<VV> Early drums from Z car

[John Kepler]

Remember that brakes 'work' by converting energy of motion to heat energy
... rapidly collected in the mass of the drum or disc then dissipating that
heat into the air over a period of  time.  Reduction of the mass reduces the
drum or discs ability to store heat.  

Uhhhhh......correct to a point!  But....."storing" heat is the very LAST
thing you want a brake to be doing!  You want the heat OUT of the brake
system as fast as is thermodynamically/mechanically practical (tires melting
off the rims a`la NASCAR this year is one of the consequences if you
don't!).  In a decent brake design, you want the mass as low as is
mechanically tolerable, and design everything to transfer the generated heat
as rapidly as is practicable (plumbing/routing the brake cooling-duct system
in a racing car is often a far more challenging problem than packaging the
brakes themselves!).  Not only are their heat-transfer issues with more
massive brakes, but a more massive brake contributes a LOT to the unsprung
weight of the suspension, making the "energy management" of that critical
system progressively more complicated and difficult.  There are reasons for
things like graphite-fiber brake disks and very light alloy calipers in
racing cars!


It is the reason that a drum or disc has a limit on how much it can be
resurfaced.

No, that has to do with the minimum web-thicknesses/mass required to react
the mechanical loads on the brake.  Those limits are structural, not
thermal.

The Datsun was a much lighter vehicle which reduces the heat generated and
the need for the mass required for a heavier vehicle.

The brakes in question were taken right off the Datsun SRL-311 Roadster, a
much older and heavier car than the Z....besides, the curb weight of the
early Datsun-Z (2355 curb-weight) was about the same as a 'Vair.

John