Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1917-12-30
s|MPL|F|ED LESSONS IN
J. PROPER CARE OF AUTOS
Few Motorists Know Cause OF
"Spark- Knock" and Car
bon KNOCK"
Seldom Comes When Car Is Travel
ing on level or Engine Is ldling,
but Occurs on Hill or When En-
Einc Slows Down because Of Load.
LESSON No. -.
rreigptttor.
,cr7,-i.hsea :si5. ny rredericA c

TIE e1c-rs< SIS spark knocK" and
'csssca-I1>-\ So WEI known 20
-,cs, --sttr;$:< yst ie~ Suow the cause
~ ;s>1, - cause 5 ;hs; there IS
p4ess-E:;N- = ;as: ,he gases are PIE
;s.,:ta = - c;Ns- words ,AA. ,he
gases ea7,>s, 50 >>en.
w>ez =, - : running Oh The
isvel - - 80 .&,i": Ihe Spays
sAcca ~: rlsa Sc piston Is ~ the
r>susr .Ae~- s., f.Eure /. The crank
ehait -ev,,vt-s - - d.7rc;icn ind!-
Gated sy ;Ne s--n~ !: Ihe speed ~:
the engine we-. extremely SLOW. - i
she case ~Aec X IS being c-suN-d -:
starting. the. when ;hs srS,k renHes
with the piston in ;he position shown.
the piston would ne driven down. and
so cause the engine 70 revolve back
wares, or. as is commonly known, Sex
back.
when the engine is turning over
fairly fast. however, the weight. or
momentum, o. the rywhce,. coupled
with tho fact that i; takes fraction
OF r. second TO ignite the gases, viii
carry the piston over the dead CEN
ter, before il can be driven backward.
This is what happens when the engine
SIS running idle or the cav is travelin:
on the level.
A, the engine speed, up. the spark
can come even sooner. and to get the
most power out OF the engine. II should
he made to come sooner, or he adj
ranccd.
II however, the spark comes so
much before The piston has rea ched
the top. az 10 permit the gases TO be
completely iEnred before tor center
IS reached, the force OF the explosion
will try 10 drive the piston backward.
hut the momentum OF the nywheei and
car will force IL TO travel onward.
Thus there Will be struggle between
tho force OF the explosion. which tends
to drive the piston back ward. and the
momentum OF tho nywheel. which tends
TO drive the piston forward.
II there be the slightest loosencss
or wear in the wrist pins or bearings.
the result; OF the above mentioned
struggle will be bad knockin: noise
in the engine. This being due To too
far advanced spark, is called spark
knock.
The spark knock seldom comes when
the car is ;ravclin: on the level, or
the engine is idlinE, as then the charge
OF gas is small, requiring longer time
20 ignite, and tho speed OF the piston
is comparatively great on = hill, how
ever, when the engine has slowed down
because OF the load not only viii the
piston be travelling slowly, but the
throttle will be wide omen, SO that
full charge is taken into the cylinders.
which VIII result IN Very powerful
and quick explosion. Thus the s;ruE-
gle between the force OF the explosion
trying to drive The piston back and the
nywhccl trying 20 force il forward VIII
he great If tho spark is too far al
Tsnced. and knock will result.
From the above thar the
spark control lever should be freely
used. In order to prevent back-kic};
when crankin:, either ny hand o. hv
the self-starter. the spark must be fully
retarded, and advanced as the engine
mus, be gradually re.afl.d Irot neces-
sarily IN. full Way &c the engine
slows down. II the gears are shifted 10
second or low. the SPARK should lie i'm
medistely advanced again
A KNOCK which VIII be almos, e1-
aetly like tn. sparE-knoek. BIZ. from
different cause. Is the ca-bon-k mock
Let Us see the reason for this knock
The carbon-knock is due to par.
ticle OF carbon becoming heated white
hot by the burning gases and SO isnit-
ing the mixture before tho spark cones
and the piston IS in the proper position
for the ignition.
Perhaps, you wonder wy this whi,e-
hot carbon does no, ignite the sase- as
they ente" on me succior stroke. bu,
waits until IN" gases have been partly
compressed There arc two reasons t,,.