I made this post in the radio equipment forums, and it seems that I may or may not have the right idea of what's going wrong. Since this does pertain to my Mustang, I feel that this post is worthy of being in the ARF forum. If you would, click on the following link and see if you can help me out any.

http://www.rcuniverse.com/forum/I%27...2345787/tm.htm

Thanks,

John

try a new crystal sounds like the crystal is cracked and the engine is in the vibration range of it causing that

Check your engine linkage I'm sure the problem is there.

Prophanger,

I've been thinking about that also. I believe I'll start the process of elimination, beginning with all metal-to-metal contact. If that doesn't take care of the problem, I'll change out the crystal.

Evfast,

So you agree with me on the metal-to-metal issue? One of the guys that responded to my post in the radio forum acted as if this was only an issue in gassers. I really didn't think that it mattered what type of engine it was. Does this cause static?

John

It does not have to be engine related either. You could have loose retracts, wheels, muffler. event the rods going back to the elevator and rudder could be vibrating and hitting each other. Start with the easy stuf like that crystal or receiver. If you have other planes, pull one from it and install it and run it up.

I would assume you allready change receivers, crystal and battery. Try to connect only the throtle servo and see what happens then connect another and another. This should narrow down your problem.


later

My Saito's have plastic throttle arms, not sure what your .91 has. If it's metal, I'd say most likely that's the problem. If it's plastic, it's doubtful that the steel pushrod is the source as long as it isn't touching any other metal.

Stick,

I evidently have one of the older models, because mine does indeed have a metal throttle arm. All of my others have plastic. I'm definately going to start there. There's been talk of maybe having a cracked crystal. It is a brand new, never used crytal/receiver. It could still be defective, but I doubt it. Once I get rid of the metal contact at the throttle arm, I'll give the crystal a try if I haven't gotten the problem fixed.

John

I had a strange one a few years ago: new JR radio, new airplane with dowel/wire combo rod wyed and going to split elevators; would glitch like crazy in flight only when I put it into a shallow dive. The prop would unload, the rpm's would go up, and when they got into a certain range, the radio would glitch like crazy. NO METAL TO METAL ANYWHERE! I finally replaced the el rod with nyrod, problem solved! Evidently, the wire ends on the el rod set up a sympathetic vibe at a certain engine rpm. The fix would be to change the resonance of the wires by changinging their length (shorter for higher rpm) or diameter (heavier wire would change it), if you must use that type of pushrod. I also had a case recently where I suspected a solid wire throttle pushrod(4c glow power); the glitch would not go away until I tried a PCM receiver.

Each control surface has it's own servo. The elevator and rudder servos are in the tail, so there's no long pushrods running through the fuse. I am running a solid control rod from the throttle servo to the throttle arm on the carb. Like I said before, I connected the rod to the carb arm by an "L" bend, with a small collar on the back side to secure it. I can try one of two things. I can reroute my solid arm to where I've enough room to add a nylon clevis to attatch to the carb arm, or, I can simply use nyrod for the throttle.

When you told of having (4c glow power) were you talking about an on-board glow system? If so, I don't have this feature.

It's odd that yours and my situations are/were the same. Glitches only at hight RPM's. This has to be a simple fix.

sorry to hijack but i really don't think pcm solved the problem, it just masked it. solve it with a ppm receiver then use a pcm.

Ditto here.

.

I would say definitely start with changing that. I have three 2-stroke glow planes with metal throttle arms and steel throttle cables attached with brass EZ-Connectors and have never had a glitch (all PPM). On the other hand, I have witnessed this type of set up cause serious glitching on other planes. There doesn't seem to be any rhyme or reason why sometimes it's OK and other times it ain't.

Jammer,

As I stated earlier, I know of one other plane I did the exact same way, and never had a problem with it. As you said, there doesn't seem to be any reason why it affects some and not others.

John

Well, I got the problem solved. I added a ball joint and nylon connector at the throttle arm. I took off the quick connector at the arm of the servo and went back with an "L" bend. I changed out the metal wing bolts with nylon bolts, which I really don't think had anything to do with my problem, but I did it anyway.

Anyway, I ended up testing it at he house. Full throttle with the transmitter antenna down around 75-100 feet away, and no glitches.

Metal to metal contact "DOES" present problems with a radio system.

That will be $100.00.... I'm glad that your problem might be fixed, do a radio check at the field again and see what happens. But from what you have reported looks like the problem might be solved.


good luck

Have to agree, but what do you do after trying 3 FM receivers ( one brand new), brand new switch, etc. Throwing in another curve, plane did not glitch for the first six flights! Still scratching my head. Range with either type rx exceeded 400 ft tx antenna down, engine running, fm glitching, pcm not.

Are you saying that you were able to get 400' away with the antenna collapsed and a PPM receiver? Any glitching beyond 100' with the antenna collapsed is quite normal for a PPM Rx. A PCM receiver won't allow any glitching. If it encounters interference or lack of signal it just locks out into failsafe until the signal is clear again.

I have to agree with Stick, anything beyond 100 feet with the antenna down, you're gonna start getting some movement. From all of the replies I've had since I started this post, I've gotten a world of info from people, things that you may need to check. There are several things that could be causing you problems, with a PPM receiver anyway. I guess as long as you don't have any problems with the plane supplied with a PCM receiver, leave it alone and fly the thing.