yard-dart

My Feedback: (35)

I maidened my Miss America Mustang yesterday. Just one problem. Every time I would go to full throttle, the plane would become irratic. I'd back off the throttle and it would act fine. I did this about two or three times and decided that was enough.

Once I got it back on the ground, I checked to see if it would still do it. It would! The only thing that I can think of is that I have some problem with metal to metal contact at my throttle. I have an "L" bend going through the throttle arm of my Saito .91 with a keeper on the back to secure it. It fits quite snug, so I definately wouldn't think that it could moveenough to cause problems. In fact, I've done this on other models without the first hint of a problem. The only other metal-to-metal in the plane is the wing bolts and blind nuts.

I have my antenna running out the side of the plane at the wing and running along the bottom of the plane, so I know that it's getting good reception. The receiver is completely surrounded by foam, so it shouldn't be catching any vibration.

Remember, problems only at full throttle in the air and ont he ground. Is the throttle linkage my problem, or could it possibly be something else?

John

cwrr5

My Feedback: (32)

Couple of questions/ideas: Does it have an onboard glow driver or remote? If so, try it without? What is your throttle servo/Have you tried a different one? Check/double check/triple check the connections at the receiver&battery.... maybe try a plastic clevis for the throttle arm? I doubt you're getting interference on just one channel, and only at high throttle - sounds more like a connection somewhere to me.... good luck, hope you find & post the culprit!

BillS

Two thoughts:
First it is usually easy to put a plastic clevis at the throttle.
Second the throttle wire often routes close to the engine case. Maybe the vibration is allowing the throttle wire to vibrate against the engine case.

You might want to thank the radio Gods. They don’t often give any warning.

yard-dart

My Feedback: (35)

In reply to both,

No, I don't have an on-board glow. I usually use a nylon clevis, but in this particular incidence, I didn't have enough room for one. I think I have figured out a way to run my throttle pushrod so that have room for a clevis. It (pushrod) definately isn't hitting the side of the engine. It is affecting all channels, not just one. Even on the ground, when I go to WOT, all of the control surfaces jump, even the throttle is affected. Once I come down to around 3/4, or even 1/2 throttle, all of the irratic movements stop.

I plan on changing my throttle linkage arrangemet and adding nylon, and changing the metal wing bolts to nylon. That will do away with all metal to metal contact in the plane. i'll also check all of my connections at the receiver, but I really don't think that's the problem.

Thanks for your input guys,

John

cwrr5

My Feedback: (32)

Well, good luck - keep us posted.

WilsonFlyer

My Feedback: (13)

What does any metal-to-metal linkage have to do with anything on a glow engine???

Are you sure you guys barking up the right tree?

yard-dart

My Feedback: (35)

As I understand it, anytime two loose metal objects come in contact with one another while there is vibration present, they will cause (static perhaps) interference to a receiver. If you disagree with this, give me your opinion as to what's happening in my situation, or what could be causing my servos to go crazy whenever I go to full throttle.

exeter_acres

My Feedback: (2)

yes...metal to metal can create radio interference... it is actually the engine itself that creates it....


have you tried a different throttle servo to isolate that the servo itself is OK?

Chris Moon

My Feedback: (8)

What kind of radio? What range do you get when you range check with the engine off? And then range check with the engine on. Also, try running the battery right into the RX to see if the switch is bad. You might un plug one servo at a time to see if one is causing the problem. Move the RX and antenns placement to see if there if is picking up noise from some close by wiring. Lots of possibilities.

JohnMac

Is the reciever really well packed in sponge foam? If not vibration can cause exactly these problems. Has the Rx Ever been crashed? If so get it checked out. Also check your crystal by swopping it. This again is tpical of a faulty crystal.
Regards,

John.

evfast

My Feedback: (31)

I had the same problem with my F90 when I installed a 1.80. Its your linkage even if the push rod comes close enough to the engine case it will cause interference.

