The sun., 1919-04-06

wheels equipped with 81 inch tires and
with reduction at the rear axle of AZ
to !. With 81 inch tires the car will
travel Forward approximately nine feet
with each revolution. IL tho car Is be-
ing driven on high speed gear. for each
nine feet OF travel on the ground the
engine shaft will make four and one
half revolutions. and as there are two
power impulses to each shaft revolution
of n four cylinder engine, there will be
nine power impulses, or one per foot.
Changing to tho intermediate speed
gear and assuming that It's reduction II
is to /, In addition TO the AZ reduc-
tion at the differential. a total OF 81,
there will be sixteen power impulses for
each nine feet of travel, or nearly two
per foot. This should make It clear
that by shifting the gears and increas-
ing the number Of power impulses we
have nearly doubled the pulling force
exerted.
On the low speed gear. with reduo-
ton ratio OF SO and the AZ reduction of
the rear axle, O total ratio Of IAN to !
is obtained, which gives 20 power I'm
pulses for each feet, or more than 9
per foot.
with ~ cylinder motor there are six
power impulses for each revolution Of
the crank shaft. and with 80 inch tires
there would be approximately on feet
of travel per revolution. With ~
ratio on the differential, 'on high speed
gear we would get 81 power impulses
for 91t feet of travel, or about per
foot; on intermediate speed gear there
would be IS power impulses. or per
foot. and on low speed gear 81 power
Impulses or 10 per foot. This does not
necessarily mean that a IL cylinder mo-
tor Is more powerful than q cylinder |;
that depends on other things, and the
IL explosions might develop much less
power than the four. But the COMPARE
tive pulling power of the several gears
is the same, no matter how many cylin-
ders there are
It should be plain from this that in
climbing a hill where the grade IL 30
steep that the motor cannot make II on
high speed gear with one power impulse
per foot of travel. II is possible to change
to intermediate and procure two power
impulses, or TO low speed and get three.
Grades usually are eYefestiInated. We
often hear persons speak of 80 per cent.
grade, when It Is doubtful II they ever
have seen a road with that grade-15
per cent seems to be about the limit
hereabout The reason for overestimat-
ing hills is that IN looking UP q grade
the distance appears to be much less
than It Is really; we seem to zee . great
rise in short distance and OF course
conceive of a steep grade. II the eye
properly Judged distance with height we
would know that perhaps It was but a
gentle slope.
When going down one grade and
about to start up another. invariably
the one ahead seems to be very steep.
because here we have even a greater
angle of observation. 1t Is like estimating
the height of waves at sea. The unac-
customed eye, when the ships bow goes
over the crest of a wave, sees the mast
tops apparently on level with the next
wave. and at once calls the wave 100
feet high, because It Is compared with
the height Of the mast. The angle of
the mast was wholly neglected.
Sometimes when touring the motor
appears to be pulling finely on an appar-
emily steep hill. while at other times the
opposite Is true and the motor labors on
what we think a slight rise. The rea-
son lies in wrong estimate IN each case.
The eye has led us to jump at a conclu-
sion by observing the grade at wrong
angle.
To test out MY eye as to grades have
been measuring some of them recently,
with the following result:
West Drive in Central Park. just be-
low 10th street, going north. f1s per
cent: going south, 8 " per cent.
Viaduct on 155th street, west OF Cen
trail Bridge, is 5h per cent, while the
slight hill at the west end OF the via
duct is 10 per cent
The we'll known Fort George hill the