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HomeAircraftHelicopterHelicopter Main Discussion › Something strange happening
02-08-2008 11:56 AM  10 years agoPost 1
flying buffalo

rrApprentice

Darwin, NT, Australia

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Hi all, 2 questions. Firstly my tail servo after just one tank of fuel is getting very hot. Its a 50 Titan with a 401 gyro and a 9254 futaba servo running on a 6 volt reciever battery. It gets that hot and is getting worse. The tail now is starting to let go and drift.
Secondly the heli is becomming unstable in a hover as it wants to keep nose diving and so having to correct with up elevator. I can still keep control and fly arround but has become a real problem. Pulled the heli apart last night thinking that the main rotor shaft bearings could be bad but found them to be ok. Reassembled but still need to correct for nose down. Every now and then it seems to dissapear but then its back. Forward and backward loops are really messy where before they were sweet. How do you know when main bearings are bad? I found no slopin these bearings.
Cheers Robert

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02-08-2008 12:19 PM  10 years agoPost 2
RobRoy

rrKey Veteran

Huntsville, Alabama

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First off, 6 volts is too much for the 9254, 5.3v should be the max, get a stepdown. As for your nosing forward problem, check for loose or missaligned paddles. Hope this helps.

Ignorance is curable, stupidity is for life.

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02-08-2008 12:29 PM  10 years agoPost 3
jester4

rrKey Veteran

Brampton, Ontario

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Agreed, a 6V pack is probably closer to 7V fully charged. You've likely put a big hurt on that servo. What about your other servos? Are they rated for 6V packs?

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02-08-2008 12:31 PM  10 years agoPost 4
flying buffalo

rrApprentice

Darwin, NT, Australia

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Tail servo hurting
Thanks for that guys, but why do you need to treat tail servo different?

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02-08-2008 12:45 PM  10 years agoPost 5
Yug

rrMaster

UK. Herts

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Thanks for that guys, but why do you need to treat tail servo different
because the 9254 is only specified to run at 4.8v. This means a 4 cell pack which, when freshly charged will supply about 5.6V. This is within spec. However, a 6v pack (5 cells) will supply about 7v when fresh, this will rapidly kill your servo.

Vegetable rights and Peace

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02-08-2008 12:49 PM  10 years agoPost 6
dkshema

rrMaster

Cedar Rapids, IA

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but why do you need to treat tail servo different?
Because not all servos are designed to operate at six volts. If you go look at the Futaba website, at the servo page, you'll see that many of their servos are NOT rated for 6 volt operation.

I recently emailed their tech hotline with the question "What is the maximum safe operating voltage for the S9254 servo?"

The reply was that the S9254 should be operated at no more than 5.8 volts.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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02-08-2008 12:52 PM  10 years agoPost 7
MartyH

rrProfessor

USA

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flying buffalo,

you're going to burn up your tail rotor servo if you havent already. It is designed for the 4.8v only. Also, you didnt say what servos you are using for the rest of the heli. Perhaps these too are 4.8v servos only?

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02-08-2008 12:55 PM  10 years agoPost 8
flying buffalo

rrApprentice

Darwin, NT, Australia

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Unstable flight
Thanks again guys on that tail servo issue, what about main rotor bearing failure, has it happened to you?, Is a failed main bearing easy to pick up? Does it totally disintegrate or just becomes sloppy?
Can a failed main bearing cause unstable flight like i described?
Cheers Robert

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02-08-2008 12:58 PM  10 years agoPost 9
Yug

rrMaster

UK. Herts

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I would work right through the entire control system, looking for anything with play or binding. Which bearings did you replace after the crash ?

Vegetable rights and Peace

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02-08-2008 01:12 PM  10 years agoPost 10
flying buffalo

rrApprentice

Darwin, NT, Australia

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Unstable flight
Hi Yug, no there was no crash, it just happened, unstable in hover(more nose down than anything) and loops both forward and backward are messy. Does go away for a few seconds then its back. Paddle and main hub are good with no slop or binding. thought it might be main shaft bearings but checked those and they seem ok. But also have this hot tail servo issue (which I have sorted thanks to you guys), which maybe could have an effect maybe on the other servos in flight.
cheers Robert

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02-08-2008 01:15 PM  10 years agoPost 11
jester4

rrKey Veteran

Brampton, Ontario

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I still say if your other servos are not rated to 6V (you haven't indicated which servos you are using), you may be getting one starting to fail? Just a thought. I had the same symptoms when I had a servo starting to go with uncommanded inputs (forward elevator)

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02-08-2008 01:22 PM  10 years agoPost 12
flying buffalo

rrApprentice

Darwin, NT, Australia

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Unstable flight
Hi jester4, the other servos are hitec hs-5985mg servos.

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02-08-2008 03:18 PM  10 years agoPost 13
BarracudaHockey

rrMaster

Jacksonville FL

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The reason the tail servo is different is because when its hooked up to the 401 its getting updated at 270hz vice the 70 hz that a servo gets from the reciever, combine that with higher voltage and also your gain is probably twice what you need and its very hard on the servo, I'd say you've already fried it.

Andy
AMA 77227
http://www.jaxrc.com

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