Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml@lancaironline.net
Date: Sat, 15 Nov 2003 08:36:32 -0500
Message-ID: <redirect-2732689@logan.com>
From: "Gary Casey" <glcasey@adelphia.net>
Subject: kinetic energy
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<<Question for you. Is this Calculated w/ 2 disks or just one? I couldn't
follow all your math[Its way beyond me] but it would seem that the kinetic
energy of the a/c is absorbed by two rotors so does this mean that there is
infact 1/2 the energy stated?  Or did I just miss that fact that you had
included that two disks [ Wouldn't be the first time I missed something!].
I'm not building a IV but I'm curiously following this discussion and
couldn't help asking.
Jarrett>>

Sorry, Jarrett, in the interest of brevity I left out some of the
calculations.  Yes, I assumed the total kinetic energy of a 3400 lbm
aircraft from 80 kts is absorbed by a total of 10 lbm of cast iron (2 brake
rotors).  Not much of an engineering feat, just a little calculation.

<<But, losses in speed due to aerodynamic drag should not be overlooked.
I normally let my 360 roll out the full length of the home field 3500 ft.
runway without braking until the last 1000 or so.  I'd guess my speed to be
only half of that 80 kts you used when I start braking.(depending on winds)
Mark Ravinski>>

Exactly, Mark, and if you do that the temperature rise will be only 1/4 of
what it would be when braking from 80 kts.  When landing my Cardinal, cg and
winds allowing, I  raise the nose just short of the tailskid dragging to use
aerodynamic drag to absorb the kinetic energy.  I was assuming the worst
case of a maximum effort stop, just like a 737 at Burbank.

<< It got to the point that I could not hold position on run up.  That is
when I changed to the "Grove" brakes and they are better that the originals
ever were.  On top of that I can now change pads without removing the
wheels.
So when push comes to stop the numbers give you the theory but the proof is
in the stopping.
Ray. >>

Right, Ray, and that brings up a question:  I have read of similar
complaints, basically of insufficient brake torque available with a
reasonable pedal force - nothing to do with brake thermal capacity.  This
could be from a degradation of friction coefficient for whatever reason or
inadequate pressure.  I'm tempted to change the master cylinder geometry to
reduce pedal force on my ES.  Anyone done that?  Is it necessary?
Desirable?  My judgment is that you should always be able to lock up the
wheels without superhuman effort.

Gary Casey