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Ailerons twiching on idle

Old 07-27-2014, 11:49 AM
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CARS II
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dirty

How about this, if the cause is vibration, what will happen if I unscrew the servos from the wing but leave them connected to the receiver then run the engine?

I could test the servo theory tonight,mmmmmmmmm also test other servos.

Last edited by CARS II; 07-27-2014 at 11:53 AM.
Old 07-27-2014, 05:30 PM
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I suspect that your ignition cut-off control or wiring is where you are getting the most coupling.

You are right on the money on this one Thi, that is where I'm getting the most coupling.

These kinds of problems can be hard to hunt down

This i know now.
Old 07-27-2014, 05:40 PM
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Just came back from the field, changed the Ail servos, It got better but it didn't solve the actual cause, the new Ail servos where twitching not as much like in the beginning but some, very little but still there, it looks like that every time I change or move something it gets better but that doesn't solve the problem ( I'm learning a lot from this )

So this time we are going to the root of the cause ( the ignition box ) like Thai said, it has to be isolated even more than what I have done so far by adding the copper grounding wires to the ignition box, also will be shortening the grounding wires by reattach them on top of the cylinders on one of the fins, that is what I will be doing next, most likely by Friday or Sat.

Last edited by CARS II; 07-27-2014 at 05:45 PM.
Old 07-27-2014, 05:56 PM
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Youi said this is used equipment. Servos as they get older will tend to hunt under vibration. In fact brand new servos will sometimes hunt under vibration. Are your ailerons static balanced? It would help if they are.
Hunting is a characteristic of low deadband strong servos. You may not see it but its there. JR servos have been set up with zero deadband. That means they will always hunt.
If I were you I would go ahead and fly it. You dont really have a problem.
Old 07-27-2014, 06:12 PM
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Originally Posted by CARS II
I suspect that your ignition cut-off control or wiring is where you are getting the most coupling.

You are right on the money on this one Thi, that is where I'm getting the most coupling.

These kinds of problems can be hard to hunt down

This i know now.
Glad to hear you are making progress. You have two systems to isolate: Your (1.) ignition system with its own battery and switch, and then your (2.) aircraft control system. You want to keep the wires and components as separate as possible between those systems. That engine cut-off unit makes that tough. You also want to try to make your ignition system as quiet as possible, and that is where the copper strap comes in.

Also.... Your aileron leads being long make good antennas and you might try twisting them rather than having them run straight. That was on old trick on television twin lead to antennas as if you run that straight, passing cars would cause noise on your picture. Twisting it allows it to isolate the interfering signal electromagnetically.

Don't rule out the vibration factor quite yet as I can see that is plausible.
Old 07-27-2014, 06:15 PM
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Carlos... By the way, what brand of kill switch are you using?
Old 07-27-2014, 06:27 PM
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Dirty

I'm with you, really want to fly her again, our club here is having a golden age event and the Gee Bee qualifies for it, I want to be ready ( a month from now )
Old 07-27-2014, 06:28 PM
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Being an older CH ignition module with an aluminum case, you could try going over the seams of the case with either aluminum or copper tape to eliminate any RF spillage out of the gaps.
Old 07-27-2014, 06:30 PM
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Originally Posted by CARS II
Dirty

I'm with you, really want to fly her again, our club here is having a golden age event and the Gee Bee qualifies for it, I want to be ready ( a month from now )
Cars, is the the Woodland Davis club? I may want to check that out. If I tell the wife there will be a Gee Bee there I'll get the green light for sure.
Old 07-27-2014, 06:36 PM
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Regarding the two systems , the radio gear ( all of it ) is 20 inches away from the ingnition system and the ignition componentes are all on top of the engine box.

The kill switch is an Rcxel V2.0, even before it was added the twitching was there end very strong, that is the only lead between the two systems
Old 07-27-2014, 06:42 PM
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Yes, WDA is having an event next moth on the 23rd

right now I know of at least 3 more Gee Bees in the area.
Attached Files
File Type: pdf
Golden_Age_Fly_In_2014.pdf (323.9 KB, 67 views)

Last edited by CARS II; 07-27-2014 at 06:49 PM.
Old 07-27-2014, 06:50 PM
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I personally don't like the opto switches, especially the RCXEL unit. I have read multiple issues like yours being caused by the switch. That being said, try the tape on the ignition module and you may want to try different antenna locations. I don't think that the RF is getting into your RX though. It seems to be getting into the aileron signal wires. Using twisted extensions was mentioned and is a good idea. Don't use Hitec Karbonite geared servos on a gasser. The gears are brittle and shear off with vibration. Does this model have rudder pull pull and if so are the cables steel?
Old 07-27-2014, 06:53 PM
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Speed

If you stop by find me ( the guy with the black and yellow Gee Bee ) maybe you can give me more pointers.
Old 07-27-2014, 06:58 PM
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The Aileron servos are carbonite and they have been removed ( today ) they feel like there is sand in them, i will replace them with metal ones, pull pull yes,not sure if metal ( will have to check ) when I get the new metal servos I will cut the lead and add a twisted lead long enough to reach the center of the wing.
Old 07-27-2014, 07:15 PM
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I will try an IBEC on my next gasser
Old 07-27-2014, 08:15 PM
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Twisting those leads will not do a thing for you. Twisting leads is used to prevent crosstalk between adjacent conductors. when you have only one line its pointless..
Old 07-27-2014, 09:03 PM
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Copy that on the twisted wire, my ears are open to more comments on the twisted wires.
Old 07-28-2014, 01:08 AM
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Originally Posted by CARS II
The Aileron servos are carbonite and they have been removed ( today ) they feel like there is sand in them, i will replace them with metal ones, pull pull yes,not sure if metal ( will have to check ) when I get the new metal servos I will cut the lead and add a twisted lead long enough to reach the center of the wing.
Karbonite servos and gassers don't mix. Hitec states not to use Karbonite servos with gassers, and not to use them in heavy models.

