pzgr40
Well-Known Member
Some General notes: The development of electrical bomb fuzes in Germany can be traced back to 1926. Under direction of Dr. H. Rhulemann it was carried out at the Rheinmetal Borsig factory. The original goal was to develop an electrical time fuze for artillery shells that could be set at the moment of firing. Somewhere down the path of development work started on Electrical bomb fuzes. This to such satisfaction that the Luftwaffe adopted the Electrical bomb fuze in 1937. The design of most Electrical fuzes is generally the same; an aluminium outer housing, to be devided in an upper and lower housing. The upper housing has a shoulder with a locating pin, enshuring that the fuze is placed in the right direction. On top is the fuze head with the electrical plugs. The upper part normally contains the horizontal - and vertical trembler switches, resistances and the depressable pistons of the electrical plug. The lower part normally contains the condensers, the delay devices (either pyrotechnic, either mechanical) and the anti disturbance devices. The gaine is screwed in the base of the fuze. The advantages of electrical fuzes are: Easy manufacturing (low number of different components for many different functions), great flexebility, instant action, low number of duds, arming only after the pilot connects the master switch, very safe. Extensive test with electrical fields around the fuze, up to 2.000.000 volts (ligtning), showed that an electric fuze, when propperly designed, is absolutely safe. One feature of German bombs is the way the fuze pocket is placed, mostly not in the longtudinal centreline (like allied bombs), but mostly in the side, perpendicular to the centerline.
Cutaway model of an El.A.Z17(Electrische Anschlag Znder 17 / Electrical impact fuze 17 ). This fuze was designed for use in 250kg to 1800 kg Sc (Spreng Cylindrische/ H.E General purpose) aircraftbombs. It could also be found in a variety of other bombs. The fuze is made up of two parts; the upper part, containing the depressable piston (4), a transparant perspex mould (6), the trembler switch (7), the condenser ( 8 ), and a thermite pellet (10). An aluminium cap (3) is placed on the fuze body (1), by means of three screws. The pin (5) enshures that the fuze can only be set in such a way that the trembler switch (7) is placed horizontal perpendicular to the centerline of the bomb. The Lower part contains a mechanical clockwork, safety devices and the gaine.
Functioning of the fuze: just before dropping the bomb, the condenser is loaded (depressed pistons), after release, the charging arm is pulled off the fuzetop ,and the deppressable pistons rise and close the electric circuit over the trembler switch (7). At impact the trembler switch closes the circuit and ignites the flame pellet(9), that ignites the Thermite pellet (10). Around the lower part of the pellet (10) is a ring clamped (11), containing a polystyrane pellet (12). This pellet melts under the heat, transferred from the buring thermite pellet (10) to the Ring (12). this enables a safety (blocking)piston (13) to rise under influence of a spring (14) and release a arc shaped brass slider to move into the chamber(15) formed by the piston moving up, releasing the firing pin(24) safety. regretfully, this safety was the only part that could not be made visable in the cutaway. Another polystyrene pellet further backward ,releases another safet piston (17) that releases the clockwork geartrain (18, 19, 20). The main gearwheel (20) contains a clock spring, a reduction gear (19) with an unbalance that enshures the clock winds off at a constant speed. A time set disc (21) is found in the base of the fuze in the form of a cam wheel and has to be rotated counterwise to set time. It can be set from 1,5 - to 80 hours after impact. Time setting is done before inserting the gaine (28 ) by means of a special key. When the striker release elbow(22) falls in the slot in the cam wheel, it will rotate, together with the pawl release arm (23), connected to it. The top of this pawl has a slot cut out that -after rotation - enables the firing pin release hook (16) to move out and release the firing pin(24) into the firing cap(25). The flame will travel down through the spaces between the gearwheels and travel into the booster. This is the Kz Zdlg.(Kurze Zundladung / short booster) C/98 (27) The Booster is made of an aluminium can, containing 17 grams of Np (Nitropenta)10 (pink). In top of the booster a sprengkapsel (detonator) 38 (26) is placed. A leather washer with a celluloid disc is placed above the detonator, the aluminium can is rimmed over the leather washer to close the booster. The booster is placed in the gaine (28 ), which is screwed in the inner sleeve of the lower part of the fuze.
Cutaway model of an El.A.Z17(Electrische Anschlag Znder 17 / Electrical impact fuze 17 ). This fuze was designed for use in 250kg to 1800 kg Sc (Spreng Cylindrische/ H.E General purpose) aircraftbombs. It could also be found in a variety of other bombs. The fuze is made up of two parts; the upper part, containing the depressable piston (4), a transparant perspex mould (6), the trembler switch (7), the condenser ( 8 ), and a thermite pellet (10). An aluminium cap (3) is placed on the fuze body (1), by means of three screws. The pin (5) enshures that the fuze can only be set in such a way that the trembler switch (7) is placed horizontal perpendicular to the centerline of the bomb. The Lower part contains a mechanical clockwork, safety devices and the gaine.
Functioning of the fuze: just before dropping the bomb, the condenser is loaded (depressed pistons), after release, the charging arm is pulled off the fuzetop ,and the deppressable pistons rise and close the electric circuit over the trembler switch (7). At impact the trembler switch closes the circuit and ignites the flame pellet(9), that ignites the Thermite pellet (10). Around the lower part of the pellet (10) is a ring clamped (11), containing a polystyrane pellet (12). This pellet melts under the heat, transferred from the buring thermite pellet (10) to the Ring (12). this enables a safety (blocking)piston (13) to rise under influence of a spring (14) and release a arc shaped brass slider to move into the chamber(15) formed by the piston moving up, releasing the firing pin(24) safety. regretfully, this safety was the only part that could not be made visable in the cutaway. Another polystyrene pellet further backward ,releases another safet piston (17) that releases the clockwork geartrain (18, 19, 20). The main gearwheel (20) contains a clock spring, a reduction gear (19) with an unbalance that enshures the clock winds off at a constant speed. A time set disc (21) is found in the base of the fuze in the form of a cam wheel and has to be rotated counterwise to set time. It can be set from 1,5 - to 80 hours after impact. Time setting is done before inserting the gaine (28 ) by means of a special key. When the striker release elbow(22) falls in the slot in the cam wheel, it will rotate, together with the pawl release arm (23), connected to it. The top of this pawl has a slot cut out that -after rotation - enables the firing pin release hook (16) to move out and release the firing pin(24) into the firing cap(25). The flame will travel down through the spaces between the gearwheels and travel into the booster. This is the Kz Zdlg.(Kurze Zundladung / short booster) C/98 (27) The Booster is made of an aluminium can, containing 17 grams of Np (Nitropenta)10 (pink). In top of the booster a sprengkapsel (detonator) 38 (26) is placed. A leather washer with a celluloid disc is placed above the detonator, the aluminium can is rimmed over the leather washer to close the booster. The booster is placed in the gaine (28 ), which is screwed in the inner sleeve of the lower part of the fuze.
