COOLING SYSTEMS
Proper cooling is a necessary feature of all gasoline motors, otherwise
the intense heat of the burning fuel would expand the pistons to such
an extent as to prevent their free motion in the cylinders, as well as
destroy the spark plugs, injure the springs, and make lubrication a
difficult matter, if not impossible, by burning up the oil.
AIR COOLING.--Cooling was originally obtained by using air, which was
blown against the cylinders; but this was not generally developed to a
satisfactory degree except for small motors.
Air does not take up heat readily, whereas water is the greatest
absorbent known, and in the primary stages of the art water was
objected to on account of its weight, and for the further reason that
the jacketing of the engine was considered a needless expense.
One of the best known devices to increase the cooling capacity with
air cooling, and now largely used in motorcycles, is to provide the
cylinders with a plurality of thin broad ribs, annularly-disposed, as
shown in Fig. 72a.
[Illustration: Fig. 72a. Increasing Cooling Area.]
AIR-COOLING DEVICES.--A highly-heated metallic surface actually repels
such a subtile fluid as air, hence it is necessary to supply the
cylinders with a blast of air, and also provide a greater cooling area,
so that if the ribs themselves can be cooled, the temperature will be
decreased in proportion to the enlarged surface thus provided.
In using water this artifice is not necessary, because it will absorb
heat instantly along the surface in contact with the metal, and quickly
change the heated particles in favor of the cooler portions.
WATER COOLING.--While heat will cause a circulation of water in a
definite direction, for the foregoing reason, it has been found that,
in practice, it is more practical to keep up the movement by mechanical
means.
This is done by a pump placed in the line of the circulating pipe, and
usually so arranged that the cold, or coldest, water is forced into the
circulating area around the cylinders.
[Illustration: Fig. 73. Movement of Heated Water.]
GRAVITY SYSTEM.--The natural circulation is founded on the principle
of the well known law, that heated water will flow upwardly, hence, if
a cylinder, such as A, Fig. 73, which has a water jacket around it,
has its lower end connected by a pipe B, from the bottom of a water
reservoir C, and the upper end of the jacket is provided with a pipe
connection D, with the upper part of the reservoir, the water will flow
from the bottom of the reservoir to the jacket, and from the top of the
jacket to the reservoir, in the direction of the arrows.
LOCATING THE RESERVOIR.--This flow would be materially increased
if the reservoir should be located a considerable distance above
the jacket. But in an automobile it would be difficult to use an
elevated reservoir, and, furthermore, as means must be provided to
cool the water, such disposition of the reservoir would be still more
impracticable.
[Illustration: Fig. 74. Cooling System.]
The area forward of the engine is the most available space for placing
the water tank, and, especially for the reasons that the radiator
itself may be utilized for inclosing the engine hood, and because the
air, which is only partially heated in passing through the radiator,
serves to keep the space within the hood reasonably cool.
FORCE SYSTEM OF COOLING.--Under the circumstances the water should be
caused to circulate by mechanical means, which, while it adds another
operative element to the machinery, is nevertheless so much more
effective that it is worth the care, attention and expense which are
involved.
THE RADIATOR CONNECTION.--In Fig. 74 a radiator, engine and circulating
system are connected together to show the relative arrangement of the
various elements, in which the pump A is placed in the pipe line B
running from the lower end of the radiator C to the manifold D at the
lower end of the water jacket of the engine.
The upper end of the radiator is connected by a pipe E with the top of
the jacket, and the pipes are thus so disposed as to be free of the
other mechanism, and are all contained within the hood of the engine.
A fan F, suitably geared to the crane shaft of the engine, provides a
means for inducing an air current through the radiator whenever the
engine is running.
RADIATORS.--Much time and money has been spent in developing a simple
and efficient type of radiator. As, of necessity, it must be made up
of a multiplicity of parts, leakage is apt to occur, and while in
the past most of the constructions depended on soldering together
the various portions, it will be seen how insecure such a system of
construction must be necessarily.
CONSTRUCTION OF RADIATOR.--In Fig. 75, is shown a front and a sectional
view of portion of a simple type, which is made up of square tubes A,
their ends being fitted into square holes formed through front and rear
plates B C, and the tubes are so arranged that there are small spaces D
between the tubes.
[Illustration: Fig. 75. Radiator Type.]
When water enters through the inlet tube E, it fills the spaces,
and being cooled moves downwardly, while the air rushing through
the open-ended tubes, cools down the water over the large area thus
afforded.
All radiators employ substantially the same construction, the
illustration given being merely to show the principle of the device.
A drain cock G, Fig. 74 should be placed in the system below the
radiator, in the pipe line B, so that water can be drained off from all
the pipes, to prevent liability of freezing. The diagram shows the fan
shaft connected and run by a belt H. This is not the best construction,
as it is not a positive drive. Most cars are provided with gearing for
this purpose.
OPERATION OF RADIATOR.--The water is thus carried from the bottom of
the radiator to the water jacket space, and from the upper end of the
jacketed area to the top of the radiator, and used over again.
More or less of the water is lost by evaporation, so more must be added
from time to time, and the radiator should be kept as full as possible
to get the best results. If the water level falls too far below the
return pipe at the top of the radiator, the area of the heating surface
and the decreased quantity of water exposed to the cooling surface, are
likely to cause undue heating, or vaporization.
THE PUMP.--A variety of pumps are used, but they are generally based
on the principle of the turbine impelling system, or on centrifugal
action. A type which utilizes both these principles is shown in Figs.
76 and 77, in which the former is a cross vertical section of 77 along
line 1, and the latter is a central vertical section on line 2 of Fig.
76.
The device comprises a cylindrical shell A, with an inlet B, at one
edge near the front wall, and an outlet C at the upper edge near the
rear wall.
PUMP CONSTRUCTION.--Within is a revoluble tubular hub D, with one end
E projecting, to which power is applied. A disk partition G is secured
to this hub, midway between its ends, and on each side of the partition
is a pair of oppositely-projecting convolute blades, those on the inlet
side, indicated by H, and the ones in the discharge side by I.
[Illustration: Fig. 76. Side View of Pump.]
[Illustration: Fig. 77. Section.]
It will be noticed that the blades H on the intake side are so disposed
that their concave surfaces are on the advance sides while those in the
discharge end of the shell have their convex faces in the retreating
side.
ACTION OF PUMP.--The hub has inlet ports J below each blade, and
discharge ports K between each of the blades I. When rotating the
points of the blades H catch the water at the inlet and drive it
inwardly through the ports J, from which it passes through the hub to
the ports K, and is then violently thrown by centrifugal motion, and by
the action of the blades I to the discharge opening C.
Should the pump cease working there is always a free passage way for
the natural circulation of water through the pump.