Let's talk about servos - Whatever is on your mind

[nidly]

Torque rods, huh? That sounds like a great name for them. They don't have a lot of travel and that's probably why they are so hard to move.

I was really more or less asking about my elevator servo and wondered why according to the calc I can get away with about 10% of the stock servo's torque. It just seemed quite odd and I wanted to make sure I didn't make a huge obvious blunder when calculating it. Realistically I'll probably get away with about 25% of the stock servos torque. I even doubled the UP elevator throw that I use for landing nicely. I just happened to spot another post where another user also used about double the stock throw for the elevator.

Hopefully it'll be all good since I am doing my first 4s powerplant, new servo, centering all rods, fiing a loose wing and installing a new battery to my e-stik. It's not much , but it's MY most powerful plane. I really enjoy flying it and now I enjoy using the servo calc.

[Aristidies]

Looking to find what servos from HK are compatible to the Hitec HS-65 and HS-85. Is there a datbase for comparison somewhere?
Thanks

[dahawk]

Might be expressed in grams or g

[Bill G]

Originally Posted by nidly

Torque rods, huh? That sounds like a great name for them. They don't have a lot of travel and that's probably why they are so hard to move.

I was really more or less asking about my elevator servo and wondered why according to the calc I can get away with about 10% of the stock servo's torque. It just seemed quite odd and I wanted to make sure I didn't make a huge obvious blunder when calculating it. Realistically I'll probably get away with about 25% of the stock servos torque. I even doubled the UP elevator throw that I use for landing nicely. I just happened to spot another post where another user also used about double the stock throw for the elevator.

Hopefully it'll be all good since I am doing my first 4s powerplant, new servo, centering all rods, fiing a loose wing and installing a new battery to my e-stik. It's not much , but it's MY most powerful plane. I really enjoy flying it and now I enjoy using the servo calc.

It's actually true that the required servo torque using real aeronautical calculations is much less than we commonly use. Your 1/10 calc sounds reasonable. Planes obviously fly much better with reduced weight, and so far I've had no issues with using servos as small as the BA2.5 on 36" jets. Maybe a 100mph jet may have flutter issues, but at 50-60mph I've had none. With low required throws, the servo gains even more advantage.

I think more of the reason folks over servo is for the redundancy. I've had at least one pushrod come unstuck during ground check, and a smaller servo may not have been strong enough to break it free. Had that sticking event been in the air without a ground check and not moved, then we all know the results. The larger servos are more reliable also, as small things tend to have issues, but a small servo with ample torque is obviously fine as long as it works. I'll keep using servos as small as possible, as the benefit in weight reduction is quite noticeable. Retracts are about the only place I've found the need for 7-9gm servos in park sized planes. Some instances where a larger servo can be mounted far forward when ballast is required, is also a reason I'll use larger servos.

[quorneng]

Generally we do seem to over estimate servo requirements.
The Boeing B29 at 120,000 lbs and 350mph had no power assisted controls, just the strength of 2 pilots.

[AEAJR]

Originally Posted by Aristidies

Looking to find what servos from HK are compatible to the Hitec HS-65 and HS-85. Is there a datbase for comparison somewhere?
Thanks

Compatible? I think you mean comparable.

I am not aware of any such table or DB but.

Look a the specs of the HS-65 and HS-85 and look for similar specs at HK. That is what I would do.

[CrimzonRider]

Google is an amazing thing....just found this......I'm kinda in the middle of a search too, for the perfect 9g mini-MG servo.
(lil bit old on the updates....09')

http://www.fatlion.com/sailplanes/servochart.html

cr

edit: found the motherload.......

http://www.servodatabase.com/servos/all

[AEAJR]

Good Find Crimson Rider. Thanks for posting the links.

I did some sorts and found some pretty tiny servos as well as some monsters intended for industrial rather than RC use.

Interesting!

[chamowllie]

Hello...Newbie pilot here...So i have a question about Servos...I have been doing nothing but googling servos and thought this to be a good place to ask. Here is my question...I am trying to find a suitable substitue for the Futaba S3107 servo. Here is the link on the specs of the 3107 wanted to know if there were any other brands alittle bit cheaper that are compatible with this type/model servo. Any help woul;d be greatly appreciated!!

