In a message dated 97-12-01 06:31:45 EST, madamson@compuserve.com writes:=
> When materials get cold, ice is an exception, they shrink. The atoms
> occupy less space due to their decreased activity. Holes in material
> become larger. A piece of material, say a piston, becomes smaller
> therefore increased clearances.
Dan Masters wrote:
<If material gets smaller when it gets cold - and it does - how can a hol=
e
get
larger? Since the interior of a hole is lined with material, and the
material
gets smaller, how can the hole the material is surrounding be bigger?>
<Ice also shrinks when it gets colder. It's just that in the transition
from
water to ice, ice occupies more space than the water. Same is true on the=
other end. Steam, at the same pressure, occupies much more space than the=
equivilent quanity of water. If you increase the temperature of steam,
again
maintaining the same pressure, it also expands. I don't know of any
material
that gets larger as the temperature decreases, but there may be something=
that does - pure unobtainium, perhaps?>
Dan,
My reply was late at night, I meant to say water instead of ice. =
Draw a plan view of your engine with the head off. You'll have a rectang=
le
with 4 holes in it. Draw arrows from all the lines denoting the perimete=
r
and the cylinder bores pointing inwards. These indicate the contraction =
of
the molecules due to decreased atom activity. The dimensions of the engi=
ne
become smaller and the bores become larger.
Another illustration of this is making molds for cast iron. Molds are ma=
de
<<larger>> than the actual piece desired to accomodate the shrinkage that=
occurs when the part cools. The exception is if you want a void in the
part. The plug for the hole is made <<smaller>> so that shrinkage resul=
ts
in a void of the proper size.
Regards,
Michael.
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