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Old 07-08-2019, 03:31 PM
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Radio acting funny at low rpm due to engine ignition

(EDIT - Root cause was found to be the motor ignition. See my last post to this thread)

All,

I have an AJ Slick (103 inch) running a DA120 that seems to get twitchy elevators at low RPM. At first I thought I had my gyro gain up to high but even off, it starts to oscillate in the air. My second thought was that I was overspeding the control surface but it seems to only happen a near idle speeds. Finally, I was able to reproduce it on the ground and at high throttle, the elevators act normal and at low throttle, they start to bounce around. (both elevator halves are running MKS (high torque digital servos).

My question to the group is has anyone seen this before. All other controls behave fine. Is it because of the very long servo wires to get to the tail? The wires run through a plastic tube. Would a filter help? Do I need to try different servos? It is also noteworthy that I run Futaba and the AJ Slick is the version with all the carbon fiber inlay.

Any advice you have is very welcome. Thanks in advance.

-Jeff
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Last edited by jdewolftx; 08-31-2019 at 06:13 PM. Reason: Adding root cause to title now that it has been found
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Old 07-08-2019, 04:43 PM
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Sounds more like vibration than a radio issue.
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Old 07-08-2019, 05:12 PM
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Brand and model of servos? Length of leads going from rx to the tail feathers?
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Old 07-09-2019, 08:29 AM
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The model of servos is MKS HBL599. The extension length is 48 inches. And to be clear, the surfaces are not just vibrating, the servos are actually swinging at least 50% of throw. Sometimes together, sometimes in the opposite direction of each other.
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Old 07-09-2019, 09:45 AM
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Quote:
Originally Posted by jdewolftx View Post
The model of servos is MKS HBL599. The extension length is 48 inches. And to be clear, the surfaces are not just vibrating, the servos are actually swinging at least 50% of throw. Sometimes together, sometimes in the opposite direction of each other.
Wow....that would be a monster to control....good luck
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Old 07-09-2019, 11:06 AM
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Where is the video of this? We got to see this one! lol
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Old 07-09-2019, 03:22 PM
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I had an ignition cap that felt tight on the plug but was a little loose and it caused my ailerons to do the exact same thing
Check the caps and make sure they are tight on and have that little retaining ring
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Old 07-09-2019, 03:23 PM
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Loose connection.
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Old 07-09-2019, 07:41 PM
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If they are swinging 50% sounds like gyro gain is too high...

Try disconnecting gyro then do run up again.

Ronster
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Old 07-09-2019, 07:45 PM
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Also sounds like a better thread name would be:

"MKS servos acting strangely"

I know, that's crazy talk, since the only possibility os the radio itself
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Old 07-09-2019, 08:02 PM
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Quote:
Originally Posted by Judge View Post
Also sounds like a better thread name would be:

"MKS servos acting strangely"

I know, that's crazy talk, since the only possibility is the radio itself
ROTFLMAO!!!!
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Old 07-09-2019, 09:14 PM
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Plug in 2 other elev servos with 48 in leads and see what they do


also swap receivers out and try new ignition cap assemblies
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Old 07-10-2019, 10:12 AM
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Thanks for all the ideas. I will check them out and report back.
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Old 07-10-2019, 02:10 PM
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I had a similar issue with a 36% Edge with BLS171 servos on the ailerons. Had been running great for a few years but at idle and lower throttle settings the ailerons bounced around at neutral. Straight and level flight at slow speed and the ailerons almost looked like flutter. It was strange though because everything appeared rock solid when not running the DA120. Swapped out the servos and presto...no more bouncing. I think the DA120 over time caused the ability of the servos to hold center to break down. I have the servos out for service. Try new servos...I bet the problem goes away. Of course that will cost ya.
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Old 07-10-2019, 02:14 PM
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Quote:
Originally Posted by jdewolftx View Post
The model of servos is MKS HBL599. The extension length is 48 inches. And to be clear, the surfaces are not just vibrating, the servos are actually swinging at least 50% of throw. Sometimes together, sometimes in the opposite direction of each other.


Ok. Well disregard my earlier reply. As others have suggested remove the gyro and use a shorter extension or new extension for testing.
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