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Old Mar 25, 2010, 05:23 AM
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Joined Mar 2010
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Help!
First time builder, tail servo and/or gyro problem (I think)

Hello, I am a first time builder (got into RC heli's a few weeks ago using my father in-law's coaxial. Instant addiction!). I purchased a "hk 450" kit + items to make a heli. I've built it and it all seems to go ok [the pitch, aileron, elevate right hand stick on mode 2 movements seem to move the swashplate the way it's supposed to. Had to reverse one servo to make it work ok, so I think I got the hang of stuff from watching finless bob videos] but when I turn on the heli, after the gyro sets up, the tail servo keeps trying to move the tail linkage rod towards the main body. It gets like a 'bouncing motion' from trying to continously moving the linkage rod, getting to the end, bouncing back a little and then doing the same thing, *wash and repeat*. A thread of some things I've tried is at and at http://www.hobbycity.com/hobbycity/f...?TID=7534&PN=2 and the post is where I say "Well, I got the blades spinning! "

The gyro is hk401b, http://hobbyking.com/hobbyking/store...dproduct=10113
Tail servo is http://www.hobbycity.com/hobbycity/s...idProduct=8511

When I took the gyro out of the equation (plugged the servo straight into the rudder of the receiver (I think it was rudder anyway), it kept doing the same thing. It seems not to do the bouncing motion when I don't have the horn not connected to the gyro but it's hard to remember some specifics as I have had nerve damage related pain for ~4 years and on a HUGE dose of pain meds (oxycontin, tramal + lyrica and more) daily which sometimes makes me recent things a little hazy, mainly as I've been working on the RC helicopter for about 40-50 hours this week and forgetting some specifics due to doing so much testing and what not.

I have no real idea if it's the servo and/or gyro having issues (or anything else??? receiver, transmitter, whatever?) and hoping someone may know anything about this or things to do to diagnose for errors so I can try to narrow down on how to fix this [hopefully].

Cheers
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Old Mar 25, 2010, 12:13 PM
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United States, AZ, Mesa
Joined Jul 2007
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Remove all trim and sub-trim from the rudder channel, make sure the two plugs from the gyro are in the right spots, and re-bind the receiver. Then watch this... some movement is normal.

Why does the servo stick to one side? (3 min 25 sec)
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Old Mar 25, 2010, 06:17 PM
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Quote:
Originally Posted by jasmine2501 View Post
Remove all trim and sub-trim from the rudder channel, make sure the two plugs from the gyro are in the right spots, and re-bind the receiver. Then watch this... some movement is normal.
Cheers, it wasn't 'just' the gyro staying to one side, it was continously moving and stuck in a 'bouncing' motion which was heating up the servo big time. Also it was making the helicopter spin when I was having the blades spin up and giving it a tiny lift off the ground.

But now,

Amazing, looks like it's working! Did another check of the servo horn + ball link connections, this time it wasn't doing the 'bouncing motion'. Took it outside and it wasn't spinning wildly as the blades were going this time and I got a little bit of lift from it. Still need to tweak it properly (pitch guage etc) but the main stuff is happening. But now it seems to not be stuck on one side and spinning as the blades are going.

*phew* But now I'm off for a ride on the bike to clear my head from this weeks frustrations of the build. I'll probably ride better knowing the helicopter is that bit closer to being "workable" Thanks for the help, now I can concentrate on the specifics of flight etc (and not from just the sim) as opposed to the basics of actual building the helicopter [only]
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Old Mar 25, 2010, 08:41 PM
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United States, AZ, Mesa
Joined Jul 2007
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Could be you have too much gain. This can cause the gyro to react rather severely to vibrations you may not be aware of. If it doesn't correct in the right direction, there should be a reversing switch on the gyro to fix that.

This is a demonstration of a helicopter with the reversing switch set wrong on the gyro.

http://www.youtube.com/watch?v=txxJPu1Dn7M
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