Ailerons twiching on idle
07-28-2014, 03:20 PM
#101
Senior Member
My Feedback: (26)
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
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
07-28-2014, 04:15 PM
#102
My Feedback: (5)
Join Date: Jan 2002
Location: San Tan Valley,
AZ
Posts: 5,768
Likes: 0
Received 0 Likes
on
0 Posts
2.4 was chosen for SS operation because it has sufficient bandwidth to make SS possible. Other free bands like 900mhz or 5.2GHZ could be used but the gvmt wont let you use 900. I dont know why. 5.2 has much higher propagation loss. Most satellites use 3.0GHZ because ih has reasonable antenna size and lower propagation loss than higher frequencies.
2.4 was chosen because it has reasonable antenna size, low cost components, and sufficient band width and available for free use. It was the best compromise
2.4 was chosen because it has reasonable antenna size, low cost components, and sufficient band width and available for free use. It was the best compromise
07-28-2014, 04:49 PM
#103
Just to clear up on a few things. Metal throttle pushrods are fine with plastic ball links. Nyrod or any other plastic pushrod will expand slightly with heat. I had it on my first 40% airplane and it was a huge pain. The idle would change a couple hundred rpm from beginning to end of flight. Twisted wires.....every peice of DC electronic equipment I built for Lockheed Martin showed twisted wire and there was a workmanship standard that gave specifications for how many twists per inch depending on the gauge wire used. I asked an engineer what effect it had and was told it sets up a small electro magnetic field that acts as a low power RF shield. Not to disregard Dirtybird as he has made good points in the past on this subject but I am on the other end of what he did, I'm the guy who puts the stuff together and makes it work. When we are talking about high frequency RF what works on paper does not always work per plan.
07-28-2014, 08:35 PM
#104
My Feedback: (5)
Join Date: Jan 2002
Location: San Tan Valley,
AZ
Posts: 5,768
Likes: 0
Received 0 Likes
on
0 Posts
That is thye reason I dont use nyrod for throttle. Its length depends on temperature.
I have to disagree with your engineer about twisting leads. All conductors have a magnetic field around them if twisted or not. All twisting does is rotate that field. It certainly does not form a shieldr. That rotatinjg field does cause coupling between conductors to cancel though. That is why you used twisting with Lockheed, You had many conductors close together. Twisting was a standard that was meant to prevent various signals from disturbing one another. Not as an RF shield.
In our case where we have only one or two cables. Twisting is pointless. That is why most of our suppliers dont bother with it.
BTW I was an engineer for Boeing. We used lots of twisted wires. In my cryogenic instrumentation design for the X-20 program I used twisted shielded pairs. Now if you are really think you need protection from RF or any other noise that is what you need.
I have to disagree with your engineer about twisting leads. All conductors have a magnetic field around them if twisted or not. All twisting does is rotate that field. It certainly does not form a shieldr. That rotatinjg field does cause coupling between conductors to cancel though. That is why you used twisting with Lockheed, You had many conductors close together. Twisting was a standard that was meant to prevent various signals from disturbing one another. Not as an RF shield.
In our case where we have only one or two cables. Twisting is pointless. That is why most of our suppliers dont bother with it.
BTW I was an engineer for Boeing. We used lots of twisted wires. In my cryogenic instrumentation design for the X-20 program I used twisted shielded pairs. Now if you are really think you need protection from RF or any other noise that is what you need.
07-29-2014, 04:18 AM
#105
DB, i have to disagree. Twisted servo extensions serve a great purpose on RC installations: It looks cool and people will be impressed when your canopy is off and they see neatly twisted wires!
Thats about the only purpose they serve in RC.
+1 on the theory you don't need nyrod. As long as you have a plastic connection so you don't have metal rubbing metal you're fine, and even metal to metal creates noise well below the freqency that we operate today that its a non issue, though less RF noise is always better than more.
Thats about the only purpose they serve in RC.
