Do I need new servos?

[Phil 9]

I am very busy saving for a new artf airframe.

The engine, servos and switch I intend to use are in my current model. They are about 3 years old. They work fine now but how long to servos last? Is there a time when even if kit works you still should replace it? I will buy new batteries for the new model .

The switch is a hobby king failover regulator switch

I need to keep cost down but I don’t want to risk losing the new model because of faulty kit

[Steve Hargreaves - Moderator]

A "how long is a piece of string?" question that Phil....wear & tear on servos obviously depends on how often & how hard they've been used......servos flown in a vintage model every other week will have an easier life than those hammered in a 3D model every weekend.

I certainly would have no problem "re-using" 3 year old servos provided they have been only moderately used during those 3 years.

New battery is a good idea.....they are so cheap these days I tend to change mine every year anyway....

The switch....h'mmm who knows!! Electronics tend to either fail almost immediately or have a long life until the failure rate starts to increase as they near the end of their life....the so caled "bath-tub curve" So you can find that you fit a new one & it fails immediately whereas the old one keeps going & going!!! A difficult call & again depends on how much use it has had & the cost of a replacement....

Not much help am I????

[Phil 9]

Thanks Steve. That mirrors my thoughts also

I guess the best I can to is thorough pre flight checks

[John Privett]

Phil, I certainly wouldn't replace a servo "just" because it was 3 years old. Most of my servos are older than that! If I have any reason to doubt a servo then I won't use it, but an arbitrary age limit is not in itself a factor for me.

Thinking back over servo failures I've had in the last 20+ years... I had a set of 4 servos that I stopped using after about a year as they gradually became jittery at switch-on for a few seconds. A few servos have been physically damaged (gears stripped, or in more extreme instances, the cases/lugs broken. Two (only two!) have failed in the air. Both were aileron servos which failed in the neutral position in models with a servo in each wing - so no problems landing. Another one or two have failed mysteriously in storage. And that's about it!

[Phil 9]

I had two fail in storage also last week. I guess that is why I asked

[FlyinBrian]

I would not change servos just because of age, check them carefully on the bench for smoothness and centering. If your Tx allows or you have a servo tester excercise them for a few minutes and check that they still operate correctly and none are getting warm.

As mentioned above new equipment can and does fail!

[crispin church]

old servos are ok even after 20 years

batterys you need to keep a eye on if you got a lipo charger that will do life batterys then i would change to life/A123 battery a lot better than AA

just keep eye on wires

[bouncebounce crunch]

I still use old servos the hitec 422 came with my first fm radio in 1987 and are happily working. althought, they are in older slopers and floaters.

[Phil 9]

Posted by crispin church on 04/06/2013 08:10:16:

old servos are ok even after 20 years

batterys you need to keep a eye on if you got a lipo charger that will do life batterys then i would change to life/A123 battery a lot better than AA

just keep eye on wires

I was planning on using lipo rx batteries. I have a petrol engine so need two batteries. The regulator switch has a constant output of 6v. also if one battery fails it acts as a fail safe and gives both supplies from the remaining good battery.

[Olly P]

I'm still using some servos in a sloper that are at least 20 years old. I will consider replacing them when she goes in for her major overhall, later this year. I probably wont though.

Olly

[Lee Smalley]

tell us the servo make and model and the airframe you are getting and people on here will tell you if it is worth getting new stuff or if the old stuff will suffice

[Phil 9]

servo used are this type and the new model is a great planes revolver 61-91

[Phil 9]

servo used are this type and the new model is a great planes revolver 61-91 they are 10kg servos so have more than enough power

Edited By Phil 9 on 04/06/2013 13:06:56

[Lee Smalley]

not what i would put in a nice model like the revolver, but if the specs are right they would be man enough for the job.

[Phil 9]

What would you choose Lee? I am using a saito fg-21 petrol engine (so do I need Metal gears)

I also have spectrum ds821 servos but they are plastic gears

Edited By Phil 9 on 04/06/2013 16:52:01

[simon barr]

I have got JR 591s in my Revolver. They are a budget 5kg torque servo, but I haven't had any problems with them. I've got an SC 1.20 two stroke up front...

[kc]

Nicads replaced every few years. I reckon to replace the elevator servo regularly and keep the others. The old replaced servo might be used only for rudder or throttle or less critical functions. Any servo or receiver that shows the slightest problem is never to be used again in the air but labelled and used only on the bench for setting up new models. One glitch and it's out. .

[Erfolg]

I am currently flying a model using a S128 servo. Now old would that be?

I would not have thought that 3 years is any age for a servo.

I have now been flying (again) for about 7 years. I know that I am using some GWS Parkflyer servos, which I purchased back then. Also purchased at the same time are some Ripmax S200 servos, which are in use.

Like many other modellers I am using a range of servos, with respect to brand and age. My failures I have all been gear train related, on 9g types, all down to impact damage.

