48. These, like the vertical wheels, may be made of almost any shape or
design. They have a hole bored in the exact centre of their nave, and up
this hole the spindle passes on which they revolve.
The annexed fig. 68 gives you one of the simplest forms of the
horizontal wheel. A wheel made according to this plan will require four
wheel-cases and a case of Chinese fire long enough to last during the
combustion of two of the wheel-cases. The quick-match is put to it in
the following manner:—Simply connect the first and second wheel-cases by
carrying a quick-match from the tail of the first to the mouth of the
second. Then from the tail of the second carry two “leaders” (as these
pieces of quick-match are called), one to the third wheel-case and the
other to the perpendicular case of Chinese fire, which will thus be
ignited at the same moment with the third wheel-case; and to complete
the wheel carry a leader from the tail of the third to the mouth of the
fourth case.
[Illustration:
Fig. 68.
]
The case of Chinese fire which I should recommend you to make for this
and for other horizontal wheels is one of the 2-oz. size, nine or ten
inches in length, and filled with composition No. 4, given in paragraph
41. It is to be affixed to the wheel thus:—There must be a small
projecting piece of wood left by the turner at the top of the nave of
the wheel, about an inch in height and five-eighths of an inch in
diameter, and if an inch of the case be left unoccupied by the
composition at its unchoked end, this end can be squeezed over the
wooden point mentioned above, or can be glued on to it if you think it
desirable.
Another and very amusing variety of the horizontal wheel is that which
my next illustration represents, and which is sometimes called the
“capricious” wheel. This carries six wheel-cases and one Chinese fire
case. The wheel-cases are arranged in the following manner:—All the
cases are placed at an angle with the plane of the wheel’s revolution;
the three upper ones have their mouths inclined upwards, the three lower
ones downwards. Care of course must be taken that all the mouths,
whether inclining upwards or downwards, be turned _in the same
direction_. They are connected thus:—Make one of the lower cases the
first to be fired; from the tail of this carry a leader to the nearest
of the upper cases, which will then burn second; from the second carry a
leader to another of the lower cases; then from this to another of the
upper ones. From this fourth case carry three leaders—one to the
remaining upper case, one to the remaining lower case, and one to the
case of Chinese fire.
[Illustration:
Fig. 69.
]
The effect of this wheel is exceedingly laughable. It does not revolve
so rapidly as the simple horizontal wheel mentioned above, the cases of
which are perfectly horizontal. The impression that its performance
always gives one is, that it is determined to do something violent: that
if one direction of fire will not answer it will try another. Each
succeeding case sends it round more rapidly than the last, on account of
the decreasing weight as the cases burn out; and if the two cases which
are to burn with the case of Chinese fire be filled with composition No.
1, given in paragraph 44, the fury of the wheel will at the last seem to
know no bounds.
It is necessary, however, to see that the hole into which the iron
spindle is to pass is truly bored and is long enough, and that the
spindle _at the top_ of the post is straight and strong. This spindle
should pass into the nave of the wheel five inches at least.
Let me press upon you one or two important hints. _The case, or cases,
that burn last on each wheel must always have their ends closed with
clay, or some incombustible substance._ If this advice be neglected your
wheel is pretty certain to fail.
I have drawn at fig. 70, a fac-simile of the spindle which I use for all
vertical wheels. It is made to screw into an iron which is represented
at fig. 71, which iron is fixed by screws to my post in the manner shown
at fig. 72. The post I employ stands about ten feet out of the ground.
Into its top is driven another spindle, on which my horizontal wheels
turn. Both these iron spindles should be made of quarter inch iron rod.
You will find the spindle drawn at fig. 70 very much more convenient
than one simply driven into the post, and having a “nut” at its end to
screw and unscrew; for it is more than probable that on a dark night,
when you are taking down one wheel that has been fired, and putting up
another, you will drop the “nut,” and feel considerably at a loss
without it. And besides this, you can by this means always remove the
spindle, and protect it from rust. Your post should be very steady.
Mr. Darby will supply you with any frameworks of wheels, made to any
pattern that you please.
I shall speak of some other wheels when we are sufficiently advanced in
pyrotechnic proficiency to be able to attempt the manufacture of _all_
their component parts.