ANTI-VIBRATORS AND SPRING FORKS.
The abstract terms of the heading have, so far, generally been applied
to certain devices constituting an elastic connection between the
standards of the wheels (1), or, more precisely, between the front
fork and backbone. The more recent forms of anti-vibrators are (2)
the spring hinge about midway in the rear frame, or backbone, of the
machine; (3) the spring joints at the extremity of the front fork
connecting with the forward wheel axle; (4) the spring fork proper,
in which the extensions are either wholly or in part elastic. The
last two are, to my mind, the most deserving of praise. In the first
named above, the shock is mainly confined to the front half of the
machine,—that is, to the front wheel, its fork, and handle-bar,—while
in the last two the front wheel alone receives the concussion to
the full extent, an intervening spring preventing the transmission
of the shock to other parts of the system. When it comes to be
fully appreciated by the fraternity that the shock sustained by the
machine and rider is not only to be treated as a matter of comfort
or discomfort, but that it has other very important claims to our
consideration, we may expect it to be more fully discussed. Not that
we care so much about the vibration loosening every joint, screw, and
pin in the entire contrivance, which makes it worn out, so called,
when it has scarcely begun to wear,—of course, in the general march of
progress, we expect to remedy that also,—but it is the momentum we are
most after. The writer has always been one who has had a constitutional
aversion to working up a speed and then having it all knocked out by a
stray stone.
[Illustration: Recent American anti-vibrator.]
The difficulty experienced by inventors in the line of anti-vibrators
appears to be, that while acquiring the desired elasticity in the
proper direction an elasticity in other directions has followed,
making the machine feel unsteady and capricious, especially in the
steering. This undoubtedly valid difficulty in the way is worthy of
careful consideration before accepting an anti-vibrator; in fact, the
very end desired can easily be missed in an imperfect device, as it
might, while holding momentum in one direction, lose it in another. I
cannot better express my opinion as to the general requirement of a
good anti-vibrator than to say, get plenty of spring, but acting in the
plane of momentum and gravity, and get it as quickly as possible; that
is, at the connection of the wheels with the forks, or at the outer
end of the spokes if it can be done without interfering with the rigid
transmission of power to the driving-rim.
It is always difficult to apply any attachment to the driving-wheel
of a machine; in the Ordinary it would be beneficial to attach an
anti-vibrator to the forward wheel, but as a matter of construction it
would be about as difficult to do this as it would be to attach it to
the rear wheel of the Safety.
We hope to see and may expect a number of devices to be offered by
makers which will fulfil all requirements. Appended find a cut of one
recently patented, of which I can speak with some confidence from
having used a similar contrivance in experiments in this connection.
The figure here, as in the patent, shows the connecting-rod swinging
through an almost useless arc of action, but the general plan is good;
not, however, as neat as some others.
A great maker has of late, however, adopted a device which, to my
mind, does _not_ fulfil all of the requirements; it is still confined
too much to a vertical action, and has really no horizontal amplitude
unless the machine is ridden by a very heavy man, in which case the
spring will assume a very abnormal position.
Other makers have adopted the joint to the centre of the frame or
backbone of the Safety type (No. 2 above), so constructed that the
pedals are also provided with a vertical motion; this certainly
helps to isolate the man from vertical concussion, and it is good;
yet the horizontal give is lacking in these machines, and the front
fork, together with the handle-bar, still receives a shock and loses
in vibration. Later, an inventor has shown a new pedal in which,
apparently, the rubber works upon a spring and has a vertical motion
under the pressure of the foot. This is a deserving though a misguided
effort. The connection of the man with the apparatus through which the
power is transmitted to the machine should be as direct and rigid as
possible: all springs should be beyond this point. An elastic pedal
is quite a different device from that named in the last preceding
paragraph, in which the crank-shaft has a vertical motion and the
“connecting-link,” together with the source of power (the man), are all
rigidly and inelastically connected together, the whole, as a system,
swinging vertically by a spring.
