Single servo glitch with engine running
09-05-2006, 08:54 PM
#26
Thread Starter
RE: Single servo glitch with engine running
Don, I did replace the switch harness, but not the battery--yes, I'll do that next. Having an extra one is not an issue because the whole plane is well over 11 lbs. I didn't do the servos one at a time--it's just too difficult to keep testing each change. Replacing the servos on a pull-pull system is a project and then I have to load this big one-piece airplane into my car and drive 25 minutes to the field before I can start testing.
What about the vibration of an aluminum Pitts muffler against the aluminum motor mount? Do you think that could generate RF noise? They are about 1/32 inch apart and surely vibrate against each other. I just got a thin piece of tough rubber wedged between them so they can't touch anymore--do you think that might have any effect?
My friend thought his AM radio ought to pick up RF noise and then he could hear it through the headset. So he put the radio near the aircraft with the engine running, and he did pick up static that would come and go as he repositioned the radio. But it turned out that the static he was detecting was coming solely from the receiver! We just didn't know what to make of it, but it wasn't helping us spot the problem.
Yes, I saw the thread, but it sounds like it was a digital servo problem. I did try the antenna in different locations with some effect, but it doesn't eliminate the problem, which sounds like the other guy's experience too.
If it's not the battery or the motor mount/muffer then I'm pretty much out of ideas. What an incredible frustration--this is a really picturesque old airplane and I'd love to enjoy it in the air. But I do appreciate the tips. I've learned things that could help me avoid problems in the future. I think one lesson is, don't buy other people's airplanes!
Jim
What about the vibration of an aluminum Pitts muffler against the aluminum motor mount? Do you think that could generate RF noise? They are about 1/32 inch apart and surely vibrate against each other. I just got a thin piece of tough rubber wedged between them so they can't touch anymore--do you think that might have any effect?
My friend thought his AM radio ought to pick up RF noise and then he could hear it through the headset. So he put the radio near the aircraft with the engine running, and he did pick up static that would come and go as he repositioned the radio. But it turned out that the static he was detecting was coming solely from the receiver! We just didn't know what to make of it, but it wasn't helping us spot the problem.
Yes, I saw the thread, but it sounds like it was a digital servo problem. I did try the antenna in different locations with some effect, but it doesn't eliminate the problem, which sounds like the other guy's experience too.
If it's not the battery or the motor mount/muffer then I'm pretty much out of ideas. What an incredible frustration--this is a really picturesque old airplane and I'd love to enjoy it in the air. But I do appreciate the tips. I've learned things that could help me avoid problems in the future. I think one lesson is, don't buy other people's airplanes!
Jim
09-06-2006, 12:14 AM
#27
Senior Member
RE: Single servo glitch with engine running
Jim
I would use some fuel line to try to isolate the muffler and motor mount. The silicon rubber can withstand some very high temps and regular rubber may make a mess with the heat.
The muffler to engine mount has me a bit puzzled. Is'nt the muffler hard mounted to the engine, and the engine hard mounted to the mount? Two reasons for the questions, If the motor and muffler or the motor and the mounts are loose, that could be a cause for the glitching. If they are tight, how is the muffler hitting the mount, is something bending and letting the two come into contact with each other. My first thoughts were that the muffler to mount couldn't be a source because all three were at the same electrical potential because they were bolted together. If something is loose there, they could be at different potential.
I'm still betting on the battery at this point though.
I had a lot of distractions this weekend and didn't get my fuel tank pulled and the lines re-run, so I'll not get to fly tomorrow. Maybe I'll get out for some runway time though. I still tend to try to turn to fast and to sharply and my wing tips are really getting beat up. When I take the wings off and run it around, I'm beating up the rudder and elevators.
By the way, early last week, I was playing with my plane without wings and everytime I would flip it on it's side, this big turkey buzzard would make a pass on it. That happened three times before he got tired and moved to more productive grounds.
Don
I would use some fuel line to try to isolate the muffler and motor mount. The silicon rubber can withstand some very high temps and regular rubber may make a mess with the heat.
