Evening capital news. (Boise, Idaho) 1901-1927, 1919-03-30
AUT0|ST SHOULD TAKE
CARE OF HIS PLUGS
Sparkling Device Very Import
ant Adjunct to Cars Opera
tion-Points Should Be Ad-
justed in Proper Manner.

Inc spark plug is simply the means
OF introducing into the combustion
chamber of the engine a spark gar
formed between the ends of two wires
Inc spark jumps this gap, imparting
ITS heat to the gas mixtures, and thus
exploding it.
Simply stated, this is the function
OF the plug-to explode the mixture by
means OF the heat of spark but
at the same time the plug itself must
De able to Withstand the tremendous
neat and pressure inside the cylinder;
1t must not allow escape of the gas
mixture, it must unfailingly transmit
current so the gap will be jumped, and
IL must do this many thousands of
times mile of running
When one considers the work a
spark plug has to do it is surprising
how well and how long this little part
remains in service. Plug trouble to-
day is not so common as it was years
ago, and l have heard of plugs func-
tioning without any attention for as
many as 10000 miles.
There are hundreds of designs of
plugs made of a variety of materials
and made in numerous shapes and
styles. 1t is easy to see how difficult
1t is to design plug to meet all the
conditions demanded of it, yet the
modern spark plug does it's work adj
mirably well. l wish to describe in
this article the construction of plugs,
the way to install them properly, the
type to get and not to get, plug trou-
bles and how they may be remedied.
Since tho and pf IA l11I1o' in
troduce gap into the combustion
chamber, there must be two wires or
electrodes with their ends separated
to form the gap. One Of these cleo
trodes which takes the current from
device must be perfectly insulated so
no current will leak out, while the
other electrode must be grounded in
some way.
This latter always is attached to the
spark plug shell or the metal part
which screws into the cylinder, while
the other one, called the center cleo
trode, always is imbedded in an in
sulator made of porcelain. stone, mica
etc. The insulator and the shell then
must be Joined together to make a
unit of the plug, and this is done either
by cementing them together, forcing
them to compression tightness by
means of a nut, etc. OF course, the
two parts must so fit together that no
mixture escapes. and the usual way of
obtaining this tightness is by intro |
ducing a gasket or two between the |
parts.
Plugs are matte with open or closed !
ends, but certain engines only will /
operate successfully with each type
Often a closed end plug gives trouble
with an engine which operating with |
open end plug gives entire satisfac-
ton.
The really important parts of the
spark plug are the insulator and cleo
trodes The former is usually made of
mica or porcelain so as to withstand |
the tremendous hea. and also changes
OF temperature without cracking. Por-
celain and various stone compositions
are used, but of course this type is
more easily cracked than mica, both
by the heat and by wrench when in
stalling.
These materials may be used in COM
bination in the same plug the best
form consisting of an outer stone insu-
lator and an inner mica one. The only
trouble with mica is that it is liable to
absorb oil, but If the construction is