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Throttle servo

Old 08-23-2007, 11:38 AM
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Default Throttle servo

I started my Taurus 52cc powered Yak for the first time and it ran great, but the throttle servo started jumping around and then just went to full throttle. The servo would not respond to the stick possition on the radio at all. When I killed the motor the servo would go back to working properly. This is my first gasser, so I am not sure if it's the servo, ignition interference, or voltage? It is a JR ST47 running on 5.7 volts. The rest of the servos are all JR 8611s and they worked just fine with the motor running. Any ideas what the problem is?

Old 08-23-2007, 11:49 AM
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Default RE: Throttle servo

Well if it works fine with the engine off and acts up with the engine running then it's RF interference.

I would highly suggest you search for RF or RF interference using the search function and do some reading before you go much further. Since it's your first gas engine and your RF is that bad you have likely broken multiple basic rules for a gas engine plane. It's worth learning in detail how to prevent this an how to have safe uneventful flights

Couple examples..

#1 You should not have metal on metal contact anywhere in your system. The exception to that rule is you can have 4 40 balllinks on your al. control arms as long as they are tighten with a 4 40 nut or loctite.

You should have your throttle linkage isolated with a nylon cleavis or ball link at each end of the rod.

Cheak all bolts to make sure they are locitited with blue loctite.

#2 Electronics should be atleast 12" away from your ignition unit. Throttle servo can be up there in some cases.. but every sistuation is different and it is better to keep it away.

Hope this helps... some pics of your setup would be helpful
Old 08-23-2007, 11:52 AM
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Default RE: Throttle servo may already know about most preventive steps to avoid RF interference. And in that case, you may have a defective spark plug cap, that is now emitting RF interference. I'm with Sinergy, toss a couple pics of your setup on here!
Old 08-23-2007, 12:21 PM
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Default RE: Throttle servo

check the servo...if all other servos are working ok, it's the servo...

sometimes vibration can play havoc on a servo that's on it's way out.
rf usually affects all servos...
Old 08-23-2007, 12:56 PM
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Default RE: Throttle servo

Also get a PCM receiver. You don't want any gasser going to full throttle during lockouts. Is should go to idle or die depending how you set it up.
Old 08-23-2007, 04:35 PM
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Default RE: Throttle servo

Another thing, not sure where your servo is, but I never mount the servo up front with the engine. I know this is easy, but your asking for trouble with RF. Mount it back with the rest, behind the wing tube, and install a pushrod isolated at both ends with nylon. Keep the ignition system and control systems as far apart as you can, in the airframe.

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