GENERAL. The development of electrical time and impact fuzes has been carried on in Germany since 1926. The greater part of the work has been done by the Rheinmetall Bor-sig organization. All the work in this line was under the direction of Herr H. Rhulemann.

The orignal object of the development was to produce an electrical time fuze for projec-tiles, which could be set at the instant of firing. This part of the development lagged in the early stages, and the development of electrical bomb fuzes was begun. This work was very successful and the electrical bomb fuze was adopted by the Luftwaffe in 1937. It is estimated that about 1 million time fuzes and 20 million impact fuzes were used since thei adoption.

CONSTRUCTION. The construction of electrical bomb fuzes has remained generally the same since they were fist adopted in 1937. For the purposes of this book, constructed will be divided into case and internal circuit construction.

A. Case Construction. The fuze cases for all electrical bomb fuzes have maintained, ge-nerally, the same external appearance even through there are six different types of con-struction. An external view of a typical electrical fuze is shown in figure 120. Figure 119 shows the six types of construction. All types of construction use aluminum for the case except type 5 which has a thin sheet steel case.

Figure 119 – Types of Fuze Construction

The raised portion on top of the fuze is called the fuze head or boss. One or two plun-gers, depending on the type of fuze, are located in the fuze head and are insulated by black ebonite collars. The side of the fuze head is grooved to accommodate the charging head from the electrical charging unit in the aircraft. The flat portion surrounding the head is referred to as the fuze shoulder. On the side of the fuze shoulder and in line with the two plungers is a small locating pin which serves to keep the fuze in the proper posi-tion in the fuze pocket. The female threads at the base of the fuze are there to receive the standard explosive gaine.

Figure 120 – Typical Electrical Bomb Fuze

B. Internal Circuit Construction. The internal construction of the typical electrical bomb fuze can be divided into two sections: the upper section, and the lower section. (See fig. 121.) Figure 122 shows the various type of trembler switches found in German fuzes. The upper section is called the switch block. It is a polystyrene moulding which has been machined to take the various plunger contacts, the trembler switches, and in some cases the long delay igniter bridge.

Figure 121 – Internal Construction of Electrical Bomb Fuze

The lower section contains the storage and firing condensers, the resistances, and the instantaneous and short-delay igniters. These parts are held in place by the black bitu-men calking substance.

The condensers are constructed of metal foil strips separated by wax paper and all wound on one cardboard cylinder. The carbon resistance normally fit into this cylinder. It may also contain the long delay cold cathode tube which is true for the El AZ (9).

The igniter block fits into the bottom of the fuze and contains the black powder flash pellet, three holes leading from the pellet to the igniter bridges, and the short delay train.

Figure 122 – Types of Trembler Switches