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Flap Servo Rotation


Dave Hopkin
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First time I have ever set up flaps so its probably a dumb question!!!

The Wing has two Aileron Servo's and Two Flap Servo's, each pair hard wired into Y Harnesses within the wing leaving me one Aileron and one flap lead going into the RX

Ailerons work fine but the flap servo's are operating in opposition (ie one pushing flaps up while the other pulls down)

TX is a DX9 RX is AR610 - flaps are assigned to switch F and AUX1

I have tried various wing set up setting and failed miserably!

So it would seem I have three options

a) Find out how to reverse the rotation of one servo

b) Reverse the servo in the mount

c) Move the control Horn to the other side of the servo center line

Options B would spoil the symmetry of the wing (all push rods are outboard of the servos) and all servo spindles forwards

Option C would involve remaking a flap and spoil the symmetry of the wing (all push rods are outboard of the servos) and all servo spindles forwards

So is there a way I can do it from the TX before I get the hammer and chisel to the wing?

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Does your radio not have an option for a 4 servo wing? You then plug all the servos into separate channels, and reverse them as needed. This also give you the ability (as long as mechanically able) to mix the ailerons to the flaps to give a higher roll rate, or on a glider to give "crow" braking. I'm sure the DX9 would have this funtionality somewhere.

A quick google shows that you can indeed setup a 4 servo wing.

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Dave easiest way out of this one would be to put each flap servo on a separate channel & reverse one servo on the transmitter assuming you have a spare channel on the receiver. You will have to assign each channel to flaps

Reversing one servo by rewiring it can be done but can be fiddly if it's a mini or micro.

Hitec, Spektrum & JR servos all go in the same direction, Futaba in the opposite so you might be able to swap one for the another make.

There is no way to fix from the TX while they are both on the same channel, whatever you do will apply to each servo.

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Ok, Thanks I will have a mooch through the spares draw for a Futaba Servo....... thats a nice easy fix

 

Failing that I will just move the horn on one flap to engage with the other side of the servo...... might get away with it on the existing flap else I whittle a new one pretty easily...... (thankfully the robart hinges are fixed to the wing but not the control surfaces yet!

Edited By Dave Hopkin on 20/10/2014 09:56:36

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Posted by Dave Hopkin on 20/10/2014 09:56:17:

Ok, Thanks I will have a mooch through the spares draw for a Futaba Servo....... thats a nice easy fix

Edited By Dave Hopkin on 20/10/2014 09:56:36

Test it out of the model first, you may find that the futaba servo moves a different angle compared to the existing servos and possibly at a different speed.

Is it not possible to use a reversing Y lead, or is the Y lead to servo plug buried in the wing.

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Is servo reversing simply a case of switching red and black leads on the servo?

 

If that's the case I can simply unsolder my splice in the two servo leads and switch one polarity round or will that create a small/large/horrendous puff of smoke in the wing?

 

 

No ignore that.... just did a search..... the puff of smoke will result!!!!!

Edited By Dave Hopkin on 20/10/2014 10:43:19

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Dave,

Plus 1 for the Turnigy 3 channel servo gizmo.

I have a Multiplex Funclub and had exactly this problem. I solved it by successfully re-soldering one servo for reverse operation. However, on my transmitter, Futaba 6EX, I only have a switch for flaps, which means instant flap deployment and an equally instant nose up attitude.

I later purchased the Turnigy item as a speed regulator for slow deployment of the flaps, but also noticed that one channel can be reversed, If I'd bought one of these right from the off it would have solved both problems at once, and saved me a lot of messing about!

GDB

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Posted by Bob Cotsford on 20/10/2014 11:01:32:

Don't worry about the symmetrical appearance of the wing, it's far more important to get both flaps moving in unison. Options B or C are by far the best ones, C being best for getting the same geometry on either wing.

I second that. Spinning in when low and slow also ruins the symmetry of the wing, believe me!

Sounds like you'll have to do some cutting and patching whatever method you use. I don't quite understand your listed options though. Is the servo mounted with the spindle pointing downwards (in which case I don't see how it can be rotated) or is the servo mounted sideways (in which case I don't see how you can swap to the opposite side of the centre line). Whichever method you use, spend some time testing it to get it right. Good luck!

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Dave

Just a point

If you do try and reverse the servo arm you also have to make sure the linkage geometry is identical on both flaps or you will find they have different motions.

The best 'mechanical' solution, given you don't have a spare channel, is to move the servo so that the layout (servo, arm, link & horn) is identical (and not a mirror image) on both sides.

You could of course always get a radio with more channels! wink 2

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Going for Option C - Means making a new flap but thats only a couple of hours graft... moving the horn to the opposite side of the servo itself (they are mounted vertically with the spline shaft pointing down) So as I am not moving the servo the movement will be identical to the other side anyway)

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