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HomeAircraftHelicopterGasser Model RC HelicoptersOther › Tail servo not holding 9254
10-12-2011 02:43 AM  6 years agoPost 1
flyinfriend

rrApprentice

North American continent

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Hi,

The servo on my Predator tail seems very squishy so I am changing it out with another 9254 I have on hand. If this fixes the squishiness I will order a Futaba bls254 which I have in my Spectra. I am using the 401 gyro.

What causes a servo to stop holding well? It wasn't moving if I applied force to it and it wasn't skipping as if teeth were stripped. It was very hot after a flight. I had turned the gain up to 40% in AVCS mode because it wasn't holding well. Not holding well means in a hover or just flying circuits. I don't/can't fly 3d.

Just wondering why do servos go 'squishy'?

Thanks,

Tom

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10-12-2011 02:49 AM  6 years agoPost 2
helixangle

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Mamaroneck, NY - USA

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as with everything...age

in this case the potentiometer is going bad, in a nut shell the potentiometer is the device that tells the motor to spin, in what direction, and for what duration

Be sure the juice is worth the sqweeze
Remember life is hard...even harder for stupid people

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10-12-2011 10:25 AM  6 years agoPost 3
Dappe Bronco

rrNovice

Belgium

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Have you checked if your tail moves really free?
On my predator, the tail moved fine when not turning but was very hard to move while rotating. The included bearings got "notchy" under load. I changed the tail out for a Rappy 90 tail and have not head any tailissues since.

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10-12-2011 05:37 PM  6 years agoPost 4
RM3

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Killeen, Texas - USA

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+1 on age,

stuff will wear down but you can delay that by keeping on top of heli maint.

The best thing to do if you want the whole tail rotor system to last is to get as much of the vibes under control. The less the gyro sees vibs (from engine, head rotor etc.) the less its correcting for them by "gittering" the tail servo (this is also dependent on gain). the less the servo gitters, the less wear and tear on the gears, potentiometer and motor driver circuits. also making sure that the servo is properly mounted on the soft rubber isolators. then work your way back to to make sure the pitch actuator mechs are smoooth as warm butter. and lastly, balance the tail rotor system, not just the blades but he whole tail rotor with blades attached and shaft(like on a tru-spin etc). You'll be surprized how many guys just slap tail blades on, then are dealing with high freq vibs resonating down the tail onto the gyro...

showing a preference will only get you into trouble, 90% of everything is crap...

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10-12-2011 10:55 PM  6 years agoPost 5
GREYEAGLE

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Flat Land's

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Maybe
Go back and reset mechanically the tail adjustment for a static fixed YAW rate.

You should not need AVCS or HH to hover

Lower the gain as far as you can get it and still get results - it's too or over sensitive, and over working the servo. I'm down around 25% on one and around 28% on the other

I run the same servo and admittedly their good but now their are better --heat is a sure sign their busy.

Futaba doe's have an additional technical white paper on the 401 operation besides the some what Chinglish instruction's. You can pick it off their website. I refer to mine at least once a year.

greyeagle

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10-13-2011 05:21 PM  6 years agoPost 6
flyinfriend

rrApprentice

North American continent

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Thanks for all the responses.

The tail control mechanism is smooth and moves freely and this just started occurring the last few flights. I tried to set it up in non-AVCS but couldn't get it to hold well. I am trying out another 9254 servo this weekend and will report back. If that's what it is then I'll get the bls254 version. The engine is running a little rich as there is smoke coming from it so I may lean it a bit.

Thanks again,

Tom

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10-14-2011 01:40 PM  6 years agoPost 7
helixangle

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Mamaroneck, NY - USA

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flyinfriend

didn't see anyone mention this, and I'm sure it goes without saying but...

...what voltage are you running through the servo?

Be sure the juice is worth the sqweeze
Remember life is hard...even harder for stupid people

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10-14-2011 04:58 PM  6 years agoPost 8
flyinfriend

rrApprentice

North American continent

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Hi helixangle,

I am only running 4.8 for my batt. Thanks for asking about it. I switched to another 9254 last night and I'll give it a shot this weekend.

Thanks,

Tom

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10-14-2011 05:10 PM  6 years agoPost 9
helixangle

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Mamaroneck, NY - USA

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k...good luck! Let us know

Be sure the juice is worth the sqweeze
Remember life is hard...even harder for stupid people

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11-09-2011 01:29 AM  6 years agoPost 10
flyinfriend

rrApprentice

North American continent

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Hi Guys,

Figured I'd give the update. Dappe Bronco called this one. Thank you Dappe Bronco!! The tail seemed smooth but once I pulled the hub off of the tail shaft and pulled out on the grips it was notchy. I took it apart and the bearings had a little rust on them and the one of the thrust bearings had two balls drop out of the ring holding them.

I emailed Paul at Century and he said he would send two new thrust bearings out. I asked him if he could send out the other bearings for the tail as well and charge me for those in the same shipment. The response I got back that afternoon was that he had already shipped the entire set of tail bearings and there was no charge. This is a heli I built almost two years ago. I don't have a chance to fly every weekend so this heli doesn't have the time on it that some would put on it but it was two years ago that I built it.

I wanted to publicly thank Paul for the great customer service, again. Paul was a huge help with any parts and build issues I had when I put this heli together.

The last thing I want to mention is once I had the tail working fine it wasn't holding as well as I wanted when putting in collective quickly. I moved the control rod out one hole to give more mechanical gain and now it is spot on.

Now if winter would only hold off for another 3 months. I shouldn't complain today was in the 60's in MA and tomorrow is supposed to be the same.

Thank you for all of your replies,

Tom

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