lots of parameters here. I have some old flying machines (20 years old, glider) that are still flying with original servos of thoses years. Two weeks ago I've changed two servo on another that were erractic one's after ten years of servicing and at least the two last years without flights (propelled working plane, tug).

I don't know I we can even qualify parameters to make a choice of change or not.

The very same servo can live 20 years on a 20kg soft glider but being killed in one season of 3D flight with a 5kg propelled plane or 90 class 3D copter...

What about with our jets ? No vibration or few for sure, but efforts ?

Interresting question.

My buddy's running 13 year old 8411's on his f16. No problems or strange behavior.

My first jet is 7 years old and has done over 500 flights, the original Futaba and JR servos are still in there and will stay there until they show signs of trouble such as increased gear slop or jittering.
H

Honestly... regular aircraft use... with no crash damage... they will live for a VERY long time. I can honestly say I've never had a name brand servo die for no reason. In my +30 years... the only servos I've had "Burn out" are tail servos on my Heli's. The problem there is... the Gyro is driving the piss out of them. In my helis... I will replace the tail servo every year.


With that said... if you have a gyro in your jets... I would replace the servo it's hooked to every year or two. (but it's still not getting driven like a heli tail)

My Flash came into service last March, it now has 210 flights on it, I should be in the 300 range by years end and well over 400 by the time the jet is one year old. I have ZERO plans to replace anything that is working properly....

We used to change them on the uav, smaller futaba servos at 200 hours... Now with that being said when I changed them, I boxed them up and shipped them home instead of trashing them. I still use them in smaller electrics and they keep on going. I had never seen one fail besides being mistreated with stripped gears.

This is an interesting question, one that I have pondered for years.
So, I am running a long term test. I have a BoBcat which is almost 10 years old with 300 flights on it. The rudders have the original JR9411 servos which are gyro activated so they are active, almost all of the time, lots of stop -starts, hardest on the motor and amplifier. As the BobCat has twin rudders a single failure will be almost inconsequential. So far they continue to work perfectly with no increase in gear play etc so the servos will remain in position until they show signs if degradation or failure. So far so good. They may even outlive me !

Regards,

David Gladwin.

I've got an old Kalt Baron heli that i've had and flown for the last 25 years, it was owned by Billy Pierce (Kalt Rep if you remember how long ago that was) and used as a demo bird at events, it's got THOUSANDS of flights on it and still using the same little stardard JR servos from its original build never even a gear set. i'd venture to say a Jet will NEVER see the kind of abuse (it's a very smooth bird but a great deal more vibration then a jet) that these servos have seen and they have never missed a beat, if it ain't broke........don't fix it.

It seems as though my thought of replacing the servos on the control surfaces every 200 flights is too conservative. I will continue to inspect everything before every flight as I always do and look for any signs of trouble. I really think it is impossible to put a number up that would represent all situations. Careful monitoring will be the key.

No, no that's about right. Just to be on the safe side change them after 100 flights.

To save them cluttering up your workshop send the old ones to me. I'll 'dispose' of them at no charge.

Hey, no need to thank me, just glad to help you out! - John.

HA.....LOL

I've got Hitec TG's on a IMAC bird that have well over 600 flights on them with absolutely no slop.

Any thoughts about mixing servos such as digital/non digital on control surfaces? For example I have several new old stock JR 4131's rated at 90oz/4.8v lying around and I plan on using 2 for flaps on a Tornado and JR digital 8411's on Aileron and Elevator. Rudder will have digital servos as well. I know we use non digital for things like brakes (smooth stops & UP-6) and retract switches with no problems but what about the other mixing possibilities? I prefer to use what I have instead of going out and buying 2 more 8411's for flaps especially a reversed one. I am using a JR 12X and as usual thanks for any useful info.

I used to use JR 2721's I believe on the flaps on king cats, had quite a few go flaky on me. The 4131 was a good servo but kind of old now and if I am not mistaken had a plastic gear train. I would personally stick with digitals on control surfaces.

