Hi - currently in the market for servo s to outfit my ARF .60 plane. What
torque ranges should I be using in this plane? Should rudder servo have
higher torque than others? How many in-oz? Thanks Newbe
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
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 indeed answer the question as asked.
"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
and scroll down to
"Calculators & Conversion charts" if the following do not appear as links on
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
RC Calculators - C.Gadd. [Servo Torque, Wing Loading, Glow to Electric etc.]
see also further down under radios, servos etc for full charts.
Alan's Hobby, Model & RC Web Links
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.
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...
"There's a Hun in the sun!"
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...
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
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.
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
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
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.