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dual trottle servos

Old 02-05-2007, 09:51 PM
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BALSABRO
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Default dual trottle servos

ok I have never used a twin engine setup before and have questions

I have two servo connected to a Y harness and both servos move the right direction------- one servo has more throw than the other is there a way to get these equal??????
Old 02-05-2007, 10:03 PM
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Geistware
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Default RE: dual trottle servos

If they are the same brand servo then one of the servos is bad.
Either replace the bad one or send it in for service.
ORIGINAL: crazieflyer

ok I have never used a twin engine setup before and have questions

I have two servo connected to a Y harness and both servos move the right direction------- one servo has more throw than the other is there a way to get these equal??????
Old 02-05-2007, 10:12 PM
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2slow2matter
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Default RE: dual trottle servos

They need to be the exact same servo on both sides. Then, options are--put them on separate channels and mix them in the radio, or use something similar to a matchbox from JR.

Mechanically, are the set up the same? (i.e. same hole at servo and same hole at carb?)
Old 02-06-2007, 12:02 AM
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Default RE: dual trottle servos

There is nothing wrong with setting up a twin with two throttle servos on a Y cord. In fact it is the most commonly used setup. I currently have three twins set up with Y cords, One Quad with a four way Y and currently working on a six pack with two three way Y's.

Like Geistware said if your matched brand and type servos are not traveling the same distance then one if faulty. Check that you are using the same length horns on the servos and engines. On the servo when Y cording the engines install an EZ just and make it accessable for matching throttle openings.

John
Old 02-06-2007, 08:37 AM
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Default RE: dual trottle servos

I wasn't suggesting not to use a Y. I have used a Y myself in the past. The OP stated that he is currently using a Y and can't get the same travel. There are other options, including the ones I mentioned. Not all planes need be set up the same.
Old 02-06-2007, 08:51 AM
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Geistware
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Default RE: dual trottle servos

He said same travel on the servo, not same travel on the throttle arm.
If the servo is not moving the same, and it is on a "Y", then it is the servo.
Old 02-06-2007, 09:15 AM
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Default RE: dual trottle servos

Cool 2 slow I probably misread your post as denoucing the use of a Y.

John
Old 02-06-2007, 09:56 AM
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Rodney
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Default RE: dual trottle servos

Expecting perfect tracking on two same brand servos is a bit much. The servo travel depends on several factor, the most prevalent being the degree of match on the feedback pots and the two resistors usually found on each end of the pot. These are typically 5% or worse tolerances in the parts used. The price on the servos would skyrocket if they were required to be precise within 1%. What is amazing is that they are usually so closely matched, not that there is often a difference. If it becomes especially important for your use, the easiest way is to try several on the bench and pick the two most identical or, open them up and tailor the resistors.
Old 02-06-2007, 11:14 AM
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2slow2matter
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Default RE: dual trottle servos

I actually use Y's everywhere I can get away with it. Save's money, and they are reliable. Nothing at all wrong with it. It is how I have my twinstat setup, and has been setup that way for years. Now if i would just fly the darn thing......
Old 02-06-2007, 12:15 PM
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Default RE: dual trottle servos

Hi crazieflyer
I use low priced servos and have never noticed if they travel the same amount when I use them for the throttles on one of my twins. I just make adjustments on the servo shaft spline changing the geometry of the movement. This is where high school geometry comes into play. Sometimes I have to work on both servos. Sometimes I'll change out one servo. I try to get the high speed close to each other and accept greater variation in the idle speed. I don't even use a tach anymore for the high speed. I tune for reliability first, last and always.

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