What's the minimum amount of torque that can be used for aileron direct drive?
 

I am bulding a pica 1/6th T28 and have just about lost all patience with the bellcrank set-up for the ailerons. I think I am going to go with 2 servos for each aileron. The rest of the plane is currently using futaba 3004 servos. To save a little on weight, is it possible to use a micro/mini servo for each aileron or would they not be strong enough (torque-wise)?

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

A mini-servo in the 40 oz-in range should be OK. The Expert SL-300 is listed with 45 oz-in, equivalent to the 3004.

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

I have had very good results using HiTec 85 servos and BlueBird brand of servo http://www.balsapr.com/
Both generate 42 - 50 oz torque on 4.8 volts. The HiTec are about 1/2 the size of a standard servo and the BlueBirds are about 1/3 the size. Depends on how thin the wing is and whether or not you want them completely concealed

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

Servos for ailerons -
The original setup of one servo -plus bellcranks is superior to any sevo in wing setup -
Problem - sloppy cheap linkages .
Ailerons try to deflect up/down depending on air loading and centering is bad.

So - IF the original setup (one servo coupled to both) , was perfect -- the load on the servo would be nothing --unless you input info for deflection.
Individual , inexpensive servos can easily be pushed up or down , around center.- try it -
Very strong digital servos hold the center far better - even cheap digitals are much better at holding position than any non digital .
has to do with providing power at the slightest variation.
Real world -
done right with max servo travel and minimum aileron deflection - any decent setup will do the job for a good sport/scale.

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

Thanks for the responses. I decided to go with the HiTec HS-81 servos, which provide 36oz at 4.8V, which compared to the 44oz 3004's, shouldn't make that much of a difference (i hope). They are also super small and weigh next to nothing. We'll see...

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

Surface loads on that plane aren't excessive, the -81s should be fine.

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

I reqally shoul have said :
Trim is vague with servos which are very weak at the first degree or two of movment.
If the surfaces are LOCKED together - then the trim stays put much more easily.
Why?
for one aileron to move (thru airloads such as pitch commands), it must move the other in the opposite direction.
Tho tiny non digital servos have enough torque-after two or thre degrees of rotation, ,typically their ability to hold a "no command input" position (center)is flat lousy .

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

I'm having second thoughts about the HS81 servos. In talking to a guy at the field yesterday, he thinks I better play it safe and use the 3004 standard servo in each wing panel. He told me to move the servo arm on the 3004 versus the hs81 and there would be a noticeable difference in the amount of resistance from the 3004. Sure enough there was more resistance. The T28 will have a 65" ws and will weigh ~6-7lbs. Plus, the sizo of the gears on the 3004 is much beefier and less prone to stripping. I could go to a micro size digital servo, but they are twice the $$$ and weigh the same as a std. servo, so I figured I'd save some $$ and just stick with the 3004. So, after all this, does anyone still think I could get away with the hs81? The only reason I ask is cause I have already cut the sheeting and mounted the servo rails to fit the 81's. So, it'll be a little bit of work if I have to modify the wing again to fit the 3004's, but no big deal. Thanks.

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

I forgot to ask, but is using the HS81 for the flaps out of the question? I would imagine the stress on that servo when the flaps are fully deployed would be too much.

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

Sorry for the bump, but I would really like somone's input asap, since I need to finish this plane soon.

RE: What's the minimum amount of torque that can be used for aileron direct drive?
 

try Hitec hs-225s, they have the torque and size you're looking for.