An English firm has for several years had upon the market a machine
which, from its external appearance, is all springs; the inventor
thereof deserves greater credit than the success of the venture has
awarded him. If in the early samples put upon the market the parts had
not been so frail and the appearance so exceedingly homely, he might
have fared better.
Several premature freaks of advancement in this matter of springs have
occurred, but the general progress has been quite logical. First, we
had the saddle provided with a very feeble amount of elasticity, then
an increased amount, until makers vied with each other in producing the
best spring for the old Ordinary; then we had the spring connection
between the front fork and backbone in the Safety, confining the shock
to the forward half of the machine; and then came the spring fork
isolating the entire system except the front wheel from the shock. So
far the inventions have been practical and are in use. Next we have a
worthy, but I fear impractical, inventor, who proposes springs between
two outer rims of the wheel or substantially at the ends of the spokes,
thereby confining the concussion to one rim of the front wheel in the
manner shown in cut. (See English spring rim.)
This appeared to be the ultimatum, but a shrewd American inventor has
“gone him one better” and proposes to confine the shock and vertical
thrust to a mere part of the rim. This invention was patented in the
United States in 1889, and, if practical, would simply cause the
wheel to roll over the obstruction almost as a man would step over in
walking,—an ideal state of affairs, to be sure! Such a wheel would not
only aid man in his transmigration over smooth roads, as claimed for
the solid wheel in the fore part of this book, but would be available
on the cross-ties of the poorly-ballasted railroad; and let the wheel
be but tall enough, and he may yet go over that old-time impediment to
cross-country locomotion, the rail fence, as unwittingly as though it
had not been there at all.
[Illustration: English spring rim.]
[Illustration: American patent flexible rim.]
One of the grandest ideas in the way of anti-vibration is suggested by
the following from the _American Athlete_:
“An inventor of Belfast, Ireland, has made what he calls a
‘Pneumatic Safety,’ the tires of which are two inches in diameter,
and of _hollow_ rubber, so that they contain air, which vastly
increases their elasticity. The result is most favorably regarded
by Irish wheelmen, and at the recent races at Belfast a rider on a
‘Pneumatic’ won all the four first prizes, the hollow rubber being
described as phenomenally successful on the rough grass track.”
If the liability of cutting and collapsing were not so apparent in this
device, I would be inclined to think it would have a great future.
By way of conclusion of the foregoing chapters on curves, momentum,
and springs, permit me to again call attention to the remarkable fact
that a rear-driving Safety of absolutely rigid construction, striking
an obstacle four inches high, loses one-half of its entire momentum and
that of the rider. Think of it! Not that we often strike a four-inch
obstruction, but that it does not take very many smaller to make one.
Thus we are continually wasting strength when there is really no
substantial necessity or occasion for it, and the writer, for one,
feels ready to maintain that even double the weight (harmful as extra
weight always is) in a machine is justifiable if in so increasing the
weight we can do away with this most potent source of loss of energy.
The bicycle, or single-track machine, too, affords an unusual chance
for proper manipulation of momentum, and the rear-driver a special
opportunity for the attachment of proper springs. In a two-track
machine, on the other hand, we are compelled to supply springs with
lateral motion as a necessary appliance for the comfort of the rider,
which lateral motion results in loss of momentum and kinetic energy,
whereas in the bicycle our comfort and energy are all confined to one
plane; so that all we want now is to have our springs adroitly and
amply applied to operate in this plane and no other, and we shall then
find that we invariably save our momentum, preserve our comfort, and
retain our strength. It will be a long time before we can expect to
realize our dream of perfection in easy riding, or to find cyclers
hunting for the rough roads; nor do we expect to see them peering
eagerly forward through the misty morning, greeting the dawning
obstacle as glad tidings of “Land ho!” but we do expect very soon to
see the discomfort and loss of power now encountered in a great measure
overcome. If some one will only get us over the sandy places as nicely
as we can reasonably expect, in the future, to glide over the rough
places, then we will all be happy.