RCKen

My Feedback: (9)

I agree that it's unlikely metal vibrating can cause interference in a 2.4 system, but it's not impossible. If the parts were vibrating fast enough it could possibly interfere, but it's unlikely to happen.

opjose

I've had ( Hitec ) servos hooked up to the throttle on a gasser react exactly the same way.

I found that the servo electronics were getting swamped by the RF from the ignition module.

I could reproduce the problem with the servo disconnected from the linkage... a replacement servo did exactly the same thing...

I switched to a different brand and the problem went away.

We also had the same thing occur, again using Hitec's, on one of three club trainers that used DLE 20 engines... switching to a different brand also cured the problem.

Joe Westrich

My Feedback: (95)

Gas is a fine way to go. I have been flying it for many years. It's way better then glow. Most of the time you don't have this interference issue.

Anyway, throughout my time with gas engines, this has come up on occation. The solutions had been different but they all relate to the ignition coil wire and cap.

I had one problem caused by a torn plug boot. There is a silicone boot inside the cap. Make sure it is not ripped. It will arc and cause interference.

Make sure you have a resister type spark plug. It normally has a "r" designation on the plug.

Someone mentioned before that the cap needs to be on all the way.... Arc problem again.

Make sure your shielding is in tact over the coil wire... Also cover it with a plastic sleeve so it doesn't get damaged fro
Vibration.

If none of that is a problem... Then I would swap out the throttle servo and lastly the ignition module.

RF donuts are only going to mask the problem. Fix the source and the donuts are not needed.

on_your_six

My Feedback: (11)

?????? What ignition wire to the receiver???????

Anyone notice in the OP's photo... the wire to the second receiver is draped over the ignition battery... you keep these two systems (ignition and radio) as far apart as you can. And there is no ignition wire to plug into the receiver.

Dlvsm

Interesting the arguments that i have started here. LOL So the most think it is not a vibration issue and it is interference. I guess I will just move the servo back behind the tanks and see if this helps. Still would love to know if there is a better servo. I was one post that the brand of servo could be an issue. I may try another brrand and see before I move things around. BTW the wires and stuff int eh back was a mess when I took the photo because I was trying to make it worse or better. I wdid have everything nicely orginized at one point. Thank you to everyone and I will let you all knwo if I figure it out.

DLVSM

757jonp

My Feedback: (48)

What is the chance that this is a radio programing issue, specifically an incorrect throttle curve causing these problems?

My setup on a Mojo 65 w/ DLE 20/Futaba 2.4 violates just about every warning here and works great (knock on wood I guess).

Dlvsm

1. The Ignition batery wire runs from the 2000MAh battery pack to the kill switch and then back doown under the gas tank to the ignition. I thought this could be an issue so I removed this and went straight from battery to ignition with no change. When I have the battery connected to the ignitino direct I did move the battery up in front of the received but there was still no change.
2. I have a ball connector that is plastic connected to a metal push rod that connects to the servo with a metal connector. this is only about 3 inches long and does not run along any wires. I am going to change this but I assumed that as long as the connector was not metal to the engine it would be ok. maybe not.

thaks for the help.

Dlvsm

Would this cause the throttle to jump and move around. I did not any curve whe I programmed i just set the servo limits.

All Day Dan

My Feedback: (5)

That metal pushrod to the carb acts like an antenna regardless of any type of connector you use. It passes through a strong electromagnetic field that exists around the engine, ignition module and any other component of the ignition system. In fact, it is a better antenna than the one in your receiver because it is much longer and the field strength around it may be higher. Dan.

Jim Branaum

My Feedback: (3)

WOW!

Setting up gassers is fairly simple if you follow several simple rules.

1. Keep everything associated with the radio separated from everything associated with the engine by at least 8 to 12 inches. The 14 you were quoted is gold plating <imnsho>. That means the switch, the battery pack, and the ignition module all need to be 8 to 12 inches away from the receiver and any servos.

