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Mehcanical Aileron Differential

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Old 08-19-2010, 02:57 PM
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KitBuilder
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Default Mehcanical Aileron Differential

I have built an older low wing kit per plan and kept it with asingle servo in the center of the wing.

I found thebelow pic on the web from this site: http://www.modelaircraft.org/mag/ftg...1/31main4.html

My question is: do I need to have the offset torque rod? I didn't think I did as long as the servo connection was
behind as it states in the picture / text. . I assume I will just get less differntial with the offset only at the servo end.
MY torque rods areinstalled more vertically
For airplanes with the servo mounted to the top of the wing, the connection to the servo should be behind the center of the wheel and the connection to the aileron horn should be in front of the hinge line.
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Old 08-19-2010, 03:06 PM
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Default RE: Mehcanical Aileron Differential



Tips and Techniques has a thread started on Uneven Aileron Throw - How To?

And after a coupole posts, that one has ended at the same question I posted here regarding torque rod relation to Aileron. Although it does have better diagrams!!

Anxiously awaiting answers......

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Old 08-19-2010, 03:24 PM
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Default RE: Mehcanical Aileron Differential

Mike, you are correct. You will get some differential with the takeoff from the servo biased towards the aileron.
Chuck
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Old 08-19-2010, 05:56 PM
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Default RE: Mehcanical Aileron Differential


ORIGINAL: KitBuilder

I have built an older low wing kit per plan and kept it with a single servo in the center of the wing.

My question is: do I need to have the offset torque rod?
Both the offset servo horn and the torque rods will provide some differential. Using one or the other will provide less than if you were using both
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Old 08-19-2010, 08:38 PM
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Default RE: Mehcanical Aileron Differential

You can get all the differential you need simply by changing the location of neutral of the servo arm.

For example, if you setup the pushrods and servo wheel as shown in the attached, with the pushrods where the red lines are, you'll get about 1:3 or 1:4 differential.
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Old 08-19-2010, 08:52 PM
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Default RE: Mehcanical Aileron Differential

I believe that the reason your example picture uses both an offset torque rod and that servo wheel setup was their choice of one servo for the wing. Using just one servo on top of the wing requires the pushrod connections to be aft, closer to the hingeline, giving less room for the pushrods to "flex". They'll have less room to move side to side, which is what the wheel does to them when trying to convert a rotary output motion to a push-pull, linear motion.

Use two servos and put 'em under the wing and you'll have a lot less of a binding problem.
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Old 08-19-2010, 09:48 PM
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Default RE: Mehcanical Aileron Differential

ORIGINAL: KitBuilder

My question is: do I need to have the offset torque rod? Seems like it would be the same result but less differential.
No.
Correct.
It is hard to determine how much aileron differential a plane will need anyway, and this central layout don't have as much flexibility for adjustment as the independent servo system.

MY torque rods are installed more vertically
Just leave them as they are.
By using a big nylon aileron horn similar to this, which has a .750" (19mm) offset, the articulation will be well away from the hinge line; hence, achieving the same effect than the offset torque roll:

http://www3.towerhobbies.com/cgi-bin...?&I=LXBWL3&P=7
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Old 08-19-2010, 11:05 PM
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Default RE: Mehcanical Aileron Differential

I have used offset horns on the torque rods coupled with offset at the servo horns. Works very well. Those round disc horns are great for 'dialing in' the offset you need in single servo uses. You just drill holes in different locations for your needs.
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Old 08-20-2010, 07:33 AM
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Default RE: Mehcanical Aileron Differential

Personally, I think you're over-analyzing the situation.

If you bought a new car, would you put new tires on it before you drove it because you think it needs a different type of tire tread? Probably not. You would drive the car and more than likely decide that the current tires work well enough.

It's the same thing here.

Build the kit according to plan and fly it. More than likely you'll be pleased with it the way it is.
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