Buzzing Servo

I have just installed new JR standard servos in the wing of my 4 Star 60 and they buzz intermittently even when they return to neutral. Wiggling of the sticks usually stops the buzz. I have read that this is indicative of a drain on the battery pack. Any suggestions as to why and how to correct would be appreciated. I'm using CA hinges and they are not as free moving as conventional hinges Everything else is according to the plans.

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are you in close proximity to the plane with the radio when this happens ? if so you are swamping the recver, and if the radio is off you will most likely get this.. also if in a place with Florescent lighting you will get this a lot.

I have had this a lot of times, and later out side with the radio placed a good distance from the model it stops.

what model servos are you using ? and are they new ?

Reply to
Dell Shannon

Try this . . .

Get the servo(s) to buzz. Note which way the servo was traveling when it stopped moving and started buzzing.

Move the stick in the opposite direction and back to neutral - not a long way, just nudge the servo off-center in the opposite direction and let it return. Don't let the stick oscillate on the springs, bring it back to neutral without any "bounce".

If the buzzing stops, the problem is the linkage - it's binding somewhere.

Standard servos have relatively low torque near center, and a slight bind in the linkage can put more load on the servo than the servo can counter when near zero deflection, and the servo can't return to neutral (zero deflection), so it sits there growling at an abnormal "idle" current.

It could be that you're using the wrong connector on one end or the other of the linkage.

One common error is to use a clevis a servo arm where the linkage does not travel in the same plane as the arm, rather it is forced to operate at an angle to the arm.

If you hold a clevis so you can look through the "fork" (as below) any movement of the clevis other than horizontal is a binding movement.

If the clevis sketched below tries to twist up or down compared to the servo arm, the clevis pin binds in the servo arm.

(maybe these crude ANSI graphics will hold together on the way through the 'net . . . )

___________ ______/ __| ________________ \________|___ ^ ^ clevis pin servo arm

The second-most common source of binding is simply a clevis pin that is too tight in the arm (servo or control horn, doesn't matter). If the pin has to be forced into the hole, it's too tight. It can't be loose, either. A "zero slop" fit is ideal.

Of course, one can compound the error by using a clevis on each end of the link, and _both_ are operating out of plane.

One solution to the problem where the linkage must operate at an angle to the arm is to use a ball joint, which is designed to operate through an arc in two planes. Of course, even ball joints have limits on how much deflection they can tolerate, but they are much more forgiving than a clevis.

You need to get the linkage operating freely without binding, and eliminate the servo growl (buzz), because the buzzing means the servo is consuming more than idle current even though it's stationary. You can drain a flight pack fairly quickly if the linkage binding is high enough.

CA hinges are a bit stiffer than pin-type hinges, but at zero deflection they should not be a factor. Cheers, Fred McClellan The House Of Balsa Dust

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Reply to
Fred McClellan

I wouldn't worry about it too much. You can probably lightly touch the aileron and stop the buzzing. I would be willing to bet that ALL the servos are buzzing while the plane is in flight.

Reply to
Paul McIntosh

You've probably got a slight binding in the linkage somewhere.

If eveything is new; - Wait for it to go away - it will after things settle - Spray a little penetrating oil lubricant on the connections (control surface side and servo side). Works perfectly.


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Is it the aileron servos? Mine on my 4*60 did it a little. The hinges were a little stiff. Even after manually moving them through there full range for many cycles. Never made any difference on flight pack time.

John VB

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The easiest way to isolate the problem is to take the screw out of the servo arm and pull it off.

If the buzzing stops, the linkage/hinges are the problem.


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On some servos, the case screws are torqued too tight. Back out the four screws just a tiny bit and see if the buzzing stops.

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"Standard" servos, and this is not particular to JR, simply do not have the resolution of premium servos, and it's not uncommon for this "buzzing" to occur as the servo is trying to find it's true center. This can be caused by many external causes, with binding being the primary cause of SEVERE buzzing.. But with a low-priced servo this buzz can also be caused by the weight of a control surface acting against the servo..

If this is the case, I wouldn't be overly concerned, as long as you know the servo is strong enough for the plane... I've seen it happen in many of my own sport ships, and it's never been a problem...

ALWAYS check that control surfaces are free, and use an ESV to monitor battery usage. Make this a normal part of your preflight routine, along with a CAT check...

C-ontrols free and in proper direction... A-ntenna extended... T-rims set properly...

This'll save a lotta grief down the road.


Reply to
Bill Fulmer

Bill is quite correct, Buzzing servos highlight a constant drain on your battery and are a no no and should be fixed before flying anything above a .25 due to the extra flight loads. Ailerons on the 4*60 models seen todate, if properly hinged, are not heavy enough to cause buzzing on a good quality standard servo.

  1. In doubt, use a Hitec "Jam Checker" or rig up a simple amp meter and check the drain.
2.CA hinges should be inserted so that there is a minimum of 1/32" or thickness of a medium T pin between the control surfaces to allow the material to flex properly. Aileron must be able to move up and down more than the servo can travel so no binding occurs at each end, including allowing for full trim or flaperon adjustments. Disconnect the servo and work the ailerons up and down by hand to free any CA which may have hardened in the gap.
  1. Double check that the hinges are inserted in a straight line, non at an angle to the hinge line nor any above or below the hinge line as either scenario will not permit the aileron to centre properly and load up the servo - only fix is to cut the hinges and insert good quality flex or pinned hinges.
  2. It is not uncommon for some of cheaper servos to buzz from new due to dirty pots or wipers not seating properly but this generally settles down after working the controls for 15 minutes or so and "breaking" the servo in. If hinges are definitely straight and free, then either return the servos for replacement or refer to
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    scroll down to = "Radio Systems, Accessories, Alterations and FAQ" sub section = "Servo & TX alterations, calculators, clonepacs, make an ESC or winch, FAQ." toward the bottom = "Servo - FAQs : " Servo - Stop the jitters. [= includes pictures of how to clean the pot on a typical servo] Servo - Troubleshooting problems "

regards Alan T. Alan's Hobby, Model & RC Web Links

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Have you ever measured current drain during flight? I suspect that there is a significant aerodynamic load on all the surfaces and that they are always buzzing during flight. If the surface is so tight that a light tap doesn't stop the buzzing, I would look for a remedy. Unless he sees significant loss of flight time available in the flight pack, I wouldn't worry about it.

Reply to
Paul McIntosh

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