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Old 11-13-2007, 08:47 PM   #1
jimmyv138
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Question Gyro/Rudder Servo "Creeping"

I am pretty new to the hobby, but I'm hooked. It didn't seem to take long to start building my collection of heli's and spending WAY too much money in the process. I picked up an old Raptor 30 from a friend and it was equipped with a JR G410T gyro. I have tried everything I can think of to set it up straight, but no matter what I do, the rudder servo still "creeps". When I turn the gain up, it creeps to the left, however, when i turn the gain down, it creeps to the right. I put a 401 on it for now, but I hate to throw a good gyro away if it's not broken. I feel like i'm missing something, but I'm not sure what else to do. When you spool it up and start to lift off, the tail will just take off. I've checked the reverse switch, and it set up correctly on the gyro. Anyone have any idea's?
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Old 11-13-2007, 10:59 PM   #2
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If the gyro is in Heading Hold, it is normal for the servo to "creep" when the heli is sitting still. With gyro in rate mode, servo should center.

By "...just take off..." do you mean the heli spins? This, of course, is not normal. Have you carefully checked for proper tail rotation (the belt could be twisted the wrong way), proper tail blade orientation, proper tail blade movement when TX stick is moved, and proper tail blade movement when the heli is moved? Another set of eyes really helps with these checks...
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Old 11-14-2007, 11:28 AM   #3
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just out of curiosity, what direction is the tail supposed to spin? in my head, it would make sense that if say the belt was twisted the wrong way and the tail blades were on flipped that your tail should still work normally? say if your looking at your heli from the right and your blades spin clockwise, what direction should the tail spin?
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Old 11-14-2007, 01:01 PM   #4
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The inside tail rotor blade should rotate into the main blades. If your tail rotor is on the right side of the bird you should have a counter clockwise rotation on the tail.
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Old 11-14-2007, 01:05 PM   #5
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First ensure your mechanical setup is sound. Your tail belt should have only 1/4 twist in it, it should be rotating counter clockwise when looking at the right side of the heli.

Next give right rudder, the servo should pull the rod to the front, if thats wrong reverse your rudder channel.
Pick up the heli and move the nose to the left (counter clockwise looking down) the servo should again pull the rod, if thats wrong reverse the gyro.

Now turn the gain all the way up and adjust the sub trim on the rudder channel till it stops drifting. You may have to bump the stick to recenter it because it will creep to the end of travel. Make the adjustment one point at a time and watch the servo. When you're done set it back to 50 percent and test fly.
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Old 11-14-2007, 05:53 PM   #6
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Thanks for the advice. I'll try adjusting the sub trim. I have checked the mechanical setup and it's good. I'll let you guy's know how it turns out. Thanks again.
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Old 11-14-2007, 09:24 PM   #7
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Quote:
Originally Posted by BarracudaHockey View Post
First ensure your mechanical setup is sound. Your tail belt should have only 1/4 twist in it, it should be rotating counter clockwise when looking at the right side of the heli.

Next give right rudder, the servo should pull the rod to the front, if thats wrong reverse your rudder channel.
Pick up the heli and move the nose to the left (counter clockwise looking down) the servo should again pull the rod, if thats wrong reverse the gyro.

Now turn the gain all the way up and adjust the sub trim on the rudder channel till it stops drifting. You may have to bump the stick to recenter it because it will creep to the end of travel. Make the adjustment one point at a time and watch the servo. When you're done set it back to 50 percent and test fly.
Wow! that's the best thing I've seen on rudder creep. I'm going to try it, a few times I've noticed just a little creep and just changed the gain a bit. Thanks for the info.
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Old 11-15-2007, 09:36 AM   #8
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That only applies to JR gyros, not Futaba. The reason is because the Futaba gyros memorize the center pulse at boot up and assume that to be neutral. The JR's assume a set center pulse value on the rudder channel as neutral and in real life it varies with recievers and transmitters just slightly so the sub trim adjusts the reciever to what the gyro thinks is neutral then it all gets along.
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Old 11-16-2007, 12:34 PM   #9
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I found my problem. I had a slight nose left drift, so I tried upping the gain, then subtrim (which I now understand is incorrect, I'm using a GY401). Then I heard a rattle and immediately landed from a low hover using throttle hold. One bearing in my CNC tailrotor box was gone on my T-rex 600. The T/R pitch change bellcrank came off the slider as the bearing failed, so If I hadn't hit throttle hold it would have gotten interesting.

Another reason to be extremely cautious if your machine isn't at 100%. If you hear anything unusual, or see a new vibratiojn you haven't seen before, land ASAP.
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