Cutaway model of an US AN –M 102A2 tail fuze , as used in US 1000, 20000 and 4000 Lb GP (General Purpose) and SAP (Semi Armour Piercing) bombs.
The fuze can be roughly divided in two parts;
-The fuze body (forward) with the inertia activated firing plunger and the M14 –delay- detonator
-The safety and arming mechanism (back)
The two parts are connected by a pipe through which the arming stem runs.
The safety and arming mechanism (picture 03) at back consists of a pressed steel gear assembly cup (1), screwed to the pipe by means of a brass connection piece (2). In the cup, the lifting collar (3) is placed, radially fixated by a gear carrier stop (4). To the top of the lifting collar the stationary gear wheel (5) is fixated. A movable gear sleeve (6) is placed over the arming stem (7) which protrudes through the safety and arming mechanism, the vane assembly (8 )is placed over the movable gear sleeve on a bearing (9). The movable gear sleeve (6)is connected to the arming stem by means of a split pin (10). The movable gear sleeve and the vane assembly rotate independent from one another. A pinion gear (11) is placed on the base of the vane assembly bushing.
The stationary gearwheel (5) on the lifting collar (3) has 29 teeth, the movable gear (6) on the gear sleeve has 30 teeth. The pinion (11) gear at the base of the vane assembly bushing is engaged to both gear wheels. When the bomb is released and the arming wire is withdrawn from the vane, it starts rotating. The pinion gear rotates around the stationary and movable gear, however as there is one tooth difference and the pinion gearwheel will force both teeth in alignment, the gearwheel on the movable gear sleeve will rotate 1 tooth per vane revolution (1/30 x 360 degrees = 12 degrees per revolution). This means the arming stem will make one revolution at each 30 revolutions of the vane assembly. As the arming stem is screwed into the brass firing plunger with 15 revolutions, the arming vane has to revolve 15x30=450 times to arm the fuze.
After retraction of the arming stem from the firing plunger the entire mechanism falls out of the gear assembly cup, leaving the pipe with the gear assembly cup (1) protruding from the back of the fuze housing.
Upon impact of the bomb, inertia throws the brass firing plunger forward, overcoming the creep spring and activating the firing cap. The flame of the firing cap activates the 0,025 second delay composition , which activates he detonator (red) in the base of the M14 delay detonator.
This will detonate the booster assembly, detonating the bomb.
Regards, DJH
The fuze can be roughly divided in two parts;
-The fuze body (forward) with the inertia activated firing plunger and the M14 –delay- detonator
-The safety and arming mechanism (back)
The two parts are connected by a pipe through which the arming stem runs.
The safety and arming mechanism (picture 03) at back consists of a pressed steel gear assembly cup (1), screwed to the pipe by means of a brass connection piece (2). In the cup, the lifting collar (3) is placed, radially fixated by a gear carrier stop (4). To the top of the lifting collar the stationary gear wheel (5) is fixated. A movable gear sleeve (6) is placed over the arming stem (7) which protrudes through the safety and arming mechanism, the vane assembly (8 )is placed over the movable gear sleeve on a bearing (9). The movable gear sleeve (6)is connected to the arming stem by means of a split pin (10). The movable gear sleeve and the vane assembly rotate independent from one another. A pinion gear (11) is placed on the base of the vane assembly bushing.
The stationary gearwheel (5) on the lifting collar (3) has 29 teeth, the movable gear (6) on the gear sleeve has 30 teeth. The pinion (11) gear at the base of the vane assembly bushing is engaged to both gear wheels. When the bomb is released and the arming wire is withdrawn from the vane, it starts rotating. The pinion gear rotates around the stationary and movable gear, however as there is one tooth difference and the pinion gearwheel will force both teeth in alignment, the gearwheel on the movable gear sleeve will rotate 1 tooth per vane revolution (1/30 x 360 degrees = 12 degrees per revolution). This means the arming stem will make one revolution at each 30 revolutions of the vane assembly. As the arming stem is screwed into the brass firing plunger with 15 revolutions, the arming vane has to revolve 15x30=450 times to arm the fuze.
After retraction of the arming stem from the firing plunger the entire mechanism falls out of the gear assembly cup, leaving the pipe with the gear assembly cup (1) protruding from the back of the fuze housing.
Upon impact of the bomb, inertia throws the brass firing plunger forward, overcoming the creep spring and activating the firing cap. The flame of the firing cap activates the 0,025 second delay composition , which activates he detonator (red) in the base of the M14 delay detonator.
This will detonate the booster assembly, detonating the bomb.
Regards, DJH
