Servo torque

what is minimum torque an RC plane servo should have? I am putting together an ARF 60 high wing design... Thanks newbee

Standard servos on all controls will do just fine...

Enough to move the control surface when the plane is at maximum speed. Dr.1 Driver "There's a Hun in the sun!"

A standard servo has 40-50 in-oz. of torque. That should be enough. Futaba 3003, 3004, 148 servos are 42 or 43 in-oz. at 4.8V. Using a 6V battery ups that about 15%. Other manufacturor's servos are similar in torque.

Jim - AMA 501383

Newbee wrote:

Great Thanks Jim... You just made my job alot easier... Newbee

you asked a generic question and got a generic answer, Had you provided more details regarding WHICH plane, and how you intend to use it, you might have gotten more specific answers. in general, a "standard" servo is enough, BUT I have one "60 size plane that requires something with at least twice that amount of torque.

so, Dr.1 Driver did >OK great answer... I'll just look for that answer on the servo specs...

"Puttiing together an ARF 60 High Wing" in almost all ARF illustrated instructions seen to date, pictures of the manufactuere's completed model shows actual servos in place. Read the numbers e.g. Hitec HS300, JR 507, Futaba S148 are almost identical in size and torque. If others used, refer to

and scroll down to "Calculators & Conversion charts" if the following do not appear as links on NG. Conversion & Calculation tables etc Convert - free download - convert units from one type to another **** Entisoft Units -- Measurement Conversion Calculator -- Multiplex Servo Analysis Performance Slide Rule Calculator - Servo torque, Horsepower, Stall Speed etc. RC Calculators - C.Gadd. [Servo Torque, Wing Loading, Glow to Electric etc.]

That's interesting! Especially since I can recall the days when servos did a measily 24 oz. Yet we flew .60s and bigger, pattern, pylon, scale and helicopters. Just have to know how to work with what you have.

Thanks AT.. A very helpful site...

DR 1 - if you didn't really intend to help then its best to just stay quiet... if I left out info that prevented you from providing a good answer and you really wanted to help then you could have asked (newbee remember)... you did neither... we have a name for folks like you... but again it probably won't help so I'll just stay quiet... Newbee

Sorry, you'll just have to put up with me unless you have killfile capability.

As for my answer, calculating the sufficient amount of torque necessary for any application is damn near impossible, and difficult to the extreme. Even given plane size, weight, speed, control surface areas and angles of deflection, and a few other items, you need to know and be able to apply physics in relation to force vectors. I'm sorry I didn't do all your work for you. Some newbees want the answers handed to them on a silver prop.

And veteran R/C'ers have names for people like you, too... Dr.1 Driver "There's a Hun in the sun!"

Keep at it Dr. I'm sure you can get even more anal about the whole thing!

i read this with a chuckle. seems the first reply about standard servos was pretty sufficient, but as always, someone always has to throw in their "knowledge". DR whatever, I have always considered you somewhat boorish, and your criticism of the question was pretty ridiculous. guys like you live for the chance to jump on the internet and be all things RC, even when half the time you have no idea what you are talking about. but to attack a new modeler because you wanted to show off....pretty tasteless. as for those of you who think there is such a thing as calculated torque for a servo, think again. this is a situation where the answer precedes the question. no one sat down and calculated that two JR 8411s on 6v would be sufficient for the 3D aileron of a 40% airplane (based upon the theoretical flight loads) - they tried it and it worked. and from there someone created this chart that shows that almost

400 oz of torque is "needed" to properly support a 40% 3D aileron. And so it begins...everything this guy needed to know was expressed in the second post, and why it had to go any further, i don't know...

So, who the hell are you? If you don't like my posts, killfile me, PLEASE. Dr.1 Driver "There's a Hun in the sun!"

If you have ever listened to a CB radio for a few minutes, you will understand this newsgroup. It is made up of all kinds of people, with various opinions and myriad styles of expression. This is an unmoderated group, so anything and everything is likely to show its face here from time to time.

Just as everyone else has the right to post here, so do you two. The greatest thing about it, though, is that no one has to read either of you, or me, for that matter.

Ed Cregger

well so much for the attachment.

snarf the excel spreadsheet here:

scroll down to post 10

If you didn't like my first answer, you would have really HATED my second choice: The TLAR system (That Looks About Right). Dr.1 Driver "There's a Hun in the sun!"

There is a servo size calculator on Multiplex website

The poor man rule is 1 ounce of torque per square inch of control surface. If an aileron is 1" wide and 20" long than 20 ounces of torque should be enough.

However, the faster you go the more torque you need to move the control surface.

With all the infinite variables involved the only true way to know if a servo is big enough is to fly the plane and see if it gets mushy or erratic at maximum speed, if so you need a bigger servo.

The next question is how well the servo holds its position. Holding torque and moving torque is very different. You need an servo that can both move and hold position.

This is were digital servo are becoming increasingly popular, they have excellent holding power but at a sacrifice of battery life.

So in the end you need a servo big enough to move and maintain a deflected position of the control surface when the plane is a maximum speed.

Unless the plane is going to fly faster than 60, 70 mph then 1 ounce of torque per square inch of control surface is probably big enough.

You might find the calculations here rather surprising.....

David