Sherman

I realize that there are other forums for radios and servos, but think maybe this belongs here as it relates to servos as recommended for ARF’s. I have always used the so-called standard Futaba servos, the S148, S3003 and S3004. I just fly the 40-46 and 60 two cycle powered aircraft, and have never even questioned whether the servos were o.k. Have used them in 60 powered planes such as the Goldberg Tiger, and 46 powered planes such as the GP Revolution and the TH Kaos. I noticed recently that more powerful servos were mentioned in the forum in discussing the Revolution, and then saw an advertisement for the Revolution that I think said a minimum of 54 oz-in was required. Also am interested in the Skylark 70, and a review indicated a minimum of 54 oz-in. Wow! This is why I avoided bigger planes, so I could use the standard servos, and knock on wood, have not had any failures (that I know of) from inadequate servos. Some of my friends assure me that the standard servos are fine (I don’t do any 3D) but am nervous going against either a manufacturer’s or reviewer’s recommendation. Any thoughts or information or ideas greatly appreciated.

tailskid

My Feedback: (34)

Don't kid yourself your 'standard' servos will work just fine. I'm fly the CG Skylark 70 with 3003 servos without any problems - if you are going "all out" perhaps it would be wise to upgrade to a stronger servo, but for the average guy standard servos will be more than adequate.

ram3500-RCU

My Feedback: (221)

Yes, don't worry about them in this size range. Just keep your linkage tight, and use closer holes on the output arm to give the servo more leverage, and you will be fine. Keep in mind, that with a more sophisticated servos comes more precise control not just more power / torque, along with the additional cost. Is it worth it to you on this plane, you must ask.

da Rock

You can also jump the spec a bit and not break the bank doing it.

Hitec makes a servo that works great for aileron setups. It's their HS225. They call it the Mighty Mini. And it works especially good in wings because it's less than an ounce and puts out almost 60 oz/in torque. And it's only about $21 each from Tower. I use 'em on ailerons and motor and save 1.5 ounces at least over standards. Most standards are over 1.5 oz each. Using 3 saves money too since Tower gives a quantity discount too. Saving over an ounce actually is worth doing, and these things are more than adequate for the job.

Worried about torque? Inner hole on the servo arm, outer hole on the surface horn. That insures you start with mechanical advantage for the servo. Then you adjust that rigging to get the throws you need and you almost always wind up with the servo torque mulitplied by the leverages. With out setups, you actually don't get more torque at the surface, you simply reduce the servo's effort. Basically the same thing, just how it actually plays out. Less stress on the servo and less battery drain.

I don't know of any other servo that is as good a deal and added advantages for the job than this one. Or I'd be mentioning those too.

krproton

I would like to "echo" what ram3500-RCU said...usually, with "stronger" (higher torque) servos comes some amount of increased precision and reliability--not only "out of the box," but in the long run too as stronger/better servos may have ball bearings and last longer as they may not be working as hard. "Standard" servos are definitely fine for most .40-size planes and some .60-size planes as well--depending on their intended use--Sunday sport flying--just "poking holes in the sky," stuff like that. But if you prefer more flight precision or if you fly more aggressively, then better servos may be required.

skiman762

Don't forget a servo is rated with a 1 inch arm so 50 oz at 1 inch is 75 oz at 3/4'' and 100 oz at 1/2'' more then enough for most 40 60 size planes unless your flying on the fringe ..
Also you can get low end digitals for under 50 bucks I never understand why some people will go through 2-3 planes at 100-200 bucks but not want to spend the money on good servos that will last for a lot longer then most planes will
plus the fact that you will enjoy much better control over your plane

ram3500-RCU

My Feedback: (221)

Great post. You are right on IMO.

Charlie P.

I fly .60 size models on the S3004 servos. I do like the HiTec 605BB High Torque (now HiTec HS 635 HB) for the rudder, even on .40 size taildragers. You definately want a "tougher" servo if it is a single aileron servo.

I'm liking the Futaba S3152 servo on bigger birds.