Even if the servos are not the cause of your problems, I suggest that you replace them with metal geared versions.

I'm in agreement that you should dump the opto kill switch, and I like the idea of grounding the ignition box. Make sure that you spark plug cap fits securely. Metall pull/pull cables can kill you. The throttle push rod, should be non metal. I use nyrod. These things keep me relatively trouble free, and may help you to be the same.

If it were me, I would not make sweeping changes. I'd try one thing at a time, testing after each change. That way, when the problem goes away, you'll know what it was.

Last edited by TomCrump; 07-28-2014 at 01:13 AM.
Old 07-28-2014, 05:33 AM
  #94  
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Originally Posted by TomCrump
... The throttle push rod, should be non metal. I use nyrod. ...
This is worth repeating. It is often overlooked.
Old 07-28-2014, 06:20 AM
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I think I am going to fashion a kill switch which is just a micro-switch driven by a wedge on the end of a nyrod control rod. Those electronic (opto-isolator) kill switches do not help the isolation challenge. Granted, the majority of the energy is electromagnetic propagation which can travel without a conductor, but anything to reduce the coupling is bound to help. I know my Tartan Twin is very noisy. So throttle and kill switch can both be nylon rods.
Old 07-28-2014, 06:47 AM
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Originally Posted by rgburrill
This is worth repeating. It is often overlooked.
Another useless old technology quote It was never even required on 72. All you neded was a plastic connector on the engine connector. I have used steel cable since 1957 on all of my airplanes.
Old 07-28-2014, 11:39 AM
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I have used metal pushrods for throttle and choke with the servos mounted at the bottom of the motor box without issue
That's not a good idea, as any metal can conduct RFI. You may get away with it, but nyrod is better.

Carlos, it looks like you have an older BME twin there with a CH ignition that has braided ground straps that attach to the cylinders. Those grounds have to be good. Try hitting the connection with an OHM meter and see what resistance you have. Do you have resistor plugs in the engine? Maybe a newer ignition with shielded wires and caps would be a consideration?
Exactly. Good caps & ground straps will fix most RF-caused glitching. (Not picking on you, SR&T, you have probably seen more installs than most.)

I've seen folks go to PCM, separate channels/receivers, and 2.4Ghz setups trying to mask glitching. If you fix it at the source (shielding the plug & wire), you'll find 99% of the troubles go away.
Old 07-28-2014, 01:05 PM
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Eddie

My next step is to add grounding straps ( X 2 ) to the ignition box and change the spark plug caps for new shielded one from CH, I will also change the spark plugs for new ones.

Last edited by CARS II; 07-28-2014 at 01:08 PM.
Old 07-28-2014, 02:35 PM
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Originally Posted by eddieC
That's not a good idea, as any metal can conduct RFI. You may get away with it, but nyrod is better.



Exactly. Good caps & ground straps will fix most RF-caused glitching. (Not picking on you, SR&T, you have probably seen more installs than most.)

I've seen folks go to PCM, separate channels/receivers, and 2.4Ghz setups trying to mask glitching. If you fix it at the source (shielding the plug & wire), you'll find 99% of the troubles go away.
In my 60+ years working in the rf field I was never able to get rf to run down a single conductor. I always had to use two conductors, coax or a waveguide.If you can do it let us know.how..But nyrod cant hurt. If it makes you feel better by all means use it.
In the old days of AM PPM if you used a metal rod without isolation to the motor, you would get a spark caused by pickup of static electricity or dissimilar metals rubbing together.That spark caused the problem. All that was needed was a plastic connector to the motorto fix the problem. AM PPM is very susceptible to RF noise. Even then I was able to use a steel cable. I flew AM PPM from 1965 to 1978 with 5 years formula 1 pylon racing.
Now we have 2.4 GHZ spread spectrum communication.Most dont realize it but SS in a tremendous break through in wireless communication. Its made all of the wireless communications we have today possible. SS allows you to reach down in the noise level by as much as 40DB. This allows you to use much less power. Without it we simply would not be able to use 2.4GHZ. There is too much propagation loss.
In SS the transmitter and receiver agree on a code for each transmission. If the receiver dont see that code it wont respond.Any kind of interference does not have that code.If there is enough interference to wipe out the band the receiver gos into failsafe. It dont glitch.
You people need to come into the 21st century. Things have changed
Old 07-28-2014, 02:43 PM
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Originally Posted by dirtybird
Another useless old technology quote It was never even required on 72. All you neded was a plastic connector on the engine connector. I have used steel cable since 1957 on all of my airplanes.
The reason for the kill switch is the ignition engine. There have been cases where the throttle plate vibrates loose and engines run full throttle until out of fuel. Not as likely with glow engines. The old 72 Mhz receivers were likely a lot more susepeptible to noise than the current 2.4 Ghz receivers.

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