Anyways, like I said I am new to this hobby and have fallen in love with it...I have found that the electric is by far the cheapest route to go...It just seems you get more bang for your buck so to speak. I am currently flying the Ares Gamma 370 w/brushless 370 motor..all upgrades that are available have been upgraded...plane flies great...So now I am venturing out to something just a tad bit more "sportier"...I recently found on CL brand new Electrify Syncro (EDF powered) comes with two separate wings (glider/trainer type and sport wing). This is an ARF model so I am putting it together and trying to find servos for it. I spent most of my money on the power plant/ESC portion of it, and am dying to get this thing in the air...lol!!! plus I bought a Heli also (MJX F45) also very fun to fly...GEEZ...if you are not careful you can easily spend more money than you think...heli is cool to fly but I want MORE!!!! LOL!!! I have been flying my Gamma for about 2 months now...do all kinds of pretty neat tricks with what power I can squeeze out of those batteries...lol!! but now I want to take this syncro and see what it can do. Any advice, info or help will be greatly appreciated!! Thanks guys!!!

[chamowllie]

Apologize...forgot the link to the Futaba servo specs:

http://www.servodatabase.com/servo/futaba/s3107

[Turner]

There are lots of different servos available and many sources. It's just a matter of comparing specs. If we knew where you were it might be easier to point you towards sources.

Here is one with similar specs:

http://www.servocity.com/html/hs-55_sub-micro.html

[AEAJR]

Originally Posted by chamowllie

Hello...Newbie pilot here...So i have a question about Servos...I have been doing nothing but googling servos and thought this to be a good place to ask. Here is my question...I am trying to find a suitable substitue for the Futaba S3107 servo. Here is the link on the specs of the 3107 wanted to know if there were any other brands alittle bit cheaper that are compatible with this type/model servo. Any help woul;d be greatly appreciated!!


Anyways, like I said I am new to this hobby and have fallen in love with it...I have found that the electric is by far the cheapest route to go...It just seems you get more bang for your buck so to speak. I am currently flying the Ares Gamma 370 w/brushless 370 motor..all upgrades that are available have been upgraded...plane flies great...So now I am venturing out to something just a tad bit more "sportier"...I recently found on CL brand new Electrify Syncro (EDF powered) comes with two separate wings (glider/trainer type and sport wing). This is an ARF model so I am putting it together and trying to find servos for it. I spent most of my money on the power plant/ESC portion of it, and am dying to get this thing in the air...lol!!! plus I bought a Heli also (MJX F45) also very fun to fly...GEEZ...if you are not careful you can easily spend more money than you think...heli is cool to fly but I want MORE!!!! LOL!!! I have been flying my Gamma for about 2 months now...do all kinds of pretty neat tricks with what power I can squeeze out of those batteries...lol!! but now I want to take this syncro and see what it can do. Any advice, info or help will be greatly appreciated!! Thanks guys!!!

Originally Posted by chamowllie

Apologize...forgot the link to the Futaba servo specs:

http://www.servodatabase.com/servo/futaba/s3107

My goal is always to help you learn to answer your own questions and help you become knowledgable rather than answer your question and keep you dependent on others.

Did you read the first post? do that first.
http://www.wattflyer.com/forums/showthread.php?t=64417

Now, why this Futaba servo? Why are you focused on this servo?

You want a suitable sub for this servo. How do we know if it is even right for the use you plan? What would you use the Futaba servo for if you were to use it?

We need more information. Read that first post FIRST, then answer.

If you REALLY want to learn about servos, read the whole thread. There is a WEALTH of info here if you will only take the time to read it. By time you get back to this post you will be telling us what servos you selected and why.

[chamowllie]

Reason for that type servo is bcoz thats what the manual calls for on the Electrify Syncro. Futaba S3107...I did read the first post...as a matter of fact I read this whole thread and spent most of my day clicking on links through this thread...lol!! I am new to this and all of this servo talk is like trying to understand a different culture...but I am certain the longer I am in it the better my understanding of what each measurement and what I can or cant use, the torque and all that information I can come up with my own answer. Here is my ordeal, the specs measurement for the Futaba S3107 "According" to the manual for the Syncro says it is 20x10x20...now when you look up the specs for the actual servo it states 22x11x20...now I know these are in mm...is 2mm really going to throw it off by that much? Also the manual states that the servo weight is 3.0oz...really? actual specs say it is 0.32...Yes I did double check to make sure I wasnt reading it wrong...3.0oz...speed and torque is about acurate 4.8v: .012/60 and Torque: 17.0 oz-in...thats why I am a little bit thrown off for a loop here...measurements and weight are off but speed and torque are exact. Also Turner I am located in Pensacola, FL.

