Los Angeles herald., 1909-12-19
THE VALUE OF LARGE WHEELS

The VALUE OF LARGE WHEELS
There can be no doubt, whatever,
considered from a mechanical point of
view, that the larger the wheel the bet
ter says Henry Sturmey in an Eng
lish magazine.
car will roll better run lighter,
ride easier, and be less subject to Sc
we're shocks. than when smaller
wheels are used. What really happens
in surmounting an obstable with a
driven wheel is, that, the power being
exerted at the center OF the hub, 1t
becomes equivalent to the work of lift
ing the weight over the obstacle by
means of a lever having the length OF
the spoke as one arm and the distance
from the top of the obstacle to the
point of ground contact as the other,
and 1t will take little perception to see
that, with a wheel GO inches in diam
eter we should have lever twice as
long with a 30-inch wheel on one arm,
and very little longer on the other, and
hence the leverage in favor of the
power applied will be very nearly dou-
bed. This means, of course, that, con-
Versely, little more than half the power
will be required to lift the weight over
the obstacle. Hence, 1t may be taken
that, with wheels of these respective
sizes. the power at present absorbed
in the work of forcing the car over
the road inequalities and out of the
road depressions-and which is going
on all the time on every journey and
Is greatest where the roads are rough
est-is reduced by nearly so per cent,
and although II Is hardly within the
realms of practical politics at the pres
ent moment to discuss wheels of such
a size as 60 inches by increasing our
wheel diameters over those employed
at present, we shall effect saving OF
power-and hence of gasoline-in exact
proportion to the increased sizes, so
that the 40-inch wheel of tomorrow, as
compared with the 30-inch wheel which
was universal but yesterday will give
us an increase of 3S1a per cent In our
leverage and a saving of 10 per cent
or IL per cent In the power required
to do equivalent work.
Then again we have the effect of the
comfort of the passengers, which Is
undoubtedly increased by the use of
larger wheels. This Improvement re-
suits from the weight of the car, when
lifted over an obstacle, being carried
through a wider arc; in other words,
the effect may be comparable to a diff
ference between ascending or descend
ing a steep staircase and ascending by
an easier one, or by an incline without
steps. When a wheel mounts an OBJ
Stacle, the incidence OF tne WelBHI upon
the periphery of the wheel Is trens'
ferred from the point of vertical con-
tact with the apex of the obst Gle,
and when, after passing over the latter,
the new point of vertical support
will be at the same distance from the
apex of the obstacle in front of 1t
as the original one was behind 1t, and
the distance between these two points
will, with the larger wheel, be greater
than with the smaller one. which
means that the weight is brought to
the ground at a less angle with the
larger wheel than with the smaller
one, and the shock of the impact will,
therefore, be proportionately less. The
time too, which is taken in raising the
weight over the obstacle from its origi-
nal to its new position will be increased
in proportion to the wheel diam eter.
and the effect of speed and angle of
incidence upon shock could. perhaps,
best be shown in a homely illustration,
by noting the difference of the effect
upon an aviator whose machine fails