The silver state. [volume] (Winnemucca, Nev.) 1909-1925, 1915-08-14
POINTS ON SCIENCE
OF LUBRICATION

Few motorists know what lubrica-
tlon really means, or can tell Just what
happens when the oil strikes the hot
cylinder walls, and how it is affected.
An article by Lieutenant G. 8. Bryan,
u. s. N, published in the February
Journal of the American Society of
Naval Engineers, throws considerable
light on the subject. He says in part:
"The luubricating value of an oil
| is due to the fact that when the sur
faces of the cylinder and piston are
separated by film of oil the friction
of these two metal surfaces is elmini-
mated and the friction that remains is
only that occasioned by the sliding ac-
| tion of the molecules of oil past each
other. In other words, it is the same
os If two layers of oil are sliding past
each other, and the friction that oc-
clrs takes place inside the oil film and
not on the surface between the film
and the metal. In other words, we
have dual film-oil working against
OIL
"Under the conditions of high rub
bing speed and small piston ring pres
sure that are generally found in motor
cylinders, light oils, such as are used
in turbines, would probably give the
most efficient results If il were not for
the high temperatures encountered in
the cylinders.
Before discussing the effect of
these high temperatures, it will be well
4 TO determine just what they are. Re-
cent experiments abroad have shown
that the maximum temperature attain
ed in an internal-combustion engine is
about 2,700 degrees F. This is the max
iinum and is obtained only at the top
OF the explosion stroke
"a recording thermometer used in
the above investigation showed that
the maximum temperature was about
200 degrees, F., the minimum about
$50 degrees, and the average during a
complete cycle about $50 degrees f.
These temperatures are those of the
Ga ses in the cylinders and are not
those of the cylinder walls. There is
greater difference between the tenn
peratures of these two AS long as the
water is not bobiling we know that
the temperature of the wall is little,
if any, higher than 267 degrees F.
cit naturally follows that the inner
ard outer surfaces of the oil film will
be exposed to quite different eondi
tions. The inner surface is exposed to
the high temperature of combustion,
ard without doubt is very greatly
damaged thereby The outer surface is
exposed only to the comparatively low
temperature of the cylinder walls, and
with film of any appreeiable thick
ness would be protected from the heat
due to low eonduetivity of this film.
fWe can consider the film as con-
sisting of two layers, the function of
one of these being to furnish The lubri-
cation, and of the other being to with
stand the destructive action of heat
and to protect this lubricating layer.
u is well known that an exceedingly
thin layer will furnish lubrication, and
il is probable that the greater part of
the thickness of the film is used up in
giving the requisite protective action
fl ON the heat. At any rate, the part
that we must look to for fabrication is
that part having the lowest tempera-
tire. which is the very thin layer next
10 the cylinder walls.
Lubricating oil does not burn very
easily or very fast, however, and time
given for it TO burn in a motor cylin-
der is very short Under the intense
heat, however, the inner surface of the
oil film will be vigorously affected.
"Some oils form a thick, viscous,
gummv deposit, which retains the car
bon formed on its surface and prevents
ii from being blown out through the
exhaust. This gummy deposit gradual
h gets thicker and harder, eventually
forming the hard carbon deposit so
veil known in cylinders.
coils made from asphalt base crudes
have shown themselves to be much bet
ter adapted to motor cylinders, as far
rs their carbon-forming proclivities are
concerned, than are the paraffine-base
Pennsylvania oils. The carbon formed
from the latter is, as rule, extremely
hard and clings to the metal surface.
while that from the former is soft and
can be easily wiped of any surface
II at il is deposited on. This would be
expected from a consideration of the
nature of the hydrocarbons composing
the oil, and IL has also been demon
rated in practice.
"The explanation lies in the fact
tnat the paraffine- babse oils are gen
erally composed of the paraffine series
~ hydrocarbons, while the asphalt
base oils are composed mainly Of the
e'hylene and napthene series. One of the
characteristics of the latter two &C.
ries as compared with the paraffine Sc
ries is their tendency to distill without
decomposition. Consequently, no gum
win be formed on the cylinder walls.
and the carbon liberated will be mostly
discharged with the exhaust gases -