mark,
back when i was fooling around at gutekunst fabricators in the late 70's
numerous discussions on cleaning and finishing brake drums came and went
over lunch. while a nice , even , pretty finish on a drum looks nice at
pebble beach in a show it was decided that it was not good for a race
application. the porosity of the casting along with the irregular casting
surface actually increases the surface area for heat dissipation. if you
paint it you begin to seal the surface to a degree. next comes the difrent
finishes! a flat finish similar to the flat black header paint has a
better heat dissipation than a shiney finish or gloss finish wich actually
insulates adding to heat build up.
also another frightening thing we discovered was never ever glass bead
blast drums or any part of the rotors in an attempt to derust or descale!
why? the glass dust gets pounded into the friction surface. you can try
to sand (a fresh lathe cut is your best way out if you glass contaminate
the friction surface) the surface but the stuff is embedded into the pores
of the metal! the end result is a first time hot brake application melts
the glass dust and glazes the brakes yeilding quite a suprise when they do
not work like they should!
powder coating may look pretty and greatly reduce needs for refinishing of
components. but i'd suspect it would act more like an insulator where you
would rather not want to be saving or building heat?
chuck
'60 saab #251
> [Original Message]
> From: Mark Palmer <mgvrmark@hotmail.com>
> To: <VRG_NewsGroup@yahoogroups.com>; <vintage-race@autox.team.net>
> Date: 01/11/2006 4:31:49 PM
> Subject: Powder coating brake drums
>
> All,
>
> Has anyone tried powder coating on brake drums? I'm tired of having to
> re-paint mine every season, the paint burns off. Have tried many types of
> high-temp paint, none last. Surface prep isn't the problem. Will
> "standard" powder coating hold up to the temperatures, or will I need
> high-temp powder coat? My coater can do either but high-temp is
expensive.
>
> Yes I suppose I could get scientific about this and measure my actual
drum
> temps with temperature-indicating paint, but our season doesn't start
around
> here until April and I'd rather get this done now. Standard powder coat
is
> cured at 400 deg F which seems higher than race conditions.
>
> Does anyone have actual experience?
>
> Mark Palmer
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