The muffler to engine mount has me a bit puzzled. Is'nt the muffler hard mounted to the engine, and the engine hard mounted to the mount? Two reasons for the questions, If the motor and muffler or the motor and the mounts are loose, that could be a cause for the glitching. If they are tight, how is the muffler hitting the mount, is something bending and letting the two come into contact with each other. My first thoughts were that the muffler to mount couldn't be a source because all three were at the same electrical potential because they were bolted together. If something is loose there, they could be at different potential.
I'm still betting on the battery at this point though.
I had a lot of distractions this weekend and didn't get my fuel tank pulled and the lines re-run, so I'll not get to fly tomorrow. Maybe I'll get out for some runway time though. I still tend to try to turn to fast and to sharply and my wing tips are really getting beat up. When I take the wings off and run it around, I'm beating up the rudder and elevators.
By the way, early last week, I was playing with my plane without wings and everytime I would flip it on it's side, this big turkey buzzard would make a pass on it. That happened three times before he got tired and moved to more productive grounds.
Don
09-06-2006, 12:18 AM
#28
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RE: Single servo glitch with engine running
Jim,
The aluminum Pitts muffler vibrating against an aluminum motor mount would most certainly cause RF noise in my opinion. If that's the source of the RF noise, then the rubber should eliminate the problem.
Marl
The aluminum Pitts muffler vibrating against an aluminum motor mount would most certainly cause RF noise in my opinion. If that's the source of the RF noise, then the rubber should eliminate the problem.
Marl
09-06-2006, 07:04 PM
#29
Thread Starter
RE: Single servo glitch with engine running
Thank you Marl and Don. It's good to know that the aluminum to aluminum could be a problem because I think there is probably a lot of vibration going on there.
I'll try to explain the geometry of the set-up. The engine is mounted at 9 o'clock. Viewed from the front, the Tatone Pitts muffler is a backwards L lying on its side. The short side of the L is clamped on to the exhaust port with a hose clamp. It's very secure. The long side is the muffler chamber running parallel to the cylinder and extending past the motor mount. It's a typical Pitts arrangement. The muffler didn't quite clear the motor mount, so the builder ground down the aluminum mount enough for the muffler chamber to clear. That leaves a narrow space that I strongly suspect vibration could bridge.
I understand your suspicions about the battery, Don, but this plane has had radio problems right from the time it was built several years ago. I think I should replace the battery just because it is old, but whatever the problem is, it has probably existed right from the start. That's why I really didn't think the equipment was the issue. But the flying wires, or the muffler/mount vibration, would be the kind of thing that would have been there from the beginning.
The plane, a fifth scale Thomas-Morse Scout, was built by a club member whose father built the full scale planes here in Ithaca during WWI. This club member also built a half scale static model which hangs in the rotunda of the local airport in memory of his dad. The local newspaper carried a story on it, and that was what got me to join the club. The flying model crashed twice due to radio trouble before he passed it along to me. The two short flights I've made, with the radio acting up occasionally, are the only flights it ever made that ended in controlled landings. I think the plane is over 10 years old. To get it flying would be a real event for the whole club.
I'm away this weekend, so the next test won't come for another week and a half. I will post results again, and try to get set up for pictures again. Oh--there is a picture of the plane in my gallery. It's in a shot of my workshop.
Jim
I'll try to explain the geometry of the set-up. The engine is mounted at 9 o'clock. Viewed from the front, the Tatone Pitts muffler is a backwards L lying on its side. The short side of the L is clamped on to the exhaust port with a hose clamp. It's very secure. The long side is the muffler chamber running parallel to the cylinder and extending past the motor mount. It's a typical Pitts arrangement. The muffler didn't quite clear the motor mount, so the builder ground down the aluminum mount enough for the muffler chamber to clear. That leaves a narrow space that I strongly suspect vibration could bridge.
