| Preamble:
‘Disc
Brakes’ up front have lost their novelty and are taken for granted
now – ever since they were first ‘seen’ by the masses
on the ubiquitous M800 - way back in 1984. Yet, many have paused to ask
how do disc brakes score over drum ones – like the good old Ambys
and Fiats had.
And, what about the Ventilated Discs that one keeps hearing about these
days and their advantages over the solid/larger dia ones?
Besides, whichever the system is, if you pressed the pedal hard, the wheels
tended to ‘lock up’ – launching a Car in a somewhat
uncontrollable skid – made worse on a wet or an otherwise ‘slippery’
surface.
Enter the ‘ABS’ – even on a people’s Car like
a Santro now – having been shod with Ventilated Discs for quite
some time now ! I have picked up a few Pebbles from the Sea Shore –
as follows...
1) Fundamentally, the 'Braking
Effort' produced by any 'System' is dependent on the degree of 'friction'
that can be generated between the moving wheel/hub and the friction material
- the brake shoe/pad lining - without the latter 'fading' away due to
over heating. It should be more than obvious that as a Car Owner, you'd
want your brakes/friction material part of it, to last forever!
2) As can be imagined, given
a particular 'quality' of the friction material, the braking effort that
can be produced will depend on - i) The contact area between it and the
Rotating part of the wheel and ii) The 'force' behind such as 'contact'.
3) The first logical development
of Auto/Brakes was to have semi-circular 'friction material 'shoes' within
a 'drum'. But this had/has it's limitations, as it's practically not possible
to ensure full surface-to-surface area contact of the shoes with the drum
- due to a funda called the 'leading/trailing edge'. We can talk about
it later if enough interest is generated on this aspect.
4) Besides, as the Cars
became heavier and faster, the drum/shoe sizes tended to become unwieldy
and the leading/trailing edge business always ended in somewhat 'unequal'
braking between two otherwise identical units. This makes them unsuitable
for use up front - as it results in side drag upon braking, particularly
on a reflex/emergency braking - which itself can be fatal.
Content
generated by S. K. Gupta. - 11/’02. |
