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Servo Chatter

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Old 05-10-2004, 04:56 AM
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crazy4rc
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Default Servo Chatter

I am having a lot of servo chatter in a new plane. I have an 8103 radio, digital servos all around except on the throttle (5 total). The aileron servos are very noisy and the elevator to a lesser degree. If I turn off the transmitter, all goes quiet. What is causing this and is it preventable? Seams that all the noise is going to run down my batteries faster.

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Old 05-10-2004, 05:52 AM
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Default RE: Servo Chatter

I'm also having the same problem with the DS-811's that came with my 8103. Mounted on an OMP profile Edge, when powered up, all of the control surfaces chatter worse than my wife on the telephone. Servos have Dubro 3D control arms installed. Chatter seems less with shorter control arms but I can't get full movement of the control surfaces with the shorter arms. Is there a fix for this problem?
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Old 05-10-2004, 09:02 AM
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Default RE: Servo Chatter

The 811 because it is a single ball bearing servo has a bit of play on the top gear. This play of the top gear combined with the servos aggressive centering abiltity has the tendency to overshoot the mark just a bit, and a slight oscillation occurs. If you can stop the jittering with light pressure there isn't anything wrong with the set up or the equipment, and it will not happen in the air due to flight loads. It would only happen on the ground. If however it takes more pressure, or does not stop with pressure, there may be a problem with the pot of the servo, or there is excessive slop, possibly in the gear train.

Also if you are using one, there is a chance that you may be having a problem with the 549 receiver as described here.

http://www.rcuniverse.com/forum/m_13...tm.htm#1350753
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Old 05-10-2004, 10:32 AM
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Default RE: Servo Chatter

I too have the 811 servos, and they are the worse. The other one that is less of a problem is the DS9411 (think that's the number) on my elevator. Is this one also susceptible to this problem?

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Old 05-10-2004, 03:36 PM
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Default RE: Servo Chatter

No, the 9411 is a dual ball bearing servo, so it doesn't have that play in the output gear that the 811 has.
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Old 11-07-2005, 10:46 AM
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Default RE: Servo Chatter

ORIGINAL: dsnyder

No, the 9411 is a dual ball bearing servo, so it doesn't have that play in the output gear that the 811 has.
Okay, so to revisit this question...... If the DS9411 does not have this problem then I would assume the DS8611 and the DS8411 also should not have this problem. I have all three in a new plane (8411 on ailerons, 9411 on elevators, and 8611 on the rudder) and they all chatter like crazy. Is this just the characteristic of digital servos? It drives me nuts! It's so bad it is nerve racking. While the plane is just sitting there not doing anything getting it ready to start and fly, I get nervous just listening to all the noise and twitching. Is there some way to isolate this? When I turn off the transmitter, instant silence.
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Old 11-07-2005, 12:11 PM
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Default RE: Servo Chatter

I would check for any slop in the control system, arm fit on the servo , and gears for any excessive play. Also I would recommend checking all your servo connections (unplug them, re-install a couple times to be sure the pins are clean and making good contact). Also be sure that your servos are not mounted too rigidly ( servo screws too tight, mounting rails tight against the servo , etc). If the oscillation stops by touching the surface with your finger, likely the pots in the servos are not worn, it is likely a slop, set up, or electrical issue. If it does stop, it won't happen in the air due to flight loads, but I would recommend giving everything a good checkover.
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Old 11-07-2005, 12:48 PM
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Default RE: Servo Chatter


ORIGINAL: dsnyder

I would check for any slop in the control system, arm fit on the servo , and gears for any excessive play. Also I would recommend checking all your servo connections (unplug them, re-install a couple times to be sure the pins are clean and making good contact). Also be sure that your servos are not mounted too rigidly ( servo screws too tight, mounting rails tight against the servo , etc). If the oscillation stops by touching the surface with your finger, likely the pots in the servos are not worn, it is likely a slop, set up, or electrical issue. If it does stop, it won't happen in the air due to flight loads, but I would recommend giving everything a good checkover.
I'm pretty sure my servos are mounted properly and not too tight ot binding. All my control surfaces are slop free and not binding, used all premium hardware. The only one I'm not sure about in your list is "electircal issue". What would that include and how would I correct it? Thanks!
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Old 11-08-2005, 12:43 AM
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Default RE: Servo Chatter


