Evening star., 1914-01-04
Capacity Of Cylinder.


I'm order that we may properly under
stand this. we must get some idea OF the
capacity of the cylinder walls for absorb
ing and carrying on heat. Let US assume
that we have a proper mixture of gas
and air confined in the compression
chamber of the cylinder Of a properly
constructed motor, with all valves closed.
no leaks of any kind. piston immovable,
compression sixty to seventy pounds, and
the charge ignited. Under these con-
ditions 1t will be seen that no heat can be
converted into work. no frictional loss
and no loss by means of exhaust: in fact
no escape except through the cylinder
, walls. Let US further assume that when
this charge is ignited it will Immediately
expand and create pressure within the
compression chamber of from 300 to $50
pounds per square inch. If We were to
ask the man who had not given this
matter careful thought, or who had made
| no practical test of it. how long it would
amount Of this heat to be carried of
through the cylinder walls to reduce the
pressure within to 100 pounds. he would
| more than likely say from five to ten
minutes. If we were to tell him that
as a matter Of fact it will take less than
two seconds he would either not believe
1t or would at once begin to realize what
| high piston speed means when 1t comes
to a question Of economy. It is thus
seen that when We increase the piston
speed there Is less time for the heat to
be carried OF through the cylinder walls,
and as a result more of it is converted
| into work. When this is done by means
OF increasing the stroke there is but little
frtctional increase, and a clear gain in
power. with less fuel consumption.
1T has also been demonstrated that
with the longer stroke the compression
can be increased over that of the short
stroke motor. without any of the bad ef-
| fects or disadvantages of too hiSh COM
preston. Increased compression Is an
other step toward more economical opera
| ton.
Observations Of Exhaust.
| pand the gases, the less heat will be car
ried Off through the exhaust. Observa-
tion Of the exhaust alone from a long and
| short stroke motor, both properly con-
| structed. should be sufficient to satisfy
the mind that the exhaust gases can be
permitted to escape under a lower pres
sure with the long-stroke motor; a prop
erly taken indicator card will show this
| clearly.
THE advantages here are covered al
most completely by the remarks as to loss
from radiation through the cylinder walls.
II we have less loss through the cylinder
| walls we require correspondingly less
cooling surface, which means saving IN
| expense as well as a reduction in weight
Smoother running qualities and less
noise are secured In the long-stroke motor
because Of the fact that the initial inn
pulse is much less. The pressure on the
piston head is the same whether the motor
has a four-inch stroke or stx-tnch stroke
| If the diameter and compression in both
| are the same II we must use the larger
bore in order to secure the same power
we must expect the natural results OF a
larger motor, or Of a larger cylinder diam
| eter with the same stroke.
| s.,rhe noise must necessarily be increased
when the motor is running at greater
| number of revolutions, because OF the IN
| creased speed of opening and closing
| valves and the movement of the othei
narts of the motor. Again. it is well
| known fact that with the long-stroke
motor you can secure better mixing ano
| yaporizing of the charge. You can throt,
| tie the motor down lower, so that 1t viii
| null much more steadily, quietly ano
smoothly on hills or on slow speed under
heavy load 1t is not difficult to see thai
the further the gases are expanded, the
less noise will be created by the escape
Of the exhaust gases: likewise, that ex
haust valves will open against less pres
| sure,