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El.A.Z 57 German WW2 Electric impact fuze


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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.Z 57 (Electrische Anschlag Znder 57 / Electrical impact fuze 57 ). 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.

Functioning of the fuze: the fuze is an electrical chemical time fuze with an antiwithdrawal mechanisn[/color][/color]. It is made up of two main components ,an upper housing(1) ,containing the electrical parts ,and a lower housing (2) containing the chemical time and the mechanical antiwithdrawal mechanisms. The electrical part has only the depressable B piston placed, piston A (3) is a blind dummy. At release from the bombrack, piston B ,used ignite the black powder pellets(5 & 6) is activated . The ignited pellet (5) presses down a narrowed piston (9), which brakes through a thin membrame. The aceton containing liquid, held in a circular hole (12) in the lower fuze body ,is pressed in the small chamber under the membrame (10). This chamber contains a celluloid disc (21), that prevents a firing pin release piston (18 ) from moving up under influence of a spring (20). The other pellet (6) ,pushes down a safety cylinder (7) through a dowel (8 ), that blocks a mechanism release pin (16). This pin blocks the movement of four parts , The upper retainer block (13), the knife edge (14) and the safety block (15). All three of them pivot around a pin ,screwed into the base of the fuze. The retainer block (13) has two balls pressed in around a slot that is just wide enough to let the firing pin (17) pass. The knife edge (14) has only one function, retaining the antiwithdrawal plunjer (23)in it's upward position if the fuze is not armed. The safety block (15) prevents the firing pin from hitting the firing cap if not armed. At impact, the mechanism release pin (16) is pushed out by the safety block (15), that is thrown forward by inertia. the knife edge is released and the antiwithdrawal plunger (23) is free to move down under influence of the spring (24). It is however held in place by additional charges placed under the fuze. The retainer block (13) however cannot move; it is locked around the antiwithdrawal plunger by wire (25). The firing pin (17) has two balls (19) ,held outward by the firing pin release piston (18 ). These balls rest on the balls in the retainer block (13). As soon as the celluloid disc (21) is dissolved, the firing pin release piston (18 ) can move up. The balls (19) move inward ,releasing the firing pin (17) into the firing cap (22). If an attempt is made to withdraw the fuze from its pocket, the antiwithrawal plunger (23) will move down, forced by the spring (24). The outside of the plunger is ribbed to pick up the wire (25) that locks the retainer block (13) in a fixed position. As the plunger (23) moves down, it pulls the wire down, out of the lock in the retainer block. The retainer block is not longer fixed ,and under influence of a sideway placed spring (26) it swings outward. This also means the balls in the retainer block (13) swivel away from under the balls (19) in the firing pin (17). This leaves enough space to let the firing pin strike the firing cap (22). The firing cap (22) ignites the Kz Zdlg.(Kurze Zundladung / short booster) C/98 (28 ). The Booster is made of an aluminium can, containing 17 grams of Np (Nitropenta)10 (pink). In top of the fuze a sprengkapsel (detonator) 38 (27) 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 (29), which is screwed in the base of the fuze. The fuze is said to be activated if only moved up for 1/16 " (1,5mm) while atempting to remove the fuze. Descriptions also note that moving the bomb or rough handling may activate the fuze. The last feature of the fuze is the antirupture device: if the bomb hits a very hard surface (concrete for instance), resulting in excessive desceleration ,both the safety block (15) and the retainer block (13) will be thrown forward by inertia. The retainer block will bend the wire(25) through the antiwithdrawal plunger ,activating the fuze instantaniously. A sleeve (30) is crimped around the fuzebody to enshure a water proof closure of the mechanical mechanisms.
Waow, very beautiful job, pzgr40,

I'll be difficult but have you perhaps a pic of the head marking of the fuze ?

Hallo PzGr 40,
I have a small question regarding your absolutely beautiful model. Are the electric igniters (black) with their legwires (red) original or reproductions? The igniters and their legwires originally were colour coded for assembly reasons, so that the mostly unskilled labourers on the assembly line would know which igniter to attach in a certain place in the circuit. Most fuzes used the high sensitivity SX5 or SX6 igniters. As far as I could determine, these had yellow and red plastic sheaths. I do not have any list of the colour codes of the different models used. Does anybody here have any more knowledge ?
The wires on the one I have have red plastic covering. The igniters were a cream colour with grooves going down the length of them.