aileron servo instl vs vibration

[Rcmaster199 at aol.com]

Xavier, Jerry's obsrevations are similar to mine.

To counter the effects of the vibration a little more, what I try 
to do is to build the aileron as light as possible. The best I have been able 
to achieve is an aileron weight of about 30 grams for a typical aileron found 
on a 2 meter plane. The idea is to reduce the amount of force translated back 
to the servo
. 

Another thing I have tried recently is statically counterbalancing the 
ailerons. The system I used wasn't stiff enough however, and shook more than I 
wanted at idle. But the idea has merit and I will pursue it further with a stiffer 
system

Yet another area to work on is the engine mounting system, such that the 
transferred vibration is minimized. The system Earl Haury was talking about the 
other day would be serendipidous for pattern modellers

Of course, as Jerry stated and Tony F and Jason S.  have already found out, a 
well thought out, balanced, electric set-up should eliminate the vibration 
completely

Matt K


> Subj:Re: aileron servo instl vs vibration 
> Date:2/21/2004 12:11:26 PM Eastern Standard Time
> From:jbudd at QNET.COM
> Reply-to:discussion at nsrca.org
> To:discussion at nsrca.org
> Sent from the Internet 
> 
> 
> 
> Hi Xavier,
> 
> A while back Dave von Linsowe tried side mounting the aileron servos 
> to see if the servo pots would be more tolerant of the motor 
> vibration.
> 
> The theory was that the rotary acceleration forces induced by the 
> motor on the airframe translate into increased vertical acceleration 
> at the aileron servos causing the pot wiper preload to vary 
> cyclically, resulting in increased rate of wear.  It was hoped that 
> the pot wear could be reduced or eliminated by orienting the plane of 
> rotation of the pot wiper in the vertical axis.
> 
> It didn't help.  Tony Frackowiak also tried it on his Gator G-202 and 
> it didn't work there either.
> 
> And that makes sense, as the pot wiper preload is not likely to be 
> affected by the inertial forces acting on the very low mass of the 
> pot wiper.
> 
> The current thought is that the inertial forces acting on the 
> ailerons are back fed into the aileron servo gear train causing the 
> aileron servos to have to work almost constantly to resist the 
> uncommanded movement.  The servo moves slightly (but nearly 
> continuously) around the commanded position to resist causing 
> excessive wear on the pot and gears (similar to servo buzz).  Since 
> the servo spends most of its time around neutral, that's where most 
> of the wear occurs.
> 
> Interestingly, the ePartner Tony Frackowiak is flying shows no 
> aileron servo pot wear through ~40 flights (go figure!).
> 
> Jerry
> 
> 
> >Is there a prefered method to install the aileron servos and protect them
> >from the high level of vibration someone was mentioning?
> >Could the servo be mounted on his side with the arm parralele to the ribs
> >wihout risking more wear of the gear ?
> >I suppose the vibration on the wing servo is mainly up-down
> >
> >Thanks
> >
> >Xavier

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