servo question

[Troy Newman]

So you are saying Pre-load ailerons down so when they blow back...they go to
neutral?

I'm not saying that.....I'm saying that if the ailerons are held as stiff
and with as little blowback as possible....it will help the loops

The amount of blowback the aileron gets in a push or pull will likely vary a
little depending on the servo, linkage, and servo mounting...By limiting the
amount they blow back with eliminate the amount of error seen and will help
the corners...The issue is not so much that they are moving....its that they
are moving un-equal amounts....The more they are allowed to move the more
error there can be.

The digital servo with its huge holding power will limit the movement thus
the error is limited as well.


am I all wet on this?

TN
----- Original Message ----- 
From: "JOddino" <JOddino at socal.rr.com>
To: <discussion at nsrca.org>
Sent: Sunday, August 03, 2003 6:00 PM
Subject: Re: servo question


> I've heard others say how they can feel the improvement in loops when they
> use digitals on ailerons.  Sounds like a case for flaperons coupled to
> elevator.
> Jim
> ----- Original Message ----- 
> From: "Troy Newman" <troy_newman at msn.com>
> To: <discussion at nsrca.org>
> Sent: Sunday, August 03, 2003 2:25 PM
> Subject: Re: servo question
>
>
> > Very good stuff....
> >
> >
> > I learned a little too....
> >
> > I subtrim the servos to get the pushrods square to the arms....This is
the
> > way I was taught to do it.
> >
> > The built expo thing will be radically changed when using the radios
expo
> > function so I can see that one going away for all practical purposes...
> >
> > But yes with the servo arms square to the pushrod....This is putting the
> > neutral point in the worst place on the servos rotation for power. You
are
> > giving the force applied from the other side the max moment arm to push
> the
> > servo against its will....But at neutral control throw how much force is
> > being applied to the servo.....very little would be my guess compared to
> > when the servo is deflecting.
> >
> > The one time that ailerons for example are neutral and have huge forces
is
> > in a pull or push. The forces of pushing or pulling a corner even a wide
> > radius will cause the ailerons to deflect....This is where the digital
> > servos EXCEL...they hold the ailerons tighter to the neutral position by
> the
> > fact of their increased holding power....So your loop segments are
> > straighter...because as the ailerons blow-back the question is are they
> > going to move the same amount....?
> >
> > The answer to that is probably not....and you know they are "trimmed" at
> the
> > neutral position. So if you can just hold them at neutral what ever it
> takes
> > it will help the looping segments.....
> >
> > Yes this power of the servo comes at a little cost the battery packs
need
> to
> > be a little larger...The power in the servo comes from somewhere and its
> the
> > battery pack.
> >
> > These forces in flight are another reason to have very stiff control
> > surfaces and linkages.....If the aileron can flex they will...An no
matter
> > how good of servo you install it won't help...Wood varies and the two
> > ailerons if allowed excessive flex will not flex the same as each
> other....
> > so minimize the flexing by making the surfaces as rigid as possible...
> >
> > You will get more consistency in your flying....Just like running a
> voltage
> > regulator...consistent voltage means same power and speed on the servos
> > throughout the flight and from flight to flight....The name of our game
is
> > consistency...If the model flies the same everytime then you can really
> > practice and learn to fly the maneuvers....If the model is changing
under
> > different conditions all the time,  all your practice time is spent
> learning
> > the model and it faults and flaws under that days conditions.....Makes
the
> > advancement of your flying skills take even more fuel burning than
needed.
> >
> > A quote from a Famous Pattern flyer....."Make the model do the
> work....tune
> > the model so that it does it for you and makes the flying as easy as
> > possible."
> >
> > TN
> > ----- Original Message ----- 
> > From: "JOddino" <JOddino at socal.rr.com>
> > To: <discussion at nsrca.org>
> > Sent: Sunday, August 03, 2003 4:11 PM
> > Subject: Re: servo question
> >
> >
> > > Hi Troy,
> > > The reason I asked this question is that I heard a guy claiming his
> > neutrals
> > > were more positive if the servo horn was perpendicular to the pushrod
at
> > > neutral.  I see you recognize the system becomes stiffer the closer
you
> > get
> > > to the servo arm being parallel to the pushrod.  That is why we used
180
> > > degree servos on landing gear.  So the servo arm perpendicular to the
> > > pushrod doesn't improve holding power at neutral.
> > >
> > > In the old days before computer radios we used to offset the servo
> > neutrals
> > > on purpose to get more up than down ailerons for example.  Now we can
> set
> > it
> > > anywhere we want so the angle isn't critical from that point.
> > >
> > > As far as expo (non-linearities) caused by linkages, it is
insignificant
> > > (with reasonable linkages) compared to the expo we add.  Forget about
> > linear
> > > distances, look at angles.  The change in lift is a function of the
> angle
> > of
> > > attack, an angle.  The angle of attack is a function of the surface
> > > deflection, an angle.  The surface deflection is a function of the
servo
> > > rotation, an angle.  Therefore the airplane responds to the servo
angle
> > not
> > > the linear change of pushrod distance.  It takes a special linkage to
> get
> > a
> > > linear relationship between servo angle and control surface angle but
> even
> > a
> > > setup that looks bad really isn't too bad after we adjust end points
and
> > add
> > > expo.  It seems to me it is more important to make sure the angles and
> > push
> > > rod lengths are the same (speaking of two elevator servos or two
servos
> > > coupled to one surface)  rather than worrying about a non-linearity
that
> > is
> > > difficult to measure.  It seems to me it is much easier to set the
> servos
> > > arms  90 degrees to the case than to try to figure out the angle that
> will
> > > make them 90 degrees to the pushrod.  In fact I'm not sure how you'd
do
> it
> > > other than by cutting and trying.  I normally strive for both,
> > perpendicular
> > > to the case and the pushrod. However, I'm building a new plane with
the
> > > servos on their sides in the wing and stab where I can't have both so
> I'll
> > > have to look at this a little closer.  I'm still betting it is
> > > insignificant.
> > > Jim
> > > ----- Original Message ----- 
> > > From: "Troy Newman" <troy_newman at msn.com>
> > > To: <discussion at nsrca.org>
> > > Sent: Friday, August 01, 2003 5:02 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
> > > >
> > > >
> > > >
> > > >
> > >
> > > =====================================
> > > # To be removed from this list, send a message to
> > > # discussion-request at nsrca.org
> > > # and put leave discussion on the first line of the body.
> > > #
> > >
> > >
> > =====================================
> > # To be removed from this list, send a message to
> > # discussion-request at nsrca.org
> > # and put leave discussion on the first line of the body.
> > #
> >
>
> =====================================
> # To be removed from this list, send a message to
> # discussion-request at nsrca.org
> # and put leave discussion on the first line of the body.
> #
>
>
=====================================
# To be removed from this list, send a message to 
# discussion-request at nsrca.org
# and put leave discussion on the first line of the body.
#