Over-all length

(with detonator)

Length of body

Width of body

The igniter has a striker, consisting of a hollow tube threaded externally at each end, projecting through one end of the igniter casings, which is of galvanized mild steel.

Pressed into one end of the striker is a steel firing pin. The striker is surrounded by a spring which presses at one end against a screwed flange and at the other against the inside of the casing.

Rotation of a galvanized mild-steel nut retracts the striker and compresses the spring, the striker being prevented from turning by a set screw riding in a groove. The striker is provided with a flange which prevents withdrawal beyond a certain point; when this point is reached, a hole through the striker coincides with a hole in the casing, thus per-mitting insertion of a 5/64-in. diameter lead shear pin.

To the other end of the igniter is screwed an aluminum adapter which is threaded exter-nally for insertion into the charge. A detonator with a flanged percussion cap pressed into its open end is fitted into the base adapter, which for this purpose is unscrewed sufficiently to allow flange of the cap to be inserted from the side into a slot in the adapter. The detonator and cap are then secured by screwing up the adapter.

To arm the igniter, the mild nut is unscrewed, causing the lead shear pin to retain the spring. Under the pressure of the spring, the shear pin eventually fails, allowing the stri-ker to fire the cap and detonator. The time delay varies up to 26 hours.

Figure 246
Time Delay Igniter (Lead Shear Wire)