47. Leaving now the triangular form of wheels, we will pass on to those
which are called _Vertical_. All triangle wheels are vertical wheels,
but all vertical wheels are not triangular; it is of non-triangular
vertical wheels that I am now about to speak. These are made with a
nave, spokes, and felloe in the same manner as a carriage wheel. The
cases may be fastened to the felloe, or the wheel may be made without a
felloe, and the cases fastened, in any way that occurs to you, to the
extremities of the spokes; either by nailing to their ends pieces of
wood at right angles with the spokes, or by cutting a groove in the end
of each spoke and tying a case into it with string. As long as the cases
be properly arranged and secured firmly to the framework it matters very
little which of the above plans is adopted. Select the plan which can
most easily be carried out by the means that you have at command, and
carry it out in the simplest possible way. Complications are not only
unnecessary, but very likely to deprive your pieces of what would
otherwise have been their complete success. The accompanying sketch
(fig. 66) gives you a representation of another arrangement of six
cases, which is, in my opinion, productive of a better effect than the
double triangle. The wheel here represented is vastly improved by the
addition of a coloured fire placed somewhere near its centre; but I have
not yet given any directions or instructions for the preparation of
colours for such a purpose, and the making of these additions must be
reserved for its proper place.
[Illustration:
Fig. 66.
]
But perhaps the most satisfactory arrangement of six cases on a vertical
wheel is that which the next sketch represents. By the plan adopted
there—_that of making the cases incline outwards_—a much larger circle
of fire is produced, and the general effect is considerably improved. It
will be perceived that the mode of “clothing,” and tying on the cases,
for all these different forms of wheels is the same, the only difference
being in the shape of the framework. The cases may be fired singly or
doubly in this wheel—that is, you may make them burn one at a time till
all are consumed by putting the quick-match to them just as my sketch
(fig. 67) represents, or you may connect with quick-match the first and
fourth cases, so that these take fire simultaneously. By this
arrangement the first and fourth cases will work together, the second
and fifth, and the third and sixth. Of course the first and fourth cases
are the only _pair_ that need be connected by quick-match, for they will
severally convey their fire to the second and fifth, and these to the
third and sixth. The framework of this wheel may be made of deal or
beech (the latter I should prefer) about three-eighths of an inch thick;
the wheel altogether should be from 15 to 18 inches in diameter. It
should by all means have some centre, like that described at fig. 60, to
secure its steady and true movement. This wheel also will be vastly
improved by the addition of a coloured fire to its centre.
[Illustration:
Fig. 67.
]