Time and percussion fuze for Schneider 75mm field guns

 

 

Schneider time & percussion fuze. It was composed by : body (1), core (3), time fuze mechanism (7), top composition ring (9), bottom composition ring (2), cover (5), screw (19) and percussion fuze mechanism (15).

 

The body (1) was made of aluminium and had a stem screwed into the shrapnel head. The upper part of the stem was cylindrical in shape and supported the two rings of the time mechanism, the bottom of them being attached on a slot (20) of the stem cap. The interior of the stem was bored and threaded to receive the core (3) of the fuze. The magazine (21) at the bottom of the core was filled with fine grain black powder and connected with the slots of the bottom ring by a horizontal channel with a vertical hole, filled with a tubule of pressed black powder.

The external end of the channel was closed with a plug (4). At the bottom the stem was closed with a bronze cap (22) with a hole in the middle to transmit the fire. The hole was closed by a copper plate.

 

The core (3) was made of bronze and contained the time and the percussion mechanisms. It was screwed in the stem and had a ring nut on the top to screw the fuze cap (5). On the inside it was divided in two stages by a bar.

 

The time fuze mechanism (7) was contained in the upper level and was composed by firing pin (6), percussion spring (7) and percussion cap (8), contained in a copper box.

The top (9) and the bottom (2) composition rings were both of aluminium. The bottom ring was mobile and was housed in the stem cap, a broadcloth disc being placed between them. A groove was formed in the under side for the time composition of pressed black powder (10). The walls of the groove were coated with red brass, to avoid that the charge was in contact with the aluminium. At the beginning of the groove there was a hole filled with a tubule of pressed black powder and a horizontal vent hole (11) for the passage of the gas when the fuze burnt.

The top ring was fixed and lay on the bottom ring, a broadcloth disc being placed between them. A groove was formed in the under side for the time composition, with a hole (23), as in the bottom ring. That point was connected with upper stage of the core by an inclined channel of red brass (12), fixed in the stem of the fuze and filled with black powder. That channel transmitted the fire from the percussion cap to the upper part of the time mechanism.

 

The percussion fuze mechanism (15) was contained in the lower stage of the core and was composed by : needle (13) screwed in the core bar; little safety spring (14); firing pin (15), carrying the percussion cap (16) and having on the axis a channel filled with a tubule of pressed black powder; retracting girdle (18); great safety spring (17); two springy segments (24). The firing pin lay on a cardboard disc (25), supported by the stem cap.

 

The cap (5) was screwed on the stem and along with the creep spring (19) caught the bottom ring of the time fuze mechanism. A hole (26) was drilled on it, to centre the fuze when the shrapnel was put into the fuze setter. The cap was kept in place by a stirrup spring, placed in the core of the fuze. Two plugs (20a) were screwed on the external surface of the stem cap and of the bottom ring of the time fuze mechanism to join the fuze setter. The lower part of the bottom ring was graduated in meters to be set by hand with the fuze wrench, according with the lines (T) engraved on the stem cap.

 

Krupp time & percussion fuze. It was similar to the Schneider fuze, even if the internal arrangements were slightly different. The body was made of aluminium and was screwed into the shrapnel. It supported the graduated ring, where were mounted the two rings of the time percussion mechanism and the fuze cap. Inside the core was double-banked, the upper level containing the time mechanism and the lower level the percussion mechanism.

As a whole, the Krupp shrapnel was composed by :

    time mechanism : body with graduated ring (a), time composition rings (b), cap (c), time pellet (d), safety pillar (e), detonating cup (f), top needle (g), base plug (h), fine grain black powder magazine (i);

    percussion mechanism : holder (k), mount (l), percussion pellet (m), safety pillar (n), detonating cup (o), bottom needle (p), retracting girdle (q), spiral spring (r).

 

AS75mmQF_KTPF

Operation of the time fuze. When the gun was fired, the firing pin of the time fire mechanism came back by inertia, compressed the percussion spring, strike the ignitable substance in the percussion cup (8), which created a flash. The flame was transmitted to the channel (12) and to the powder of the top ring of the time fuze mechanism. Then it went through the hole in the bottom ring, was transmitted to the powder of the bottom ring, went through the hole in the stem cup and ignited the fine grain powder of the stem magazine. Finally it went through the central tube of the shrapnel, reached the powder chamber, ignited the bursting charge the and the shrapnel burst.

When the top ring of the time fuze mechanism was set at 0, the vertical holes on the fuze cap, on the top ring and on the bottom ring were lined up and directly connected with the powder stored in the stem magazine. Thus the shrapnel burst just after it left the muzzle. Turning the bottom ring of the time fuze mechanism, its hole moved away from the other two holes and thus the fire was transmitted by the powder contained in the grooves of the two parts of the time fuze mechanism : the more the top ring was turned (i.e. the more the holes were distant), the more the transmission of fire took time. However the grooves of the time fuze rings were not perfectly circular, but there was a sort of gap, called bridge. When the top ring was turned so that the bridges were in front of the holes (with the line on the graduated ring on T), the fire could not be transmitted and the fuze was ready to be employed for percussion fire.

 

Operation of the percussion fuze. When the gun was fired, the retracting girdle of the percussion mechanism dropped back and fell on the firing pin. Thus the great safety spring was bent, but the retracting girdle could not went back, since it was held on the firing pin by the springy segments : the firing pin with percussion cap was then kept away from the needle only by the little safety spring. When the shrapnel hit the target, the impact caused the firing pin and the retracting girdle to snap up against the percussion cap, after compressing the little safety spring. The ignitable substance in the percussion cup (16), created a flash, the flame was transmitted to the central tube of the shrapnel by the hole in the firing pin, reached the powder chamber, ignited the bursting charge and the shrapnel burst.

 

 

 

AS75mmQF_STPF2

1. Position of the rings with fuze set at 0

2. Position of the rings with fuze set for time firing

3. Position of the rings with fuze set for percussion firing

К fuze toggle

Т fuze cap with its hole в

г top ring with its hole а

д bottom ring with its hole б

 

 

 

Cartridge

Shrapnel

T&P Fuze

H.E. Shell

Data