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Old Dec 11, 2009, 09:52 AM
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Dallas, TX
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Backfire F5F owners ( question regarding servo/aileron/flap setup)

I've been working on getting my Backfire F5F up and running, however I've been trying to get my ailerons to work properly, as in trying to get rid of double neutral. I've tried adding oil to reduce friction, checking for slop and what not. I'm about to give up on this thing! Short of changing the servos what else could be suggested?

Given the short distance between the servo and the aileron horn, it looks like Z bends was the only way to connect the servos to the ailerons. The servos are new Hyperion DS11-AMBs.

I would like to know how other fellow Backfire owners did their aileron linkages, top drive or bottom drive? Ball links, z bends, clevices?

I will try to take a picture and post how mine looks to better illustrate how mine looks now.
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Old Dec 11, 2009, 10:05 AM
Bro
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Backfire

Han,
This may help..
http://picasaweb.google.com/alpruf/Backfire#

Best,
Bob
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Old Dec 11, 2009, 10:05 AM
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Is it on both sides or only one? Is one side worse than the other? Have you tried cycling the servos for a while with them installed to potentially grind away any unseen friction?
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Old Dec 11, 2009, 10:05 AM
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I am thinking of something like this ( http://picasaweb.google.com/alpruf/B...77316191479922 ) but the problem is that I opted to go for a bottom drive setup - thinking that it's better as it minimizes slop.
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Old Dec 11, 2009, 10:33 AM
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Thanks for the suggestions, I also downloaded the pdf manual they posted online for tips, but they've also opted for top drive.

Regarding cycling the servos, yes, I tried it with the ailerons hooked up and without. I might even record a small video apart from the pics to better illustrate this issue.
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Old Dec 11, 2009, 10:50 AM
Needs to do 52 legs !!
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Verenigd Koninkrijk, Fareham
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Without pictures it's very hard to understand what your issue is.

Don't even know how you have set it up.

As a general rule, the controll surface horn/linkage should always be on the opposite side of the hinge line. What side the servo has it's horn does not really matter.
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Old Dec 11, 2009, 11:36 PM
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Dallas, TX
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Well, here are the pics of how the linkage looks now. I'm not sure if I did the mistake of opting for a bottom drive vs. top drive, or is it the servos. Perhaps the culprit is with the z bends. Given the short distance between the servo arm and aileron horn, what kind of linkages would be recommended?

The double neutral is not readily apparent when looking at a distance, however when one looks closely the surfaces never truly return to the middle, if not just 1mm off. I'm worried even this amount of double neutral will cause roll.

The problem I have now , apart from the ailerons double neutral is that the Flaps still have slop in them, enough to worry about flutter at high speeds. However the Flaps do not suffer from double neutral.


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Old Dec 12, 2009, 06:22 AM
Needs to do 52 legs !!
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Verenigd Koninkrijk, Fareham
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Hi, it is hard to see but it looks like the black line in the pictures is the hinge line. Meaning you have your controll horns on the same side as the hinge line. Not so good.

If you had put the same controll horn on the other side you would have had 2x effective length of the horn due to the thickness of the wing.

It also seems like you could have put the hole closer to the centre on the servo arm. I know you will say that then maybe when the servo arm moved forward the linkage rod will bind against the output shaft of the servo, this is only because you used a Z bend and didn't go with the way pictured in the above links where they used a threaded piece of wire.

The other way to avoid this binding problem is to make a double L bend. Basically it looks the same as your Z bend but rather then the retaining part pointing forward it now point 90 degrees to the linkage and 90 degrees to the wing servo..... basically away from the servo. This will allow 90 degrees rotation of the servo arm in both directions.

There is a little bit of this double zero problem with the Hyperion servo's. It is due to the gears being very tight. This is not a bad thing. Better then a lot of slop as like you say this could result in flutter.

You might want to have a look here, for both how to fit the top drive horns and how to do the double L bends.

http://www.rcgroups.com/forums/showthread.php?t=1136715

Joe
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Old Dec 12, 2009, 08:49 AM
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Quote:
Originally Posted by jjmouris View Post
Hi, it is hard to see but it looks like the black line in the pictures is the hinge line. Meaning you have your controll horns on the same side as the hinge line. Not so good.
Joe
Joe, what thickness do you recommend for rods here? Is 4-40 necessary or would 2-56 suffice?
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Old Dec 12, 2009, 10:04 AM
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A top driven linkage may have been better, as Joe suggests, but your installation doesn't look unreasonable. A double neutral is often a sign of something binding. Maybe the clevis pin is tight in the control horn hole, maybe the hole in the servo arm is too small? It's a balancing act between too tight creating a double neutral and too loose creating slop.

Good luck,
Lenny
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Old Dec 12, 2009, 10:09 AM
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Dallas, TX
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Thanks for the suggestions, I wasn't aware of this issue of double zero on the Hyperions given that on the Flaps I am using Airtronics 761s and there is no such issue.

THe wire thickness I used is 2-56s, don't know if I could use any thinner.
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Old Dec 12, 2009, 10:37 AM
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Lenny,

Many thanks for the input. I thought about this too, and apart from adding oil to both holes, I also increased the hole on the servo arm - enough that I ended up having to put some CA glue to fill the gaps due to the z bend moving around and creating slop.

Unfortunately, I still had double neutral before and after these modifications - I must be doing something wrong! I might end up replacing these servos altogether, removing it and re-doing the whole thing.
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Old Dec 12, 2009, 10:45 AM
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Are you detecting the slop with the servos powered on or not? What did you program the deadband to be? Out of the box, I don;t think it is dialed to zero...
I am going ds095 for whole wing, and ds11 on tail so taht I can run 6v without any headaches (its an issue with ds09)
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Old Dec 12, 2009, 11:21 AM
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Hi,

That's a good suggestion I ought to give a shot, I never thought about the deadband issue. I also have the Hyperion servo programmer so will give that a go.
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Old Dec 12, 2009, 11:33 AM
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taking the servos out is a hard gig it may damage the servo or the wing,,,try the dead band first as richard sugested.....you can always go top drive and hope it corrects the isue.
ben
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