After almost at year with a strange servo jitter that was taking all the fun out of my UAV hobby i finally found the source. A bad servo.

 

The jitter was intermittent and made and erratic +- 5 mm throws on the elevator or rudder even when i tried flying  in "manual mode".

 

The little bastard finally decided show its real face today by giving a "full down" (and i mean FULL) right after start, giving my Easy Star a nice sucker punch right on the nose.

 

So, Turnigy S 3317 S. Your life was short and noisy, and you will not be missed.

I am moving on now and will look for a more dependable partner. :-)

 

I know some of you are doing UAV flying for a living. What brands of servos are you using?

 

 

 

 

Views: 1101


Distributor
Comment by Martint BuildYourOwnDrone.co.uk on April 14, 2011 at 12:47am
I hope your other servos take note of what is to come should they let the team down, an international name and shame! :)

I have always used Futaba servos, and to date not had one fail, so my vote is to use Futaba.

Regards

Martin.

www.buildyourowndrone.co.uk
Comment by DaveyWaveyBunsenBurner on April 14, 2011 at 1:51am

I'm with Martin!

 

Futaba servo's are expensive but very good quality. I had experimented with Hi-Tec's in my previous easystar but they twitched all over the place, the interference suppresion seemed absolutely zero.

 

I would imagine all the major brands are equally good.

Comment by Andrés on April 14, 2011 at 1:52am
Nice pic, remembers me somehow to when I was in school ;)

Well, I do not do UAV flying for a living, but I have consumed a lot of servos in the last years. Just to give you and example, my latest project, a Horten IV, has a total of eight servos... I've had gears broken, servos burned, even once a friend had a crash and the magnets of the servo-motor fell appart (the metal gear was still fine). So, I've learned one thing the hard way, do not try to save money in critical components such as servos. One does not necessarily need the best and most expensive "titan gear fancy high voltage" servo, but some extras should be considered. A crash due to a broken servo can be a lot more expensive and depending on the airframe can costs you hundreds of hours of work. Therefore

1) Broken gears are anoying, in particular if changing the servo is difficult => use metal gears
2) Unprecise servos can be a pain in the neck => check experience reports in internet
3) Overdimensionalising a servo costs weight and money, a too weak servo might cost you an ariplane => Choose servo strength according to expected forces
4) Digital servos keep position much more precisely, but they consume also a lot more electricity => check your electric supply, do not be too confident on the BEC and use a reciever battery if necessary (a double supply is safer).
5) there is a whole chain between you and the servos => the best servos do not help you, if you have e.g. a bad reciever...


I've had good experiences with:

Futaba:
S3150, S3156

Graupner:
DES478, DES488, DES448, DS3288

Hitec:
HS-82MG
HS-225MG (had no problems, but other people had temperature issues)

Dymond:
D60S (good but had some with broken gears)
D 200 BX BB (plastic gear, but have not broken one, usable for non-critial things)
D 250 BX BB/MG (good but somewhat unprecise)
D 5000 BB MG (unpreciese but still ok)

Bad experiences:

Mutliplex:
POLO 4 (servo burned! Keep your fingers off)

Hitec:
HS-81 and HS-85MG (just stopped working without a reason)


Turnigy:
1660A (to weak gears, got them and broke the gear with my hand => I threw these straight away, I'll never buy again Turnigy servos)


Conrad electronics:
some really cheap and small ones, but I forgot the name (gear broke directly at the first usage without load).


You see that sticking to a company is no guarantee for a good servo. Check therefore for reports in the internet. If you want to be sure, stick to e.g. Futaba or Graupner. They costs somewhat more, but they have good quality and crashing your airplane with APM, Camera, etc. on it might costs you several hours of work and hundreds of €... Keep your finger off servos that cost less than 10 €. I had with such servos only bad experiences. For a good analog metal gear servo, you'll have to count with about 20€. Count with 30 to 40 € for a good digital mg servo.

I hope that helped you,

Andrés

Moderator
Comment by Gary Mortimer on April 14, 2011 at 2:11am
Ya gets what ya pays for.
Comment by Russell B. Sutton on April 14, 2011 at 2:16am
I like my Jr digital servo's.  Servo voltage and power supply is very important as well.  Good Luck
Comment by Russell B. Sutton on April 14, 2011 at 2:26am

This is a nice way to tune your servo power voltage. 

http://www.robotshop.com/dimension-engineering-de-swadj.html


Distributor
Comment by RC Tech.se on April 14, 2011 at 2:27am
Thanks for your insight. It sounds like metal geared servos are the dish of the day
Comment by DaveyWaveyBunsenBurner on April 14, 2011 at 2:29am

@Stefan

 

There are also some new gear materials that are the best of both worlds coming out from suppliers. Metal gears have a tendancy to wear quite quickly, plus they are heavy. The new plastics are tougher than nylon but wear less....

Comment by I.S. on April 14, 2011 at 5:33am

What about the famous HXT900 servos?

They are dirty cheap, but people use to like them.

@Davey

you mean the carbon enriched plastics or alike?

could you give us some item examples of those new plastics servo?

Comment by DaveyWaveyBunsenBurner on April 14, 2011 at 5:44am

@I.S

Yes, I believe its called karbonite, but believe other manufacturers are also releasing similar:

http://www.modelzone.co.uk/hitec-635-high-torque-karbonite-gear-ser...

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