elombana

I have an Aeroworks 50CC Yak54 with these servos moving all control surfaces. It is a single servo per surface type of plane. These things vibrate the surface like there´s no tomorrow in static, engine-out mode. You may imagine when the engine is on, they eat all the battery very quickly just vibrating away, I guess trying to find their center (which they never do). So it is quite anoying and I have not been able to correct this condition. Not even shortening the futaba 1.5" aluminum arms.

I have a 6 cell 2000 mh pack connected to a regulator which sends accurate 6V signal to the receiver. The receiver is an R138DP 8 PCM type.

No other aircraft of the type has had this type of problem.......I guess migrating to Hitec is an option? [:'(], a pain actually 'cause I paid 109,00 each!!!![:@]

To get help would be great.

Bax

My Feedback: (11)

Digital servos work at holding a commanded position. If you have large control surfaces, they try to deflect just under gravity. The servo will push back, working to hold the surface at neutral. This will make them buzz...and it's a normal thing.

Do you still get them vibrating/buzzing if you disconnect the pushrod from the servo? If they don't stop, then you may have a problem. However, it's not very likely that you have several bad servos, unless they've seen a lot of heavy use in other models.

Smaller models have lighter surfaces that don't pull on the servos as much, so you likely don't notice this effect.

In flight, aerodynamic forces will tend to keep the surfaces in trail, unless you have to add trim to deflect them slightly. In that case, the servos will also pull quite a bit of current to hold position.

Digital servos consume a lot more battery power than the older-style for just this reason...they are always working. That's why you need to go with larger battery packs in the model, or recharge them after a flight or two with a field charger.

Supra25

Bax,

I don't think he means the "digital" buzz that's common with most digital servos. I read it like he has the same problem that I have experienced on my 2.6m Comp ARF's with these servos.
The servos really vibrate like crazy in neutral position. They don't just buzz, but the control surfaces move up to several millimeters in a kinda violent manner when there is no load. It appears as though they go into a kind of self loop catch 22 mode where the servo starts working against it self. The only way to stop this is to apply force or load to the control surface. When taking the linkage off the servo it behaves normally.
If my recollection is correct this issue has been brought up on RCU before without there having been any informative conclusion made. I have had this happen to me with brand new 9351's on elevator, rudder and ailerons.
Typically re-arranging the linkage geometry could solve the problem, but seeing as (in my case) that is not an optin deflection-wise and other servos work just fine (Futaba and Hitec) this has to be a 9351 related problem. Surely Futaba is aware of this issue and can come upwith some worthwhile comment?

I can add that the 9451's on the same surfaces do not have this problem.

Krysta

Hi elombana,

The reason you are seeing this with your S9351 servos is they were not made for use in aircraft but made for car/boat application. They are not as steady at center as the ones made specifically for aircraft.

We have had many, many people try using these servos in aircraft because they want the torque and speed that they offer, even though this is against Futaba's recommendation for these servos. But to help our customers out who are wanting to use these, Futaba has manufactured the S9155, which is the same torque and speed, but has better centering and precision which is required for aircraft use. You may want to check these out, our stock number for these is FUTM0215

I hope you find this information helpful. You can also reach our Futaba support technical team at 217-398-8970, or via fax at 217-398-7721.

Sincerely,
Krysta Hunt
Product Development & Support Specialist
Futaba Service Center USA

elombana

Thank you for the answer, your are right I tested a different aircraft type servos and the vibration is gone. I purchased these at Tower Hobbies but I am having a hard time exchanging or getting credit on them as they have been used for 15 flights now. Can you help in any way? They are terribly expensive and I would not like to loose my money or go Hictec which have a 1/2 priced hi torque digitals which probably serve the same purpose.

Supra25

Krysta,

Didn't know that. Thanks for letting us know!

ljones5000

My Feedback: (2)

[quote]ORIGINAL: Krysta



We have had many, many people try using these servos in aircraft because they want the torque and speed that they offer, even though this is against Futaba's recommendation for these servos. But to help our customers out who are wanting to use these, Futaba has manufactured the S9155, which is the same torque and speed, but has better centering and precision which is required for aircraft use. You may want to check these out, our stock number for these is FUTM0215



Sincerely,
Krysta Hunt
Product Development & Support Specialist
Futaba Service Center USA

I can't find the S9155 servo on the Futaba website. I have looked at all their servos and no S9155. I am interested because I bought a 1/3 scale GP Cap580 from a friend who was transferred out of state and couldn't take his plane which is outfitted with JR DS8411 servos. The DS8411s on the elevator bounce and I have already replaced them once. I was thinking if I have to replace them again, I'd like to put something comparable from Futaba (I have always had Futaba for 25 years, this is my first experience with JR).

What Futaba servo would be comparable to a DS8411...they cost $115 and have 140 lb/in torque(approx), digital, metal gears? Do you have any specs on a S9155?

Larry

JRS

I have exactly the same problem with my two 9252 powering the elevators on my QS 72" Yak. The problem arised after som static running of the MVVS petrol engine - and now they can start vibrating after quick centering. Its irritating since the plane is new. My conclusion is that the servos just don't suit this purpose. I will continue testing them for a while - if the problem persist, I will change to hitec digitals..

Fly safe!

madman75

Why does the Futaba site say these are compatible for airplane use? I used "Find your perfect servo" on the web site and it suggested the S9351 for air use. I used 6.0 V, digital for type, standard size, put in 160 for min torque and 200 for max torque, and chose air. If these aren't designed for air use, then the web site should be fixed so people don't get this choice. I hope Tower will take these back as they have never been used.

blikseme300

My Feedback: (118)

It is interesting that Futaba's own website lists these servos for ground & air use.

I am using these in my Comp-ARF Extra 2.6 with great results. Just lucky, I guess.

Safe Flying!

madman75

I talked to a friend who had these in a H9 Sukoui and he had the same problem. He thought it was due to something else besides the servos. After I told him what I read on this forum about them, he said that makes sense. Too bad he had to buy new servos to solve his problem.
I've had mine more than 30 days so I hope Tower will exchange them for S9155 servos since I feel this is misadvertisement and no fault of mine. I haven't even taken them out of the box. I just ordered what Futaba site suggested. Funny thing is, if I do the "Find your perfect servo" search now, it still doesn't show the S9155. I also looked in the Tower catalog and it says the S9351 can be used in aircraft. Somebody needs to get this stuff straightened out.

Edge 540

Then why does Futaba recommend them for aircraft use? What exactly is different? Different potentiometer...different coreless motor?

Edge 540

Tower's website is flawed. Put S9155 in the search box and you will find them. It has to have the S too, because 9155 produces nothing. Tower has the best website layout by far of any RC manufacturer but they have the worst search engine.

Bax

My Feedback: (11)

Sorry, but no. The servo IS an S9155. That's the correct model number. The Tower search engine is just about the finest one you'll find online...you DO have to give it a good description, though.

Bass1

Boy, I'm glad I read this thread as I was 2 seconds away from purhasing 9351s' for my 50cc Yak. The 2007 Tower catalog says that these servos are also for aircraft! Maybe someone needs to let them know before others have problems.