1] When I test the control of the servos I hear a vibrating or humming sound coming from the servos. This usually only happens when I press the transmitter lever all the way in a certain direction (i.e: servo/lever all the way extended to the full down or up of the elevator, extended to the full left or right of the rudder, AND ESPECIALLY the full extent of the throttle either all the way open or closed). The rods and tubes all all straight, unobstructed, and not binding with anything or bending and I have coated them with graphite before inserting the rods into the tubes. The servos are tight in the tray and the tray securely glued to the inside of the fuselage. I tighten the servo screws until the grommets start to compress then loosen the screws about a half-turn just enough not to compress the grommets.

What could be causing the vibrating humming sound from the servos?????

2] I know this has been asked before but I will ask it anyway : What is the proper order of turning the radio system on and off? Is it transmitter on first and the receiver? Then reversed to turn off?



Thank you in advance.

The way I remember it is that you never want your plane on without the radio being on. So, yes - radio on, plane on....plane off, radio off. As far as the humming, I'm guessing that the servos are trying to move the control surfaces and the throttle arm farther than they can. If they don't hum if you disconnect the servo arm from the servo then there's a good chance that that is the problem. What kind of a radio do you have? If you have a computer radio, you can change the endpoints so the control surfaces don't move as far. Otherwise, you could just move the pushrods in closer on the servo arm or out farther on the surface control horn.

It is a computer radio, the exact name is not with me now, I am at the office and the radio is at the house.

I don't have a clue about what end-points are or how to correct them. Anyone wanna help if they can on how to adjust a computer radio's end-points? Thank you!!!!

P.S: I have (or my roommate has that is) misplaced my radio's instruction booklet and the internet service I have at present is too slow to download a booklet at this time.

By-the-way, the control surfaces themselves are NOT connected to the pushrods yet, the pushrods are only connected in the servo compartment.

Tigerdude 426, depending on what radio you have, the travel adjust of your servos may be listed under different names, like tarvel adjust , endpoint adjust or adjustable travel volume. This function will be found in the computer programming function of your radio. So it would help if you can find out the name of your radio, so we can then help you to programme it without guessing is it this or that. Second answer is radio ON, aircraft ON, then Aircraft OFF, radio OFF.

Tigerdude,
Yes, you want to turn your radio on first and then your receiver. Turning off it exactly the opposite, receiver off first and then the radio off.

As far as your servos. First thing. Disconnect all of the control rods from all of the servos and turn your radio on again. Is the buzzing still there??

Yes, then there could be something wrong with the radio and may need to be checked out. Unplug all the servos and plug them back in one at a time until you find the one that is buzzing. It's possible that you have a bad servo.

No, then the problem is with the linkages/control rods/control surfaces. One at a time reconnect the control rods back to the servos and note when the buzzing starts again. That will tell you where the problem is and you can start to see if there is binding, tightness, or other problems with that control surface.

Try these out and let us know what you find out. If you can at least narrow it down some then we can start trying to figure out how to correct the problem you have.

Hope this helps

Ken

As far as your servos. First thing. Disconnect all of the control rods from all of the servos and turn your radio on again. Is the buzzing still there?? . . . No Ken, the servos by themselves work fine and never any buzzing without the connections (pushrods, etc.) attached. I disconnect all the pushrods so that its just the bare servos and they work great.

Yes, then there could be something wrong with the radio and may need to be checked out. Unplug all the servos and plug them back in one at a time until you find the one that is buzzing. It's possible that you have a bad servo. . . . The radio works great and as stated above, all works good without pushrods.

