Smoke Float No. 1 Mks II, III, IV, and IVZ (Service)

Description: The Smoke Float No. 1 Mk IV comprises a cylindrical body, closed at one end by a conical head and a heavy nose. A retarding band is secured to the body adja-cent to the head. A tail cone, carrying three vanes to support the vane ring, is secured to the  opposite end of the body. The end of the tail cone houses a pistol adapter for the tail pistol, which is locked in place by a grub screw. Inserted in the pistol adapter is a cup, containing a cartridge base and a small quantity of flash composition, sealed with a paper disc. A sleeve leads from the bottom of the pistol adapter into the funnel-shaped upper end of the tube, known as the container cap tube. The container for the smoke composition has a fuzible cup inserted into the top of the smoke composition, which is filled with pressed priming composition. Above this is a layer of loose priming composition, and a primed cambric disc through which is threaded a length of quickmatch. The contai-ner is closed by a container cap. A central cylinder, provided with a ring of holes, sur-rounds the container. The rest of the body and the tail cone comprise a buoyancy cham-ber. The tail cone is provided with a sinking disc, which is scored, so that if a flaoting smoke float is found, the disc can be easily pierced to sink the float, the water entering the tail cone and passing into the body through the holes in the central cylinder.

Functioning: When the fuzed smoke float has been dropped from the aircraft, impact of the nose on surface of the water causes the striker of the pistol to hit the cartridge base, and the ensuring flash ignites the flash composition. The flash from the flash com-position passes down the container cap tube and ignites the primed cambric disc and quickmatch, which ignite the primings. The fusible cup melts, and the priming ignite the smoke composition. Smoke rises up the container cap tube, and as the pressure increa-ses, bursts the seal of the tail cone. The short period between impact with water and bursting of the seal is sufficient to enable the smoke float, after submerging, to rise to the surface, owing ot its buoyancy.

Suspension: A suspension lug provided on the body permits attachment of the smoke float to a Light Series Bomb carrier.

Remarks: In the Float No. 1 Mk II, the container cap tube serves only to carry smoke from the container to the sealed hole in the tail cone. A length of safety fuse, giving a 20-sec. delay, extends between the pistol adapter and the container. In the Float No. 1 Mk III, the container cap tube also serves only to carry the smoke from the container to the sealed hole in the tail cone. A separate flash tube guides the flash from the flash composition to the container. The Float No. 1 Mk IVZ differs from the Float No. 1 Mk IV only in the nature of the smoke composition used.

Should water, expecially salt water, come inot contact with the smoke composition, it is liable to spontaneous combustion due to chemical action.

Figure 96 - Smoke Float No. 1 Mk IV