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HomeAircraftHelicopterHelicopter Main Discussion › Question about possible cause of servo twitching
04-18-2011 08:34 PM  7 years agoPost 1
daronjrrNovice - Baton Rouge, La. - My Posts: All  Forum  Topic

I have an HK 450 and on two occasions, while hovering in idle up, the heli just drove itself into the ground as if I had given it full negative pitch. After rebuilding, I spooled it up and noticed that the cyclic servos were twitching, almost like rx interference. I have tried a number of things to identify the problem like a different ESC/UBEC and a different receiver (They are spektrum ar6100 and I am using a JR 10x), but the problem persists. I have 3 other helis and numerous planes that do not exhibit this behavior so I think it's unique to this particular bird. Oh I also have a different Gyro and different cyclic servos installed since the problem began. Not sure where to go from here. I'd appreciate some advice.

Thanks~

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04-18-2011 09:17 PM  7 years agoPost 2
Gyronut

rrProfessor

Martinsville In.

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You might want to check your wiring for any type of shorts to any carbon or metal frame components.

Are you glitches independant of heli orientation..??

Where is your rcvr ant in relationship to the Motor and esc..??

Check your rcvr antenna and make sure they are not broken and just being held on with the wire insulation.

Rick

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04-18-2011 10:14 PM  7 years agoPost 3
oldfart

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Vancouver, Canada

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What servos? - they may have some stripped gears.

Phil

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04-18-2011 11:20 PM  7 years agoPost 4
daronj

rrNovice

Baton Rouge, La.

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Tried two recievers, both good. Rx is mounted on the bottom plate on the rear of heli, esc is beside to motor on the front. I will go over the wiring to check for shorts. Oh, the glitches occur regardless of the heli orientation.

Thanks

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04-18-2011 11:22 PM  7 years agoPost 5
daronj

rrNovice

Baton Rouge, La.

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Servos are inexpensive Tower Pro 9g with plastic gears. I'll double check, but I think the gears are fine. All servos are twitching at the same time.

Thanks-

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04-19-2011 12:45 AM  7 years agoPost 6
Eagle2bravo

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Out flying somewhere

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Servos DO twitch when they are bad but you say ALL are twitching??...humm. The Eflight s75's were famous for that...after like 10 flights or so..lol. Could have fried them with that last crash. Sounds like it was bad. Good luck
Rob

T-rex 600n super pro , Trex 450 se, Gaui 200, Trex 500, Blade cx, . "If ya plant corn, ya get c

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04-19-2011 03:01 AM  7 years agoPost 7
daronj

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Baton Rouge, La.

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Okay, did some serious testing this evening. Strapped the heli to my bench and removed the blades. Spun it up and immediately the cyclic servos began to twitch. Having checked all the wires for shorts, found none, I began unplugging servos one at a time and spinning up. No luck on the cyclic servos. However, when I unplugged the tail servo and gyro, the twitching was reduced dramatically, but still there. Swapped the tail servo and gyro for a spare set and the twitching came back.

On the advice of a friend I tried grounding the tail boom to the frame by sanding the paint off the tail boom and strapping a wire from the boom to the frame. Spun the heli up and to my surprise, no twitching.

I decided to google tail belt static discharge and it really sounds a lot like what I am experiencing. Don't know for sure, but I can't wait to take it up for a test hover. I did just recently upgrade to an EXI full metal tail from the plastic one and I also installed an Align metal tail boom.

We'll see. Thanks for all of the advice.

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04-19-2011 03:23 AM  7 years agoPost 8
RCHSF

rrKey Veteran

NC

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Sounds like static. What gyro?, make sure you have the gyro set for standard servo, and not set to digital.

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04-19-2011 03:35 AM  7 years agoPost 9
daronj

rrNovice

Baton Rouge, La.

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Hoping that is all it was. I am using an Align GP750 Gyro. It is set to Analog Servo.

Thanks-

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04-19-2011 03:35 AM  7 years agoPost 10
Raffy

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Chicago, Illinois

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Check your battery. One cell might be going bad. Try another ESC.

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04-19-2011 03:43 AM  7 years agoPost 11
RCHSF

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NC

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Also keep your rudder, and gyro wires as far away from your esc wire as possible. And make sure your 2.4ghz antenna wire does not touch any carbon fiber frame. If your frame is carbon. And make sure your linkage rods will fall if you hold them horizontal and drop them. If they are tight, a bunch of them to tight will draw a lot of excess power, and may cause flutter of servos, not getting enough power. It could be a host of issues working together, sometimes it's hard to pin down, just try to eliminate one thing at a time. Like you did with unplugging one servo at a time. Good Luck....

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04-20-2011 05:36 AM  7 years agoPost 12
daronj

rrNovice

Baton Rouge, La.

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Just a follow-up. Took the 450 up and flew a full pack with not one servo glitch this evening. Resolution was grounding the tail boom to the frame and spraying the drive belt down with silicon spray. Flew like a champ.

Thanks for all of the assistance. I appreciate it.

Daron

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