im sorry but if you don't want to do "the math" maybe not build a scale aircraft , I think it will be the last plane you get to work on!

Why would you want to have rc radio equipment in a full scale anyway?

I am probably using a bit of over kill but my personal rule of thumb which hasn't let me down yet is this for an unlimited aerobat. Each servo must have enough torque to be able to pick the entire airframe off of the ground with no problem. EX a 28 pound plane with 450oz on every surface except the throttle and 1.5 x the weight of the plane on the rudder . guaranteed no blowback .

Appropriately sized and powered boost tabs may be the answer you are looking for. They have been used in full sized planes for years.

The company I worked for once outfitted a C-172 with a system that moved the control surfaces. It was a box that took the place of the seat and it was connected to all of the controls. Pretty cool idea for what they were using it for.

a truly cold weather thread.
Only during building season would a thread like this come about

Originally Posted by Cryhavoc38

a truly cold weather thread.
Only during building season would a thread like this come about

I just notice that. lol

Love this thread lol would this be of any use -

http://www.mnbigbirds.com/Servo%20To...0Caculator.htm

Just use a 7990 or 7980 servo and be done with it
OR
If you can squeeze one of the killer Seiko servos in the hole even better - bit of a weight penalty though

Originally Posted by rtfm

Hi guys,
I am trying to estimate how much torque is required to deflect a given control surface. Is there a simple (ie not based on advanced math) way to calculate this?

What I am trying to do is to activate the control surfaces of my full size plane (single seat) with servos. I have split the control surfaces (ailerons, flaps and rudder) into a number of separate panels both so that I can tailor each panel's deflection to correspond to the lift distribution of the wing/rudder, but also to make servo activation more manageable.

The benefits of controlling the control surfaces with a RC transmitter are quite exciting. I'd like to leverage the huge benefits of all the mixing which is available on today's RC transmitters. I will build in a full cable-activated backup to a separate control stick in case of radio failure. But I'm not expecting to use it. Modern RC kit is pretty reliable.

For example, I am working with the following actual numbers for one of my aileron control surfaces:
Span: 8.7 inches
Chord: 5 inches
Deflection: 35 deg
Speed: 155 mph

The big question is, using the above parameters, what size servo would I need to do the job?

Another more demanding control surface is at the rudder:
Span: 10 inches
Chord: 8.2 inches
Deflection: 30 deg
Speed: 155mph

Anyone care to give me a hand with this?

Regards,
Duncan

According to servo calc http://www.radiocontrolinfo.com/info...ulator/#Torque

The torque needed would be 198 ozin (315 ozin recommended) assuming the throw is 15 dgrees each way and servo arm moves 15 degrees each way Timees X 2 if you assume 30 Degrees servo arm throw and 30 degrees deflection each way. so recommended would be 730ozin or 53kg cm

Oh and in case someone points out the original post was ages ago The calc may be useful to others

A bit late to the party...

A long time ago I found this spreadsheet tool for calculating servo loads. Its very well done and I wish I could remember who the author was to give proper credit. Its one of my invaluable setup tools along with P.E. Rivers prop power worksheet

See attached.

The mnbigbirds is one of the most accurate measuring calcs that I have ran test on. At first it seems the oz-in given is very low but when put to the test of actual loading was it the most accurate.

Originally Posted by acerc

The mnbigbirds is one of the most accurate measuring calcs that I have ran test on. At first it seems the oz-in given is very low but when put to the test of actual loading was it the most accurate.

I just plugged in some numbers, that page gives the exact same result as the spreadsheet I posted up. They are probably using the same formulas on the back end.


I'm not surprised the numbers sound low... Marketing and internet forum one upmanship over the years have gotten guys expectations of servo torque requirements all out of whack. This is why we see posts telling new guys to stick 500oz servos in quarter scale planes

Originally Posted by jharkin

I just plugged in some numbers, that page gives the exact same result as the spreadsheet I posted up. They are probably using the same formulas on the back end.


I'm not surprised the numbers sound low... Marketing and internet forum one upmanship over the years have gotten guys expectations of servo torque requirements all out of whack. This is why we see posts telling new guys to stick 500oz servos in quarter scale planes

I have been using it for a while now. I have been running some of the lowest flight energy consumptions imaginable. A 46% Pitts with nine servos only burning around 400 mah per ten minute flight. If the servos were not up to the task the mah would be much higher if not failing.

Yep, sounds about right.. I use about 250-300mAh on my 30% for a 15 min flight.


People go so far overboard on servos and batteries today its kinda funny.