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Thunder Tiger 60/70/90 Raptor 60/70/90 Helicopters


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Old 06-16-2012, 03:44 PM   #1
raptorpilot
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Default Raptor 70 tail servo twitching

I have an older Raptor 70 and having a problem with the tail servo twitching approx. 1/4 inch. The other servos are rock solid. I switched out the servo for a different one and got the same result so its not the servo. I am using a CSM 540 gyro that is probably 10 years old, a 6v lipoly with a regulator, and not using a govenor. I suspect the gyro due to its age, but not sure. Any ideas?
Thanks!
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Old 06-22-2012, 08:52 PM   #2
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Not familar w that gyro but my friend had one on his 600 and said the same thing (tail twitching) He ended up buying a new gyro and tail servo $$$ problem solved. I wouldn't have the money for that but that gyro is pretty old right?
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Old 06-23-2012, 09:57 PM   #3
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yeah, the gyro itself if probably at least 8 years old. The CSM gyros are popular in the UK, and are supposed to be pretty good gyros. I think this one has seen better days. I bought the heli used and got a good price on it so can't complain too much. I think I will just replace it with a futaba 401.
thanks for the reply.
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Old 07-02-2012, 10:26 PM   #4
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The 401 is also old but still good I have a 401 with a9253 on the tail ,9202 on cyclic my heli is all old stuff still working on some of the issues with my cyclic.To slow for my flying style. Im thinking about moving the balls on the horn to speed it up, ""not sure".
I have a few other helis all have the 401 (except for my 250, 780 stock gyro I think) I have had problems with learning the setup and doesn't hold as well on my 450 but i see other friends fly with more exspensive gyro's and have the same problem. Make sure you use the right gyro tape. Thats been one of my problems. I fired up my R 70 today with the new mavrikk 680 blades on it. Was good fun.
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Old 07-04-2012, 08:44 PM   #5
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After ruling out several other things as the source of the problem, I have a new 401 ordered. I was planning on using the stock double sided foam tape that it comes with. What is the best way to mount the gyro?
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Old 07-05-2012, 01:50 AM   #6
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I have had several issues in the past with proper tape. I mount mine on the back above where the boom slips in the frame should come with some double stick GYRO TAPE. I always make sure I clean booth surfaces before putting the tape on. Try to do it in one shot so the adhesive on the tape is not compromised. If for any reason in flight your gyro was to come off you wouldn't be able to control your tail.
Hook your wires up to the receiver and your ready to set your sensitivity up. Look up the 401 in finless bob set up for that
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Old 07-05-2012, 09:46 PM   #7
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Thanks for the help! I should have it installed and test flown this weekend. I will let you know how it turns out.
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Old 07-09-2012, 09:01 PM   #8
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The twitching servo problem is now completely resolved after replacing the gyro. Thanks for the help DJAYPRO. Now my only problem is a bad tail vibration. I was hoping it was the cheap blades but after replacing both main and tail rotor blades with good carbon fiber blades the problem continues. Any ideas on what to replace next?
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Old 07-26-2012, 10:46 AM   #9
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My guess is this "bad vibration" was the root cause of the original tail wag.

I had a similar situation - replaced the servo, the gyro etc and it never went away.
It turned out it was a bad main shaft.

For you, I'd check the run out on the tail rotor shaft (is it bent?), bevel gears (are they chipped or the bearings shot) and the TR shaft bearings.
Also check the torque tube & the torque tube bearings.
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Old 07-31-2012, 11:07 PM   #10
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Actually, the servo twitch was from the bad gyro. I suspected that since it would twitch on the ground without being started. As for the vibration, I have replaced the blades for good carbon fiber blades, and replaced everything from the boom attachment back. Still have the vibration. Must be something on the head. Just not sure what to start replacing first on the head.
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Old 10-17-2012, 07:51 PM   #11
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Update, after replacing several parts on the raptor 70 (probably needed to be replaced anyway) I finally got to the root of my problems. Here is what I found:
Rudder servo twitching was from bad/old gyro, replaced it with futaba 401
Tail vibration was caused by head speed being too low since the engine was too rich.
The heli flies GREAT now with no vibration or bad habits!!
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Old 10-22-2012, 12:25 PM   #12
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What head speed did you bump it up to?

BTW: When ever my engine starts to act up, I see it in the tail first.
Too rich on the engine causes a yaw vibration as the engine sputters (almost undetectable from the sound the engine is making) and the gyro / fbl controller tries to compensate.
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