Possible Actions: Long delay time – 1 1/2 to 80 hours delay after impact. Set to operate 2 to 72 hours after impact with ± 10% accuracy.

Principal Markings: El.A.Z. (17) A; may be unmarked; L.Zt.Z. (17) A*.

Secondary Markings: Rh.S. 1940; may have none; bmv 1942; bp 1941.

DESCRIPTION. The fuze is of type 4 construction and has a single electric firing circuit under plunger B. Depression of plunger B switches off the arming circuit. The A plunger is usually missing in this fuze. The wiring diagram for the (17) fuze also applies the the (17) A.

The clock mechanism and its case are held in position under the electric fuze by an alu- minum or a mild steel sleeve which threads onto the electric fuze. (See fig. 153A.) The steel sleeve has a rubber sleeve around its lower section. The clock case may be made of aluminum or plastic.

The clockwork is similar to that in the (17) with the addition of a safety pawl which with-holds the striker from the detonator. This is a spring loaded sliding pawl, and not a pivot. The pawl is held by the safety plunger, which rests against a polystryene pellet held in an aluminum collar. The collar is set into a plastic moulding in the top of the clock case (fig. 153A) and fits around the aluminum projection on the bottom of the electric fuze. This projection contains a charge of thermite. The clockwork is inverted to place the timing disc directly above the gaine hole and so simplify winding and setting the clock. A flash channel, leading from the detonator to the gaine, is cut in the side of the clock case. (See fig. 153A.)

Figure 153A – (17) A Electrical Clockwork Time Fuze

OPERATION. On impact the electrical fuze operates and fires the thermite charge which melts the two polystryene pellets (m.p. = 90° C.). The pellet on the left (fig. 153A) al-lows the safety plunger to move up and release the safety pawl, which slides away from the striker shoulder. The pellet on the right allows the clock release plunger to operate freeing the balance wheel. The clock starts and rotates the timing disc in a counter-clockwise direction through a system of reduction gears. When the tripping slot comes to the elbow piece, the spring-loaded elbow piece falls into it allowing the pawl release arm to rotate and free its cam from the tripping pawl. This pawl is forced by the spring loa-ded striker. The striker hits the detonator which flashes through the channel and fires the gaine.

REMARKS. L.Zt.Z. (17) A* is similar to the (17) A but has a longer delay between the time the impact switch functions and the starting of the clock. The circuit is similar to the (17) (fig. 153B).

Figure 153B  (17) A Electrical Clockwork Time Fute Wiring Diagram