turnnburn

My Feedback: (49)

I have a TF P-51 with DLE 55 engine. I purchased it ready to fly from a local fellow and made 10 or so flights on it when I decided I wanted to switch from the Hitec TX and RX that it came with to my JR 12x radio. The Hitec was working fine but the switch locations are not all in the same places as I am used to with my trusty JR radio. I found a Spektrum AR9 Rx in my shop that wasn't being used and installed it with two remove receivers. Got the tx all programmed and had it ready to fly. I decided it would be a good idea to run the engine at home to make sure I had the choke servo working properly with correct amount of throw and to make sure the throttle had proper throw (proper idle and full throttle).

I put the wing on and luckily I plugged in the ailerons and flaps. Got the engine started and running at idle and noticed the ailerons both jumping and deflecting up and down randomly sometimes moving a small amount but also sometimes going to full or near full travel and then back to center. This random movement of JUST the ailerons did not start until engine was running and stopped as soon as the engine was shut down. So I figure I have either a vibration issue with the rx or some sort of noise issue from the electronic ignition system system, but I figured with either a vibration issue or a noise issue most if not all the servos should be effected which is NOT the case.

I next changed the rx mounting to a more padded with foam rubber set up and ran the engine again. No help, still have random movement of ailerons. So that leaves me thinking it is a noise issue from the ignition, maybe being picked up in the cables running to the remote mounted rx's. The remote rx cables do not appear to me to be in close proximity to any wires for the ignition system except for the red and black power wires to and from the on/off switch. Both of the remote rx cables are overly long and I have folded up the excess and tied them into neat bundles as I have done on many different planes in the past but never with anything with electronic ignition, I have limited experience with gas powered, electronic ignition aircraft.

Now I am trying to figure out what to try next. My options are :
- put the Hitec radio back in that worked fine
-disconnect one at a time and then both remote rx;'s to see if that is where the noise is being picked up (if it is a noise issue)
-relocate the remote rx;s and their cables and see if that fixes it.

I am not ready to give up and put the Hitec back in quite yet. Plus I would really like to figure out what the problem is.

In the middle of the night I thought of one other thing. The are for the choke where clevis is attached is metal and yes, you guess it, he has a metal clevis on it and it is attached to a nice metal wire actuating rod that runs right by the main and rx and one of the remotes. But it was also set up this way with Hitec rx and had no issues.

I am open to ideas and suggestions. Are the Spektrum AR rx's known to be sensitive to noise ?? I am unware of it if they are. I don't currently have any other JR or Spektrum rx's not in use that have enough channels except for a Spektrum AR9300 carbon fuselage that I just got a couple days ago and have not used in anything. It has slots for 2 remote rx's but only came with one. It uses a slightly different remote rx than the normal JR/Spektrum remotes. The remotes maybe the same but the antenna is different for sure. Maybe I will try putting it in with only one remote and doing an engine run to see what happens. The main rx also has different antennas than a typical AR rx. Two lengths of wire about 7 or 8 inches long. If used in a carbon fuse the instructions say to run the wire antennas outside of the fuse. for proper reception.

I look forward to ideas and suggestions.

RCFlyerDan

My Feedback: (54)

turnnburn

My Feedback: (49)

I don't know anything about a spring in the cap ? Like I said, I am pretty new to gas and ignition engines. I did have the cap off and on as part of this changeover. What is the purpose of the spring ?

RCFlyerDan

My Feedback: (54)

BarracudaHockey

My Feedback: (11)

Make sure, and I mean darn sure, the plug cap is seated fully. If you don't have a semi-permanent dent in your hand you probably didn't push hard enough.

Metal to metal clevis won't bother 2.4 the interference is simply out of the range of the RX, but a loose plug cap will swamp just about any receiver.

rgburrill

I'd start with the metal clevis on the choke. I had a noise problem once and it was fixed by replacing a metal clevis on the throttle with a nylon one.