I understand your suspicions about the battery, Don, but this plane has had radio problems right from the time it was built several years ago. I think I should replace the battery just because it is old, but whatever the problem is, it has probably existed right from the start. That's why I really didn't think the equipment was the issue. But the flying wires, or the muffler/mount vibration, would be the kind of thing that would have been there from the beginning.
The plane, a fifth scale Thomas-Morse Scout, was built by a club member whose father built the full scale planes here in Ithaca during WWI. This club member also built a half scale static model which hangs in the rotunda of the local airport in memory of his dad. The local newspaper carried a story on it, and that was what got me to join the club. The flying model crashed twice due to radio trouble before he passed it along to me. The two short flights I've made, with the radio acting up occasionally, are the only flights it ever made that ended in controlled landings. I think the plane is over 10 years old. To get it flying would be a real event for the whole club.
I'm away this weekend, so the next test won't come for another week and a half. I will post results again, and try to get set up for pictures again. Oh--there is a picture of the plane in my gallery. It's in a shot of my workshop.
Jim
09-17-2006, 10:26 PM
#30
Thread Starter
RE: Single servo glitch with engine running
I've tried a new battery, moved the rx high in the cockpit away from the servos, etc., tried different antenna locations, put a rubber piece between the muffler and the motor mount and also tried disconnecting each servo and running up the engine--same result--fine without the engine running, but glitches once it is running. These days I am running out of range at about 20 yards with the antenna collapsed and engine running. I had gotten much better than that once before for no apparent reason, but the plane still glitched in flight.
I did read on a scale forum that some people who build wire braced biplanes find they have to use PCM. When I look up PCM I find a lot of arguments about whether it really helps or not. I assume it does help, but it would cost me $95 to buy a PCM receiver compatible with my Tx, and then it might work or it might not. Any opinions on how likely it would be to work?
I've given up now. I'll store the plane away instead of burning it as I almost did this afternoon. Maybe some day better radios will get cheaper and I will try again. I really appreciate all the advice. I know that when I build my own WWI plane someday all this will have a big influence on my construction and radio installation, so hopefully I will never go through a nightmare like this again. Jim
I did read on a scale forum that some people who build wire braced biplanes find they have to use PCM. When I look up PCM I find a lot of arguments about whether it really helps or not. I assume it does help, but it would cost me $95 to buy a PCM receiver compatible with my Tx, and then it might work or it might not. Any opinions on how likely it would be to work?
I've given up now. I'll store the plane away instead of burning it as I almost did this afternoon. Maybe some day better radios will get cheaper and I will try again. I really appreciate all the advice. I know that when I build my own WWI plane someday all this will have a big influence on my construction and radio installation, so hopefully I will never go through a nightmare like this again. Jim
09-17-2006, 11:29 PM
#31
Senior Member
RE: Single servo glitch with engine running
Hi Jim
Man, this is a rough one. What engine is you plane using? Any chance you could swap it out?? I really have my doubts that the wing wires are the issue.
That's to sweet a plane to put on a shelf, and it is also to sweet to crash.
Do you have another plane that is performing OK? If so, you might move the whole radio setup to the trouble plane. See what happens then. It would be a pain to do, but you have spent 10 times that amount of effort already.
You mentioned you got the plane ready built. Is there a chance that there is some electronics built into the plane that isn't obvious? The reason I ask is that I bought out a guys entire collection a weel and a half back and in one plane, a huge trainer looking thing, I see an IC sticking it's head above a former in the rear of the cockpit area. I haven't dug it out yet to see what it is, but for the life of me I can't imagine what it might be. Is there a chance you have a susprise hidden like this one??
Good luck.
Don
Man, this is a rough one. What engine is you plane using? Any chance you could swap it out?? I really have my doubts that the wing wires are the issue.
That's to sweet a plane to put on a shelf, and it is also to sweet to crash.
Do you have another plane that is performing OK? If so, you might move the whole radio setup to the trouble plane. See what happens then. It would be a pain to do, but you have spent 10 times that amount of effort already.
