Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1920-11-28
'sIMPL|F|ED LESSONS IN
CARE OF AUTOMOBILES
4Guerrlich Explains Results of Pre-
ignition. Described as spark
~ Knock" and carbon Knock
Lesson No. 10.


The expressions. "spark-knock" and
most motorists. Yet few know the
there is prc-iEnition. or that the
4 gases are pre-iEnited. or in other
words, that the gases explode too
When tho car is running on the
level, or tho engine is idling, the
i spark should come when the piston
IS In the position shown IN Fig. l, the
y trankshaft revolving in the direction
q indicated by the arrow. If the speed
SI the engine We're extremely slow.
q crnnked for starting, then when the
spark comes With The piston in the
position shown the piston would be
I driven down. ana $50 cause the engine
Z 10 revclre backwards. or. as ii is COM
monty known. kick back.
MheG the engine is turning over
momentum. Of the iiywheel. coupled
with the fact that it takes u fraction
OF second 10 Ignite the gases. viii
ter. before II can he driven back ward.
This is what happens when the en-
CINE is running idle or the car is
travelling on the level.
AS the engine speeds up. the spark
( can come even sooner, and to get tho
most power out OF the engine, il
should be made ito come sooner, or
If. however, the spark comes SO
much before the piston has reached
completely ignited before top center
is reached. the force OF the explosion
NH try TO drive the piston back ward;
and car will force II to travel on
ward. Thus there viii he a struggle
between the force OF the explosion.
Which tends to drive the piston back
ward; and the momentum Of the fly
wheel which tends 10 drive the p!s-
Ton forward.
Cause. Knocking Noise.
K II there be the slightest looScncss
or wear in the wrist-p.ns or bearings
the result OF the above mentioned
strnEsie will be q bad Knocking noise
far advanced a spark, is called
spark-knock
The spark-knock seldom comes
Level, or the engine is idl!ng. as then
the charge of gas is small, requiring
longer time 10 ignite, and the
speed OF the piston is comparatively
engine has slowed down because of
the load. not only will the piston he
stravel!nS slowly. but the throttle
charge is taken into the cylinders.
which VIII result in very power
fnl and quick explosion; Thus the
back. and the nywhcei trying
TO force it forward. viii be great ii
knock will result.
From the above we SEQ that the
spark control should he freely used.
-crankinE, either by hand or by the
self starter, the spark must be fully
retarded. and advanced as the en-
spark must be gradually retarded
mot necessarily the fun way) as the
engine slows down. II the gears are
should be Immediately advanced
again.
\ knock. which will be almost cx-
actl% like the spark knock, but from
this knock.
The carbon-knocN is due to
particle of carbon becoming heated
white hot by the burning gases and
so ignitinE the mixture before the
spark comes and the piston Is in the
Pe;-laps YOU wonder why this white
hot carbon does not ignite the gases
rs MS they enter the suction Hrolte.
partly compressed. There are TWO
reasons for this:
,rI 1t takes KS certain temperature to
higher than that which the whlt"-hot
cSrhon has. SO that the entering
gases will not he icnitcd when
sn iitt,a are he compressed: however. quite
neat, when added 10 the heat of the
carbon, will he enough. ut some
point OF inc compression, to ignite
the gases. thus causing a too-eariy
explosion, jas. as the ton-far-ad-
vanced spark did SO there is prn-
ignition, or Ignition before the proper
time.
Have IIot-Tube Section.
Many stationary gas engines have
no electrical ignition system. hui
have. instead, what Is called "a hotH
tube ignition" In these a hollow
tube Is screwed into the comprcssion
chamber OF the engine and n n,n,n
constantly played UPON It 10 AS 10
Keen II white hot.- The mixture &c
S<SSxS<SSS.SssSxs.-