BarracudaHockey

My Feedback: (11)

All due respect, and I mean that because you have excellent advice, but I've seen this a number of times and I've never seen a 2.4 installation with a metal clevis cause this. Not that it can't but its for sure not the first stop IMO

turnnburn

My Feedback: (49)

I tried disconnecting one remote rx and then the other and then both. No help. Infact it seemed worse with no remotes plugged in. I went ahead and replaced metal cleivs with nylon. No help. I then swapped aileron and elevator plugs at the rx,. To my surprise the ailerons were still jumping and twitching while the elevator was rock solid. So with that in mind I am now thinking it has something to do with the lengthy aileron extension cables in the wings for the aileron servos. During the last couple engine runs I did notice that the jumping and jittering goes away completely around 2/3 throttle with the engine running. I find this a bit puzzling as well. If the jumping and twitching was caused by the ignition system I would have thought the higher the rpm the more ignition noise would be present and the worse the condition would be. I'm debating my next move. One think I might try is a couple of servos plugged into the aileron channel with a short 6 or 8 inch "Y" connector and see happens. I am also considering putting the Hitec radio back in at this point and see what happens. I will think about it over night and see what I come up with plus I can see what guys on here come up with as well. I will double check the tightness and security of the ignition plug and press like crazy on it. The ignition battery and ignition box are pretty far from the rx.. There are some ignition switch harness wires and the switch close to very cloe to the rx.. Keep In mind that all these items are in the same locations and distances are the same as they were with the Hitec radio in I had no problems or issues when it was in there.

speedracerntrixie

My Feedback: (29)

pkoury

My Feedback: (7)

Seen this multiple times and it is ALWAYS the plug cap. Most times it is the plug cap not being completely seated. I have also seen completely seated caps that were damaged either by ground strike or pulling to hard on the plug wire trying to remove the cap. 9 times out of 10 it is a cap that is not completely seated, Can you see any of the hex nut section of the spark plug sticking out below the spark plug cap?

tedsander

A couple of other suggestions:
Get a small hose clamp at the hardware store and put it around the plug cap, to make sure it really is tight to the plug.
Verify the exact brand of plug your ignition is designed to use. I fought a noise issue for over a year. Even though all seemed fine for years in a prior plane, with the new one and the transplanted engine, the noise made it unflyable. Turns out the ignition cap was designed to use an NGK plug while I was running a Champion. The cap seemed to fit (and I did the hose clamp thing). Replacement Champion plugs had no effect. Changed to NGK, and it all went away. (not saying you should use an NGK - you should use what the cap was made to fit).

The next order would be to replace those nice metal pushrods to the choke/throttle with something non-conductive like nyrods. Even though you replaced the clevis, the wire push rod can still pick up the noise and provide a path for it to get to any wires/electronics they pass near.
Then move on to really separating ALL flight control wiring and electronics away from the engine (including choke servos). Old school advice was to have 12" complete separation between them. That's really extreme these days, but even a few inches can make the difference. Yes, that means a totally separate ignition battery and switch way up front. Everything else kept well away.

The last two items are unlikely to be needed - the highest odds are an issue with the cap.

Your aileron wiring will be very unlikely to be the issue - it's far enough back to not pick up anything directly (unless those metal pushrods pass near). Something else is providing a path for the RF noise into the receiver. Long leads used to be a big problem in the olden days, needing ferrite coils or electronic "noise traps" patched in. But should not be an issue at all with any modern system.

speedracerntrixie

My Feedback: (29)

RCFlyerDan

My Feedback: (54)

There is a reason that I had you swap the aileron servos with the elevator servos. This was to see if the problem stayed with the ailerons. It did! So, this means that you have a bad connection between the aileron servos and the receiver. IF you are using a "Y", (this is why both servos are jumping) then it is the "Y" or the short lead that you connect between the "Y" and the short lead to the receiver. Because this lead is plugged and unplugged a LOT, the wires become loose in the plugs and the connections become weak. I suspect that if you replace the "Y" and the small lead that goes from the receiver to the aileron's "Y" lead, your issues will go away. As long as you checked the other things that I recommended. You other guys are getting it...........the problem followed the ailerons! IF it was ignition, then the elevators would have been jumping around swapped, due to that channel being compromised by the ignition interference. Just because it works without the engine running, doesn't mean that it is a good connection and the ignition is picked up on that lead. The "antenna" effect of the long leads I doubt is the issue. I have had longer leads in 40%. Poor connections on the leads will pick up the RF before the length of the lead.

tedsander

Excellent points, and a solid way to isolate a part of the system to see where the problem lies. The good news about the problem is that the OP can replicate it consistently, which goes a long way when testing by simplifying or swapping things out. Easy thing to test, and high likelihood that that is the issue. You may find that it is a vibration related intermittent, and RF noise isn't part of the equation.

