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Dual elevator servos?

Old 01-03-2015, 03:31 AM
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abufletcher
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Default Dual elevator servos?

I've never had a model with a servo for each elevator half (in the tail). So how do I do the radio setup for this? In my hazy thinking I imagined I could just connect the two with a Y-harness and then a long lead to the Rx. But the Y-harness reverses one servo. Or is there some other type of Y-harness needed? Or is the additional elevator servo also connected to the Rx, and if so how?

I'm using an 8-ch Airtronics RDS8000.
Old 01-03-2015, 04:27 AM
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Teus
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Or why don't you use just one servo? A good strong servo will do the job perfect. Just something to think about.
Old 01-03-2015, 07:11 AM
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abufletcher
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This 30% ARF is designed for two (mounted externally in the tail as on aerobatic models). I don't want to mess with that. There must be a standard way of doing this since it's very common with large aerobatic models.
Old 01-03-2015, 07:52 AM
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049flyer
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You can use a reversing Y cable which will reverse one side of the Y. Available from MPI - Max products. The problem with this set up is that each servo may not move at the exact same speed or the exact same degree of throw on one side or the other. Sometimes you can adjust the programming of digital servos to even things up. Another problem is that long wire runs sometimes cause problems, ether because of voltage drop or the introduction of interference.

If you have a computer radio that supports dual elevator mixing then the problem is much easier and depending on the radio you can adjust throw and speed directly from the transmitter so the servos operate exactly the same.

Hopefully some of the giant scale guys will jump in and offer more specific help.
Old 01-03-2015, 08:02 AM
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049flyer
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Your Airtronics radio should support dual elevator mixing. You might try posting in the radio support section asking for help with dual elevator mixing with the Airtronics RDS8000.
Old 01-03-2015, 11:53 AM
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R/C Art
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Hey Don - (read the manual)

Sorry, couldn't resist. It's not too complicated ..... I've been using dual servos for years.
Old 01-03-2015, 01:32 PM
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abufletcher
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Originally Posted by R/C Art
Hey Don - (read the manual)
Art, I always read the manual...right after I try everything else and come to my wit's end. Seriously, I just didn't even think about this since the dual setup seems so common. When I was ordering the long (twisted) servo leads, almost without thinking I order enough for both servos. It was only much later that it occurred to me to wonder where I would plug in TWO elevator leads.

Anyhoo, looks like it's RTFM time. (My worst fear is that I'll discover that "you can't get there from here" i.e. that I can't do this with my current Tx.)
Old 01-03-2015, 01:38 PM
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BarracudaHockey
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Ahh the twisted leads, the cure for everything from the mumps to hangovers.

Your radio will do it, look into setting up your ailerons that way as well, much greater control over setup.
Old 01-03-2015, 01:41 PM
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speedracerntrixie
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If your TX does not support dual elevator servos you can look into a Smart Fly Equalizer. This little device will plug into your elevator channel, and then you plug your elevator servos into it. The device allows you to reverse either one of the servos, adjust their center and end points independently so you can match up the elevator travels perfectly. Something you just can't get with a reversing Y.
Old 01-03-2015, 01:46 PM
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speedracerntrixie
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Originally Posted by BarracudaHockey
Ahh the twisted leads, the cure for everything from the mumps to hangovers.
.
Andy, you just couldn't resist could you? LOL. IMO, there is some evidence that it can help in some cases. You are correct that twisted leads are not a fix but more of a piece of the puzzle to prevention. I say it can't hurt so why not go twisted?
Old 01-03-2015, 02:13 PM
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abufletcher
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That Smart Fly Equalizer looks like I clever bit of electronics...and at a reasonable price. And I'll reconsider my assumptions about the aileron connections as well. This large model is challenging a lot of my "standard" knowledge about RC.
Old 01-03-2015, 02:33 PM
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JR Matchbox, Smart Fly equalizer are both viable options but really, why spend the money when your radio will do it for free?

