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Help possible ignition interferance problem???

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Old 07-28-2018, 11:50 AM
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raron455
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Default Help possible ignition interferance problem???

Ok Fellas, I need your help,,
I have a giant ESM 96" B-25. I have probably about 15 flights on it now and have a problem that has me stumped. I fly with a spektrumDX-18 G2, it is a proven radio, I have been flying with it for 2 years, never any issues, and all of my other planes and turbine jets fly just as they should . My B-25 has two DLE-35 gas engines , the ignitions are controlled with a smart-fly regulated dual igntion fiber optic cut-off Ignition Cutoff, Regulated for Dual Ignition Engines , powered by a 2600 fromeco LI-ION. The receiver is a spektrum 20ch powersafe telemetry receiver. The Rudders on the B-25 are in each stab, so one servo per rudder,, they are however together with a Y-harness on a single channel. The servos are hitec HS225, they were brand new for the plane, as well as the Y-harness and extensions.


Now,,,,, Here is the problem, and it does not happen all the time, just random but when it happens its consistent and dangerous. The rudders will deflect, and go a substantial amount either direction on their own, This will only happen when the engines are running, and usually get worse as you advance the throttle as observed on the ground after landing. When the engines are not running it is rock solid, I shake and bounce the plane to see if it is a loose connection and the rudders never move, it only happens when the engines are running. I have had it happen to me a couple times in flight, forcing a fairly tense landing, the plane will yaw side to side unpredictably sometimes worse than others, once landed you can see the rudders pulse side to side, give it throttle and see it get worse, and I am not talking about the normal shake from vibration, this is alot of movement I am talking about. kill the engines, and the rudders are rock solid again. Wait for a little bit, start the plane back up, do a preflight check and the rudders dont do it, but while in flight it will happen again.

I have verified my caps are secure on the plugs,, my best guess is there is some kind of interference with the ignitions causing the rudder movement? but why only the rudders? and How can I be getting this interference using a fiber optic ignition kill? How can I fix this, guy at the field mentioned some kind of magnetic ring. Of course another member believes its a bad connection at the Y harness, although I always use servo safety clips. Another club member believes the rudder has "a dirty Pot" I looked at him and told him there are two rudder servos, he said probably both of them are that way, but I
dont buy that idea at all. I am always learning and hoping someone can put their input or experience in on this to help me out as this is the first time I have had this kind of problem, Thanks Fellas
Ronnie Dean

Last edited by raron455; 07-28-2018 at 12:20 PM.
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Old 07-28-2018, 05:57 PM
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Zeeb
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Well the first thing I'd do is check the servo connectors, are they gold or silver? Tight or a bit loose? Any sign of corrosion? How big a wire, I like to use the 20g stuff especially on longer runs. If that doesn't work, get rid of the Y-harness and get you some of those Hitec signal amplifiers.Loose sparks from engine ignitions will usually do it constantly. Those goofy ferrite rings don't do anything.

Hope that helps.....
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Old 07-28-2018, 06:09 PM
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maybe try a different RX.
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Old 07-30-2018, 06:23 AM
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How long are the runs to the servos?

Add a SPMCP to the rudder (and I'm guessing elevator) servos at the receiver. This will boost the signal so that the ignition noise (there IS ignition noise) does not overcome the actual signal in the servo leads.

Are you using a good resistor spark system? The oldtimers that refuse to use suppression systems regularly complain that their radios experience symptoms like that. Between poor suppression and the long leads, you could just be shooting yourself in the foot.

Andy
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Old 07-30-2018, 04:37 PM
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raron455
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Originally Posted by AndyKunz View Post
How long are the runs to the servos?

Add a SPMCP to the rudder (and I'm guessing elevator) servos at the receiver. This will boost the signal so that the ignition noise (there IS ignition noise) does not overcome the actual signal in the servo leads.

Are you using a good resistor spark system? The oldtimers that refuse to use suppression systems regularly complain that their radios experience symptoms like that. Between poor suppression and the long leads, you could just be shooting yourself in the foot.

