Armstrong Percussion Fuse.
The Armstrong time-fuse is made of gun-metal. A ring of fuse composition similar to that of the old Bormann fuse is pressed in a channel whose outer wall is marked in inches and tenths. This fuse composition is covered by a movable collar which is kept in place by a nut. Attached to this movable collar is a small chamber containing a detonator. When the gun is fired, this detonator ignites the composition at the point at which it is set, and the flame travels around until it meets the magazine, or blowing-chamber, which communicates the flame to the shell-charge.
The Pettman percussion fuse is made up of seven principal parts—the body, top plug, steady plug, detonating ball, cone plug, lead cap, and bottom plug. The top and bottom plugs are set fast; the shock of firing sets back all the other parts, crushing the lead cap over the cone and bottom plugs, which by their shape are all held fast when jammed together. The detonating ball, whose surface is covered with a detonating composition, is carried straight back and prevented from coming in contact with the sides of the chamber by the steady plug. When the projectile strikes, however, the steady plug starts forward and releases the ball, which, coming in contact with the sides of the fuse, explodes the detonating powder and the flame is carried by holes through the lower plugs to the charge.
Pettman Percussion Fuse.
Laboratory Percussion Fuse.
PRIMERS.
