servo question

[Bob Pastorello]

May be TMI for some, but a very concise, and accurate description of a
seldom-discussed geometry problem.
    Great job, Troy!

Bob Pastorello, Oklahoma
NSRCA 199, AMA 46373
rcaerobob at cox.net
www.rcaerobats.net


----- Original Message ----- 
From: "Troy Newman" <troy_newman at msn.com>
To: <discussion at nsrca.org>
Sent: Friday, August 01, 2003 7:02 PM
Subject: Re: servo question


> Oh come on Jim....
>
> For the rest of the guys...The servo moves in a  rotational motion...So
the
> linear distance traveled by a pushrod attached to the arm or wheel will be
> greatest right off of center and will reduce the amount of linear travel
of
> the rod as it rotates around. A linkage not setup this will have a funny
> expo like knee in it...But it will be as the arm passes through the square
> position so it would be like adding expo on only one side of the servos
> travel...and reverse expo on the other side of travel.......
>
> Also it could be way up high on the travel of in a funny middle spot...and
> you will get more throw one side than the other....
>
> This sq to the pushrod also gives the servo best mechanical advantage
> through the range...as the servo gets to the endpoints say full travel up
> elevator..the highest force is being applied the surface...and the servo
arm
> is rotated in such a way to reduce the moment arm on the servo by the
> pushrod pushing back.....The arm travels in an arc and the arm gets closer
> to the center of the servo as it rotates off of "center"....This moment
arm
> is leverage for the pushrod to pushback on the servo.....So if you reduce
> this distance when the forces are higher then it will make the servo have
a
> mechanically better shot and holding its position.
>
> did I get it right Jim?
> anything to add Jim?...I'm by far not the expert on this stuff...
>
> Ok Still TMI....
>
> TN
>
>
>
> ----- Original Message ----- 
> From: "JOddino" <JOddino at socal.rr.com>
> To: <discussion at nsrca.org>
> Sent: Friday, August 01, 2003 5:29 PM
> Subject: Re: servo question
>
>
> > Troy,
> > As you know I have been a proponent for using the full dynamic range of
> the
> > control system.  I crank my ATV to 140, subtrim to zero and set my AFR
to
> > the linear limits.  The use of programmable servos then gives me options
> as
> > far as the push rods go.
> > I've heard this before but please explain why the servo arm should be
> > perpendicular to the push rod.
> > Jim
> > ----- Original Message ----- 
> > From: "Troy Newman" <troy_newman at msn.com>
> > To: <discussion at nsrca.org>
> > Sent: Friday, August 01, 2003 10:01 AM
> > Subject: Re: servo question
> >
> >
> > > Jon,
> > >
> > > you will be surprised at the precision you gain.....I was believe
> > me....its
> > > huge....60% low rates are killing the precision of your model. If you
> are
> > > going to try to improve your flying you need to improve your setup.
> > >
> > > I have been doing this a long time and been fairly successful with
> > it...and
> > > just this past spring I found that I was not using the equipment to
its
> > > potential....my answer was well I'm close and my setup is clean and
> > > neat....followed all the rules about square pushrod to the servo horn
> (not
> > > the servo case but the arm)...and use stiff friction free
> linkages....and
> > so
> > > on...Well my low rates that I do everything on were down in the 60-70%
> > > range.
> >
> > =====================================
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> > # and put leave discussion on the first line of the body.
> > #
> >
> >
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>

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