Control horns, is it just me or... ?

[Buff Miller]

Keith,

Yes, this is it.  At the angle that this picture was taken the elevator
pushrod and control horn kind of get in the way.  Of course this is not part
of the pull-pull system.

I'll try to get some pictures at different angles.

To be continued.

Buff
----- Original Message ----- 
From: <davel322 at comcast.net>
To: <discussion at nsrca.org>
Sent: Sunday, September 07, 2003 10:15 AM
Subject: Re: Control horns, is it just me or... ?


> Keith,
>
> Independantly developed and implemented, I have been using a similar
system to
> what Buff described.  There are several pictures of my EMCs on Xavier
Mouraux's
> website at http://pattern-canada.mouraux.com/glen.html - one of the pics
> towards the end shows the plywood disc / control "horn" mounted in the
rudder.
>
> Regards,
>
> Dave Lockhart
> DaveL322 at comcast.net
> > Do you have pictures?
> >
> > Keith
> >   ----- Original Message ----- 
> >   From: Buff Miller
> >   To: discussion at nsrca.org
> >   Sent: Friday, September 05, 2003 8:42 PM
> >   Subject: Re: Control horns, is it just me or... ?
> >
> >
> >   Keith,
> >
> >   I've been following this thread for the past few days with great
interest.
> > The discussion has been very informative and interesting, but I have to
throw in
> > a concept that has yet to be mentioned.  I suspect everyone has been "to
close
> > to the forest to see the trees" thinking control horns and geometry.
I've been
> > using a system for the past ten years that I developed from an article
Gene
> > Rogers, former District 6 VP, covered in the K-Factor back in the early
1990's.
> >
> >   This system does not use control horns for the pull-pull setup on the
rudder.
> > It uses two equal diameter pulleys.  One on the rudder the other on the
servo.
> > I make the pulleys out of ply, three circles sandwiched together.  The
two outer
> > circles of 1/32" ply are roughly 2 - 2 1/2" in diameter.  The inner
circle is of
> > 1/16" ply about 1/8" - 3/16" smaller in diameter.  I bevel the edges of
the two
> > outer circles so that when I glue the three circles concentrically
together they
> > form a "V" pulley.  Also, dremel two notches in the "V" for the cable
ends to
> > pass out and back into the "V" much like a Hanger 9 aluminum servo wheel
to
> > enable anchoring the cable to the pulley.  Drill a small hole for a tiny
wood
> > screw, no larger than a #2.  On the servo pulley the middle of the cable
can
> > duck out of the "V" pass under the washered wood screw and back into the
"V" on
> > the other side of the screw.  The loose ends of the single cable will
pass under
> > and around the wood screw of the rudder pulley.
> >
> >   Install the rudder pulley in a slot cut in the rudder equal to the
thickness
> > of the pulley, 1/8", and a depth of the radius of the pulley.  Make
certain that
> > the center of the pulley is centered right at the edge of the bevel or
hinge
> > line of the rudder.  This keeps all of the geometry intact. Epoxy it in
place
> > after MonoKoting the rudder but prior to hinging the rudder to the fuse.
Nearly
> > one of the last steps in the construction of your plane.  In preparation
for the
> > pulley cut a similar 1/8" notch, also equal or slightly larger than the
radius
> > of the pulley in the fuselage.  I epoxy a balsa block internally in this
area if
> > it is an fiberglass fuse to beef up this area.
> >
> >   The servo pulley is simply bolted with two 2-56 socket head bolts to a
round
> > servo wheel.  All tightening of the cables are done at the rudder pulley
outside
> > of the fuse.
> >
> >   The main advantage of this system is that the servo is able to
maintain
> > constant torque on the rudder through out the entire deflection of the
rudder
> > without any cable slacking or binding issue.  Plus you couldn't get any
other
> > system much cheaper.  You can also increase the torque of the servo, at
the
> > price of reducing the throw of the rudder, by making the servo pulley
smaller in
> > diameter than the rudder pulley.  Or, increase the throw of the rudder,
at the
> > price of reducing the torque of the servo, by making the servo pulley
larger
> > than the rudder pulley.  If the rudder is positioned quite far back in
relation
> > to the elevator, such as on a CAP 232, the rudder could in theory be
made to
> > rotate nearly 150 degrees or more assuming you double bevel the rudder
and fuse
> > at acute angles on the hinge line.
> >
> >   Just another idea to consider.  It almost took longer to write this
> > explanation than it takes to make such a system.  Enjoy.
> >
> >   Buff Miller
> >     ----- Original Message ----- 
> >     From: Keith Black
> >     To: discussion at nsrca.org
> >     Sent: Tuesday, September 02, 2003 9:57 PM
> >     Subject: Control horns, is it just me or... ?
> >
> >
> >     When it comes to control horns for pattern planes it seems to me
that some
> > of the most commonly used choices have a major flaw.
> >
> >     On my last plane I used the MK Aluminum Horns on all surfaces except
for the
> > rudder where I used the IM pull-pull horns. Both of these are nice horns
except
> > they have a major flaw when using a pull-pull setup. The flaw is that
the little
> > black plastic arm that screws onto the horn and connects to the clevis
is so
> > short that it doesn't extend out over the hinge line. I know that with
pull-pull
> > systems it isn't *absolutely* necessary for the connection to be exactly
above
> > the hinge, but the further back it is the more slack there will be in
the cable
> > that is not pulling.  In my opinion with these horns the connection
point is too
> > far away from the hinge unless the horn is virtually mounted on the
control
> > surface bevel (especially when it comes to rudder). This can easily be
seen in
> > these "instructions" for installing the MK horns
> > http://www.centralhobbies.com/buildingtips/mkhorns/mkhornsinst.html.
Notice that
> > in this picture there surface isn't beveled yet and the horn is almost
on the
> > edge.
> >
> >     On my new plane I wanted to avoid this problem so I did some
searching to
> > find a better solution. To begin with I looked for a longer arm to
connect to
> > the MK horn, one that would extend out to the hinge line. I found two
options
> > from Sullivan but both require too big of a horn thread (6-32 and 8-32).
My
> > search then led me to two other choices that seem to be good
alternatives. The
> > first is the ZNLine aluminum control horns, but these are apparently
only
> > distributed by ZNLine
> >
(http://www.znline.com/produits.php?langue=english&cle_menus=1025879382&cle_
data
> > =1025901639) which means an international order. The other solution I've
found
> > is by RC Model Enterprises
(http://home.att.net/~rc-enterprises/rcme_014.htm)
> > but these control horns seem very pricey!
> >
> >     If anyone could point me to a longer 3mm connecting arm that will
fit on the
> > MK and IM horns I'd be happy (BTW, I've used the MK BB connectors on the
MK horn
> > and they still aren't really long enough).
> >
> >     Is it just me, or have others experienced this dilemma as well?
> >
> >     Thanks,
> >     Keith Black
> >
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