Ignition Interference Problems
 

My dad is having trouble with his 1/4 scale Patty Wagstaff Extra 300S ARF and he put a Fuji 50 cc gas engine in her and its ignition system, he used digital servoes(dont know what kind) and regulars for the rest of the plane and a Eclipse 7 for the radio. Now when we range check it, it gets about 230ft. without flutters with the engine off, and not even 50ft. with the engine started and only the rudder goes nuts, but when the engine revs up or bogs down the rudder starts to flutter, and a recent post on RCU had the same problems with his gasser and someone said that Hi-Tech isnt a good radio to go with on an gas engine, so we gutted another plane and put a JR 223 on it and it seemed to get worse with the engine started and all of the sufaces go nuts, we've tried everying bypass crap, replace recievers, change mufflers/run it with no muffler. So if anyone has any info on this problem please post it, it would be apprieciated




Edited title to garner more wisdom...

RE: Servo Problems
 

The servo brand is not the problem. If you have good connections throughout the installation, no metal to metal rattles from loose connections and loose nuts and bolts, and the ignition/magneto is properly installed then there should not be a problem with any type or maker of servo. First check to see that a resistor plug was used on the engine. This can usually be determined by an "R" in the plug numerical designator. Next go back through the instructions that came with the engine and see if the installation was properly performed. I'm betting that something may have been overlooked in the installation process. Tape the crystal into the receiver opening to prevent it from being shaken loose or fractured by engine vibration. Protect the receiver from vibration better than you would with a glow engine.

Don't fly the plane until you can get 150 feet of range test or better with the engine running. A good installation will often provide a range test with the engine running the same as with the engine off. In any case there should not be more than a 10% difference between the two checks.

RE: Servo Problems
 

The first and most obvious question. Is your ignition and any wires from it and switches at least 12" away from the receiver and switches? Are you using a PCM receiver?

Also make sure there is no metal to metal contact on the throttle linkage.

Good Luck!

RE: Servo Problems
 

Also, a metal pushrod for the throttle is a no-no also. Good luck!

RE: Servo Problems
 

The Hitec Eclipse with a standard Supreme RX will work admirably in your gas model... Of course this is providing your not introducing in stray EMI/RFI, that said do NOT use a PCM RX to solve your problems.

As SiliverSurfer suggested look very closely at the engine installation, specifically the ignition system. Look for metal to metal abrasion, loose or not completely seated spark-plug and plug wire boot, fouled sparkplugs, Resistor type plug, damaged or loose ground conductors.

Make sure NO additional ground cables have been introduced, the only correct method of grounding the ignition system is provided via the module directly to the engine block. In most cases the sparkplug wire is shielded or contains a braided wire mesh which either encompasses the high tension lead or is a separate cable all together, one end is attached to the module and the latter to engine and or sparkplug base.

I’m assuming your ignition switch and battery is separated from the rest of the radio system i.e., an independent system and there is some physical distance separating them as well?

RE: Ignition Interference Problems
 

Michael G.,

Thank you for adding the part about NOT using a PCM receiver at the moment. Far too many people use one from the first day they start a new model and wonder why they lose the plane a few flights later due to "interference". Usually it was there all the time at a small enough level where the PCM receiver would reject it and not "fail safe" long enough to be noticed. Once it became bad enough they usually "fail safe" into the dirt.

Always use a standard, or FM receiver to check for RFI issues prior to installing a PCM receiver. Do not install a PCM receiver untill ALL RFI issues have been resolved using the standard receiver. Yep, it takes a little longer and a bit more effort to do it this way but you get to keep your plane a lot longer.

RE: Ignition Interference Problems
 

If you could post pictures of your setup or give some detail to how it is wired and placement of your electronics would allow us to give you a better opinion of a solution.

RE: Ignition Interference Problems
 

Do yourself a favour and take off the cowl and try it :)

I know 1 guy who had to redo his cowl in white at the front because the gold checked tape was causing interference. There have been many ppl with this issue although with 3 different engines in a Patty I have never had the problem.]