ORIGINAL: crazy4rc


ORIGINAL: dsnyder

I would check for any slop in the control system, arm fit on the servo , and gears for any excessive play. Also I would recommend checking all your servo connections (unplug them, re-install a couple times to be sure the pins are clean and making good contact). Also be sure that your servos are not mounted too rigidly ( servo screws too tight, mounting rails tight against the servo , etc). If the oscillation stops by touching the surface with your finger, likely the pots in the servos are not worn, it is likely a slop, set up, or electrical issue. If it does stop, it won't happen in the air due to flight loads, but I would recommend giving everything a good check over.
I'm pretty sure my servos are mounted properly and not too tight or binding. All my control surfaces are slop free and not binding, used all premium hardware. The only one I'm not sure about in your list is "electrical issue". What would that include and how would I correct it? Thanks!
More info.... I looked over everything again and all but the elev servos will settle down (for the most part) with a little pressure as you said. The DS9411's on the elev still jitter a little even with the pressure. Could the long servo wires be causing this? I'm using a 7ch JR receiver, can't remember which model (too lazy to walk out to the barn . Also another thing I noticed about these 9411 is they have a lot of gear slop! All the other servos are tight, and these 9411's are almost new. Is that a characteristic of them?
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Old 11-08-2005, 10:25 AM
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Default RE: Servo Chatter

All metal geared servos will have a small amount of play in them. It is not possible for a metal geared servo to be 100% slop free. I would recommend checking to see if it is the arm fit on the servo or the servo itself, if it is the arm fit on the servo you may need different arms.

I didn't say anything about electrical noise, though that could be another source though more difficult to track down. You could try installing filters on the leads to see if it helps (Part number JRPA028 or JRPA029). JR recommends using filters when the leads are over 36", so if the extension used is 36" or over, a filter is recommended. What I was mentioning was electrical contacts i.e. the connectors. Make sure your connectors are making solid contact and are clean. We often also see customers use aftermarket extensions that do not make good contact with the pins in the connector and cause problems.
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Old 11-08-2005, 10:44 AM
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Default RE: Servo Chatter

Danny

I notice in a lot of your replies that you mention to plug and plug connections several times to make sure contacts are clean

Is there any type of contact cleaner that can sprayed on connectors.

Thanks
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Old 11-09-2005, 03:50 PM
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Default RE: Servo Chatter

Yes, there are electrical contact cleaners out there that can be used. Plugging them together a few times usually helps though.
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Old 11-26-2005, 09:51 PM
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Default RE: Servo Chatter

I have three JR DS8411s and two DS9411s, all brand new, that make noise only when the transmitter is on. There is no noticeable movement of the servo arms when they are making the noise. The receiver is a Futaba R148DF, but I have also tried a R127DF with the same effect. The batteries are two 1950 mAH 6V NiMHs, but I know about the problem with freshly charged 6V batteries so I have also tried a single 4.8V NiCd with the same effect.
I have also done the following to try to solve this problem:
- Broke and re-made connections 5-6 times.
- Tested servos out of plane.
- Transmitter antenna up and down.
- Transmitter close by and fourty feet away.
- Different combinations of servos connected.
- Touched/pushed/pulled servos or arms.
- Twisted servo and battery leads (electronic ignition, but not tested yet with engine running).
So far nothing seems to help.

This is my first experience with digital servos, but this racket doesn't seem quite right.

Do you have any more ideas for how to eliminate this noise? Is it unsafe to fly with this problem?

I appreciate your support.

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Old 11-28-2005, 11:09 AM
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Default RE: Servo Chatter

All digital servos will make noise when on, as will most coreless servos and some standard servos and is nothing to be concerned about.
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Old 11-29-2005, 05:46 PM
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Default RE: Servo Chatter

Danny,

Appreciate the good news! I'll fly 'em and not worry. I know these servos are sure fast and strong!

I did like one forum member's recommendation on how to eliminate the servo noise: "Start the engine!"

Appreciate your fast response.

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