I hate to call out speedracerntrixie, as he consistently gives good advice....but just flat out untrue that 2.4 is immune to ignition interference. There would be no need for shielded plug wires or caps otherwise. Yes, modern systems are far better at filtering/rejecting ignition noise - but it has happened to too many to say it can't happen.

Appowner

Ignition noise is what we in the industry call white noise. The Sun also gives off white noise and like ignition noise, it covers the entire RF spectrum to include 2.4 GHz. The difference is modern systems use better technology and modulation schemes to find and lock on to their respective signals. I've deployed satellite systems where my receive signal could not be seen in the noise floor on the Spec Annie. But I locked on to it just the same.

turnnburn

My Feedback: (49)

One responder asked me about a spring in the ignition cap, asking if it was there or missing. I would like more info about this spring. How big is, where does it go , its purpose and other pertinent info. My cap has a black rubber boot that is permanently attached inside the cap. Above the boot at or very near the very top of that cap I see something metal that I presume makes the contact with the plug tip. It sort of looks like it might be a small spring.

I did notice yesterday during my engine runs that my cap can be pressed on while on the plug and it will go down another very small about (maybe 1/16" to 3/32 ") but once I stop pressing or pushing down on it pops back up the same 1/16" almost like a spring. 'is this normal or do I need it to stay ALL the way down onto the plug .

There was one run yesterday where I had disconnected one of the remote rx that I saw NO jumping. At the time I thought it was an indication that the wiring leading to that remote was it to close proximity to the music wire push rods used for throttle and servo operated choke. That is when I decided to change out the metal clevis for nylon (doing so required removing the cowl and that requires removing the ignition cap). As I stated above changing to nylon clevis did not help. I now feel that the cap is the issue as mentioned by several of you. I assume that during the one run where the remote was disconnected that the cap must have been on correctly and for all other runs it was not. The loose cap probably also explains why on some runs the interference was considerably worse (momentary full or near full control deflection and on other runs it would be considerably less. I had the cap on and off numerous times during my test runs. There was even one run ( I think it was the last one or next to last) where I had disconnected BOTH (all) remotes and also saw for the first and only time some momentary movements of the flaps. I assume that the cap was looser on that run and the noise was greater to where it effected the flaps also. As the rpm increased the flaps settled down much sooner with only a small amount of RPM increase. As you might expect the flap servos are much closer to wing root than aileron and I presume have much shorter extensions.

Clearly my next step is to inspect the cap and ignition wires and possibly swap out the spark plug and perhaps put a heater hose type clamp on the cap. I guess my next step SHOULD also be to replace the two music wire pushrods on throttle and choke with ........?????? I guess nyrod or wodden dowel or solid plastic dowel or...other suggestions please.

I have concluded that the Hitec radio may or may not better at handling this sort or noise. I suspect the real truth and the biggest factor in this particular airplane is that the Hitec rx antennas both exit the rear of the rx and were a bit further away from the metal pushrods and or the ignition cap was on tight and properly seated then. I have the Spektrum rx in the same exact location but the antennas from the main rx are in very VERY close proximity to the push rods.

Is there an easy way to shield these pushrods ?

Thanks for all of you input, it has been a big big help.

I

RCFlyerDan

My Feedback: (54)

turnnburn

My Feedback: (49)

I put on a heater hose clamp, pushed the ignition cap down as far as it would go , held it there and tightened the clamp so it would hold the cap down that last little 1/16 or 3/32 ". I also moved the main rx to a temporary location that got the two rx antennas 3 or 4 inches away from the metal pushrods. I normally only change one thing at a time and violated that rule this time as I just want it fixed. I put the wing on, fired up the engine and...............
problem appears to be SOLVED !! I forgot that I still had elevator and aileron plugged in to each others slots but ALL controls look rock solid no twitching, no jumping. FINALLY !! I did NOT change out the metal push (music wire) pushrods. I did only have the one remote rx installed and plugged in.The one that is furthest from the metal push rods. So Im not totally out of the woods yet. Next I will swap aileron and elevator back where they belong. Reinstall the second remote rx (probably in different location well away from the metal push rods) . Figure out a more permanent main rx location further away from metal push rods. Put the engine cowl back on give it another test run. As you can surmise I am really trying to not have to replace the music wire pushrods but will it becomes apparent that I need to.

