The Saint Paul globe. (St. Paul, Minn.) 1896-1905, 1903-07-02

natural law that he obeyS is extremely
simple and perfectly certain in it's OPP
Grafton. If he observes all the require
ments of that law it will never fail
him. so that his safety depends entire
ly upon himself. He must develop a
centrifugal force great enough to coun-
terbalance his weight when he is at the
top of the circle. Mathematics, know
ing 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 riding
down a steep slope. How high must
the starting point be? A general rule,
applying to all such cases, is that the
elevation of the point from which he
starts must be to the elevation of the
top of the loop in the ratio exceeding
that of to 4.
To Overcome Gravitation.
Suppose that the actual loop is twen-
ty feet in diameter. Then from our
rule, it is evident that the starting
platform must be at a height of at
least twenty-five feet. In descending
vertical height of twenty-five feet
under the force of gravitation, and
neglecting all the effects of friction and
resistance of the air, the rider would
acquire a velocity of forty feet a sec
ond or more than twenty-seven miles
an hour. This would just suffice to
carry him around the loop, loss from
resistance and friction again being
neglected.
But in actual practice no loss can be
| I,
| friction must all be carefully allowed
for, and this is the business Of the en-
gineer who plans the apparatus. Ac-
cordingly 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 Immediately and rapidly
falls off as he commences 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 Cor the effect OF
| gravitation) by a margin sufficiently
large to insure his safety.
| Terrific Pressure on Him.
Next, let us put ourselves in imagina-
ton in the riders place and conside.
his situation with regard to the forces
| of which he has now become the play
| thing. AS the bicycle strikes the curve
| of the loop and begins to ascend, the
wheels are pressed against the track
| with tremendous force, and the rider is
! pitched forward with an energy which
only practice and trained muscles can
| enable him to Withstand. 1t is as if the
weight of half dozen men had sud-
denly been thrown upon him and his
] machine. If we estimate the actual
weight Of bicycle and rider at zoe
| pounds, then it can be shown that their
combined weight, or rather their pres
! sure upon the track owing to centrifu-
gal force, becomes, as they begin the
ascent of the loop, more than thou
sand pounds. And this, too, at the min
| imum speed theoretically required te
carry them around. In practice this
/ pressure may be considerably greater
Here, then, would seem to be point OF
special danger. The rider must be pre-
pared for this instantaneous increase
of virtual weight. He has to keep his
nerves steady and his head clear, and