[Lee Smalley]

I hear all the replies already but in my experience other cheap makes of servo suffer from various problems some have very poor resistance to vibration others soon develop poor centering and gear train slop, some are just utter rubbish, personally you have a really nice model fitted with a great engine i do not understand why you would fit cheap unbranded servos, it seems bizarre to me, but hey whatever, if i had to go with a servo, i would stick with a good brand and fit something like hs5625mg on the primary controls and if you need to save money budget on throttle. With a petrol engine you really should fit mg servos just in case

[Phil 9]

Posted by Lee Smalley on 04/06/2013 22:56:45:
I hear all the replies already but in my experience other cheap makes of servo suffer from various problems some have very poor resistance to vibration others soon develop poor centering and gear train slop, some are just utter rubbish, personally you have a really nice model fitted with a great engine i do not understand why you would fit cheap unbranded servos, it seems bizarre to me, but hey whatever, if i had to go with a servo, i would stick with a good brand and fit something like hs5625mg on the primary controls and if you need to save money budget on throttle. With a petrol engine you really should fit mg servos just in case

I considered using these servos because I already have them. But I guess I must have doubts about using them or I would have not asked the question in the first place. I do not want to waste money by buying new servos unnecessarily but I don’t want to spoil the ship for a haporth of tar. This will be my main ic model that I hope will last a while so I think new branded servos are in order. Many thaks for the advice

Edited By Phil 9 on 04/06/2013 23:32:16

[Erfolg]

I do think we need to emphasis the differences in the duty experienced with a typical IC model and electric models, particularly small models.

All IC models operate in an environment of substantial vibration. In some instances there can be oil to contended with. The average IC model starts in size, where many electric models are considered to be medium to large (generally speaking).

In the case of the electric model, there is almost no vibration to contend with. If there is oil, it is a puzzle where it can come from. Then there is the size issue, the bigger and or faster the model, more powerful and possibly faster servo speed can be required. Though these are not normally models people learn with.

When I have had centring issues, it normally has been due to slop or binding in my hinging or drive set up. Now I endeavour to have as near direct drive as possible, using short push rods. Hinging is a real issue for me requiring a lot of care and effort. From past experience I now avoid long push rods, keeping them light and stiff is struggle. Also more gear trains seem to be wiped out by pushrods than any other cause. The inertia when landing heavily or that could be called ariving. Second best then comes Sullivan snakes in my experience, other makes can suffer from high friction, particularly with time and gundge.

It is interesting the issue of cheap servos, i use generally very cheap servos for my ailerons, SG90s, some metal geared. I have had less issues (that is none) than two brands, mid priced, that have been recommended a number of times in the past, where a tooth was lost in one case mid flight, in another, the servo ran to an extreme position, then stalled against the stop. I am not convinced that all cheap servos are not fit for purpose, and that all mid priced servos, are all they are cracked up to be.

[Lee Smalley]

the only failures i have had to date, are 2 off tower pro 996 i think, both in a big moki powered unit (throttle) both have failed and are now in the bin, a raft of blue servos from BRC hobbies, they are all in the bin, they were laughably bad, and 1 hs85mg in an electric model! personally due to the reliability i have had with Hitec and Jr servos over the years these are the only ones i put in good new models now, when my airframe costs a few hundreds of pounds and the gear inside also costs why risk it to save 50 quid, i have had a few hobby king servos and whilst they have not failed the manufacture inside was not the best, and support for the electronics and wires against vibration were none existant, so whilst they still work they will never go anywhere near something i have invested a fair bit of money in. my opinion about the original post was given the quality of his model and the engine, i dont see the point of controlling it with cheap servos, his original servos has seemed to been ok but i do not know if they have been used on something with such vibration levels,

Personally i have given up trying to save a few pounds by fitting cheap servos, i have often found it to be a false economy.

[Erfolg]

Lee

Your comments I do belief emphasis the wide variation of model size, cost and duty that as a group we fly.

I suspect at lot of your models are to me large, that is +80" weighting 5kg or so. In my case large is 1.3m aero plane or 2m glider, weighing up to 2kg.

You talk of models costing many hundreds of pounds to construct. In my case my bare airframes cost possibly circa £20.

You are flying models With a Moki, what ever one of those is, i guess a big petrol engine. My idea of big is 350-400w,

Probably the biggest difference is vibration, you have vibration as a given. I have no vibration, when it ocurs, ot comes the prop balancer,

In many ways it all emphasis our different perception, wants and needs.

What all of this emphasis to me we have to carefully consider all the issues. As can be seen, you have issues with SG 90s, I have none. Again you have faith in the brands you use, wheras my mid priced HS servos were pants. Could both our experiences have some commonality, in that it is the duty and the way we use similar if not identical servos.

I guess this is what makes servo recommendation so difficult. That is other I can say all my Futaba S128 and 100 are well over 3 years old, still work fine for me, other than they are heavy.

[Lee Smalley]

I do have some large aircraft but some small ones too, horses for courses obviously, but the point i am trying to make is that when your investment is substantial i really do not understand why some people fit very cheap servos, it just seems daft to me, your models are not like that, so it would be silly to fit servos costing more than the model, i have some very old servos too and they are fine but they are fitted only to throttle now

[Erfolg]

Totally agree on the point of model cost, if I could afford a £1000 model and our club has quite a number of this type, I would expect to use good servos. Although I know my idea of good would not be the same as some others.

Then again, I would want a top notch Tx and Rx. Not because I have seen any convincing evidence that they are any better than some well known tier 2 suppliers. They are reassuringly expensive and Futaba has a good reputation.

At the end of the spectrum I am occupying and from personal experience, i find that for my duty, the way I use equipment, SG90s work, as do my old servos.

It is horses for courses.

The disquieting note, I have seen some very expensive models with the best badges go in, not all though. Where I would cry and be beside myself, many of these modellers are unmoved.

In many ways I do not see the obvious pattern between cost and reliability. I feel there is a stronger relationship between modellers and how they treat equipment, plus what their equipment is put through.