First time builder, tail servo and/or gyro problem (I think) - RC Groups
Thread Tools
Mar 25, 2010, 05:23 AM
Registered User

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 and the post is where I say "Well, I got the blades spinning! "

The gyro is hk401b,
Tail servo is

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].

Sign up now
to remove ads between posts
Mar 25, 2010, 12:13 PM
Rocket Programmer
jasmine2501's Avatar
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)
Mar 25, 2010, 06:17 PM
Registered User
Originally Posted by jasmine2501
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]
Mar 25, 2010, 08:41 PM
Rocket Programmer
jasmine2501's Avatar
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.

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Best Balsa Plane for first time builder Preacherman11 Beginner Training Area (Fuel) 12 Mar 11, 2010 04:00 PM
Discussion Problem combining tail gyro and cyclic servos hidavi Micro Helis 7 Mar 04, 2010 11:17 PM
Discussion Radian or similar for first time? flitelab Beginner Training Area (Aircraft-Electric) 15 Mar 02, 2010 10:54 AM
Help! First time flyer/Builder will fly first solo tommorow Fulanito_chile Beginner Training Area (Aircraft-Electric) 4 Aug 23, 2008 03:20 PM
For Sale Low time Futaba GY601 Gyro--Everything except tail servo-140$ shipped Jag72 Aircraft - General - Radio Equipment (FS/W) 3 Dec 08, 2007 12:59 PM