The Tabor independent. [volume] (Tabor, S.D.) 1913-19??, 1913-05-15
GEAR CHANGING, ART
THAT REQUIRES STUDY
Care Is Required to Attain
Quietness and Is One Of the
Fine Points.

tndu lHdI Oh BOhI Hlh. ouc tlhJ
be possessed OF ample theoretical
knowledge OF motors, and OF ar en-6
tirely adequate practical ability TO
keep a car In good running order. and
yet be classed by ones friends as q
bad driver simply through inability to
change gear quietly, avs q writer In
Country Life, There are many mel
who may claim an accurate judgment
of speed and distance, a delicate touch
the ability to anticipate and correct
side slip, but who are vet rough n
unpleasant drivers through unskillful
handling OF the yea lever.
4 1t Is frequently said a On one
particular car II Is difficult to change
speed, and In the case OF a. few old
3 machines there may possibly be some
grounds for the statement, but In the
vast majority OF cases the fault lies
either In the adjustment OF clutch and
Gluten stop or In the hands OF the
driver. whichever OF these latter x
plantations be the true one, the remedy
lies In a thorough understanding ~
what happens to the car mechanism
when aSchange OF speed Is effected.
1t Is common knowledge that for n
given speed OF the car the engine must
be turning faster when on a low gear
h on the next higher one. "A fact
that is not so generally realized IL that,
Tor q quiet change OF gear, the driven
member Of the clutch must be reyol-
wing at exactly the same speed az lf
the gear to be engaged were already
In mesh. Suppose, for example, that a
car Is travelling at is miles per hour,
that the third speed Is engaged and
that 1t is desired To engage h fourth
speed. 1t NAV further be assumed
that n gear ratios are such that on
top gear the engine must turn at 500
revolutions per minute 20 drive the
car at 15 miles per hour, also that, to
attain h same speed on third gear,
the engine must be turning at 1900
revolutions per minutes We will as
sumo that. the operation of changing
gear Is carried out quickly, so that
there Is no appreciable variation from
ID miles per hour on the part OF the
car. The third speed Is engaged, the
engine and clutch shaft are running at
1.2O0 revolutions per minute and the
driver Is about to charge to fourth
e First he disengages his clutch:
II ne releases the acceierator at the
same time, as he should DO, the engine
VIII slow UP, and with II the driving
part or the clutch. The point that
most people do not realize is that the
driven part or the clutch Is still rota-
ting at exactly the same speed, 1900
revolutions per minute: the only diff
ference Is that the car, Is driving the
clutch instead of the clutch driving the
car The next step is to slip the gear
lever to neutral" and ii is mot until
this Is done that the clutch shaft will
begin to slow up. .M
We have already seen that, for Is
miles per hour on top speed, the engine.
ana consequently the clutch, must be
turning at 500 revolutions per minute.
Clearly, then. for a quiet change, the
operator must wait with his lever In
neutral until experience tells him that
the clutch has had true to slow down
from I,200 revolutions per minute to
500 revolutions per minute; the lever
- then moved noiselessly to top speed
and the clutch pedal lre-engaged. The.
reason for many noisy changes of speed
Is that drivers. knowing a certain in-
teryal must elapse 20 allow the driven
clutch member to slow down, Judge this
interval from the moment OF disengag-
Ing THE clutch. This, OF course. Is quite
wrong; as Just explained, the driven
portion OF the clutch goes on running
at exactly the same pace until the gear
lever is brought to neutral and the
interval found by experience to be
necessary before the top speed can be
engaged must be counted from the mo-
ment of coming into neutral, not with
reference 70 disengaging the clutch. In
practice, or course, the problem Is.
slightly complicated by the fact that
the car will slow up to a small extent
while the ~changesis being effected. In
other words. 1t may haye dropped from
is to IA miles per hour by the time the
fourth speed Ia engaged; consequently,
the driven member of the clutch will
have to slow down to d little under,
800 revolutions per minute to effect a.
quiet change.
The actual time taken varies with
every car. IL the clutch be heavy II
will take a long time to slow UP. and
a very perceptibfe pause will be re-.
CURED In passing from third to top.
speed. On the other hand, q very light
clutch, or the use OF very thick lubri-
cant In the gear box, may cause the
clutch to slow up very rapidly. so that
the gear lever must be pulled quickly
through from one speed to the other to
effect a quiet change. The adjustment
OF the clutch stop further complexities
matters. IL Ii be set up too tight, SO
that Ii begins to hold the driven mems
Der of the clutch beforetit Is sfullyNdts-
engaged from the driving member, 1t
may be stopped so suddenly that q
quiet change is Impossible, even IL the
lever be snatched through from M
gear to the other as rapidly as possible
The clutch stop should be set 50 that
there is an ample period between the
freeing OF the clutch from the engine
and the commencement Of engagement
OF the stop. The driver. then has the
clutch properly under control. II, on
0lIktLl1N CPL y Wv ~ 80 AAASF
the interval between the gears, for q
quiet change. Is unduly long, he can
correct II by depressing the pedal to
q greater, ext Vt, thus slowing the
driven portion, OF the clutch by aid of
the clutch stop. Exactly the same
principles apply in changing from
'.irst's to second" or second TO
'third," except that In the latter case
the lever usually a to pass through
the gate" This occupies a little long
err. SO that the clutch has more time
to slow up: consequently there will be
less need TO use the clutch stop.
So far, we have only considered
changing from a low gear to o higher
one. but IL the principles involved are
| thoroughly understood, changing down
will present no great difficulty. Sup
pose. now, the car be travelling at 10
niles per hour on top gear the engine
turning at 500 revolutions per minute.
and that II is desired to change to uhlrd
speed. Assuming, as before, the car
continues TO travel at Is miles per hour,
IL Is clear that the clutch nus be
| speeded up to 1900 revolutions per min
ute. Clearly, At Is impossible to change
quitely by simply pushing the Yer
Through from fourth" to third. If
the clutch be fully disengaged, 1t viii
! be travelling at less than 800 reyolu-
lions per minute by the time h third
speed gears come into mesh, which they
will do with a great deal Of grind
srba common nrocadura 40 m disen-