No, then the problem is with the linkages/control rods/control surfaces. One at a time reconnect the control rods back to the servos and note when the buzzing starts again. That will tell you where the problem is and you can start to see if there is binding, tightness, or other problems with that control surface. . . .
servo linkages and pushrods for the rudder and elevator all seem to be gliding smoothly without any binding or tightness. I don't believe the nosegear is binding or catching in any way so I don't think it is that. As far as the throttle, that is apparently where most of the buzzing is coming from, especially when it is full open or closed, but again can't be sure. The problem occured BEFORE the control surfaces were connected (just the servos connected). I WILL CERTAINLY DO AS SUGGESTED HERE ABOUT RECONNECTING ONE AT A TIME, AND I WILL GET BACK TO YOU ASAP.

Could it possibly just be the endpoints as suggested by Gravityisnotmyfriend? My computer radio does have the endpoint adjustments but without the booklet can't know how to do it?

By-the-way, my radio is a Futaba T4EXA. I found the booklet on the net but my internet is so slow it takes forever to open the link. I will keep trying and when I get the whole booklet displayed I will print out all the pages.

Tigerdude,
Ok, if I read what you said properly you are getting the buzzing from the throttle servo. This is probably caused by the fact that the servo is trying to push the throttle further than it can physically travel. The throttle has reached it's limit, but the throttle is still trying to move it. You need to adjust the amount that the throttle servo moves. First of all, at the throttle end put the control rod in the outer most hole in the control arm. At the control end the further away from the control surface means less travel. At the servo end it is the exact opposite. The further out the control rod is means more travel. So you may want to move the control rod one hole in on the servo arm. See if this helps any. You want to get your control throws as close as possible before you start trying to adjust it with the radio. If you try to adjust with the radio before you have it mechanically correct it will usually just cause more problems. If you can't get it adjusted mechanically you can then use the End Point Adjustments (EPA) on your radio to adjust where the servo stops it's travel. But I've you should be able to get it with mechanical adjustment, so I would worry about that first.

Hope this helps

Ken

Perhaps understanding what is going on will help you troubleshoot more:

The servo has a little motor inside and a little knob attached the the gears that tell it what position it's in. When the servo gets a signal that tells it to be in a new position the motor starts up until that position is reached then stops. If the arm gets moved then it's not in the right position anymore and the motor comes back on. Sometimes when some linkage binds up the motor turns on and pushes the linkage, but then when the position is found and the motor turns off, the linkage doesn't stay in the new position and goes back to the old. This can cause the motor to turn off and on to make a buzzing sound. If your linkage can't travel to the end of the servo travel then going to one end or the other would cause the servo to try to go to a position it can't physically be in which causes it to buzz.

To resolve these problems you want to make sure that the linkage can physically move to the very end of the servo travel or you can limit the servo travel if you have a computer radio as others suggested. It is always better to fix the linkage by using more or less servo arm leverage because you don't loose some of the servos resolution when you limit it's travel and because it doesn't depend on a computer radio and it's configuration.

If the servo buzzes while in the middle of the travel then your linkage is binding up. You need to make sure everything moves freely and smoothly.

To test if the linkage or the servo itself is bad simply do as Ken suggests and remove the servo horn and see if it still buzzes. If it does then for whatever reason the servo can't place it's arm where the signal is telling it to. If the buzzing goes away then it is working correctly.

It is important to fix servo buzz because it can overheat and damage your servos and because it will greatly reduce battery life which usually results in a crash unless your paying very close attention.

Hope that helps,
schu

NEXT DAY OF ADJUSTMENT:

Throttle - bent the pushrod to better pass through the pushrod tube. Changed the servo arm with a brand new one and moved the servo end of the pushrod to the 2nd hole in (middle hole). Buzzing appears to have stopped. Now I have a couple of questions . . .

1] When the throttle is full-open the entire carburetor opening is visible to the eye, but when it is full-closed there is still about 1/16" that is still visibly open. Is this enough of an opening to interfere with the operation or idle of the engine? Is it acceptable or should it be corrected?

2] With my radio setup the way it is now a full up stick closes the carburetor while a full down stick opens it. Shouldn't this be the opposite? The instruction booklet for the LT-40 says 'stick forward' for carburetor to be fully open while 'stick back' is fully closed. Am I correct in understanding that 'forward' means up stick while 'back' means down stick? Shouldn't I reverse the servo to follow what the LT-40 instruction booklet says?