Also, when you get into larger aerobatic designs most of us go to metal servo arms like Seacraft or SWB. Unlike a standard 4 prong plastic arm where you can center the servo and rotate the servo arm around until you find the place on the spline where it lines up 90 degrees, you're pretty much stuck with as close as you can get with a metal arm. This is where you get into needing sub trim for each servo get your linkage geometry correct. Your radio already does all this, just take the time to figure out how

Ahh twisted extensions...... yes there is no reason not to use them but for RC they don't provide any benefit, other than looks, they do look pretty

I know that places like Tail Dragger that sell heavy duty extensions made of 20g silicon wire, they twist them because they have no choice because that wire gauge isn't available in ribbon strips like 22g servo wire. But hey, if it makes you feel better, then it is better.
Old 01-03-2015, 02:36 PM
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rcguy59
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That's what I love about the Z-series Futaba radios. The first step in setting up a model is telling the radio how many elev. channels, how many ail. channels, etc. Once you do, the radio assigns everything to it's own channel. Then you go to the function menu to see what the channel numbers are and plug the servos in accordingly. The radio does all the mixing for you. The DX6 and DX9 that I played with worked the same way. Enough to make a guy lazy.
Old 01-03-2015, 02:43 PM
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Originally Posted by rcguy59
That's what I love about the Z-series Futaba radios. The first step in setting up a model is telling the radio how many elev. channels, how many ail. channels, etc. Once you do, the radio assigns everything to it's own channel. Then you go to the function menu to see what the channel numbers are and plug the servos in accordingly. The radio does all the mixing for you. The DX6 and DX9 that I played with worked the same way. Enough to make a guy lazy.
My Hitec Aurora 9 does the same thing and it's touch screen. Very under rated radio.
Old 01-03-2015, 02:52 PM
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abufletcher
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I'll definitely be reading my RDS8000 manual today. The Equalizer would be an alternative to having to buy a new Tx/Rx system, if the RDS8000 doesn't have this feature. And, yeah, I know what you mean about that "closest gear" problem. That occurred to me as I was setting up the linkages. On this ARF, the kit includes heavy duty servo arm extensions that bolt onto the standard circular "arm" that comes with the metal gear servo.
Old 01-03-2015, 03:04 PM
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Yea, about those, they work but you might want to think about something better. I have used those before but depending on your flying style you risk the plastic wheel skipping a tooth, especially on the rudder. Flying scale I wouldn't sweat it too much but you plan on cranking up the throws and hammering it, you might want to think about metal arms. If not, then dont sweat it.
Old 01-03-2015, 03:13 PM
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abufletcher
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I only plan of making pretty circles around the sky with this model. Maybe eventually, after I pull the engine out to use on a truly scale WWI model, I'll replace it was a gasser and then get those metal arms.

Just checked the RDS8000 manual. No prob. Dual elevator mixing by plugging the left elevator into the normal channel 1 and the right half into channel 7. This then allows separate adjusting of EPA, REV, CENTER, and FAILSAFE positions.
Old 01-03-2015, 03:23 PM
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rcguy59
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Sounds like that type of programming is becoming universal. 'Bout time. Too bad getting a decent touchscreen is still expensive.
Old 01-03-2015, 04:18 PM
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It appears the poster knows little about the transmitter and the functions it will support. I just looked at specs' of this radio and it does support dual elevators.
Old 01-03-2015, 05:09 PM
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There is a theory that 2 elevator servos gives you a slight safety benefit due to the redundancy. That if one elevator servo screws up, you have a chance of being able to save the airplane. Like if the ailerons go, you still have the rudder. I am NOT volunteering to test the theory.
Old 01-03-2015, 05:12 PM
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Also do you need the electronic reversing? Could you run the pushrod off the other side of the servo? Wouldn't that reverse the pushrod motion?
Old 01-03-2015, 06:08 PM
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Airtronics RDS8000 is right up my alley! How many channels on your receiver?
Old 01-03-2015, 06:39 PM
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abufletcher
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Guys, up to now, I've just had no need for anything fancier than a basic 4-5 servo setup. So there wasn't much need to "read the manual." But it's good to try new things. The RDS8000 is an 8-channel Tx and I've always used it with the 8-ch Rx it comes bundled with. The only time I've used anything other than E, A, R, and T channels was when I set up aileron differential on one model.
Old 01-03-2015, 06:39 PM
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Originally Posted by rcguy59
Sounds like that type of programming is becoming universal. 'Bout time. Too bad getting a decent touchscreen is still expensive.
Expensive is subjective, but when it comes to touch screens and bucks spent for bang received, the Hitec A9 is a step in the right direction if nothing else...
Old 01-03-2015, 06:43 PM
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Originally Posted by wnewbury
There is a theory that 2 elevator servos gives you a slight safety benefit due to the redundancy. That if one elevator servo screws up, you have a chance of being able to save the airplane. Like if the ailerons go, you still have the rudder. I am NOT volunteering to test the theory.
That's what I've heard too. And, yeah, I sure wouldn't want to test that out...particularly if one half died in anything other than the neutral position.

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