I also just inspect the servos, my BVM Phantom is 11 years old and still has the original servos in it with over 1000 flights. I have replaced a few extensions. I am going back through it this winter replacing fuel lines and airlines if needed. I'll pull out servos and look at them as well while I'm in it, but I suspect I will put them back in.

DR

I have sports models with hundreds and hundreds of flights over 20 years plus, I always use quality servos and have always coined the phase a quality servo is always a quality servo, budget is fast track to the bin! I have jets that are 10 years old and still on the same servos, OK not a huge amount of flying, but my Classic Flash is on the original servos you see in the manual pictures and that has between 6 and 700 flights, I lost track after 3 changes of Tx in its time and a turbine swap while the original P-120 was serviced. Stevie Roberts CF is around the same number of flights but a younger model, both have original JR servos in.
As I've said before I run in all my new servos and this gives them an easy birth. Brushed motors and load straight away is a recipe for trouble. Check your surfaces, ball-links and clevis for tight spots and servos should last for years in our low vibration installations. I've only really badly damaged one jet in 11 years of flying and that was an elevator servo problem from ground vibration making the surface "buzz" madly on the ground and it killed a pot.

Dw

i used the all analog package that came with my tornado with no problems at all.

Hi,
Some newer servos has brushless motors in them today and one manufacturer claim these motors has up to 5 times longer life thanbrushed motors.
But they are expensive.
"At least FIVE TIMES longer-lasting than brushed servos".
Source: http://www.futaba-rc.com/servos/brushless.html

So a brushlessmotor can at least help for a longer servo life.

I know JR have brushless motor on some of their servos also - any other manufacturer?

/Bo

JR has the MP line of brushless servos but the only one I found on Horizon's website was the tail rotor servo @48 in/oz of torque hardly suitable for control surfaces on a jet. I think we will see more of them in the future but not real common yet. I have installed and serviced hundreds of industrial servo motors, albeit larger motors, but constantly moving on CNC equipment and industrial applications that run for hours on end with. Dry little if any maintenance required. I have seen very little "brush" issues. I think the current crop of premium coreless digital servos are very good and have been giving a lot of us very good service. Initial servo setup, with proper linkages, including proper mechanical setup is probably the most important factor affecting servo life. As a model ages if you start noticing gear slop, servos not centering, erratic movements, or physical damage then you change them. Otherwise no need to just replace them. YMMV....

DR

Thanks for answer David, KC the question was "What about a mix of Digital and Analog servos for control surfaces? I opted not to use all analog for the Tornado project since I have several digital 8411 laying around unused (just not enough for the flaps!!!).

I have a box full of new unopened JR 4131 and JR 8101 analog servos which were considered "High Quality" when they came out and it seems a shame to let them sit for another project (although I may find a winter project to put them in). So I may end up putting them on the flaps after I call the service techs at JR..................

Ken,

i've got several planes with a mix of digital and analog, never had an issue with it.

Thanks KC,
I did not think it would really matter but I remember some time in the past people use to warn about mixing the two due to some sort of mismatch problem which I am sure has been resolved, especially with power distro and 2.4 systems. There was a time period I quit R/C cold turkey due to not being home for some crazy reason (???????) and I temporarily lost touch with what technology was out there. My 10x became obsolete along with my AMT AT-180's and JR 4131's, 8101's and 3321's and not to mention about a dozen high end RX's I had squirreled away. Maybe I will start a thread with some old school photos of the ancient stuff such as my Brand new old stock Crow Aviation (CAI) hat, the DF parts still new in package and the SCUBA start up tanks I still have in my garage........sorry to go off topic though and thanks again for the info.

i sold my last two JR 72 MHz high end scan select receivers last weekend for a whopping 20 bucks..........no not each, for the pair

There is nothing wrong with high-end analog servos, AMT-180's, or the 10X. I would upgrade the 10X to 2.4 using a module, but all of the rest of the stuff is still good-to-go...

Bob

Had over 800 flights on my Mibo A-10. I was using the 8611 servos. They seemed to hold up fine.

Billy