Helijack

I am not a math person. Need some advice on how much torque I need in servos for a scratch build 1/6th scale Storch. I think I want to go the 1 servo per control surface route, ailerons, elev(2), rudder, throttle, and flaps(2). I think I want to mount them similarly to the latest method of in the rear fuse for tail and in the wing for the wing stuff. Partly because of convenience and partly to be able to do the cockpit.

This is a 93" wingspan, electric power, estimated weight of 12-15 pounds RTF. I am guessing top speed will be around 25 mph. My flying style is such I would not be doing aerobatics, maybe a stall turn and occasional loop at altitude, I prefer to play touch and go, STOL stuff, scale slow flight.

I really would like to use mid sized servos, digital, not cheap stuff. Will be a PCM system, preference to JR and Futaba servos, will not even consider other brands. Size and weight is very important to me, just as much as being able to control the surface effectively.

Thanks
Jack

BMatthews

There's online servo torque calculators linked in this thread in Aerodynamics....

http://www.rcuniverse.com/forum/m_2867994/tm.htm

Be sure you select some worst case conditions and when it tells you how much torque you need then figure on servos that can deliver at least 150% of that amount to ensure they do not load down and stall or even come near to it. Servos that grunt are slower and more prone to failure. Servos rated for twice what you get as a figure from the program are ideal.

Helijack

Thank you, that should give me a new toy for awhile.

Campy

My Feedback: (1)

here is another link for calculating servo torque.

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

johnnyo

My Feedback: (7)

A good rule of thumb on servo selection. is 1oz of torque for each sqare inch of control surface. Example: Elevator half (not the entire stab) is 12 inches x 4inches this equals 48 square inches (12x4=48) a servo with aronund the 48 in oz of torque would be adiquate for each elevator half. You can use this method on all the control surfaces.
All servo manufactures list their torque output some where in their literature. Some list it for both 4.8 volt and 6 volt..
JohnnyO