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servo mounting on wing

Old 08-14-2015, 01:16 PM
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rye
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Default servo mounting on wing

hi
i have a taper wing on a chipmunk what is the proper way to mount the wing servo mounting in the wing so it work the aileron with out binding
thanks
Old 08-14-2015, 02:52 PM
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daveopam
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One servo in the center or one in each wing panel?
Old 08-14-2015, 06:48 PM
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rye
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thanks but do i angle the servo so that its in line with the aileron or keep it straight in the wing
Old 08-15-2015, 01:23 AM
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RBACONS
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It does not matter. It is only important that the linkage, at neutral, is perpendicular to the control surface leading edge. This can be done by having the servo arm perpendicular to the servo case and angling the servo case or by having the servo case parallel to the wing ribs and angling the servo arm. 6 of one, half-dozen of another.
Old 08-15-2015, 02:24 AM
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Rbacons +1
Old 08-15-2015, 03:42 AM
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Jennifer Curtis
 
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If you mount the servo parallel to the
wing ribs, the pushrod should go straight
back from the servo arm 1/4 to 1/2 inch,
then bend out so the end of it points
directly at the aileron.

Jenny
Old 08-15-2015, 06:19 AM
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All Day Dan
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Here's what I do. Dan.


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Old 08-15-2015, 07:09 AM
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Sorry I did not totally understand your question. You got great advice above. I like to make sure the arm and servo case are parallel to the hinge line.


david
Old 08-15-2015, 08:08 AM
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flycatch
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http://www.rcuniverse.com/forum/gian...-geometry.html
Old 08-15-2015, 08:20 AM
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Originally Posted by Jennifer Curtis View Post
If you mount the servo parallel to the
wing ribs, the pushrod should go straight
back from the servo arm 1/4 to 1/2 inch,
then bend out so the end of it points
directly at the aileron.

Jenny
The above is not best practice. Avoid bends in pushrods if you can. Short straight pushrods are best.

Also it will make no difference to the aileron movement in relation to servo movement.

Post 9 has a link which is worth reading through.

It does not matter what angle the servo is mounted. What does matter is the angle of the servo ARM in relation to the hinge line of the aileron. If you want equal amounts of UP and DOWN aileron then the servo arm should be at 90 degrees at rest.The control horn holes should be above the hinge line.

For a model like a Chipmunk it is not too critical but slightly more up aileron than down is good. Don't sweat it and go fly it.

HOWEVER with some models you want large unequal amounts of up and down. EG my Stampe biplane I had about double the UP compared to down. It is possible to do this mechanically or if your TX allows it on the servo set up. With equal amounts you would have severe adverse yaw which could result in the model turning right when a left turn was commanded by aileron.

Last edited by j.duncker; 08-15-2015 at 08:46 AM.
Old 08-15-2015, 06:31 PM
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Originally Posted by Jennifer Curtis View Post
If you mount the servo parallel to the
wing ribs, the pushrod should go straight
back from the servo arm 1/4 to 1/2 inch,
then bend out so the end of it points
directly at the aileron.

Jenny
Do not do this.
Old 08-16-2015, 03:29 AM
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Originally Posted by j.duncker View Post
The above is not best practice. .
Did you miss the 1/4 to 1/2 inch part? If this bend is
this close to the servo horn, no bending will happen.
Even in a crash, any bending will happen midway
along the pushrod. I know this from experience, and
no the crash was not caused by the bending, it was
caused by not extending the 72 MHz antenna.

Jenny
Old 08-16-2015, 04:18 AM
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RBACONS
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Any bend introduces a point which facilitates flexing of the pushrod. Is it a big deal? Not on small planes or slow-flying planes and I've used it on occasion but nonetheless it is still not an ideal geometry.
Old 08-16-2015, 12:41 PM
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jester_s1
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I had a bend in my aileron pushrods once similar to this with no ill effects. The pushrod only needs to be as strong as the servo torque. If you can command full deflection while holding the surface still and the pushrod doesn't bend significantly, the linkage is fine.
Old 08-16-2015, 02:47 PM
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j.duncker
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Originally Posted by jester_s1 View Post
I had a bend in my aileron pushrods once similar to this with no ill effects. The pushrod only needs to be as strong as the servo torque. If you can command full deflection while holding the surface still and the pushrod doesn't bend significantly, the linkage is fine.
This is not as simple as that.

FLUTTER is the issue. OK with something slow it will not happen often but get the speed up and one day you risk hearing the dreaded BRRRRRRP followed by the model coming apart in mid air.

Keep those pushrods short and straight.

Last edited by j.duncker; 08-16-2015 at 02:50 PM.
Old 08-16-2015, 04:19 PM
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Jennifer Curtis
 
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Flutter is what will happen if the servo horns get
the holes worn from not putting the slight bend
in the pushrod, and just let the z-bend force its
way at the incorrect angle.

Jenny
Old 08-16-2015, 04:37 PM
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drac1
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Originally Posted by j.duncker View Post
This is not as simple as that.

FLUTTER is the issue. OK with something slow it will not happen often but get the speed up and one day you risk hearing the dreaded BRRRRRRP followed by the model coming apart in mid air.

Keep those pushrods short and straight.
+1
Old 08-18-2015, 09:06 AM
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flycatch
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Simple fix for a push rod that is bending is to sleeve it with copper tubing.
Old 08-18-2015, 01:06 PM
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Even better is carbon fiber tubing. Light and stiff.

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