OK, I'm looking at an estimated weight of 23-25lbs on an 85" wing... how much torque do you think I'll need in my servos?

AILERON (2)
ELEVATOR (1)
RUDDER (1)
SPLIT FLAPS (1)
SPLIT DIVE BRAKES (1)
THROTTLE (1) (probably for a G62)

I'm looking at the new Hitec HS5975HB servos which have:
Torque: 109oz @ 6v
Weight: 1/75oz
Price: $36 each

I also was looking at the HS5645MG servo at $55 each, with 164oz of torque, but they are a little heavier, cost more and may be overkill on torque?

Also, I've heard that the new resin gears in the 5975's have less play than the metal gears in the 5645's and are stronger than the plastic ones. But, my main concern is having enough torque for a my primary control surfaces without taking out a second mortgage for 7 servos.

I really like Hitec servos and have had great luck with them in the past. Competitive pricing too.

Opinions?

Neo

bump

Use this utility:

http://www.multiplexrc.com/calcservo.htm

- George

Neo.....Elevators/ailerons take the highest priority for flight.....can be flown with rudder instead of aileron but these high wing loaded warbirds prefer ailerons......so the way I select is for your model @ 25lbs (Warbird) elevators/ailerons 75 -90 ozs torque is good....rudder I like using 1/4 scale servo generally also has to turn a tail wheel as well....I use metal gear servos but only for flaps.....I like the Hitech 625mg/645mg for flaps....throttle/ldg gear valve servo can be any standard servo...they really dont carry much of a load.....Good Luck....Bill....

Try this. Let us know what you think of it. (Nope! I didn't write it and I don't know how accurate it is!)

This Excel spreadsheet has a LOT of useful info and many useful tools.

The linkage geometry work in this is nothing short of awesum.

I've noticed that the torque requirement calculations herein don't seem to ask for much torque on aileron servos. This is both consistent AND inconsistent with what I've read here online. Some folks say to use strong aileron servos yet offer no real justification or evidence to support the claim. Others say that while they have noticed a need for a good deal of torque on rudder, and a bit less on the elevator, they successfully use standard servos on 1/4 scale aerobats.


There's an underlying motive here - I'm trying to determine how useful the torque requirement calculations are.

Guys,

Thanks for kicking in some feedback.

I tried the "multiplex calc" but it kept giving me a "page not found" error when I hit the "calculate" button. Tried it from both a Mac & a PC... same error.

I tried the Excel zip file too, which worked. However it's a little over my head. From my best attempt at deciphering the info there, it looks like 75-90 oz are called for.

I don't want to loose a huge investment like this to save 10 or 20 bucks on a servo, so the 90oz would be my minimum torque. Running on a 6v battery, I can get 133oz from a HS645 for $40 each, and they only weigh about 2oz each. I think I'll use them for AIL, ELE, RDR, & FLAPS/BRKS.

I can drop to a 605BB with 94oz, at $29 and 1.7oz wgt, for my throttle.

I'll just use standard servos for retract & bomb drop.

Now, for rudder/tailwheel, I'm still trying to decide between the 645 @ 133oz versus the 5645 @168oz... probably just the 645's.

Thanks!

Neo