Message-ID: <38834395.B9419CEE@mc.net>
Date: Mon, 17 Jan 2000 10:30:13 -0600
From: jerry@mc.net
To: "lancair.list" <lancair.list@olsusa.com>
Subject: Re: LNC2 - Adjustable rudder pedals
References: <000CACBA.CE21031@molex.com>
Mime-Version: 1.0

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These questions are for those who have the inflight adjustable rudder
pedals, and are specifically addressed to the LNC2 installation.

I'm in the process of reinventing the wheel, so to speak.  I'm not satisfied
with the rudder/brake assemblies, as supplied from the factory, which are
designed to adjust via a plywood slide.  I also have a problem with
uncommanded brake being applied when commanding rudder throw only.

I am about half way through a new approach using overhead suspended pedals
pivoting on a 4130 steel tube fixed between the nose tunnel and the left
side wall of the leg tunnel. The ball of the foot will be the rudder input
pressure and, of course, the toes will still command brake pressure.

Goal #1 is to have Cleveland master cylinders operated with the factory
original cast aluminum pedals.  A full scale model has proved the idea
works.  Some fine tuning is ahead to smooth out the operation.

Goal #2 is to have the rudder pedal pivot tubes adjustable, fore and aft,
with a simple control near the bottom of the instrument panel.  The force of
the rudder/brake application will be absorbed by a firewall mounting of the
adjusting mechanism.  The adjusting system will be rock steady and positive
but changes to adjustments easily made. The system is simple and cheap to
design and light weight.

Most of the design work is complete

I need some answers on the following:

The factory option, inflight adjustable pedals use an "S" shaped tube on the
sides of the rudder pedal support arms.  This "S" shaped tube has the rudder
cable threaded through it and (to my understanding) allows the cable to slip
inside the tube for the fore and aft adjustment but at the same time allows
the cable to pull on the rudder when rudder is commanded.

I must admit I don't understand the principle behind these two
possibilities.
Can someone explain how this "S" shaped tube does what it does?

Where does the rudder cable attach after emerging from the forward end of
the "S"?

Could this "S" tube idea be used with a continuous length of cable coming
from the left side rudder attach point forward through both left and right
"S" tubes and then back to the right rudder attach point?

All answers and suggestions appreciated.

Jerry Grimmonpre'


[Jerry, the S-shaped tube which allows for the rudder pedal assembly
position adjustment is quite an ingenious little device... if you were 
to picture the "S" as seen from the side its function can be pretty easily 
understood.   In order for them to function there have to be a couple of
"givens"...

1...  use a regular "S" to envision what's going on
2...  moving the "S" to the left moves it forward and to the right rearward
3...  the rudder pivot is colocated with the bottom left termination
of the "S"
4...  the fixed end of the cable is at the firewall, to the left of the "S"
5...  the movable ends (from the top of the "S") of the cable attach to
the rudder belcrank

Now, if your thread the cable through the bottom of the "S" and send it
rearward after it emerges from the top, by moving the entire "S" left and
right you'll see that the cable length remains fixed.  Once the L/R
position is fixed, any rotation around the bottom infeed end of the "S"
will cause the emerging end at the top to move forward and backward.  That,
in a nutshell, is how those adjusters work.

To carry this a bit further, if you were to terminate the forward ends 
of the cable with a loop whose center point could be moved left and 
right, connecting that center point to an adjuster would give you 
rudder trim.  How's that for some food for thought?

   <Marv>    ]  

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