However I can think of 2 ppl off the top of my head who had this problem with a Fuji and a Patty

RE: Ignition Interference Problems
 

Hello all! This is flat top's old man. Like he said, I am using a Hitec Eclipse radio with a RCD 3500 rx 3600 Mah bat on rx, 700mah on ignition. The only part of the ignition system in airframe is battery and switch which are 8" away from the receiver. We have bypassed servos and all switches. As of last try, battery and ignition hooked direct on engine box 17" away from receiver. This didn't resolve the problem. The wire and boot on this eis is just like the one you would see on your car. I can't find any loose bolts? Could the eis have a crack or anything like that? The push rods are all nyrod and ball links. I will try to get some pics on in the next few days.

Thanks to all of you that have posted! Hopefully we will get this bird to fly...

RE: Ignition Interference Problems
 

By any chance have you used any clear or colored mylar type of tape to hold the receiver antenna on the outside of the fuselage? I've seen this be a problem several times. If so, remove the tape.

Is there any type of ground strap that runs from the plug wire that needs to be connected to a ground location on the engine? Di-electric silicone grease, available at most auto parts stores, applied inside the cap may also help. Make certain that the product is di-electric silicone, not regular silicone.

Check thw wires entering and exiting the switch. Is it a new one or one that has been used several times before? Replace with new.

Battery leads, new or old? check condition and replace if any doubt. Loose motor mount or landing gear bolt and/or nut? BTW, 700mAh is a bit on the low side for an ignition battery. I would be having some serious concerns after about 1/2 way through the third flight.

RE: Ignition Interference Problems
 

Silverserfer, I have no tape on the plane, ant. held a length with rubber band. As for ground strap nothing, just one ground wire coming out of plastic eis box. I have connected that wire to rear of engine where instructed. This is my first gas engine so I'm looking for as much info. as possible, Thank you.

RE: Ignition Interference Problems
 

Have you done it with teh cowl off?

RE: Ignition Interference Problems
 

The cowl has been removed.

RE: Ignition Interference Problems
 

Buy some ferrite rings form the local electronic store and loop each servo lead through a ring. Put the rings at the receiver end. That will help iron out some interference.

This also works well on any plane with long servo lead runs, regardless of engine type.

RE: Ignition Interference Problems
 

Another opinion from one that has used the ferrite rings is not to bother. If you really want to try them pay the postage and I'll send you some rather useless extra weight.

Moving on, it's possible that the ground location specified is not functioning properly. Try moving the ground wire to another convienient location of the engine. Check to see that the wire is secure at the ignition end. Check that the spark plug cap is as far down on the plug as it can go. More important, call Tower in the morning to get their take on the situation since they are the distributor. Try lightly tapping on the rx with the engine off to see if you get any glitching, indicating a crystal, antenna, filter, or other rx issue. Do the same with the tx though I don't think you will come across anything there. Change out the switch and the battery, one item at a time, to see if the problem is solved.

Most important, though time consuming, is to only try one item at a time and then run the engine for a very brief period.

The most common causes have been pretty well covered in all the posts so far. Michael Glavin's suggestion of posting several clear and detailed pictures of your installation is a very good one. Trust in his judgement of what he sees. He's very good at what he does.

Good luck,
Pat

RE: Ignition Interference Problems
 

join the club of emi i did all that you have done and a lot more still i have the problem and a pcm or one with a failsafe is not gona make life easer i am putting a standard hitec in mine so i can see the interferance when running it is the most anoying thing to find i even tryied different tx it made a big change but not enough to want to fly it also look at your switch to battery as a lot with the vibration can cause a fault i tried direct to the reciever but it was not where my emi is i am still looking i am about to pay for a guy with a spectrom analiser to locate the problem . how far away is your battery and ing battery they should be at leeast 10 inch away from motor ant 5 inch from each other .
what is your spark plug gap .
has it got a sheilded spark plug cap . if not look at getting one .

