From: "Scott Dahlgren" <dahlgren@itsnet.com>
To: "___Lancair list" <lancair.list@olsusa.com>
Subject: DH Brake lines
Date: Mon, 15 Feb 1999 18:17:40 -0700
Message-ID: <NBBBIPBKBOKGEELJMONFAEDGCFAA.dahlgren@itsnet.com>
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Marshall Michaelian,

>As for needing more than 150deg C....where are you flying????You'll have
more to worry about than brake lines at that temp.


the temperature constraints are due to the heat fatiguing that polymers such
as nylon and kevlar are subject to. Even high grade nylon, such as is being
used in nylaflow tubing, is very strong because it is made stiff but
degrades rapidly when flex or heat cycled such as when braking (it has a use
temperature around 110°C). Remember, the brakes job is to convert 1600 lbs x
70mph worth of dynamic energy into heat, and to keep the brake mechanism
light and efficiency high, you transfer energy at high temperatures. there
have been numerous instances reported to the LNN where the nylaflow tubing
burst or melted right off of the brakes of a moving 320, which can give you
a new outlook on temporal existence. The DH tubing is made for ambient
temperatures and instruments, so they told me when I called, and not
engineered to be used as a brake line. Neither DH's kevlar or Nylon has
sufficient flexibility for long service or UV exposure (nylon degrades
rapidly in sunlight). AQ 666 was engineered for brake type applications with
millions of hours to back it up. Why risk your life in such a critical
application?

Scott