+1 on the theory you don't need nyrod. As long as you have a plastic connection so you don't have metal rubbing metal you're fine, and even metal to metal creates noise well below the freqency that we operate today that its a non issue, though less RF noise is always better than more.
07-29-2014, 04:33 AM
#106
Here is a layman's explanation of how twisted pairs work. Granted, our three line servo wires aren't exactly a transmission line, but the thing happening here is cancellation which was certainly a topic in my electrical engineering education. It does help, and that is the reason that television twin lead and amateur radio balanced lines were twisted: To cancel out the EMI from high energy ignition sources or other sources of EMI. It is also the reason that ARINC data lines in modern transport aircraft are twisted to help make them impervious to various sources of noise in an aircraft. The electromagnetic laws governing this would certainly make me think that it is worth twisting servo lines to help reduce the noise from the ignition coil. And it does indeed look cool!
http://en.wikipedia.org/wiki/Twisted_pair
http://en.wikipedia.org/wiki/Twisted_pair
07-29-2014, 07:50 AM
#108
My Feedback: (5)
Join Date: Jan 2002
Location: San Tan Valley,
AZ
Posts: 5,768
Likes: 0
Received 0 Likes
on
0 Posts
Here is the first line of your Wikipedia quote
Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. It was invented by Alexander Graham Bell
I have never seen TP used for TV. All of the TV twin leads I have seen are untwisted.
They use twin leads or coax.
I would not use Tp for a transmission line. It increases the line length and begins to look like an RF choke.
Amateur radio operators are just what the name says, Amateur. They tend to follow what the most most forceful persons advice, good or not ..
I am going to leave this thread. I have made the following points:
The OP does not now have a problem. He may have had a bad servo in the begining.
All of the old 72mhz cures are now pointless.except for shielding of the spark plug lead and proper seating of its connection.
Nyrod is a poor choice for a throttle cable.
Twisting leads does not make a shield.
Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. It was invented by Alexander Graham Bell
I have never seen TP used for TV. All of the TV twin leads I have seen are untwisted.
They use twin leads or coax.
I would not use Tp for a transmission line. It increases the line length and begins to look like an RF choke.
Amateur radio operators are just what the name says, Amateur. They tend to follow what the most most forceful persons advice, good or not ..
I am going to leave this thread. I have made the following points:
The OP does not now have a problem. He may have had a bad servo in the begining.
All of the old 72mhz cures are now pointless.except for shielding of the spark plug lead and proper seating of its connection.
Nyrod is a poor choice for a throttle cable.
Twisting leads does not make a shield.
07-29-2014, 10:04 AM
#109
Thank you for all the info posted here DB, I have learn a lot from all the info posted here regarding RF, that gives me a better understanding on how to make a more robust installation on my future gas airplanes.
Thank you to all that participated posting info on RF and how it affects our model airplanes.
I will continue working on the Gee Bee on Friday and will post any changes that may happen with the new changes on the ignition box and cables.
Thank you to all that participated posting info on RF and how it affects our model airplanes.
I will continue working on the Gee Bee on Friday and will post any changes that may happen with the new changes on the ignition box and cables.
07-29-2014, 05:58 PM
#112
Carlos... Just ran across this interesting test tool on ebay that allows one to fire the ignition system at various RPM without the engine running. Probably would be difficult for you to get fast enough but thought I would at least pass it along.
My suspicion is that that your ignition coil or its wiring is putting out an electromagnetic pulse that your aileron servo leads are picking up, OR there is coupling in your kill switch module. Your servo signal input is of high impedance so that the fast rise time pulse from the coil is actually looking like a servo positioning edge on the servo signal line. (I.E. your situation probably has nothing to do with interfering with the 2.4 Ghz radio portion, but rather the energy is being picked up in your servo wiring, either coupling through the kill module or being picked up on the aileron servo leads acting as an antenna.) That could explain why the problem only occurs at some RPM settings. Putting an oscilloscope on that servo signal line would likely reveal a lot of spikes from your engine. Looking forward to hearing what you end up finding.
