Pierre weekly free press. (Pierre, S.D.) 1889-19??, 1913-05-15
GEAR CHANGING / ! 7 ART
THAT REQUIRES STUDY

Care d Required to Attain
Quietness and Is One Of the
Fine Points.
There Ii no greater difficulty con-
fronting the average amateur driver
be possessed Of ample theoretical
knowledge of motors, and OF an en-
tirely adequate practical ability to
keep car in good running order, and
yet be classed by ones friends as
bad driver simply through inability to
change gear quietly, says q writer in
Country Life. There are many men
who may claim an accurate judgment
of speed and distance, q delicate touch
on accelerator and steering wheel and
the ability to anticipate and correct
side slip. but who are yet rough and
unpleasant drivers through unskillful
handling of the gear lever.
1t is frequently said that on some
particular car it is difficult to- change
speed. and in the case of few old
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
clutch stop or In the hands OF the
driver. Whichever OF these latter ex-
plantations be the true one, the remedy
lies in a thorough understanding If
what happens to the car mechanism
when change Of speed is effected.
1t is common knowledge that for q
given speed of the car the engine must
be turning faster when on a low gear
than on the next higher one. A fact
that IL not so generally realized is that,
Tor quiet change of gear, the driven
member of the clutch must be revol-
wing at exactly the same speed as IL
the gear to be engaged were already
IN mesh. Suppose, for example, that
car Is travelling at Is miles per hour
that the third speed Is engaged and
that 1T Is desired to engage the fourth
speed. 1t may further be assumed
that the gear ratios are such that ION
top gear the engine must turn at 800
revolutions per minute 60 drive the
car at 15 miles per hour. also that, to
attain the same speed on third gear,
the engine must be turning att 200
revolutions per minute. We will as
sumo that the operation Of changing
gear 10 carried out quickly, so that
lnere IS no appreciate variation from
10 miles per hour on the part of the
car. The third speed Is engaged, the
engine and clutch shaft are running at
i,zO0 revolutions per minute and thu.
oriver IS about to- change to fourth
gear. First he dtsengages his clutch:
n ne releases the accelerator at the
same time. as he should do, the engine
Will slow up, and with 1t the driving
part OF the clutch. The point that
most people do not realize is that the
driven driven part OF the clutch is still rota-
ing az 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 1t is not until
ms 10 done that the clutch shaft viii
Degin to SLOW up.
we nave already seen that, for Is
niles per hour on top speed, the engine.
ana consequently the clutch mnst he
turning at 500 revolutions per minute.
Ciearly. then, for quiet Change. the
operator must wait with his lever in
the clutch has had time to slow down
from l.20O revolutions per minute to.
oOO revolutions per minute; the lever
ls then moved noiselessly to top speed,
and the clutch pedal re-engaged. The
reason Tor many noisy changes OF speed
IS that drivers. knowing a certain in
terval 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 runnint.
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 to disengaging the clutch In
practice, OF course, the problem is
slightly complicated by the fact that
the car Will slow up to a small extent
while the change is being erected In
other words. it may have dropped from
70 to - miles per hour by the time the
fourth speed is engaged: consequently,
the driven member of the clutch will
have to slow down to a little under
800 revolutions per minute to effect a
quiet change.
The actual time taken varies with
every car. II the clutch be heavy it
| VIII take long time to slow up, and
sa very perceptible pause will be re-
4 CURED in passing from third to top
| speed. On the other hand, very light
clutch. or the use OF very thick lubril
Iscant In the gear box. may cause the
Iclutch to slow up very rapidly, so that
the gear lever must be pulled quickly
through from one speed to the other to
effect quiet change. The adjustment
OF the clutch stop further compile
matters. Il II be set up too tight. SO
that II begins to hold hesdriven mem
Der Of the clutch before 1t is fully dis
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 one
| gear; to the other as rapidly as possible,
The clutch stop should be set SO that
| there is an ample period between the
| freeing OF the clutch from the engine
i and the commencement Of engagement
/ Of the stop. The driver then has the
clutch properly under control. II. on
slightly depressing the pedal. he finds
the interval between the gears. for q
quiet change. IL unduly long, he can
correct 1t BY depressing the pedal to
! greater extent. thus slowing the
driven portion of the clutch by aid of
the clutch stop. Exactly the same
principles apply Ia changing from
s.first'.S TO second or second" to
..third.s except that in the latter case
the lever usually has TO pass through
/ the gate !. This occupies q little long
81. % that the clutch has more time
u slow up; conseQuen there Will be
less need 70 us the clutch nt0p.
So Tar, We q have only corsidered
chansing from 8 low gear to q higher
ono. but X the principles involved are
i xh0r0uehly underatood, changing down
VIII present no great difficulty. Sup