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Home✈️Aircraft🚁HelicopterAlignT-REX 700N › 700N Spartin Tail twitch
04-24-2009 08:18 PM  10 years ago
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b1833

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Logan, Utah, USA

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700N Spartin Tail twitch
I have a twitching or hunting in my tail of my new 700N. It twitches in hover and forward flight.. I don't do backward flight yet. Doing FF and flips/rolls etc it seems to smooth out. My buddy throws it around and doesn't notice it until we slow down to land..

New machine. I am running the Spartin gyro, YS91SR engine. I has 2 gallons of fuel through it. Adjusting carb doesnt seem to affect it. Gain holds when buddy flying backwards and wringing it out. He set gain to just hold through the hard 3D maneuvers. Tail is smooth, no binding. 3 different heli guys have gone through this thing and we cant solve the twitch. Gain adjustment doesn't help..

I'm looking for creative thinking.. Doesn't seem to be the usual causes. Any ideas?

Thanks,
Duane
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04-24-2009 08:33 PM  10 years ago
baddynergy

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sierra madre, ca- usa

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Need more info about your set-up. Tail twitches could be anything from running to rich to vibes to pcm glitches (especially with carbon frames).**Unattended children will be givin a shot of espresso and a puppy**
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04-24-2009 09:33 PM  10 years ago
b1833

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Logan, Utah, USA

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Trex 700N
YS 91SR 2 gallons
Spectrum AR7100 & TP 3400R batt (2s2p)
two remote rx on the AR7100
Spartan ds760 w Futaba BLS 251
Futaba BLS 451 on CCPM
Futaba 9650 Servo on Throttle

The CCPM servos are running on the batt voltage where the gyro, bls251 & throttle servos run on the regulated voltages. Gyro mounted with the metal plate sandwiched between the foam as per Spartans' instructions.

Anything else needed?
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04-24-2009 09:49 PM  10 years ago
b1833

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Logan, Utah, USA

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Attention AR7100 and AR7100R owners
I've been looking around to see if there are any AR7100 issues in helis.. I found this on Spektrum's website. Describes my problem perfectly...

We have received three reports of antennas wires detaching from the main receiver. Because the AR7100 utilizes one or optionally two remotely mounted receivers in most cases the user won’t realize the main antenna is detached. In some cases a slight “tail twitching” may be noticed as the antenna intermittently make contact however in many cases the issue may not be detected. It’s important to do the following check to verify that your antenna is properly connected.

Firmly pull on the antenna.

The antenna should be securely attached.

I will investigate this issue then report back.

Thanks,
Duane
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04-24-2009 09:52 PM  10 years ago
Ghostrider

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San Diego, CA

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Make sure the first 1 inch of the wire coming out of the Spartan is not touching anything or tied down to anything.

Also make sure your ball link on the tail servo is not binding on the servo horn/wheel.
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04-24-2009 09:57 PM  10 years ago
b1833

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Logan, Utah, USA

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Thanks Ghostrider. Will do...
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04-24-2009 10:21 PM  10 years ago
jameswill4

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Pineville KY

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I just sent my 7100r to horizon today with tail twitching problems. I lost a 770 and 8900 last week to it (sent it in as well) I put a align gp750 and 620 on it and solved it for 6 flights and it came back today. We will see what they have to say. My antenna was not loose and i doubt it is 2 brand new gyro tail servo combos bad.
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04-24-2009 10:47 PM  10 years ago
thorpdrvr

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san antonio, tx

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I have a new 700 with about 25 flights on it with the same problem. It has a mini-g gyro and 8900g servo. Adjusting mixture had no effect.

I have the gyro mounted according to instructions with two pieces of foam beneath the metal plate and one piece above it. It is a pretty squishy mount. I had a loose velcro strap around the gyro on the earlier flights. Today I tightened it up to limit the movement of the gyro and it seemed to greatly lessen the tail jerks. It didn't totally eliminate them, but it is much better now.

I have the Align 91h with stock shim on head. Running 30% Magnum fuel. Thinking another shim may eliminate the rest of it, but have not tried it yet.
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04-30-2009 05:12 PM  10 years ago
b1833

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Logan, Utah, USA

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thorpdrvr,
Will you let me know what you find out? I checked my antenna and it does not feel loose or anything.. Removed the rx case and saw no problems. I have a spektrum flight logger on order to test what all the antennas are returning. That should be in later today.

I'll let the list know what I find.

Thanks,
Duane
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05-01-2009 02:55 AM  10 years ago
bmapope

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TN

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i just witnessed something similar at a fun fly recently. i think the 251 has no deadband whatsoever..which is bad. try a 8900 or something that is known to have a little deadband and this will probably resolve your issue. good luck.
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05-01-2009 04:33 AM  10 years ago
Divot

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Mesa, AZ

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. Adjusting carb doesnt seem to affect it.
Keep tuning, your engine is to rich.
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05-01-2009 05:36 PM  10 years ago
f penfold

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uk

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how have you installed the gyro did you use the 3mm foam the the metal plate then the double sided tape How old is the mounting foam they do have to be replaced form time to time
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05-01-2009 06:04 PM  10 years ago
raptorheli2

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rip off britain and no changing it

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i had this exact problem. the thrust bearings in the tail were jammed full of loctite in the end and bearings not greased (i couldn't get them apart during build so left them)

cheers

www.waterfoothelis.com
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05-01-2009 06:43 PM  10 years ago
bmapope

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TN

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i also had that same thing with loctite in the tail thrust bearing, heat it up tear it apart tri flo it and good to go!
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07-06-2009 03:20 PM  10 years ago
b1833

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Logan, Utah, USA

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I forgot to update this thread with my findings.

After chasing false motor tuning issues (motor is running sweet) and speaking with spartin etc.. I disassembled my tail hub & head to verify thrust bearing direction and if loctite is in the bearings.

Way back in December I had a real tough time getting the main blade grips on one side to tighten up. As it turns out, my outer thrust bearing race is almost 1 thousandth of an inch smaller ID than the spindle... Somehow, I actually got the race onto the spindle but the bearings were never properly seated, causing the spindle to sit out of balance. After correcting, the tail twitch is gone and she flies smooth.

Thanks All.

duane
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