You mentioned you got the plane ready built. Is there a chance that there is some electronics built into the plane that isn't obvious? The reason I ask is that I bought out a guys entire collection a weel and a half back and in one plane, a huge trainer looking thing, I see an IC sticking it's head above a former in the rear of the cockpit area. I haven't dug it out yet to see what it is, but for the life of me I can't imagine what it might be. Is there a chance you have a susprise hidden like this one??
Good luck.
Don
09-18-2006, 11:45 AM
#32
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RE: Single servo glitch with engine running
Jim,
For a while, I was using a metal field stand (I've since been using a nice wooden one). As it turned out, the metal legs of the field stand were vibrating on the fold-able table part and creating radio noise. On one of my planes (FM), the control surfaces would go absolutely crazy with the engine running (even at idle). On another plane (PCM), there was no glitching whatsoever. Different planes and perhaps coincidental, but it might be worth a try to go with PCM. Another thought: are the lengths of the metal wire braces a fraction of a wavelength at 72 MHz (e.g., 1/4 wave)? Maybe experimenting with the routing of your antenna would yield positive results.
Marl
For a while, I was using a metal field stand (I've since been using a nice wooden one). As it turned out, the metal legs of the field stand were vibrating on the fold-able table part and creating radio noise. On one of my planes (FM), the control surfaces would go absolutely crazy with the engine running (even at idle). On another plane (PCM), there was no glitching whatsoever. Different planes and perhaps coincidental, but it might be worth a try to go with PCM. Another thought: are the lengths of the metal wire braces a fraction of a wavelength at 72 MHz (e.g., 1/4 wave)? Maybe experimenting with the routing of your antenna would yield positive results.
Marl
09-18-2006, 09:35 PM
#33
Thread Starter
RE: Single servo glitch with engine running
Thanks Marl, it's good to hear stories of PCM receivers solving problems like this. Still don't know if I'm willing to spend so much money to find out if it would solve mine.
I did check the flying wire lengths--about 24 inches. One went through tubing in the fuse from one wing to the other and that was about 54 inches. I cut the tubing inside the fuse and crimped each side.
Jim
I did check the flying wire lengths--about 24 inches. One went through tubing in the fuse from one wing to the other and that was about 54 inches. I cut the tubing inside the fuse and crimped each side.
Jim
09-18-2006, 09:46 PM
#34
Thread Starter
RE: Single servo glitch with engine running
Don, I've tried five different receivers and some of them have flown in other planes; so have the various servos I've tried.
I think there has to be something inside that plane somewhere that is vibrating that I can't see. It is a definite problem with trying to fly other people's planes--I don't really know what's in there, and it would be a big project to take aparty. I've wondered about the coiled landing gear springs on the rear V struts, but they look very tight.
Yes, too sweet to shelve and too sweet to crash--that is certainly my dilemma. I've oiled up the engine, I'll protect everything from dust, and maybe next year I'll spring for a PCM receiver, or maybe I'll wait till they're cheaper. I'm happy that I got the ASP .91 running really well, I've learned some things about radio problems, I got over my fear of flying a big WWI scale bipe and found out they can be a great flyers, and I got to see it in the air for a couple of minutes. So it hasn't been a total loss. Thanks again for the advise.
Jim
I think there has to be something inside that plane somewhere that is vibrating that I can't see. It is a definite problem with trying to fly other people's planes--I don't really know what's in there, and it would be a big project to take aparty. I've wondered about the coiled landing gear springs on the rear V struts, but they look very tight.
Yes, too sweet to shelve and too sweet to crash--that is certainly my dilemma. I've oiled up the engine, I'll protect everything from dust, and maybe next year I'll spring for a PCM receiver, or maybe I'll wait till they're cheaper. I'm happy that I got the ASP .91 running really well, I've learned some things about radio problems, I got over my fear of flying a big WWI scale bipe and found out they can be a great flyers, and I got to see it in the air for a couple of minutes. So it hasn't been a total loss. Thanks again for the advise.
Jim
