Problems with ailerons
 

Why do the ailerons go down farther then they go up.i.e., turning to the left--left aileron going up and right aileron going down. The right one goes down farther than the left one goes up--turning right--right aileron going up and left one going down. The left one goes down farther than the right one goes up. What do I need to do to make them even. (if they are supposed to be even)

RE: Problems with ailerons
 

Make sure your trim and sub trims are centered then reposition the control horns on the servo splines one spline - that would even it out or give offset with a little more up aileron.

RE: Problems with ailerons
 

There could be a lot of reasons why this is happening. One could be the "neutral" or "center" position of the arm on the servo. Another could be not having the horn positioned correctly in relation to the hinge line of the aileron. For most high wing/sport plane a little "differential" is nice in the ailerons BUT in the other direction. This is because it helps prevent adverse yaw during turns. This is also used in full scale planes.

Desirable = more up than down.

Can you post a pic of your servo installation and linkages?

RE: Problems with ailerons
 

Generally, especially on high wing planes like a J3 Cub, you want the aileron going up to have much more travel than the one going down. You do this by the way you couple the servo arms to the push rod usually. If the servo arm (when controles are at neautral and servo on lower side of wing)by having the arm on the servo positioned so that the arm is forward of the center shaft. You can also do this by having the pivot point on the control horn on the surface being moved ahead of the hinge line. Now if the servos are mounted above the wing, then you reverse this procedure; i.e. servo arm canted aft or pivot point aft of hinge line at the moveable surface. Of course, if you have a computerised transmitter, you can often program the degree of throw in each direction.

RE: Problems with ailerons
 

Here is the pictures I hope--

RE: Problems with ailerons
 

Rodney--this is on a Goldberg Cub

RE: Problems with ailerons
 

on a flat bottom wing(trainer or cub) the aileron going down causes more lift and rolls the plane. I.E. down right aileron is rolling your plane left. if your plane handles well with the diferential it curently has your good to go;)

RE: Problems with ailerons
 

Hard to tell from the pics but it appears the the torque rod arm may have a fairly large lean forward toward the servo. This will automatically induce some differential. BTW - some sill give you a hassle for using those connectors on the servo arms but I won't because I use them too. Just be sure to use the metal retainers and get the screws tight enough.
Try a 6 arm wheel and install it with an arm dead ahead and aft but don't connect to those. Attach to the pair that are toaard the leading edge and see how that works out. This will induce differential.

RE: Problems with ailerons
 

Sorry, you have it backwards it part. The aileron that goes down DOES lift the wing but it also creates MORE drag than the the other aileron does when it goes up. THIS is what causes ADVERSE yaw.

RE: Problems with ailerons
 

From the RCU Glossary:
It is the down aileron that causes greater drag and pulls the plane in the opposite direction one would expect ie left stick rt aileron down and nose to the rt unless rudder is properly applied. A cub is a good example of this characteristic.
To correct for this many computer radios will allow you to program in differential to give more up than down aileron.

RE: Problems with ailerons
 

Whenever the servo arm and the pushrod do not make a 90degree angle, the pushrod will be moved more in one direction than the other.
Same situation where the pushrod connects to those torque rods in your picture.
AND same situation where those torque rods bend down inside the wing and go out into the ailerons.

The servo does its moving in a circle. The circular motion winds up being sort of a straightline push and pull for the pushrod. When the pushrod is connected on the servo wheel or arm at a 90 degree angle, the pushrod is basically at the center of that circular motion it will see when being pushed or pulled. So when the servo moves 45degrees either way, the pusrod moves the same amount both directions. But say you were to connect the pushrod on a servo wheel at the 45degree location.

Clockface example.......
Pushrod connected at 3 o'clock.
Servo move to 1 o'clock or to 5 o'clock and the pushrod moves the same UP and DOWN.

Now connect the pushrod at 1 o'clock.
Servo moves from 1 to 11. How far would the pushrod move? Almost wouldn't move up and then would move just as little back down
Servo moves from 1 to 3 and the pushrod moves down as much as it did moving from 3 to 5 when it was connected at 3.
That's how people get differential out of their pushrod rigging.

And that's also an example of what happens when the angles aren't 90degrees.

RE: Problems with ailerons
 

Hey, goirish, do me a favor and check something while you're messing with your ailerons.

Hold the torque rod fixed with one hand and try to move that aileron up and down. If it moves at all, there is a simple fix. And more to the point, that sometimes causes the ailerons to be out of square (the 90degree angle deal) and show more throw one way or the other. Needless to say, check both ailerons.

You know, this needs a picture or two.

RE: Problems with ailerons
 

Here we have a servo wheel with a pushrod connected. Pushrod is blue and connected at 12o'clock. You move your stick 15degrees and the servo moves the amount shown by the blue dots. Pushrod moves the light blue amount.

Now connect the pushrod to either of the holes at the red dots. Move your TX stick 15 degrees and the servo moves the same rotation it did just before. But the pushrod barely moves except sideways.

That's how differential happens at the servo.

RE: Problems with ailerons
 

Using a computer radio to program aileron diferential is a great idea but it requires dual aileron servos. This plane uses one aileron servo.

RE: Problems with ailerons
 

OK, let's try another busy picture.

The picture shows 3 pushrods, a blue, a green, and a red one. They are attached to a round servo wheel.

When the servo wheel moves 20degrees, the blue pushrod is pulled to the left the amount shown by the purple bar.
When the wheel moved that 20 degrees, the red pushrod is pulled the tiny little amount shown by the pink bar.
That shows how the same movement of a servo wheel in a circle can wind up moving pushrods different amounts in a straight line.

Now lets look at how to use that to drive a pushrod one way a lot and pull it the other way just a little, from the same amount of rotation. The amount you get when you move your TX aileron stick full left or full right.

The green pushrod is hooked to the servo wheel as shown. And the servo is sitting at neutral. Your aileron stick is centered in the TX.

You move the stick all the way right, and let's say that moves the servo wheel clockwise about 45degrees. The pushrod moves to the right the amount shown by the big green arrow.
Now you move the stick all the way left, and the servo wheel would move counter-clockwise. The pushrod end moves to the left and down but only moves left the amount shown by the little green arrow.

If the green pushrod had been hooked to an aileron, it would have pulled it a little bit one way, but would have pushed it about 2-3 times as much the other way.

RE: Problems with ailerons
 

Is this the same as + "Ackerman" ?


Bob

RE: Problems with ailerons
 

Yup caught it myself and edited[:@] thanks

RE: Problems with ailerons
 

I just copied the glossary to explain the effect. I didn't say it ALL applied to him.

RE: Problems with ailerons
 

Sorry for the delay in getting back with you all. 2 questions: 1) should I then use a round wheel so I can adjust the throw or 2) should I go to 2 servos? If I stay with one servos should I attach both pushrods like the green color in DaRock's post #15? I have remove both ailerons and will be putting on both new ones. One had a slight warp or twist, not bad but might as well fix it now as later because of a crash---ugh--I hate that word.

RE: Problems with ailerons
 

Dual servos and NOT using torque rods would be the best solution. Install the servos out in the wing and use horns attached to the ailerons directly. Any type of output wheel could then be used and differential be gained by connecting with the arm at a point between the blue and green position. Experiment to find the angle that gives you the result you like best.