2b] Also the rudder control is reversed so that right is left and vice-versa, and with the elevator (which is supposed to be the one that is reversed according to the booklet) up is up and down is down. According to what I read right is right, left is left, up is down, down is up, full-throttle is stick forward (or up), and full-closed throttle is stick back (or down). If this is the way the booklets say it is shouldn't it be that way? Do all companies ship radios with the opposite setup? and why if the responses are as mentioned here?

I have attempted for more than an hour to adjust the nosegear of the LT-40 to no avail. No matter how I bend the rod it still causes the servo to buzz. I have wasted two music wire pieces in my attempts to have the wire pass smoothly through the tube, and I have just purchased another two 30" lengths of music wire to try another attempt. I am afraid if something doesn't give soon I will end up putting this model down in the cellar with the rest of my builds. What makes it hard is that both ends of the wire have to be bent. The steering arm end has to be bent slightly down to pass smoothly while the servo end has to be bent also, and that is hard to do with the wire inserted in the tube. The wire has to be in the tube to do the second bend at the opposite end for the reason of it not being able to be put into the tube with both ends bent. And its hard to reach into the fuselage with pliers to do the bend. But I will keep up the attempt until the servo buzzing stops and the wire slides smoothly, and NOT lose my temper I hope[:@].

Other news today: The buzzing of the servos do not occur while the pushrods are disconnected and its just the bare servos. The elevator no longer buzzes as I changed the control linkage from the 7" threaded rod to a 1" threaded linkage. The rudder no longer buzzes as I also changed the control linkage from the 7" threaded rod to a 1" threaded linkage. I also played with the End Point Adjustments and the buzzing almost stopped when the percentage got down to 50% which is way too low so that idea is out.

So . . . the elevator and rudder no longer buzz, the throttle buzzing appears to have been fixed. It's just the nosegear to configure to the point where it no longer buzzes and glides smoothly in the tube . . . what a job I have cut out for me.

EDIT > > > Could it be possible for me to try a ball link connector in place of the pushrod connector for the nosegear? I hope so, I think that would be so much easier for me.

Wish me luck, any advice would be greatly appreciated.

I know these are quite a few questions but I hope to get them all answered.

Thank you!!!

~Steve~

If the controls are operating backwards, you can correct this one of two ways. One is to reverse the servo arm(if it comes off one side only) or move the linkage to the oposiite side of the arm. The second option is to use the Servo reversing program to reverse the direction the servos move. If you have the manual(or can download it), the instructions on reversing servo direction is on Page 10. If you do EXACTLY what it says, you should have no problems .

You REALLY NEED to get the entire manual http://www.futaba-rc.com/manuals/4ex-manual.pdf but I'll try to post bits of it here if I can.

To reverse a servo-
1- Enter programming mode. Use mode key to select "reverse" function
2- use select key to select channel you wish to change
3- push data input lever up or dn to change direction of servo to desired direction
4- use select key to go to next channel to change or exit programming mode

enter or leave programming mode by pressing "mode" and "select" keys simultaneously and holding for about one second.

Set end points as above but choose "EPA" mode.
1- select channel to adjust EPA of
2- Move control stick fully to one end of travel in direction wished to be changed and hold if needed.
3- Use data input lever up/dn to change value to desired amount. Do not overdo this without checking result, you can always go back and do more.
4- Move control stick in other direction if desired to change other end EPA also and use input lever to adjust.
5- Each end of each channel may be adjusted if desired/needed. Be SURE before doing this that you have made all mechanical adjustments that you can first.
6- Exit programming mode
This only effects the plane for the memory position you are working with, not the others.

Now download the rest of the manual.

Gee Bruce, did I forget to look up the end point adjustments?

