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Old Nov 21, 2007, 02:27 AM
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Vancouver Island, Canada
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Trex - help taiming the tail on my bird

Hello everyone,

I got a chance to put a few more flights on my Trex today, what a blast! Thats 5 flights now and shes still in one piece lol. Anyway, the tail on this bird is jerking back and forth a little. I've turned the gain down from 40% all the way down to 25% and that helped greatly, but it still does it a little. When I turn the gain down to 20% the gyro no longer holds the tail perfectly. Whats the normal condition that I should expect? Do I have a problem maybe? Maybe my gyro isnt in a good spot or vibration is affecting it?

I've got a Gy 401 and a Futaba 9650 on the tail. Set to digital and set on "A" in the gyro menu.

I was adjusting the gain with the heli on the ground but the main rotor still spinning. Do I have to unplug the gyro and then plug it back in to complete the change?

What are you guys running your Gy401's at for gain?

Thanks in advance everyone.. I know one of you will help this brotha out!

Bob
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Old Nov 21, 2007, 03:20 AM
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ukgroucho's Avatar
Stratford upon Avon
Joined Jul 2004
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Have you set it up properly for throws (limit)?
No binding anywhere?
Delay on 401 set to 0?
What HS are you running?

Can you describe the tail behaviour a bit more... is it wagging in forward flight? or in a hover? or does it hunt around at the end of a turn / piro?
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Old Nov 22, 2007, 01:05 AM
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Heres some more info..

I've only got 5 flights on my heli so I'm still in the hovering mode.
When I'm hovering about 3 or 4 feet off the ground, tail towards me, the tail makes quick little jerks. The movement is very small, and its usually one way then the other but not always. I would say it moves maybe once or twice a minute, and the jerks are a second or two apart. I should really figure out how to upload video to youtube. That was with the gain at 35%. When I turned it down to 25%, the jerks lessened or so it would seem, but the tail would gradually let the heli turn counterclockwise. Maybe it would turn 45 degrees in two minutes. It doesnt seem to get any better when I turn the gain down any lower.

I have the gyro set to zero delay and on digital. Ive got the throw set to the maximum I can get. I'm using a 9650 with the pushrod perfectly straight but with a slight curve at the pushrod guide. It was the best I could possible get, I tried everything to get it better but from what I could tell, there is little if any resistance.
I removed the zbend at the servo and installed a ball link instead. There is NO slop at all in that pushrod.
One thing I did notice though, the gyro light flickers a little every once in awhile. I'm not sure if thats the Rx acting up or if thats normal.
I've read somewhere else that vibration or close proximity to motors/wires can affect the gyro. Have a look at my setup and tell me what you think. I spaced the gyro with a piece of 6mm Depron to get it to sit flush.

I wonder if its just the cheap plastic parts that I have on this SA model heli.

The other thing I wonder is if this is just normal behavior and I just need to get used to it. I dont live anywhere near a club for help so I'm on my own on this one. Anyway, there you have it in a nutshell. Any input on this would be appreciated. Let me know if you have any more questions..

Bob
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Old Nov 22, 2007, 02:19 AM
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Michigan
Joined Apr 2001
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I had a similar tail wag in my 450 S that I chased for quite a while. I finally found that it was caused by using governor mode on the Align ESC. The Align governor is far from ideal - some other brands are reported to function better and the CC ESC's even have a setting for governor gain. I changed to non-governor mode and the tail is perfectly behaved. The difference was quite pronounced while hovering. There are other possible causes for a tail wag, as I'm sure you are aware, like vibration, gyro set up, etc.
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Old Nov 22, 2007, 03:08 AM
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swatson144's Avatar
Hampton Roads Va.
Joined Oct 2004
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As I understand it you are saying it works well most of the time but a couple times a min it kicks, then works correctly?

If so I'd look more towards glitching. Try seperating the tail wires from other servo wires. As a rule of thumb I keep them apart when I build to help avoid the gyro picking up stray signals. Normally the cyclic and esc on one side and the tail wires on the other, better yet cyclic on one side ESC and tail on the other side but tail going aft and esc fwd.

Steve
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Old Nov 22, 2007, 03:42 AM
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I'd also lean towards chasing a glitch. In HH mode the gyro LED will flicker when it sees input so if you are not moving the rudder then it's seeing a spurious input (glitch)

Looks like you have a Berg Rx (good) but I don't like what you have done with your antenna. In general crossing the antennal over itself (wrapping excess around the antenna tube for example) is not a good thing to do.

Search for the ways that other folks have routed their antennas - or get a "stubby" antenna (base loaded) like a deans whip antenna.
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Old Nov 22, 2007, 02:30 PM
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Hmm, ok I just got in from running a few lipos through the bird and I'm with you guys on it being a glitching problem.
I played with the gain settings, ran it up to 40% and then down to 10% and it still does it. I did get some wag at 40% so I think I know what that looks like now.
I actually changed the antenna after I took these pictures so that might not be it. Heres a post of my new antenna routing.
I'll try and seperate the wires more. I'm also wondering if the gyro gives off anything that would affect the Rx? The way I have the gyro mounted it sits very close to the Rx.
To tell you the truth I'm not sure if its not normal behavior its so minor. Is the tail supposed to hold position and NEVER move even if its a little windy? I can certainly handle it the way it is, its not like I'm worried when it happens that its going to crash.
I'll start moving all the wires farther apart and try to get the Rx a little farther away from the motor. Then I'll try some different antenna routing options.

Thanks for all the suggestions everyone. I appreciate it.

Bob
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Old Nov 22, 2007, 02:50 PM
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Whoops forgot the pictures. I drilled some tiny holes in the landing struts to run the wire through. I see now that the antenna runs really close to the motor wires. I'll cut those wires shorter and tidy them up. I've also got a big mess of wires on my Rx but I couldnt seem to make it clean. Some of the servo wires barely make it to the Rx so I dont have many options with them.
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Old Nov 23, 2007, 10:08 PM
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Got er I'm not sure what I did that fixed it but something I did worked. I found the tail rotor belt wasnt tight anymore so I tightened that up. It could have been jumping a gear it was soo loose. It was tight when I started but I guess it needed a break in period. Then I rerouted the wires and spaced them about as best I could. Long story short the heli holds its position nice and steady now. I'm running it at 30% gain. Thanks everyone for all the input.

Bob
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