geoff_nwt

Hi im just finishing of a kangke cap 232 120 size
In the manuel it says install two servo for the elevators in the tail

I have got a spare 7 channel futaba receiver im going to use so I cant use channel 2 & 8 for the two servos so I have installed them with a Y lead so one of the elevators is working in reverse

in order to get them both working in the same sense you have to reverse one of the servo horns The only problem is the Geometry is now different from one side to the other and one elevator has more movement than the other
Any one know how to overcome this problem ?
many thanks
Geoff

bckyrdbshr

My Feedback: (35)

As far as I know you don't have to use a Y on the servos if your using channel 2 & 8 it should tell you in your radio manual how to go into the radio and set it up that is if your using a computer radio.

Nakajima

Buy a Y harness with a reverser on one side - it will allow to adjust the servo travel and automatically reverse it.

Rcpilot

My Feedback: (78)

A Y-harness WILL NOT allow you to adjust the servo travel. It only allows for centering adjustments. you will still get differential travel.

Either use your radio to mix it out or buy a JR Matchbox. You can also buy something similar to the Matchbox from Futaba. There is a cheaper version called an Equalizer. www.smart-fly.com

Make sure that your linkages are the exact same length. And mount the servos so that the center point of the output shaft is the same distance from the control horn on both sides.

I like to use H9 Pro Links on my elevators and ailerons. Kinda pricey, but perfect length and geometry every time. With the Pro Links- you get exactly matched lengths with both rods.

MinnFlyer

My Feedback: (4)

You can also cut another hole and mount the servo closer to the stab.

Nakajima

Sorry, that's what I meant to say. If you buy the reverser, it will reverse the servo so you can put the arms in the same position on each one . Make the control rods the same length - hence the same throw in each arm while still being able to center the second servo.

Rcpilot

My Feedback: (78)

A reversing Y-harness simply won't work.

Here's why:
Servos don't travel the same amount in both directions. Any given servo- be it a high end coreless digital or a cheap analog servo-- will never travel the same amount in both sirections.

For example; a servo might travel 60degrees clockwise--but it will only travel 56degrees counterclockwise. This is a fact. It's a mechanical limitation of every servo. Don't know why- it just is.

So then, what happens when you reverse one servo is this:
Just an example-- play along for arguments sake:
The left elevator will travel up 1" and down 3/4". Reverse the right servo with a Y-harness and it will travel up 3/4" and down 1".

Since the servos are on opposite sides of the plane and one is reversed; they are effectively traveling at different amounts-- in opposite directions.

I've been through this. I tried to get this to work with a Reversing Y-harness one time. I messed with it for two weeks and never could get it just perfect. I got it really close, by messing with the linkages and lengths of rods and control horns-- but never perfect. By having one elevator side moving more than the other on an aerobatic plane--you wind up with a plane that flies like poop. Every time you pull back or push on the elevator-- the plane wants to corkscrew-- because one side is moving more than the other.

The best way to fix the problem is as I indicated in my original post. Mix it out with your computer radio, or get an Equalizer or a Matchbox or the device that Futaba sells to match servos. Only way to do it right.

Hope this helps.

Miloh

I used a standard y harness on my ultra stick .60 and put mini servos in the tail one rite side up one upside down then played with the linkages till I got it to work.
I know it can't be made perfect this way but it was close enough for the plane to perform 3D like crazy. the 3d was performed by my one of my buds at the field and he was impressed it worked. Just lucky I guess. did well enough that I never saw a reason to change anything. Who knows you might get lucky too.

Miloh.

Leo

I reversed one of the elevator servos in my GP Ryan,
by reversing the connections to the servo motor and
potentiometer. Of course, this operation requires a
suitable soldering iron.

/Leo

Nakajima

Re: Servo Reversing Harness

I am using them on 2 different planes and they are working fine and traveling the same in both directions. I'm using Futaba servos - hmm, perhaps I just got lucky!

geoff_nwt

Thanks for all your replies lads
I went down to our field today and some one more familiar with the mixing on a 9 CHP than me sorted it out

I thought u had to use channel 2 & 8 for two elevator servos but you dont
I have now used 2 and mixed it with 6 (flaps)
Thanks any way
Geoff