With that in mind.......is there a way to shield them, a way that is easier than replacing them ? Not that replacing them is that hard, it just appears that it wont be required.

Thanks again for all of your help. Couldn't have done it without you guys. RCU to the rescue yet again.

PS Should I find it to be required I most certainly WILL change out the aileron and flap connectors. At this point it doesn't look like that will be required however.

speedracerntrixie

My Feedback: (29)

Truckracer

My Feedback: (19)

DLE provides a large coil spring they suggest should be installed inside the plug cap to improve contact between the cap and the plug. While this seems like a good idea, in practice it can get cocked inside the cap preventing the cap from going all the way onto the plug which can cause the very same problem the spring is there to prevent. DLE uses RCexl ignitions that are used on many different engines and only DLE provides the springs. I have never found the need to use the springs and even DLE is no longer supplying the springs with new engines. In my opinion, they were a bad idea from the beginning and they have now gone away with newer engines. By the way, this spring is large and goes in the base of the cap and rests on the hex part of the plug. The small spring in the top of the cap is the electrode contact.

You say the insulator in your cap is black looking. It should be a translucent, sort or clear colored material. Think of clear silicone rubber for a comparison. If it is black, the cap may have been loose over time or overheated and the insulator may be breaking down causing internal arcing. Might be a good idea to replace that cap. $10 or less from most sources.

Regarding ignition noise causing interference with 2.4 radios ...... No, ignition noise will not cause interference in the traditional sense ... that is coming in radio through the antenna and I won't go into the theory why. But ignition noise can affect the low speed parts of the receiver and the servos by coming in what some would call the "back door" of the receiver. That is the servos, wiring, connectors, etc. Many have experienced this with a loose plug cap or damaged plug lead and a loose plug cap will almost guarantee interference! A cap has to fully cover the hex part of the plug and be snug on the plug. If it will turn easily when fully seated, either replace the cap or put a small worm type hose clamp around the base of the cap.

turnnburn

My Feedback: (49)

I put the plane all back together and ready to fly , put in both remotes, swapped aileron and elevator back to where they belong put in both remotes , I even put a ground wire on both of my music wire pushrods, put the cowl on and did one last engine run to make sure I was flight ready. And then it had a new problem, The radio was still rock solid but the engine wasn;t starting or running right. It was missing and died numerous times. it took a couple more tries of tightening the ignition cap and heater hose but finally I must have got it on tight and right because he went back running like a champ. At some point in there where it was missing sputtering and dying I got my data log out and checked and all looked perfect. Not a single missed or lost frame. After I finally got engine running right again I took it out to the street and did a range check (with engine NOT running).. More than double the required minimum range and still going so I charged it up and went to the flying field. Started the engine and did a range check with engine running at idle or a little above, same range as at home and still going. Made one flight, engine ran perfect, radio worked perfect, pilot worked....well......not perfect but good enough. Took it back to the pits, removed wing plugged in data log. A minimal about of frames lost on each antenna, no fades, no holds.

So.....................thanks in large part to the men and women (could be ) and in small part to my determination and desire to get it working right.....it is infact ....working right. For now !!! Didn't have time for another flight plus it was a bit breezy. Will get it out again soon. I need to stop by a hardware store or auto parts store and get a heater hose clamp that is a little smaller but otherwise I am very happy....... for now !! LOL

Thanks again to all responders, I couldn't have done it without you.

Truckracer

My Feedback: (19)

turnnburn

My Feedback: (49)

I will look further I into it. I would appreciate confirming and or dissenting opinions on this issue as well. I didn't look a it real close but it looked like black rubber to me.

tedsander

Congrats on getting a handle on it. I would be concerned about the long term viability of the fix - since you had to do it a couple of times to get the cap on right. Methinks 'tis time for a whole replacement cap assembly....

BarracudaHockey

My Feedback: (11)

This came up before but its worth noting.

If you're running a plug with a DLE stamp on it, smash it with a hammer and put a genuine NGK CM6 or one of the iridium tip plugs that RC Extreme Power sells, set the gap with an exacto blade and enjoy much more reliable service

http://www.wrongwayrc.com/index.php?...&product_id=60