Concussion fuzes and spherical shells

Concussion fuzes and spherical shells
Early use in the French navy. Dr BALLIET J.M. – 2004 - rev. 2013
The cannon ball was the primary projectile in the navy even if the spherical explosive shell was used in all types of cannons in the 1830s French navy. A classical time-delayed wooden fuze was used.
In 1837-1938, the French navy artillery commission (Commission de Gâvre) made some tests to establish the combustion delay in the wooden fuzes. A "Canon-obusier de 30" of Paixhan's design was used for the trials. The conclusion were quite appealing: irregular and inconsistent function. At that stage, these wooden fuzes were thought to be pretty ineffective against ships and since several years, it was given thought to an concussion fuzed [spherical] shell. But the solution wasn't at hand: the impact did occur on any place of the projectile.
The colonel Jure, belonging to the French marine artillery, made some studies on this case for ten years and, in 1834, his fuze system was adopted by the French navy. It used an iron stem, which under the shock came to strike a starter. Even if theoretically the fuze had to be effective at any point of impact, the author had given some thought as to maximize the chance of impacting on the fuze head: an iron rope was attached to the spherical projectile! The results were rather hazardous: premature explosion in the cannon bore, lack of reliability on impact... Promptly some studies were conducted in view to overcome the shortcomings.
These improvements weren't made by the author but y a member of the 1833's artillery commission, the lieutenant Billette. Soon adopted under the name "Projectile Billette" a used a principle so secret that even the French navy, which adopted the projectile didn't know how the shell and fuzes were fabricated and it's exact effectiveness!
Fig. 1 Lieutenant Billette’s impact fuze
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