I used ny-rod to fix the problem, check the engine and carb assembly very carefully you will find the problem there.

mecaloj

I hate to bring up the obviouse, but does the servo stall out at full throttle. It could be as simple as the stalling servo drawing power off the battery and causing a glitch situation. If the throttle arm hits the stop before the servo throw is used up it can stall the servo.

yard-dart

My Feedback: (35)

In response to the last five replies....

exeter,

That's what I've always been told, and experienced in a few other incidences.

ual,

Futaba 7C. I usually do a range check with the engine shut off, Trans. antenna down, 100 ft. away. I know this may not be a good practice, but 75% of the time, I don't range check with the engine running. Luckily, I've never had a problem. This time, I didn't do it either. Luckily I only had a problem at WOT and got out of it when I started having glitches. I'll definately do some of the things you reccomended.

Mac,

The receiver is extremely well packed in foam. It is brand new, never been used. Although it is new, that doesn't rule out a faulty crystal. I'm going to check it by swapping it with another.

evfast,

I will start the process of elimination by doing that first. I have a strong feeling that's my problem.

Mecaloj,

I don't believe that's my problem. If I'm not badly mistaken, I had plenty of travel left when I was setting my end point. I will double check it though. Even if that was the case, I'm running a 1100 Mah pack that is fully charged, and a little load on the battery because of this isn't going to create the problem I'm having, I don't think. This was the first flight, so the battery was at max charge. I could see this being the problem if the battery was more on the weak side. Like I said, I'll double check it.

Thanks for all the responses guys, your input is much appreciated.

John

50+AirYears

I had a similar problem several years ago, although it only showed up in flite. I eventually traced the cause to the spring type connectors for the crystal to plug into had loosened up, and under the in-air vibration created problems. Apparently, when the plane was restrained on the ground, there was enough dampening of vibration that the problem didn't show up.

Mikes machines

I would suspect a loose connection caused by the vibration. It sounds like it may be a loose crystal in the rx or a loose connection in the power switch. It could also be a bad connection where the antennae is soldered to the circuit board. Let is know what you find because you know we will all check it on our planes.

mack845

HI,
Have you given any thought to the throtle pot, it could be dirty at the top end.
Norman UK

hebertjj

John,

I'm mainly adding my 2 cents worth because I want an email notice to find out what happens here. I vote for the Rx vibration problem so swap out the xtal and then the whole Rx to see if that fixes it. If you want to add a nylon clevis on the motor throttle arm connection and you don't have room between the throttle and the firewall, you can have the pushrod go past the throttle and put a "U" bend in it so it comes back and connects to the throttle arm (hope this explanation is understandable.)

Joel

yard-dart

My Feedback: (35)

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.

cwrr5

My Feedback: (32)

Great news! Go fly!

I figured it was either the throttle connection or a plug into the receiver/battery, those are the usual culprits for glo, along with shorted glo driver as a distant third.
Didn't think it was external if the glitches were just at full power. (although possible in theory I guess)

yard-dart

My Feedback: (35)

After I got the problem solved, I was telling a buddy of mine what had happened. He first asked me where my receiver was located in conjunction to the throttle servo. I told him that the receiver was located about an inch behing the throttle servo. His response was "that's your problem right there". He explained that the metal to metal at the throttle arm on the carb was sending vibrations down the throttle pushrod, and the pushrod is located only an inch away, at the most. This was sending a false signal to the receiver, whenever it got to WOT, which was when the most vibration was present. He told me that if the receiver had been located elsewhere, farther away from the throttle pushrod, this irratic movement may have never occured.

Now that I understand all of this, it makes sense. It's odd how a tiny piece of nylon can change so much when it comes to radio interference.

Rodney

Yes, any metal to metal contact that vibrates does create electromagnetic impulses that can create interferance, makes no difference what type motor, even an electic motor could cause it. Chances are good that it was the throttle connection at the throttle arm on the motor. Glad you have the problem corrected, regardless of cause. As a general rule, never used metal clevisis on a metal arm. If two metals must touch, make sure the connection is very firm, absolutely no play.