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Setting Up Control Throws

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Old 06-02-2009, 08:40 AM
  #1
DaddySam
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Default Setting Up Control Throws



My son and I attended an IMAC boot camp a few weeks ago and now he's moving from his Astro Hog to a Phoenix Models Extra 330. I'm setting up the plane for him and we were adjusting the control throws, end points, etc.. A question occurred to me which I haven't thought about before. When measuring the control surface deflection, what is the best way to assure that the throws are equal in each direction? Adjustment of the control horn and linkage or with the radio?Wee set up the linkages as identically as we could, but there will always be minute differences in the exact location of the servo mounting holes, the control horn holes, etc.. However, when we measured the actual deflection of the control surface, we found that one aileron would deflect 1/4" more in one direction andthe other 1/4" morein the other. By adjusting the individual endpoints back we were able to equalize the throws. So basically although the servos have different amounts of motion, the control surfaces such as the ailerons now deflect equally. Does this sound like the right way to do it?
Thanks in advance,
Sam

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Old 06-02-2009, 04:25 PM
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Jake Ruddy
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Default RE: Setting Up Control Throws

What you want to do is to 2 long straight bamboo skeewers or something similar and either tape them to the elevators in the exact same spot or glue them to clothes pins.

Then you can attach them to the elevator and watch to make sure the surfaces travel evenly throughout the range of travel.  I would bet they do not right now.

You want to get your subtrims as close to 0 for each servo as possible.  Then adjust your linkage to get the surfaces equal. Remember that the distance between the control horn and the surface should be identical on both surfaces as well. Preferably the distance from the center of the surface to the center of the control horn connection should be equal to the length of your servo arm.

To get it right takes some time and patience, you will be surprised how much of a difference 1 turn on the ball link will make in the overall travel and how well it matches the other surface.

It can be a real pain to get it right, but worth it all the same
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Old 06-02-2009, 05:50 PM
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DaddySam
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Default RE: Setting Up Control Throws

Thanks a bunch, Jake.  I'll get some skewers or something and spend some time making adjustments.
Sam
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Old 06-04-2009, 10:11 AM
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Jake Ruddy
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Default RE: Setting Up Control Throws

No Problem, happy to help!
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Old 06-05-2009, 09:41 AM
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Default RE: Setting Up Control Throws


Quote:
ORIGINAL: DaddySam

Thanks a bunch, Jake. I'll get some skewers or something and spend some time making adjustments.
Sam
Hey Sam,

Gettin into the IMAC stuff huh????

You asked about ailerons and Jake gave you some tips on elevators....

It was good advice for the elevators and what I use to track 'em is a couple of carbon fiber rods I got from the LHS. Light weight, straight and don't flex. Also, it's time to get rid of the ruler and go for some degree gauges,protractors or deflection meters. I got mine from Central Hobbies up in Montana and the've got lots of neat stuff if you've never been over there, they are really big into the pattern stuff. I think AeroWorks sells something very similar and I've seen 'em other places as well. Hangar 9 has got some nifty digital versions, but in my experience they are just to heavy.

http://www.centralhobbies.com/Tools/tool1.html#THROW


Now Jake's advice is spot on and for your initial efforts, some differences in the ATV settings on the radio for aileron deflections to get the throws to match isn't going to be a big issue. Get 'em as close as possible with the mechanical setup and just do the rest with the radio but I'd attempt to use subtrim first to center up things. The reason this will be an issue down the road is when you start using mixes such as a rudder/aileron mix where the rudder is master with the ailerons as slave. This is commonly done to eliminate roll coupling when doing precision aerobatics and if the servo travels are disimilar in the ailerons, you'll get an un-even deflection when you roll in a mix. It can also be an issue if you use multiple rates on the control surfaces like I usually set my stuff up with what I call a low rate for snaps and such, a high rate where I usually fly and 3D rates. How you do that or what you might want depends on your radio capability.

Most of that stuff isn't something you'll really get into initially, but will if your son keeps flying as he gets better and starts asking more of the airframe. So don't get wound up about it too much right now, just set 'em as close as you can get and go for it.....
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