Tx stolen.4in1 from Twister CP V2 hacked but ELE servo goes wrong way on throttle-up? - RC Groups
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Feb 20, 2009, 06:52 PM
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Tx stolen.4in1 from Twister CP V2 hacked but ELE servo goes wrong way on throttle-up?


The above 2 posts talk about a fixed pitch 4in1 hack to replace the Rx part.
I have attempted to do this hack to use a Rx Tx pair from a busted King 2 heli which is also a 120 deg CCPM heli. However, when I throttle-up the front servo [ELE I believe] goes the wrong way. I tried to reverse this channel on the front of the Tx but it didn't work.
Is there a way to make it work properly? The Tx is not programmable.
Any help appreciated.

Would REVersing servo on Tx and mounting ELE servo upside down work?
Last edited by turnbui; Feb 20, 2009 at 07:27 PM.
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Feb 22, 2009, 06:55 AM
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Would REVersing servo on Tx and mounting ELE servo upside down work?

It didn't!
Feb 22, 2009, 09:58 AM
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You can rewire the srevo pretty easily to run the other direction, or if it is anything other than a hitec servo switch to a hitec (they run backwards).
Feb 22, 2009, 07:15 PM
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jppizhere: Thanks. The servo works properly when the Mode 2 right stick is pushed/pulled just not when throttle is applied. I've tried both the E-sky xtals and the orig Twisters xtals but both cause the throttle to operate the front servo the wrong way. I've read some posts but none refer to this particular problem. They mention CCPM and negative/positive shift. I guess I've got to somehow hack the throttle electronics in the Tx but this is beyond my capabilities.
Feb 22, 2009, 09:42 PM
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The crystals have nothing to do with servo rotation.

Negative and positive shift have nothing to do with servo rotation.

I am surprised that flipping the servo upside down and reversing the transmitter switch did not work.

Flipping the servo upside down would keep the rotation direction the same.
This means that if the arm is not changed, the swash will now move in the correct direction with throttle.

Reversing the elevator transmitter switch should then correct the now reversed elevator which I don't believe affects the CCPM mixing.
Last edited by Martyn McKinney; Feb 23, 2009 at 09:32 AM.
Feb 23, 2009, 06:13 AM
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Is it actually the servo? Does pitch work correct und just elevator in the wrong direction? If so, it's a problem in the swashplate mixing and not the servo...
Feb 23, 2009, 02:26 PM
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Martyn McKinney: Thanks for your input. As far as the right stick [made 2] is concerned mounting the front servo upside down , REVersing ELE on the TX and using a longer conection to the swash did work fine. However, the same problem was experienced when the throttle was applied, ie. the ELE servo didn't move in the same direction as the AIL and pitch servos. On the Twister the servos move down pulling the back of the main blades down to increase pitch so the heli lifts off. This is the opposite on my King 2 where the front of the main bldes are pushed up by the servos when throttle is applied. Is this what negative & positive shift refer to?
I guess that somehow I need to get at the electronics in the Tx to operate the ELE servo the opposite way when throttle is applied leaving the functioning of the rest as is.

daybyter: Thanks. Yes AIL and pitch servos work fine, it's just the front [ELE I believe] servo working opposite to the other 2 servos but only when throttle is applied.
Feb 23, 2009, 03:33 PM
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What happens if you turn the servo upside down, rotate the arm 180 degrees and don't flip the elevator switch on the transmitter?

This should correct the swash problem but leave the elevator (right stick) untouched.

One of these combinations has to work!
Feb 24, 2009, 07:21 AM
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Martyn McKinney: Thanks for responding Martyn. I think you might have found the problem. I was forced to rotate the arm 180 deg when I installed the servo upside down otherwise the link would have been at an impossible angle. I had hoped to be able to mount the servo without rotating the arm but there was not enough room on the otherside of the main shaft housing. I will try it out tonight pretending to mount it the other side of the main shaft and report back just for future info and my peace of mind.
Nice one.
Feb 24, 2009, 12:45 PM
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The only way [unless I'm missing something obvious] is to mount the regular servo on the opposite side of the main shaft, not change the arm and not REV the servo on the Tx!?! But this is not possible as there is not enough room. Even if there was enough room the arm is no longer perpendicular to the swash connecting rod which would mess up the CCPM synchro?? How frustrating. I have never used a servo that runs the opposite way so perhaps there is a way to do it with one of these - a Hitec?
Last edited by turnbui; Feb 24, 2009 at 01:01 PM.

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