2. Always use a golden rod to connect the throttle linkage to the throttle servo that is back by the radio gear in line with Rule #1.

3. Always use a resistor plug.

4. Never allow metal to touch the engine or its mounts because it WILL create RFI you don't want.

I see by your pictures and text that you violated at least 3 of those rules and that is probably why you have a problem. I think if you correct those, your problems will go away. I very strongly suspect the solid throttle rod is playing antenna and transmitting RFI splatter to the throttle servo lead which is carrying it back to the receiver. Even in 2.4GHz systems, the IF strip inside can be swamped.



Now having said all that, a friend addressed this problem back in the 72mHz days by building a transmitter that plugs into the throttle slot on the receiver and a receiver that is mounted by the engine with the throttle servo and a switch that puts that servo on the ignition battery pack and turns the ignition system and throttle servo off. The 2 units are linked by optical cable so there is no electrical connection. I paid him $45 each for 10 and still have 4 left unused. I do use the other 3 he made me with my 2.4GHz radios because *I* am a coward and always take the safer way out. The other 3 were very special and had smoke and throttle servo controls at the engine.

raptureboy

Not. There are tons of us running metal rods with nylon ball connecters on the end, without interference. My bet is on the cap not being on all the way. If you don't push down hard on that sucker and feel a good solid snap it's not on all the way. Again, read the gas engine for noobies sticky and make sure your running your radio in range test mode to really make sure you have the issue fixed. Change one thing at a timeuntil you have eliminatedall the possibilities. Anybody remember the old days when your car radio would make ignition noise? It was a sure sign you had a leaky plug wire or cracked distributer cap.That went away when electronic ignitions became std on cars.

warbird_1

My Feedback: (61)

i've been flying gas for many years and i don't think you problem is the setup . you said that the throttle goes full and then glitches at times. if the ignition was affecting your radio i would think that it would effect all the channels i'm wondering if you have a bad servo being affected by vibration. having the servo that close to the carb i would think would allow a lot of vibration to find it's way to the servo. From what i was told, RF from ignition systems and from metal to metal is pretty much a thing of the past with 2.4 . As a rule in old school setups ..you want to keep the receiver as far as possible from the ignition . that includes the ignition batteries as RF can travel back to the batteries. hope this helps And BTW.. don't let anyone tell you that starting out on gas is a bad thing. an engine is an engine. each has a preferred way of being tuned. i can tell you once you set a gas burner you don't have to keep screwing with it like a glow.

BarracudaHockey

My Feedback: (11)

I think its been mentioned but the first thing you want to check is that the plug cap is seated correctly. Then check the servo. Then make sure all of your connections are tight.

I hate to be blunt but there's everything ranging from wives tales to outright poor information floating around in this thread.

To be fair, there's also some excellent advice, sorry you have to go through so much chaff to find the wheat.

dirtybird

My Feedback: (5)

PCM, Although it uses the same 72MHZ frequency, can give you as much as 3db processor gain which is the same as doubling the transmitter power. Its not a cure all but it can make hell of a difference.
In spread spectrum Technology I have seen as much as 40db processor gain claimed although I find it hard to believe.
Your SS 2.4 system spreads its data over a 1 mz band(4mhz with FSST systems) according to a pseudo random key(sequence) developed within your system. TO interfere with your rf the interference needs that key. The chances of that are virtually nil.
40 db is four orders of magnitude. There has to be a lot of power in that spark to swamp the receiver.
The other servos are working. Does that not give you a clue that the receiver is still working?
You guys can continue to punish yourself with obsolete rules if you like. Have at it.

rcmichael

My Feedback: (21)

I am not going to address the interference issue. You already have enough advice on that . I did notice that the fuel lines are not secured with zip ties or any other method. I suggest soldering barbs on all line connections then putting on the line and zip tie over the barbed area. Gasser lines can swell and come off if not properly secured.

