The silver messenger. (Challis, Idaho) 1890-1912, 1902-06-03

The bicycle loop presents a most
interesting demonstration of a great
scientific principle, which plays its
part in preventing the earth from
dropping into the sun. and the moon
from being precipitated upon the
earth, no less than in keeping the
rider and his wheel from falling to
the ground when he hangs, head
downward, In midair, at the top of
the loop.
centrifugal force Is the agent con-
cerned in this seemingly miraculous
Feat, force that has many appliances
In everyday life, some of which-like
the swinging of a bucketful of water
around the head without splitting
astonish the uninitiated, while Others
are so familiar that nobody stops to
mink OF them. But when applied in
the case now under consideration.
centrifugal force presents itself in
most sensational form.
Yet, thrilling though it is to watch
the bold rider defying gravitation.
like fly on the ceiling, without any
thing except his motion to hold him
IN place, the natural law that he
oDeys Is extremely simple and per-
fectly certain in It's operation. If he
observes all the requirements of that
law 1t will never fail him, so that
his safety depends. entirely upon him
self.
He must develop centrifugal force
great enough to counterbaIance his
weight when he is at the ton of the
circle. Mathematics, knowing the
size OF the loop, is able to tell him
how to develop the force needed. The
force depends upon the velocity with
which he moves. He acquires that
velocity, not by pedaling, but by rid
Ing down a steep slope. How high
must the starting point be? A gen
eral rule, applying to all such cases.
is that the elevation of the point from
which he starts must be to the eleya-
tion OF the top of the loop in a ratio
exceeding that of five to four.
The air resistance and the friction
must all be carefully allowed for,
and this Is the business of the engin-
eer who plans the apparatus. Accord
ingly, If the loop is twenty feet high.
the starting platform must be more
than twenty-five feet in height, and
the acquired velocity must exceed
that named above. OF course, the loop
may be less than twenty feet in height
and then all the other dimensions
will be proportionately reduced.
1t is probable that. in the actual
case considered, the velocity with
which the rider arrives at the bottom
OF the slope and begins the ascent of
the circular loop is at least thirty
miles an hour. This velocity immedi-
ately and rapidly falls off as he com
mences the ascent OF the steepening
curve, so that when he reaches the
top he is moving only fast enough to
impart a centrifugal force exceeding
his weight Tor the effect Of gravita-
tion) by margin sufficiently large to
insure his safety.
AS the bicycle strikes the curve az
the loop and begins to ascend. the
wheels are pressed against the track
l'-N-- SANAAShuOuS lOICb anu LOe rider /
Is pitching forward with an energy
which only practice and trained mus
cles can enable him to Withstand. Il
Is as II the weight of half dozen men
had suddenly been thrown upon him
and his machine. II we estimate the
actual weight of bicycle and rider at
zoo pounds, then it can be shown that
their combined weight, or rather their
pressure upon the track, owing to cen
trifugal force, becomes, as they begin
the ascent of the loop, more than q
thousand pounds; And this, too, at
the minimum speed theoretically re-
CURED to carry them around. In prac-
tice this pressure may be considerably
greater.
Here, then, would seem to be a point
Oh special danger. The rider must be
for this instantaneous in
crease Of virtual weight. He has to
keep his nerves steady and his head