Fuzes Classification.

Fuses are classified as:

(a) Percussion if it acts on impact, producing a low order of explosion.

(b) Time when it acts in the air at a certain point of the trajectory.

(d) Detonating when it contains a fulminate which will bring about detonation upon impact.

The detonator may be separate or incorporated in the fuse. For the 75-mm gun and the 155-mm howitzer it forms a part of the fuze.

Many fuzes are armed on set-back. An exception to this is the long detonating fuse, MK 111, which is armed by the unrolling of a brass spiral holding together two half rings made of steel so fitted as to prevent the anvil and the head of the fuse from getting close together. The spiral unrolls when the rotational velocity of the projectile reaches a certain speed, thus drawing away the two steel rings and arming the fuse.

DETONATING FUZE—MARK-III.

DETONATING FUZE—MARK-V.

It is of great importance that the spiral spring be not unrolled during transportation or storage. This is prevented by winding a tape of tarred canvas around the spirals, the head being covered by a thin band of tinfoil. Just before loading the projectile the head and tape are removed by pulling the free end of the tape.

The following precautions concerning fuses must be rigidly observed to prevent grave accidents:

1. All detonators and detonating point fuses must be fitted with a felt washer underneath, thus insuring proper seating in the central tube.

2. Never disassemble a fuse by unscrewing.

3. Any fuse, the parts of which have become accidentally unscrewed, must be destroyed at once. If fired it may cause a premature burst; if handled a grave accident may result.

4. Any fuse or projectile which has been fired is dangerous, because it may then be able to detonate by a very slight shock. It is forbidden to touch it.

5. Never remove the tin hood from the long fuse before having screwed the fuse in the central tube.

6. After having removed the tin hood, be sure that the spiral is in its proper position. Never use a long fuse without the spiral.

7. Be sure the men understand that this spiral must not be removed. It has happened that men have removed this spiral, thinking that it was a device similar to the safety ring in trench mortar fuzes, MK VII E.

8. See that the ring of the long fuze which connects the powder train to the fuze body cannot be unscrewed. If it can be unscrewed the fuze should be sent back to the depot.

9. If it is necessary to remove a shell with a long fuze by means of the rammer, be sure to have a special rammer cup in the shape of a hollow cylinder of wood which will fit between the shell and the rammer.

10. Time and combination fuzes cannot be made absolutely water-tight; the cover must therefore not be removed until the projectile is about to be loaded.