RE: Ignition Interference Problems
 

While I haven't used ferrite rings myself (but will shortly on my gasser) I helped a friend install some on his 86inch Canadair. There was definite jittering with the long servo leads but once the rings were installed the issue went away.

In his aircraft the engines were standard nitro motors so his exposure to interference would be expected to be much lower than a normal magneto ignitioned engine. I wouldn't expect the ferrite rings to block everything but they should help.

Luckily my RX is almost 24inches from the ignition source. Limited testing shows no intereference from a magneto ignition to my Hitec RX....however final testing is still required.

I wonder if a light alloy (printers plate) style firewall would help shield the interference to the RX? Just an idea but it should help minimise the EMI directed back towards the RX and antenna....

RE: Ignition Interference Problems
 

Excellent advice! However, since the only channel showing symptoms is the rudder, do the same "tap test" directly on the rudder servo to see if it is acting up due to vibration. I've had this very problem before with failing/defective servos. You can use the handle end of a screw driver or something similar that is of hard material. Tapping with your finger may not be enough. Better yet, replace the rudder servo with a different one and try it. Also make sure your servos are isolated from vibration with the supplied rubber grommets.

Through this thread, I've seen the advice given to make sure there is a resistor plug in the engine. I have not seen a response to this. Have you verified that you have a resistor plug?

What kind of cable are you using for the pull-pull? If metal braided cable, try switching to Kevlar. Sometimes running the receiver antenna parallel to the metal pull-pull cables through the fuselage can cause some issues as well.

Another simple test to try is to temporarily route your receiver antenna out from under the canopy and to the top of the vertical stab or out to one of the wing tips. This would just be a test to see of the antenna is in close proximity to the offending RF noise. It is possible that the ignition is not the culprit. As someone already pointed out, it could be metal-to-metal vibration that's causing the problem.

RE: Ignition Interference Problems
 

One other thing that comes to mind is the spark plug cap. If it's the type of plug that has a screw on cap, make sure it's tight using pliers. If your ignition has a rubber molded cap on the end of the plug wire with the metal "loop" inside for snapping onto the plug cap, you can try squeezing it (very slightly) with pliers to make sure it fits the plug cap as snug as possible. If it's loose, it can cause lots of stray RF. If your spark plug connector is of the hard plastic or metal variety, then at least inspect it and try to determine if it fits the plug cap tightly.

If after trying all the good suggestions in this thread, you still can't solve the problem, it could be that your iginition module may be faulty. It would be worth sending it in to be checked out and serviced rather than trying to fly the plane with it.

RE: Ignition Interference Problems
 

Hey Westbender you were wondering about the plug it is a RCJ6Y . My son left out that it is all surfaces are affected, as for cables there are none. The rudder has 2 servos in tail, and removable stab. I called Hobby services about the problem. They seem to think that I have something loose inside the engine. I'm pulling engine tonight and sending it in on there request. "Thank you all" I will let you all Know what they find with this.

RE: Ignition Interference Problems
 

Thanks for the update. Please let us know how it all works out.

RE: Ignition Interference Problems
 

Hello Flat Top all good posts here. Had a reciever battery cause this same problem, and you might change the ign. battery as well. Hope you find the problem. Have never heard of an engine causing this kind of problem, and dont think its that. however anything is possible. Regards to all Jack

RE: Ignition Interference Problems
 

rather than use rings which cause weight you are better off to twist all your extensions or used pre twisted extentions. This way the signal cant really travel up your lines because there are no parallel lines.

Hopefully they will fine something when they get the engine back.

RE: Ignition Interference Problems
 

True. My HS-654MGs already have twisted leads but the extensions are standard, hence I'll stick some rings on anyhow. The weight penalty isn't a concern given the aircraft is already at the 6Kg mark (12+ pounds).

RE: Ignition Interference Problems
 

i found my problem or problems i think
1 x hitec eclips 7 modual was a litlle off feq now adjusted
2 x reciever antenna wrong lenght from factory new installed
3 x the best for last battery was rubbing on landing bracket made metal to metal contact to the outside off 1 cell . better padding and location