[AEAJR]

Originally Posted by chamowllie

Reason for that type servo is bcoz thats what the manual calls for on the Electrify Syncro. Futaba S3107...I did read the first post...as a matter of fact I read this whole thread and spent most of my day clicking on links through this thread...lol!! I am new to this and all of this servo talk is like trying to understand a different culture...but I am certain the longer I am in it the better my understanding of what each measurement and what I can or cant use, the torque and all that information I can come up with my own answer. Here is my ordeal, the specs measurement for the Futaba S3107 "According" to the manual for the Syncro says it is 20x10x20...now when you look up the specs for the actual servo it states 22x11x20...now I know these are in mm...is 2mm really going to throw it off by that much? Also the manual states that the servo weight is 3.0oz...really? actual specs say it is 0.32...Yes I did double check to make sure I wasnt reading it wrong...3.0oz...speed and torque is about acurate 4.8v: .012/60 and Torque: 17.0 oz-in...thats why I am a little bit thrown off for a loop here...measurements and weight are off but speed and torque are exact. Also Turner I am located in Pensacola, FL.

OK, great, now we are getting somewhere.

So, I will restate that my goal is to help you learn rather than just give you the answers so bear with me as I walk through this.

If you want you can go to the torque calculator to see how much you NEED, but I would bet it is under 12 oz-in for this plane. You would need the size of the surfaces, angle of deflection at max throw and the speed, which you probably don't know. But let's guestimate at 60 mph. Run the numbers if you like. If you don't know deflection, use 30 degrees as a good guess.

Looking at the manual - page 6 I see this is a foam wing and that the pocket is cut for the Futaba servo. But foam is easy to trim, so we have quite a bit of latitude in what we do. If the servo is a hair bigger or a hair deeper we can just cut away some foam. If it is a bit smaller we can fill with foam tape or some kind of glue that fills gaps. A couple MM isn't going to hurt anything.

We probably don't want to go more than 50% heavier as that starts to add up on a plane this size.


Here is the Futaba Servo and the specs that we will look at - $18
http://www3.towerhobbies.com/cgi-bin...&I=LXDTB5&P=ML

SPECS:
Speed: .12 sec/60° @ 4.8V
Torque: 17 oz-in (1.2 kg-cm) @ 4.8V
Dimensions: 0.9 x 0.4 x 0.8" (7/8 x 7/16 x 13/16")
(22 x 11 x 20mm)
Weight: 0.32 ounce (5/16oz) (9.0 grams)

So we want a servo that, in my estimation, as 15 oz-in of torque or higher at .5 oz or less in weight. That would be most servos in the 9 gram class.


I have had good success with GWS servos in small electrics. Here is one that would be a good fit.


GWS Naro+F/HP/BB $9
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHHB3&P=7

Length: 22.2mm (.87")
Width: 11mm (.43")
Height: 24.95mm (.98")
Weight: 10g (.35 oz)
Speed: .10 sec/60°
Torque: 24 oz-in




I have also had very good luck with Hitec HS-55s for this type of use - $10
http://www3.towerhobbies.com/cgi-bin...&I=LXTX42&P=ML

SPECS: Speed: 0.17 sec at 60°
Output Torque: 15.27 oz-in (1.1 kg-cm)
Weight: 0.27oz (7.8g)
Length: 0.89" (22.8mm)
Width: 0.45" (11.6mm)
Height: 0.94" (24mm)


There are dozens out there in the "9 Gram" class but these would be my recommendations based on personal experience. Note that the GWS and Futaba servos are about 25% faster than the Hitec HS-55. Normally I would not worry about that but if this is a very high speed plane, excess of 75 mph, I would pay attention to that. Or if it were a 3D plane, that might be important.

Though the HS-55 is a little slower, I don't think that you will notice.

So now you have some choices or you can go looking for others.