And I use S3004 servos on throttles up into the large gas engine models. No sense hooking up a big $ servo for a little job.

gunfighterII

Here's an interesting servo torque calculator for your amusement.

http://www.csd.net/~cgadd/eflight/calcs_servo.htm

MinnFlyer

My Feedback: (4)

Another thing that is interesting is how back in the 70's we used to fly some BIG airplanes with a single standard servo for BOTH ailerons, but now they say you need two on a 40-size plane.

Ever think they're just trying to sell more servos?

Charlie P.

You remember ANY .40 sized models in the 70's that had a 2" aileron throw? We're control surface happy now-a-days.

MinnFlyer

My Feedback: (4)

Good point Charlie, and for 3-D, two servos is a must.

But on a trainer???

Charlie P.

True enough. True enough. We overdo things a lot in the US of A.

Look at the Sig Kadet Senior. 80" wingspan with a .40 size engine. That's a design that would have fit in during the 1970's. Most 80" models I now see at my IMAA club have 40 to 50cc gas engines or 1.2 to 1.60 glow. I remember .40 being a "large" engine and a lot of .074 and .15 size models that we now would slap .46 size engines on. We also fly models a LOT harder than I remember seeing as a kid/teenager. I flew mine like they were eggshells - and stick and tissue isn't much less fragile. We're suffering a bit for the weight penalty of iron-on coverings and solid fuselages.

Bigger servos and heavier linkages need bigger engines which add weight and require bigger servos and heavier linkages which add weight and . . .

A vicious circle.

MinnFlyer

My Feedback: (4)

In the 80's I built a Goldberg Chipmunk with an OS 90 4-stroke that had a single standard aileron servo, and you couldn't fly a plane in a more punishing way that I did.

Now, a 40-size airplane is set up for two servos.

The answer is simple, a few years ago, going to two servos was the rage and every manufacturer jumped on the bandwagon.

Last year's "rage" was lipos and brushless motors.

This year it's 2.4GHz systems

Every few years manufacturers need to have something to make their products "New and Improved". I'm not being cynical, that's just life in the world of sales. Sometimes, something truly unique and innovative comes along (Like brushless motors and 2.4gig systems). But when it doesn't, they have to rely on creative marketing to make you THINK you can't live without whatever the "flavor of the month" is.

jrf

My Feedback: (551)

Use the servo torque calculator link above and enter a normal control surface with 15 degrees of deflection. (Normal for sport flying.) Then just change the deflection to 45 degrees. (Normal for 3D.) That explains a lot.

Jim

Charlie P.

Or four. Ultra, Hot, Wild Stiks, etc. I just dropped seven sevos into a .46 size Hot Stik.

Can't deny we are supposed to hop on every trend and new concept in R/C. I love 2.4GHz - the only other frequent flyer at my club on my channel just got one so now I don't need it. It's not just R/C.

I think I'll go put on some groovy Vinyl 33-1/3rds or an 8-track and type a long, nasty letter to the AMA on my Commadore 64.

My solution is to boycott S.P.A.D.s, LiPo batteries and electric flight motors, helicopters, turbine jets and rechargable wireless glow-plug drivers. That, and I'm already too heavily invested n toys.

MinnFlyer

My Feedback: (4)

Oh, I'm not saying that progress is bad, quite the contrary. I LOVE my 2.4GHx, and for electrics, Brushless motors and LiPos are revolutionary.

It's those times when they need to create something just for the sake of making their product "New and Improved" that gets me

Charlie P.

I gotta believe that's pretty accurate, but it is astounding what effect speed has on required torque! No wonder we see "3-D" models rip themselves apart! I suspected but now I'm convinced I fly way too fast! Having 2-56 contol and/or flexible rods has probably saved me lots of models and certainly servo gear teeth!

MinnFlyer

My Feedback: (4)

HiTec just unveiled a new mini servo with a twist... It's geard will slip if they are over loaded, but the servo will still return to center.

I'll bet we'll be seeing that in a lot of larger servos soon - nice feature!

tailskid

My Feedback: (34)

two servos in the wing solved the problem of the single servo/pushrods hitting the servos/pushrods that were already in the fuselage