Andy
Hello Andy, Thanks for the advice
I just purchased two of the SPMCP boosters, and will put them in for the rudders and elevator, both located at the back of the plane. the servo extensions may be a little too long maybe up to 6in longer than needed to guarantee they reached. as far as a resistor spark system,?? I am using the Stock DLE CDI ignition system, with the exception of the spark plug, I am running a NGK CM6 plug, same plug in all my other planes, I believe it is a resistor type plug. I don't have the conical springs in the plug caps, maybe I can try that, I have heard that the spring makes no difference, but maybe it does. I guess I will pull it back down, and check the Y harnesses and such again, although I have them plugged in tight and use the plastic servo safety clips.
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Old 08-05-2018, 05:32 AM
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Yes, it is ignition noise getting into your RC system. Remember it is RF noise - so can easily jump gaps from one component to another.
In the olden days, the recommendation was to separate the radio system from the engine systems completely. NOTHING metallic running between the two - wires, pushrods, etc. This includes anything not connected to the systems (strip of CF in the fuse running front to back that could conduct RF). For mechanical connections, make sure there is no metal on metal rubbing - like push rod connector pins on a metal servo arm, etc. The separation should be a foot or more from closest thing to closest thing. Yes, even switches too close can pick it up. Yes, you have to use seperate batteries for the engine vs the flight system - and they too have to be super separated.
2.4 is only marginally better at fighting through this - as you can tell, it still happens.
Signal boosters just help overcome problems with long leads, but if the noise is being injected directly into the receiver (via other leads, battery wires, etc.) then they do nothing as the signal is already compromised.
Going after just the rudder issue is faulty - at a different signal strength and receiver orientation (like when flying), it can easily become aileron, elevator or everything failures.

Check with the manufacturer of your ignition system for the specific plug they designed for. In my case, I was running Champion Plugs, but RCExcel is set up for NGK. The cap seemed like it fit, but doesn't. Changing the plug brand cured the problem. The spark end may be the same between brands, but the connection end can be very different.
Put small hose clamps on the plug caps, in order to really snug them down to the plugs.
If your engine ignition has a ground wire, make sure it is grounded very firmly to the engine.
Make sure your plug caps are exactly what originally came with - if it had springs, put them in. If it didn't, leave them out - they can interfere with the fit and therefore shielding if system was not designed for them.

Still no go? Then your only choice is to start trial separation of components. Get rid of interconnections between the two, such as IBEC's, Optical kill switches, etc. Then move on to the harder stuff to relocate. Test a lot before trusting you have cured the issue.

Added later:
The most likely issue, by far, is the plug cap fit. Whether new plugs, new caps or just a tighter fit, that will most likely cure the issue. Start there, and get it as perfect as you can before moving on.
As far as moving stuff, the advice above is, of course, the extreme. You may find just moving one thing a couple of inches, separating wires, or some other small change resolves the issue. Just test extensively, including range checks where the signal is at the edge of dependability.

Last edited by tedsander; 08-05-2018 at 07:23 AM. Reason: addendum
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Old 08-08-2018, 08:18 AM
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Originally Posted by AndyKunz View Post

Are you using a good resistor spark system? The oldtimers that refuse to use suppression systems regularly complain that their radios experience symptoms like that. Between poor suppression and the long leads, you could just be shooting yourself in the foot.

Andy
Andy, the DLE35 uses the very common NGK CM-6 plug that is non resistor. But, there is a resistor in the plug cap to compensate for the non resistor plug. Very common system on engines that use this plug.
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Old 08-08-2018, 08:28 AM
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The way to test this is to bring your AM radio (the "transistor radio" type we had as kids) near to the turning engine (it doesn't need to be running - kill the fuel flow and spin it over so the points are operating) and see how well you hear the engine. If you hear the spark in your AM radio, your ignition system isn't sufficiently suppressed.

Andy
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Old 08-08-2018, 08:31 AM
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First off, there is a tiny bit RF energy being emitted from the ignition system in ALL ignition systems. It can be seen on a sprectrum analyzer and this is normal. Most ignition systems keep this to a reasonable level that can be tolerated by most modern radio systems.

If there are no other symptoms, my guess is the problem might be the long leads to the rudder servos combined with the analog servos. Have you tried the digital equivalent or something better than the 225 servos you are using. Sometimes just this simple change will resolve a problem like this as most digital servos are more tolerant to the ignition environment. A different problem might be the Y connector. I have seen servos on Y cables act strange even without ignition noise being present. Any way you can run separate leads to the servos.
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Old 08-13-2018, 08:21 AM
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Jesse Open
 
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What is your throttle connection made of? (Everything between the carb and servo) A metallic wire from carb to servo may re-radiate EMI from the ignition, right back to the control system, especially the componentry and wiring in the vicinty of the throttle servo.

Last edited by Jesse Open; 08-13-2018 at 08:33 AM.
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