No 14 Switch
Switch,
Nice to see a sectioned No 14 Switch, very unusual. As you say it is for pinning up charges in situations where the ordinary magnet method is unsatisfactory. Obviously non-magnetic targets require an alternative method of charge fixing but also the magnetic charge could be unreliable on a steel ship hence a version of the switch that could nail into steel. The other motivation was where the use of magnets could interfere with navigation (of the assault team) such as in the Sleeping Beauty submersible canoe where the compass could be affected. A number of alternative methods of fixing charges were experimented with which included a hand-spike, a hook mounted on a suction bellows, and adhesive.
The Switch No 14 is quite a neat design insofar as when fired the piston carrying the nail seals the barrel on firing so there is no tell-tail underwater blast; of course the nail makes a hell of a noise when it strikes say, a steel hull but such noises are commonplace on a merchant vessel. A cut down 9mm cartridge is used to provide the percussion cap for igniting the propellant held in the piston.
The idea to use a nail gun to fix the charge to a target was picked up first by the OSS in 1943 and samples were sent to SOE. Station IX worked up a design, based on the US model but smaller and using a 0.32-inch cartridge the bullet of which acted as the piston to drive in the nail. This was for wooden targets. The design was later scrapped in favour of a modification of the nail gun being developed at the same time to fix into steel targets.
Major Reeves and Mr Norman (both famous for other SOE weapons) worked on both types of nail guns and by April 1944 the nail gun (steel targets) looked pretty much like the version you show in your photograph. 200 were made at Station XII for functional trials and some changes were made prior to full production. They were available in two flavours, one for wooden targets and one for steel targets, the differences being the propellant, the nail and a minor identification feature on the switch. The nail gun is fixed into a socket on the charge and fired manually or slightly remotely using specially adapted Limpet Placing Rod. The socket will also take the US/OSS pin-up device.
[For TimG: Another type that is occasionally seen has three fixing screws. This is French and probably post-war.]
