South Bend news-times. (South Bend, Ind.) 1913-1938, 1919-10-26

cd TO the practice OF slipping the /
clutch, however very few stop 70
think jus. what happens on these /
occasions It is the purpose Of this
article 20 discuss these features and
the advantages and Disadvantages
81 the practice OF slipping the clutch
in driving. There are three main
reasons why clutch slipping IS re
sorted 20: I. To aid in accelera-
tion Of the car from state Of rest.
2. To reduce the vehicle speed be
low that at which the motor viii
drive IL with closed throttle and
fully retarded spark. without chang
ing 70 a lower gear. 3. To help the
car over the crest of a hill or
through some short stretch OF diff
cult going When the clutch is in
contact. but not sufficiently en-
gagged to start the car or 20 keep it
in motion. its efficiency IS zero. and
the energy which 10 is absorbing
from the motor is equal 10 the fric-
tiOnal toruue existing between the
two clutch members at their mean
radiu4 times the peripheral speed
OF the engine driven member in
feet per minute at this radius. This
energy Is dissipated AS heat at the
contact surfaces. When the clutch
IS engaged sufficiently to accelerate
the car on a Level road but al the
same time slipping the efficiency is
greater than zero. the output OF the
motor at any instant. minus the in
put called for at this instant TO eff
feet the acceleration of the car be
ing the rate OF dissipation Of energy
81 the clutch surfaces I'm the form
of heat II the car is IN motion on
a level road surface. but at a speed
less than that at which the insfan-
taneous speed Of the motor would
drive n fully cIutched IN. the diff
ference between the motor output
and input received by the car 10
overcome traction resistances rep
resents the input which is convert
- ed into heat at the clutch.
What Happens When Starting.
When a car is to be gently start
ed from rest. on a Level surface. the
motor is usually speeded up 10 per
haps 500 or more revolutions per
minute and the clutch is very light
Is engaged. when the car starts in
10 very slow motion. At this in
slant the throttle must be opened
somewhat 70 keep up the speed of
the motor and at this instant the
clutch Is allowed 90 engage a little
more positively. Thus the car
speed IS further increased with re-
gard 20 that OF the engine and by
degrees the speeds OF the two ap-
proach and finally attain CORES
ponding speeds, at which time the
clutch is in full engagement. After
this the throttle opening may be
r. reduced from that which had pre-
viously prevailed and the car will
still move at the speed TO which il
had been accelerated. Thus. wher
the motor has been accelerated and
previous 20 the slightest engage
ment OF the clutch. the former is
delivering no output. all the energy
developed being dissipated In en-.
zine friction. The fiywheel. how
ever. possesses a certain amount OF
energy. II the clutch is lightly en-
Cagcd. without opening the throttle
the motor will slow down and at It's
reduced speed does a small amoun
of external work a part of the en-
erey formerly consumed in its owl
friction being usefully available
since piston and other frictiona
losses decrease with decreasing
speed.
Car Can be Started.
Even though the motor may fur
ush the slightest amount OF pow
cr. the vehicle, if on a level. smC otl
surface. can be started by very care
fully letting in the clutch withou
further engine speeding. If th'
car will start from rest at all with
cont stalhnc the motor 10 can usu
.Iy he brought 10 speed cor es
ronding 10 that OF the motor pre-
Vious TO clutch engagement At tn,
first or the car motion there IS
very large discrepancy between tn,
sara engine speeds; the efiicicnc,
OF The clutch as a transmission de
VICE is very AtWs anu very lAAAlt an
crgy ia applied TO the car VIII
each increment OF car speed. how
ever. the transmission of the clutcl
increases and greater portion @
the efficiency available output of tn
motor is applied TO the moving car
and less is wasted as heat as tn
clutch. so that the nearer car an,
engine speeds coincide, the NOR
rapic Is the tendency for them q
come into complete coincidence an,
the more rapidly the clutch may b
let in. II the throttle is opened a
soon as the clutch begins 10 en-
gage the turning power viii be TO
= portionately greater. and the clutcl
may be let in proportionately NOR
rapidly without danger OF reducing
motor speed 20 the stalling point.
II. during the operation OF start
ing. matters are so regulated tina
the engine speed hardly change
from the time the clutch has Jus
been touched in and that az whic'
engine and car are at correspondent
speeds. the stored energy in the fy