IF WELL “SLICKED” THE ENGINE RUNS
If we scuff our feet on the bare pavement we wear out our shoes,
develop a lot of heat, and notice considerable resistance; but if we
step on a banana peel, a piece of ice, or a patch of oil or grease, our
passage is facilitated, and our feet are likely to slide out from under
us and we sit down with little effort. Now this is just like the auto
engine. If the parts were all made perfect and fitted together properly
and the engine started without lubrication, there would be so much
friction that the parts would very quickly wear out.
As a matter of fact an engine could be wrecked in less than half an
hour’s running, unless there were something introduced to prevent
friction.
The lubrication of the modern auto engine is so simple that most
owners do not realize its importance. It is the things which normally
take care of themselves that are most likely to be neglected; the
things about which we know the least, when they do go wrong, cause the
greatest damage, not the things with which we have become familiar
through frequent tinkering.
The instruction books issued by the manufacturers say to inspect the
oil reservoir of the engine each time before leaving the garage to see
if the required amount of oil is there; and this inspection should not
be neglected; with most owners it is “by guess and begorry.”
The most usual scheme of engine lubrication used to-day is to carry a
certain amount of oil in a compartment in the bottom of the crank case,
called the sump. There is a pump which operates whenever the engine is
running and which pumps the oil to some sort of an indicator on the
dash, so that the driver can see if it is circulating. From this point
it flows by gravity to the splash pans located under the connecting
rods, and above the sump. Here the oil is held at such a level that
when the crank shaft revolves the ends of the connecting rods dip into
the oil and splash it over practically all the working parts of the
engine. This splashing and agitation of the oil creates a fog of oil
in the crank case, and the rapid motion of the piston and other parts
circulates the vaporized oil over the moving members, so that a film of
oil is deposited even on those parts where the splash itself does
not reach.
[Illustration:
Courtesy of Tide Water Oil Co.
SECTIONAL VIEWS OF A FOUR-CYLINDER ENGINE WITH SPECIAL REFERENCE TO
PARTS CONNECTED WITH LUBRICATION
A Sump
B Oil Pump
C Crank-case
D Troughs for Oil
E Connecting Rods
F Oil Cups
G Main Bearings
H Crank Pin Bearings
I Cylinders
K Pistons
L Wrist Pins
M Basin in which Crank Shaft Gear Runs
N Piston Rings
O Oil Pockets
S Drain Cock or Oil Gauge
T Push Rods
]
The pump circulates more oil than is used and the splash pans are
arranged with overflow openings so that the excess simply drops back
into the sump and again is passed through the system by the pump.
It is this oil which enables the engine to move without friction. It
is the effect of the banana peel under your heel in that it makes the
parts slip over each other easily. In addition to this the oil between
the piston and the cylinder wall makes a seal which prevents gas from
leaking by on compression and explosion strokes. If too much oil is fed
a great deal will be drawn past the piston on the suction stroke and
get in the cylinder where it will burn, forming carbon and giving out
smoke from the exhaust.
In this type of system the principal causes of trouble are too much
oil in the sump, so that the level reaches above the splash pans,
and projections upon the connecting rods that are so large that too
much oil is splashed when the level is normal. In the latter case the
trouble often may be remedied by narrowing the projections of the
connecting rod which dip into the oil. It is not wise to shorten these
projections, because it is very difficult to get an even graduation
that will insure sufficient oil without giving too much.
If the oil should run out while the car is in use, the engine will get
stiff, lose its power, and the friction of the unlubricated parts will
generate sufficient heat to melt out the lining of the bearings, and
if the engine runs for any length of time in this condition it may be
wrecked beyond repair.
This means that although the oiling system needs very little or no
attention, it should be inspected each time before leaving the garage
and on the road occasionally if long trips are taken, to make sure that
oil is present in sufficient quantity and is circulating.
Oil in a sense does wear out and in this sort of a system it should be
replaced with new oil occasionally. Some of it will work up past the
piston and be burned up and some will work out around the different
parts of the engine and be lost, but most of it will remain in the sump
longer than it is advisable to use it. All of the gasoline that is
taken into the cylinder is usually not consumed. Some of it is forced
past the piston on the compression stroke into the crank case, where
it condenses and mixes with the oil. This thins the oil sometimes to a
point where it has little or no lubricating value. Also the oil on the
inside of the piston head burns and drops down into the crank case,
and there is some wear of the moving parts which causes a deposit of
metal in the oil. These things, together with the small amount of road
dust sucked in through the breather pipe, make the oil in a short time
unfit for use.
In this circulating splash system, where the oil is used over and
over again, the oil should be drained out entirely about every 1000
miles, more or less, depending upon the grade of the oil and fit of the
piston. The following things all enter into the lubricating value of
the oil after 1000 miles’ performance:
Grade of the oil
Fit of the pistons
Temperature at which the engine is run
Grade of the gasoline
Adjustment of the carburetor.
There are some other things, but the above are the chief factors. It
would be well to acquire the habit of examining the oil every few days
to determine just how it stands up in the particular engine.
After the oil is drained out, a half gallon or so of kerosene should be
poured into the sump and the engine run for about one minute or less,
the idea being to get a complete circulation of kerosene through the
lubricating system. The kerosene should then be drained off and the
splash pans under the connecting rods be wiped out if possible. The
screen of the oil pump also should be removed and washed carefully in
kerosene and replaced. Then the sump should be filled to the proper
level with fresh oil.
Aside from getting under the car to remove the drain plug, this is not
a dirty job. Still one would better put on old clothes and overalls to
prevent the possibility of getting grease on a perfectly good suit.
While oil is expensive, it is poor economy to use it beyond its useful
stage, because damage may be done to the machinery which will cost much
more than a year’s supply of good oil.