http://www.ebay.com/itm/Complete-Gas...p2056016.l4276
My suspicion is that that your ignition coil or its wiring is putting out an electromagnetic pulse that your aileron servo leads are picking up, OR there is coupling in your kill switch module. Your servo signal input is of high impedance so that the fast rise time pulse from the coil is actually looking like a servo positioning edge on the servo signal line. (I.E. your situation probably has nothing to do with interfering with the 2.4 Ghz radio portion, but rather the energy is being picked up in your servo wiring, either coupling through the kill module or being picked up on the aileron servo leads acting as an antenna.) That could explain why the problem only occurs at some RPM settings. Putting an oscilloscope on that servo signal line would likely reveal a lot of spikes from your engine. Looking forward to hearing what you end up finding.
http://www.ebay.com/itm/Complete-Gas...p2056016.l4276
07-30-2014, 09:39 AM
#115
http://www.youtube.com/watch?v=zf-2MdeknOM
Check this video and pay attention the Ailerons at the start of the video, at 014 it can be seen clearly that the Ailerons are bouncing ( left Aileron is clear ) my Gee Bee was doing it that much but it has change to almost nothing with all the things that I have done to eliminate the gliching.
Check this video and pay attention the Ailerons at the start of the video, at 014 it can be seen clearly that the Ailerons are bouncing ( left Aileron is clear ) my Gee Bee was doing it that much but it has change to almost nothing with all the things that I have done to eliminate the gliching.
Last edited by CARS II; 07-30-2014 at 09:56 AM.
08-11-2014, 12:03 AM
#117
These are some of the changes I made last nigt, cut the grounding wires from the spark plugs short and secured them to the head of the cylinders, grounded the ing box with the left over braided wire for now to see if it helps and have now digital servos on all the control surfaces.
Last edited by CARS II; 08-11-2014 at 12:08 AM.
08-11-2014, 05:10 PM
#119
I like the idea of the tape, I will also try the tape by this Friday, I will go to the field and run the engine without the grounding wire to see what is it doing i ( if any ) then ( if any ) I will ground the ing box, run the engine then ( if any ) I will add the tape, I will be adding the tape anyways I just want to see if there is any improvements with each step.
Thanks to all for all this suggestions, I'm actually learning during all this testing.
Thanks to all for all this suggestions, I'm actually learning during all this testing.
08-15-2014, 06:44 PM
#123
Took the Gee Bee to do some testing with the new mods, I run it with the grounding wire that was added to the ing box, on this run I did not noticed any twitching on the Ailerons, I run the engine to the lowest RPM possible and got no twitching.
Second run, no grounding wire this time, no twitching again, then I replaced the grounding wire.
With these good results I went ahead and gave the Gee bee a test flight, over all the flight was good, it needed some left Aileron and down Elevator, after the trimming I was going full throttle doing laps around the field, around the forth or fifth lap the engine quit and I had to do a dead stick landing but I was in a good landing positions and end up on the runway, no damage.
The engine quit probably because the high temps around here now, I adjusted the low and high end needles to get extra fuel to the engine to help keep it cool, the next run showed a steady low RPM.
I think the high end digital servos fixed the Aileron problem but i like to have the ing box grounded to the engine and will be adding some copper tape to the ing box soon.
Second run, no grounding wire this time, no twitching again, then I replaced the grounding wire.
With these good results I went ahead and gave the Gee bee a test flight, over all the flight was good, it needed some left Aileron and down Elevator, after the trimming I was going full throttle doing laps around the field, around the forth or fifth lap the engine quit and I had to do a dead stick landing but I was in a good landing positions and end up on the runway, no damage.
The engine quit probably because the high temps around here now, I adjusted the low and high end needles to get extra fuel to the engine to help keep it cool, the next run showed a steady low RPM.
I think the high end digital servos fixed the Aileron problem but i like to have the ing box grounded to the engine and will be adding some copper tape to the ing box soon.
Last edited by CARS II; 08-16-2014 at 09:17 AM.
