AN IMPROVE- MENT IN PROJECTILES
Year: 1863

page_text: PROVISIONAL SPECIFICATION left by Henry Hennessy at the Office of
the Commissioners of Patents, with bis Petition, on the 20th October
.1863.
1, HENRY HENNESSY, of Wynnefield, Charleville Road, in the County of
Dublin, do hereby declare the nature of the said Invention for "AN IMPROVE-
MENT IN PROJECTILES," to be as follows:-
The base of the improved projectile contains a depression shaped so as to
admit of the keying in of a disk or flange in such a way that when the disk
twists around an axis parallel to the axis of flight of the projectile, it will fit
tightly in one direction, while it will become loose when the disk twists in the
opposite direction. Forming one solid piece with the disk, an archimedean
screw of two or more blades projects in such a position that an impulse which
would tend to drive the projectile out of the gun would also firmly key the
disk into the posterior depression of the projectile, and consequently produce
a rotation of the whole mass. When the impulse ceases on the emergence of
the projectile from the muzzle of the gun, and when the projectile passes into
a resisting medium, the lateral resistance of the medium will tend to reverse
the rotation of the screw relatively to the projectile. Thus the disk would be
unkeyed, and together with the screw become detached from the projectile.
The loosening of the disk is facilitated by the peculiar shape of the posterior
depression in the projectile, and partly by the interposition between the said
surface and the disk of a soft elastic substance, or of an unguent of suitable
composition. All attempts hitherto made to apply screws to projectiles with

page_text: a view to cause rotation have failed, because the screw neutralized after
leaving the gun whatever rotatory motion it had impressed on the projectile
while in the gun.
By the Invention which I now describe I claim to destroy all connexion
between the projectile and the screw immediately after the latter has had
performed its work of causing the projectile to rotate.
I also contemplate the following methods of effecting or facilitating the
same substantive result.
First; by the insertion of a spring within the body of the disk, the foot of
which spring should press against the base of the projectile, and before the
firing of the gun would keep the disk back from the depression in the projec-
tile already described. The explosion would compress the disk upon the
spring, and would allow the said disk to become firmly keyed into the depres-
sion at the base of the projectile, as already specified. The cessation of the
compressing force on the emergence of the projectile from the gun would
allow the spring to expand, whereby the surface of the disk would be again.
separated from the projectile.
Secondly, when the improved projectile should be employed with a breech-
loading gun, the disk and screw might be perforated so as to admit of the
insertion of a pivot passing through the axis of the screw, about which it could
freely revolve without slipping. To the end of the said pivot farthest from the
projectile a slender chain should be fixed. In loading the gun the chain should
be coiled around the firing charge, and then its end firmly fixed by a swivel to
the back of the breech of the gun. By this arrangement the chain could not
sensibly impede the motions of the projectile, while it would assist in detaching
the disk and screw immediately after their emergence from the gun.