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Why two elv servos

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Old 06-01-2003, 12:33 AM
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J W Dazzler
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Default Why two elv servos

I have New Dazzler and it requires two servos for the Elevator and I can'nt get the two sides travel the same. is there any one can help me.
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Old 06-01-2003, 02:02 AM
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Ed_Moorman
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Default 2 elevator servos

Ideally, you put each side on a different channel and mix them. This way you can adjust each side individually. Some of the newer radios have this function built in. My JR 8103 does not, but it's an easy mix.

If you don't have a computer radio, try some of the control horns that are threaded bolts with a plastic fitting. This way you can make fine adjustments on each side to get the moving together.
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Old 06-01-2003, 02:28 AM
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J W Dazzler
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Default Why two elv servos

thanks Ed I have a jr 662 I think I can mix with this radio. I'll read my book some more. the guy that sold it to me said to use a y harness and it has a dial to ujust but it only move one servo. I will try puting each servo on its own chanel like you said thanks
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Old 06-01-2003, 12:10 PM
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Gene Chernosky
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Default OR...

Expert, carried by Horizon and others, makes a reversing 'Y' with a centering adjustment...it will solve all of your problems if you are using two of the same servos. It allows mirror-image operation of the two servos and allows you to make the midpoint, or neutral, on both exactly the same. I'm thinking it is around $10.
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Old 06-01-2003, 10:37 PM
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Default Reversing Y-Harness

Definetly use a Matchbox or your radio to program out the differences.

Forget about using a reversing Y-harness. A servo will never travel the same amount in both directions. Let's say a servo will travel clockwise 85 degrees. It will only travel 80 degrees counterclockwise. This is true of every servo I've ever seen. Even digital servos. They always travel more in one direction. Using the reversing Y-harness only makes the control surfaces move different amounts.

Let's say your using 2 elevator servos. You need one to be reversed. Using the reversing Y-harness will make your elevators move in different amounts in the same direction. Your LEFT elevator will move UP 1" and DOWN 3/4" and your RIGHT elvator will move UP 3/4" and DOWN 1". Totally opposite. Because one is traveling 85 degrees and the other is traveling 80 degrees. Because they are doing it in OPPOSITE directions, relative to the pot on each servo.

Even with the centering pot on the Expert Y-harness; you will have problems. That Y-harness has a small pot that allows you at adjust the center point of the reversed servo. It doesn't do you a bit of good to adjust the center point of the servo. You will still have differential throws in your elevators.

I beat my head against the wall with this one for about 2 weeks one time. Yes, you can tweak the linkages and the control horns to get is very CLOSE, but you can't get it perfect. If you want to fly precision aerobatics or pattern- you need it perfect.

I just recently bought my first Matchbox. All I can say is COOL COOL COOL !!! You can adjust the Neutral points of each servo and you can adjust the Travel points of each servo. I think it was definetly worth the money. And it's cheaper than buying a new radio that is capable of mixing the differentials out of the servos. I have a JR652. It's a decent computer radio, but it won't do the mixing needed to run dual servos on elevators.

I did reverse a servo internally once. It was a hitec 625MG. I took the case apart and reversed the wires on the motor and I switched the wires on the pot. It reversed the servo and solved my problem. Both servos would travel the same amount in the same direction. But, resoldering the wires on the motor and the pot is a point of weakenss on the servo now. I simply can't solder as well as a robot in a factory.

I went back to JR servos and I couldn't bring my self to tear into a brand new $90 servo and start soldering wires on the pot and the motor. Thats why I went with the matchbox.
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Old 06-02-2003, 12:03 AM
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Default Why two elv servos

I have a Super Skybolt with two elevator servos mounted just forward of the tail on the fuse sides.
The center of the servo (where the horn screw is) is in line with the last hole of the control horn on the elevator. One pushrod goes up to the horn on the elevator the other goes down.
One pushrod is at the top of one servo and the bottom of the one opposite so they each travel the same direction and also move each half equally.
I, also, was concerned with equal movement of each half and with my servos mounted in the way described they move equally.
I painstakingly measured each one and they move the same on low and high rate, and throughout their travel.

Tom
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Old 06-02-2003, 12:18 AM
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Default Why two elv servos

J W Dazzler,

I believe you have posted this question in another forum. Are we talking about a Great Planes Dazzler? .40 size? That plane does not need two elevator servos.
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Old 06-02-2003, 12:43 AM
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Default Why two elv servos

no its a 60 size ART and was designed for two servos for the elevator
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Old 06-02-2003, 12:45 AM
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Default Why two elv servos

Thanks for all your replys . what is a matchbox
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