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Home✈️Aircraft🚁HelicopterGasser Model RC HelicoptersOther › Dancing throttle servo??
08-05-2007 02:49 PM  13 years ago
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gorn

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Western Australia

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Dancing throttle servo??
Started my Maxum today.
First thing that happens is the throttle starts headbanging.
Now I know my Maxum is brilliant and has attitude to burn ,
but this was just to much lol.
On the bench the servo works great, as soon as the engine fires it moves fairly briskly back and forth through about 1/4 of its travel.
The servo has had zero use, came bundled with my old Hitec Optic 6.
They gave me 4, so I figure Im gonna use em till they crap out.
But not THIS quick lol.
Ozace had the same dancing servo problem with his QWW 20cc.
We are both using the DX7 with the AR9000 RX.
Any ideas on whats happening here people??
Cheers
For the love of the hobby
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08-05-2007 03:51 PM  13 years ago
loewermx

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Alexandria, La

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I had this happen on an old Min Air Gasser. Found out that it was RF noise. Moved some things around and shielded the spark plug good and all was well.

I am not sure if the same thing happens on 2.4 though.
Cajun Aircraft
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08-05-2007 04:03 PM  13 years ago
nicholasdugas

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new iberia Louisiana

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I had the same thing on a 50cc gas plane you need to move your stuff around loewermx is right its rf noise
Team Cajun Helicopters
Trex 700 8717's YS91SR X9303
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08-05-2007 04:23 PM  13 years ago
FCM

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Surrey, England

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As you are running a DX7 Rx, you may be picking up interference from the throttle servo leads. The DX7 is supposed to be immune to all RF. Is the throttle servo located near to the ignition coil or spark plug?

Paul.
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08-05-2007 04:57 PM  13 years ago
victor55ca

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Vancouver BC

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Have you tried a higher end servo like a 9252 or a JR on the throtle?
You have a large investment in these gassers, go the extra bit and invest in some high end servos. Crashes cost way more that new servos!

Vince
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08-05-2007 05:08 PM  13 years ago
gorn

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Western Australia

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It really shouldnt matter what servo it is when it has had zero use, and is basically in a no load situation.
At least in my mind, I cant see why.
I hear you on the servo, have to wait a week.
See the pic for servo location in regard to distance to the plug lead.

For the love of the hobby
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08-05-2007 08:58 PM  13 years ago
Coolrunnin

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Manchester U.K.

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Your servo is very close to the HT lead/plug so most servos, no matter what quality will tend to twitch due interference.

First, try fitting a suppressed plug cap (NGK make good screw-in ones) rather than the stock Zenoah spring you have currently which can even arc inside the HT lead and cause interference due to the way it is fitted. Just slice off the red silicone boot then the spring inside should be easy to pull out from the side of the HT lead so you can keep the full HT length for the new plug cap.

If the servo still kicks then look at moving it to a location away from the plug and make up a new pushrod to suit. This will work as a last resort.

Hope that helps
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08-05-2007 09:08 PM  13 years ago
bwarkent

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Houston Tx

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Gorn, didn't you post a while back about the same problem with one of your other helis? Something about hitec servos and the dx7?
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08-05-2007 09:29 PM  13 years ago
copperclad

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NY

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hi gorn
i just had a similar problem with a brand new hitec servo on throttle , trading out the servo was the fix , hth , dana
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08-05-2007 11:51 PM  13 years ago
ozace

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melbourne, australia

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I have swapped out my servo (nib hitec) for a different model hitec (nib as well) to see if it makes a difference. I also put a ferrite ring on the servo lead now.we can never have too many, can we ?
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08-06-2007 01:44 AM  13 years ago
shuttlepilot

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Mullins, South Carolina

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I too have had issues with twitching Hitec servos on my gasser. I opted for 9252's and a 3151 on the throttle and all is fine now. Now I have used Hitecs in all of my nitro birds, but for some reason they did not like the gasser. It does look like the ignition plug lead is a little too close to the servo for me......my .02Gas is Great
Camper Fuel is Better!!
QWW Helis
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08-06-2007 02:21 AM  13 years ago
Wayne R

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Kirkland Lake,Ontario,Canada

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I have four Hitec servos ( three digital 6965's on the cyclics and a digital 6635 for the throttle ) and a Futaba 9251 on my Predator SE gasser and so far have not had a single problem after four gallons worth of flying. This of course is with a Futaba 9 channel PCM receiver.

Wayne Reid
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08-06-2007 03:59 AM  13 years ago
gorn

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Western Australia

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That other Hitec servo was a dirty pot issue. Replaced with a new one and all is well.

I will try a different servo first, then the plug cap if that doesnt work.

There isnt really anywhere else to mount the throttle servo, so I will just ahve to work on it for a while.

Thanks for your input guys
For the love of the hobby
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08-06-2007 04:31 AM  13 years ago
turboomni

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East of the Equator

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Can you flip the servo so the wire goes the other way?Setup is everything, All my heli's can fly far better than I can pilot them
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08-06-2007 04:13 PM  13 years ago
gorn

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Western Australia

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Turboomni
This is exactly what I did
And presto, she works like a charm now
For the love of the hobby
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08-06-2007 04:34 PM  13 years ago
JEEPWORLD2002

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BLUEBELL PA USA

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gorn I also had a problem like this where the sense wire was broken off the servo pc board. but would make contact untill I would spool up. then it would twitch itself crazy. and being on the elevator. It made for a nasty spool up. Just for fun take a look at the wiring inside the servo kevinTrex600n Trex500 Mikado LoGo5003d// Hacker, CastleCreations,Ys 50, JR 7703d/8900, Radix
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08-06-2007 04:59 PM  13 years ago
gorn

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Western Australia

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Thanks Kevin
My problem appears to be solved, but I will do that out of curiosity anyway.
Cheers
For the love of the hobby
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08-06-2007 05:09 PM  13 years ago
turboomni

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East of the Equator

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Turboomni
This is exactly what I did
And presto, she works like a charm now
Great news!
Setup is everything, All my heli's can fly far better than I can pilot them
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08-06-2007 05:38 PM  13 years ago
AceBird

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Utica, NY USA

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Your servo is very close to the HT lead/plug so most servos, no matter what quality will tend to twitch due interference.
Heed the warning and move the throttle servo. That’s no place for any servo.
Ace
What could be more fun?
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08-06-2007 05:52 PM  13 years ago
gorn

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Western Australia

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Uh yeah, well where am I supposed to magically put it?
There is nowhere else to mount it, and for now its working fine.
I will keep my eye on it, first sign of trouble, I'll investigate further.
No way am I cutting holes in the Maxum chassis, and even then, really on the throttle side, there isnt room.
I understand the concerns about its proximity, but other Maxum owners are flying theirs just fine.
For now we will see.
Cheers
For the love of the hobby
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