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Chapter XX
THE CONSTRUCTION OF THE CROSSBOW (Continued)
THE REVOLVING NUT AND ITS SOCKET
FIG.
48.-SIDE (I), FRONT (II), AND PERSPECTIVE (III), OF THE CIRCULAR
STEEL, OR IVORY NUT WHICH HOLDS THE BOWSTRING WHEN THE BOW IS BENT.
Half full size.
THE
notch A, in the nut, is exactly below - i.e. opposite to - the
curved fingers which hold the bow-string.
The notch is 1/2 in.
wide, ans 1/8 in. deep on its squared face where it engages the point
of the trigger inside the stock.
FIG.
49.-SIDE (I), END (II), AND SURFACE VIEW (III), OF THE METAL SOCKET
IN WHICH THE NUT REVOLVES. Half full size.
The longditudinal
opening B (1/2 in. wide), is cut through the under side of the
socket, to allow the point of the trigger to reach, and then engage
in the notch in the nut, as shown in fig. 55, p.98.
The nut and
its socket should be of steel, and turned in a lathe to fit each
other exactly, so that the nut ma revolve accurately and closely in
its socket. The nut is 1 1/2 in. diameter and 1 1/4 in. thick.
In
outline the nut is, of course, a circle. The socket in which it
revolves, is 1/4 in. more than a half circle, so as to bring the
centre-hole of the nut 1/4 in. below the surface of the socket, and
also of the stock of the crossbow,1 as
shown in fig. 50.
FIG. 50.-SIDE AND SURFACE VIEW OF THE REVOLVING NUT IN ITS SOCKET. Half full size.
The
pin (1/8 in. diameter) which passes through the 3/16 in. hole in the
centre of the nut, and also through the lock-plates, is merely
intended, without receiving any pressure, to hold the nut in its
position in the socket.
The socket should take all the pressure of
the nut when the bow-string is stretched over the fingers of the
latter, and for this reason the pin is slightly smaller than the hole
in the centre of the nut. If any strain came upon the pin which
passes through the nut, it would bend and the nut would not then
revolve.
In many mediaeval crossbows, the pin through the
nut was omitted, though sometimes present in the form of a thin
length of catgut passed several times through the hole in the nut,
and then round the socket, just to prevent the nut from falling out
of its socket and being lost, fig. 51.
FIG. 51-A NUT SECURED BY CATGUT
More
often, however, the nut being only of horn, was not weakened by
having a hole bored through its centre, but was held in its socket by
two little screw-pins, one through each lock-plate, neither of which
pins penetrated the opposite centres of the nut more than 1/4 in.,
fig. 52.
FIG.
52-THE HORN NUT OF THE MEDIAEVAL CROSSBOW AND ITS STEEL WEDGE. Half
full size.
The nut and its socket were formerly
both made of horn.2
The nut was usually cut from the crown of a stag's antlers. This was
a very tough material for the purpose, and also one that was light,
and therefore free and quick in use and loose as applied to its
connection with the bow-string. In Scandinavia, however, walrus tusk
was commonly used for the nut of a crossbow.
The horn nut always
had its notch protected by a small wedge of hardened steel, which met
the point of the trigger inside the stock. Fig 52 shows this kind of
nut, and A, B, the front and side view of its steel wedge separate
from it.
FIG.
53.- SIDE AND SURFACE VIEW OF THE STOCK OF THE CROSSBOW, WITH THE NUT
AND ITS SOCKET IN POSITION. Scale 1/8 in. = 1 in.
The
centre hole of the nut is 14 in. from the upper point of the fore-end
of the stock. (D-C, fig. 46, p.92.)
1. This
prevents the pin which passes through the nut from being too near the
upper edge of the stock. It also gives the revolving nut more 'centre
bearing' against its socket to withstand the strain of the
bow-string.
2. Steel nuts and sockets were not generally fitted to
crossbows till about 1640-1650.
| Chapter XX | The Construction Of The Crossbow (Continued) The revolving nut and its socket |
| Chapter XLIX | The Chinese Repeating Crossbow |
| Chapter LIV | The Distances to which Ancient Siege Engines cast their Projectiles |
| Chapter LV | The Catapult, its Construction and Management |
| Chapter LVI | The Catapult, its Construction and Management (Continued) |
| Chapter LVII | The Balista, its Construction and Management |
| Chapter LVIII | The Trebuchet |
| Chapter LIX | The Spring Engine |
| Appendix | The Balista |
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