jester_s1

Assuming I'm on to something here, you'll need to move the servo back. If you've never taken a servo apart, the pot has these fine brushes that run along a resistive surface. Vibration can cause those brushes to bounce around, giving false feedback. I imagine a bigger servo would have a beefier pot would would be more vibration resistant, but you're so much better off just eliminating the problem. As for why it doesn't bother it all the time, everything that vibrates has certain frequencies where it is affected more. So the pot can be affected at idle but not full throttle because the vibration frequency is different.

dirtybird

My Feedback: (5)

I have delineated a number of things I don't think it can be, lets see take a shot at what I think it can be.
If you have tried another servo and it still does it, it might be a loose connection in the output receptacle of that receiver channel. Or an intermittent connection in the electronics for that channel. Plug it into another channel and see if does the same.
If you still have the problem, then the only thing it can be is the ignition unit is putting out so much garbage it interferes with the pulse that is coming from the receiver. If the shield on the plug lead is intact and the cap is firmly on the spark plug, get rid if the ignition unit. Its an accident ready to happen.
Hobbyking has ignition units for about $25. I have three of them. They work fine.
Lets see the PRF of the servo is about 20ms. Thats about 3000rpm or high idle speed. Now if you increase the motor speed to 6000 the servo would get twice the pulses if the ignition unit is putting out that much garbage.
Sound interesting?

Mikecam

Oh man, I'm with Baracuda, with all this help you should sell the plane and start collecting stamps. Where's CGretired, not one mention of it being complicated on page two, slacker!!!![:-]

To be serious your plane and it's gas engine is a great choice and no it is not complicated. I'm sure CGretired enjoys cutting his grass and weedwacking his weeds with his glow powered lawn care tools cause god knows small gas engines are too complicated for him.

Your install looks fine for someone who is doing it the first time and once you lick this one issue it will be clear sailing after that, and with zero cleanup.

So stick at it and make sure you lick it before it licks you.

PS Don't ty wrap the tygon fuel lines, they pinch and cause fuel/air leaks. Just cut off 1/4 inch from some spare tygon, use needle-nose pliers to spread it open and slide it over the end of the fuel line that gets pushed on to the brass fittings.

sensei

I think I would relocate and change out the servo at the same time, for one, I don't care for that servo, but that is just me, two, getting the servo back further in the fuse allows more damping through the airframe and changes the resonation that servo is seeing on throttle up. Just a note: If your propeller is out of balance it can effect the servo into what your experiencing. It is highly doubtful that batteries, and ignition source placement is causing any issues in a 2.4 application. I say this because in early 2007 I switched to 2.4 and as a test of over 500 flights I powered two receiver's, and my ignition module from a single Fromeco switch I had custom built for the application, it was two batteries input and three outputs. If you having RF noise issues it would be effecting more then just the throttle servo. It is also doubtful that metal to metal contact would cause an issue with 2.4 but it is also just plain ignorant and wrong to assemble with metal to metal contact in the first place. Here are a couple of typical installation pictures, the one showing the duel Spectrum receiver installation is the one I powered the two receiver's and the ignition from a single circuit. In these applications I am showing, the batteries and ignition modules are in close proximity with no issues. just saying.

Bob

Luchnia

My Feedback: (21)

I have a DX7 and two DLE 30 gassers and both have the servo just in front of the fuel tank no more than five inches from the ignition (if not much closer) and not one minute's problem ever. I agree with some of the posters that imply to isolate this down one thing at the time until you nail it.

Dlvsm

 First off thank you to everyone who helped or had advice! Thank to one poster I did not see who as there are many replies and I had tried just about everything here but alas I finally figured out the RF issue I have been having. I was about to move the servo but before I did this I thought I would try a different brand servo like one poster had suggested. I had used a Hitech and the first install but it got fried so I bought another one but was still having the issue but just not frying up as I had added limiter or resistor whatever it is called to the receiver. So this time I bought a Spektrum servo that was about $5 more but I figured it matched the receiver and sure enough problem fixed. Not the kill switch or any of the mess of wires I have in there just a simple crappy servo! Now off to the field to see if this thing will fly!! Thanks again!