I don't know. But he has already said that he is having trouble downloading the manual. Giving page numbers may not have been enough. I only expanded upon the the ideas you started. Hope you don't mind.

Why, I'll bet that I was just trying to help. Just like you. What cha think?

Hey, I have no problem if someone wants to take the ball and run with it. I missed the part about having trouble with the download, so a little extra help is a good thing. Who knows, I might have posted bad info, which has happened once or twice. If I'm wrong, I would hope someone with correct info would tell me so. As I see it, I'd rather be told I'm wrong and get correct info to those that need it than worry about ruffled feathers

Are the reciever, and/or receiver connected to the charger?
The servos "flutter"[sm=bananahead.gif] If I try to operate the transmitter, with the charger attached[:-]
Just an idea.

If the switch harness is properly connected and not damaged, the charger is disconnected when the receiver is turned on. You should see the charging indicator go off on your wall-wart charger. The transmitter also disconnects from it's charger when turned on. One of the reasons for this is to keep the slightly elevated charging voltages from reaching the electronics of the radios and causing possible damage. Aftermarket fast chargers may cause even more damage without this protection.

Since you are not going to fly with the charger attached, I would not worry about the flutter unless you see it with the charger removed

Make sure your switch harness is properly installed. The switch should still turn the radio on/off even if the charger is plugged in. If not, something is wrong

Thank you all for your great help. I was able to download the instruction booklet for the radio. It took about 15 minutes on slow dial-up to open the link fully, but I really needed that booklet so the wait was worth it.

I have all the buzzing removed except for the nosegear still has a slight buzz once in awhile. Is that little bit of buzz a major problem that needs to be solved or is it livable????

The less buzz the better. When does it buzz? In the middle or at the ends of travel or everywhere?

bruce - No matter what hookup I use (nylon pushrod, wire pushrod, pushrod connector, ball-link, Z-bend) I get a slight buzz at full turn mostly left but seldom right also. It is perfectly quiet in rest position (neutral) and when pushrods are disconnected so it is not the servo. Most often than not it quiets after a few seconds but sometimes it is longer. At this moment it is connected at the nose end (steering arm) with a Z-bend and at the servo end with a EZ-link, and that seems to be the quietest hookup thus far. I had to cut the first hole off the steering arm because I pulled the old pushrod tube out and installed a wider tube in a different hole I had to drill next to the old hole. The servo end is attached to the 2nd hole in on the servo arm.

Any advice? Could the lack of putting the washers under the servo screws have anything to do with the buzzing? I know I will have to take the servos off to put the washers on but time is limited the next few days but it will be done.

Washers? Do you mean the brass grommets? They need to be there but that is not causing the buzz. If you are adding extra washers above the grommets, that is OK but won't help the buzz either. If you are only getting the buzz at full throw I would not worry about that. You will be in that condition less that 0.5% of the time and probably much less than that. Try reducing your EPA 10-15% since you are going to have too much throw anyway for steering. If your radio has exponential, you may want to use that too. Will make taxiing easier as well as T.O. & landing.

Grommets are on, but I have seen pics in some threads that have washers also. Full throw, is that what you call it? I am still learning . Yes, it is only at full throw, and mostly stops after a few seconds. I will have too much throw you think? But if I change the nosegear EPA won't that change too much of the rudder EPA? Plans call for the rudder to turn each direction as close to an inch as possible and I believe it is already a bit less than an inch? How much of that EPA will change at 10%-15%. Yes, I believe I also have exponential, how much should I change that to and what exactly is exponential? Thank you.

If you are set up as in pic 6 here
http://www.rcuniverse.com/forum/fb.asp?m=3774382 then all you need to do to get back your rudder throw is move the clevis "in" on the rudder control horn. This will increase the amount of throw. Crank down the nose wheel and then reset the rudder clevis as needed.

Exponential "softens" the response you get near the neutral stick position but still allows full deviation if you push the stick all the way over. It is also adjusted by percentage and maybe 30% would be a good starting point.