Date:         Sat, 9 Sep 2006 20:37:18 -0700
Reply-To:     Pensioner <al_knoll@PACBELL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Pensioner <al_knoll@PACBELL.NET>
Subject:      Cryogenic cycling and other such things
In-Reply-To:  <200609090406.k8946uWr006364@flpi097.sbcis.sbc.com>
Content-Type: text/plain; charset="iso-8859-1"

So if I get the drift of this cryo-doodad stuff they say their brakes LAST
longer.  Do they stop better?  On a 5000lb truck?  No data yet.  But the
fizzix says that a particular deceleration requires a particular amount of
kinetic energy to be dissipated by the brakes in the form of heat.  Some
materials are better at doing this and likely over the years the industrial
trucking industry who has a pressing commercial need to have the very best
brakes for mountain driving with large loads has pretty much sorted out the
technology.  A disk brake just doesn't cut it on a 50000lb truck.  However
on a UJM ricerocket they look kewl.  The big boys use massive drums and
often water cooling.

Neither of these are vanagons.

Our application is best suited by cast iron rotors (great heat dissipation
and conduction) and medium duty pads.  Soft pads that wear out in 25Kmi are
much preferred to those that last 50Kmi but don't stop very well.  Bodywork
is much more expensive than brakework.

Severe temperature cycling can change the crystalline structure somewhat but
does that improve the braking aspect?  No data.  Stainless disks don't rust
but they also don't provide much braking force because they don't dissipate
heat as well as cast iron.  Aluminum is great for heat transfer but lacks
the wear resistance necessary for a vanagon application.  The vented disk
dissipates heat from inside the braking disk via the vents and provide more
heat dissipation capability.  Better than the solid disk much better than a
stainless disk.

In the bicycle world some years ago there was a fad to have anodized rims.
The anodization process produces a really kewl looking black rim that
doesn't stop as well as plain aluminum because the surface treatment doesn't
conduct the heat through the surface as well as un treated aluminum.  MA-2
vs MA-40 by Mavic.  In the absence of real data of which I have none, the
Cryo-treatment smells suspiciously like snake oil (in a vanagon application
sort of way).

Fizzix and materials science (more fizzix).

You can't win, you can't break even, and you can't get out of the game --
Thermodynamics for the common man.