remorales

Accidentally posted this in the nonelectric airplane beginner area:

Hello,

I just flew my HZ Supercub for the second time and I am having a great time with it. However, I noticed that the elevator servo has started to twitch back and forth. I switched batteries, turned the radio on and off and it continued to twitch. The twitching will stop after several seconds and then when I give the elevator an input it will start up again. I've searched a bit on servo twitching and have found very little. Any thoughts on what it might be? servo? receiver? interference? Thanks.

-pkh-

My Feedback: (2)

Sounds like it's the servo. Servos have potentiometers (variable resistors that are used as position sensors), and if those are defective or have film/dirt on the contacts it can cause it to twitch. The twitching can clear the film/dirt and it can settle out, then when you move it again, it will twitch some more. If you can swap the servo connections to the receiver, you can verify that it is the servo, and not just the elevator channel on the receiver.

guapoman2000

Oh, I have documented many times at RCGroups.com and can tell you that I have made a Video of this same thing. I believe it is the BLACK BOX electronic package as the commutation is performed there and not within the servo so, I really doubt it is your servo!!!

The 5-wire servo's that come in the HobbyZone Supercubs. From what I've been able to gleam from from some RC aircraft web sites, it appears that it is a dumbed down servo, where much of the servo's brains reside outside the servo in the RC aircrafts's circuitry.

Here's a typical question/response on this topic over at the other thread board.
http://www.rcgroups.com/forums/showthread.php?t=652907

guapoman2000

My Video of Twitchy Servos:

http://www.youtube.com/watch?v=w6uLvWhl3Ao

-pkh-

My Feedback: (2)

I believe the 5 wire servos have the motor and potentiometer (position sensor) in the servo housing, and the sense amp (for the position sensor) and motor controller (for the servo motor) are on the main board. If you swap the servo connections to the main board, and still find the same servo is twitching, that tells you that it is not the main board, but the servo. Since the pot is still in the 5-wire servos, and that is a common cause of twitching, replacing the servo can solve the problem.

Of course, pulling out the stock electronics and replacing it all with better quality, standard electronics would be a good solution as well, but I'm sure it would be much more costly.

scottware

My Feedback: (5)

You may be able to minimize the twitchyness with either of these suggestions:

1. Check that the capacitors on the motor are still soldered in place and not smushed against the motor. If you need to resolder them or straighten them out, do that and then have another test flight.

2. Still twitchy? You may want to try following a motor break-in procedure if you haven’t done that already to your Super Cub. Specifically remove the motor from the SC, remove the prop, connect it to a D cell battery and run it in a cup of water for 30 minutes, dry it thoroughly (ideally with compressed air), oil both shaft bushings and reinstall in your SC.

Those two things are likely to help your situation if the twitchyness is caused by motor interference. If it's still an issue then it's more likely electronics related like others have suggested.

Good luck!

Scott
www.TheXPortZone.com
Hobbyzone / Parkzone Upgrades and Accessories