The Daily Ardmoreite. [volume] (Ardmore, Okla.) 1893-current, 1921-11-06

oie is found
A spark knock is produced by ad-
7anciHg the spark 100 lar for the
ipeed Of the engine. We retard
Inc spark when starting an engine
20 as 10 have il occur at the begin
ninS Of the power stroke.
After the engine starts we advance
Z to give more power. This brings
he spark over the dead center into the
md of the compression stroke, which
means that the piston is travelling
inward when the spark occurs. But
ne flywheel turns so fast that the
piston is brought to upper dead cen.
er and started down on the power
stroke before the full force of the ex-
Jlosion is developed. Now if the
park Is too far advanced or the en-
.ine slows down under load, such ~
when negotiating a steep hill the eX'
3iosion occur too soon and the result
~ q knock. The force Of the eXplo-
sion pressing downward meets the
piston coming up, and the result is
y lAttl - hllONlA ~ u spa A4ApNfNs
rhis can be readily PROV ed when go
ing from a level road to hill. The
=ngine Will begin TO knock unless the
spark Is retarded. OF course, this
Mil occur only If the spark has been
sept advanced as it should be, up to
mat time. The rule for spark ad-
vance is to advance it rs far as (
rin go without q knock. Then when
laayy roads or a grade are met the
snock viii start, but must ne stopped
Immediately as it reduces the power
md tends to Gatten out the bearings.
50 retard the spark but only enough
To stop the noise.
The next type Of knock is one due
. overheating. Because Of some fail
are OF the heating system the cylinder
walls and Distons get so hot that they
set fire TO the gas in the cylinders
with out the electric spark. At first
this seli-iGnition comes at about the
same time as the electric ignition, and
go produces no bad effect. But as the
temperature rises the gas is exploded
sooner and 1t then occurs 50 much
before dead center as TO make
knock. This is always accompanied
by other symptoms of overheating,
such as steaming radiator, etc, and
if the switch is shut off the engine
will continue to run by selfiGnition.
This symptom is usually called pre-
Ignition" because the charge is ig-
nited before dead center This trou.
BILE can he readily recognized by the
symptoms of overheating already
mentioned.
Carbon knock is another case Of pre-
ignition but due to an accumulation Of
carbon in the combustion space and on
top of the piston. When the deposit
becomes fairly thick it catches fire
from the repeated explosion going
on around It and sets fire to the mix
ture before il should. If il comes with
the electric spark it makes no diff
ference, but as the engine heats mp
and the carbon glows more intensely
the gas is exploded before dead cen
ter, as the piston rises, and the eX.
plosion meeting the piston makes
knock as already explained. 1t will
ne evident from what has gone before
that the three cases just considered
spark, overheating and calon knocks.
car all be classified und., the head #
preignition, because tho explosion
occurs before dead center. II carbon
is suspected it is an easy matter TO
remove the spark plug and inspect
the end OF 1t or 10 glance into the
cylinder. II accumulatcs first around
the exhaust valve and from there
spreads TO all parts of tho cylinder and
piston head. When Il becomes trouble
some IL should be removed immediately
as So Is O. serious cause o. loss OF
power.
We now como so q totally different
cause or causes Of knocking ug-locse or
Worn parts. This covers an OF the me.
chancal parts of the engine. THE
knock may be heavy. as from a main
bearing being loose or burned out not
so heavy, as from a loose connecting
rod or very light. as from a valve
tappet. A. lhe valve tappcts are ,hc
only parts accessible from the out.
side. ,he engine must come down 20
locate any other knock. The iuvcstiga-
Tor may got "a general idD1 of the
nature Of the knock and i,s locator
by holding a piece of dowc'llnr or n
light steel rod against differrr; parts
OF Tho engine, tho other end r.p.uc
his egr. after tho manner of
..f 'ore. This IS merely an alc
s as the engine must come
down tcpairs.
one knock which does no
'.r H ,s simply annoying. That
u or knock ~ is due tc
.h. H. and cylinders bcin~ sd
I.. a. .., there is enough PLAY
...u.H m to make noise. Thi,
Uo. nd is usually neglect.
rl .1Ur,s rcerinding OF the
.c.Iul.. .I tHe fitting of larger
I uet0Us noIy &c. But the engine
ifu . Gown to determine whether
fne uu duo to this or some other
e.1..
800 o ,onal knock o. caused by
or. CYLINDER walls This will cause O
knock at first. but the oil soor
works up and the knock stops Their
u Eht knock, which starts when IN,
inc starts and soon disappears
D be disreRarded
Ne now come to tho question o
deciding which one OF the abov,
llaes is producing the knock. Nv
riCncod repair men can usuelly tel
uy listening carefully and trying ou
tle ear for few minutes ON th'
read. The best way Tor the beginner q
so go over the above list in the ordu
named and eliminate one cause are
fu.'tr unu ih e. use b. ~ nf. 4
spark knock can be stopped by retard
ing the spark. An overheating knoc,
is always accompanied by symrtnm
of uyerhca,ing. a carbon knock vii
be shown by carbon on the sparl
plugs and IN the cylinders. if mono O