Detonator (railway)

This illustration from an 1882 Leslie's Monthly portrays an engineer (fireman) finding a torpedo on the track

A railway detonator (also called a "torpedo" in the U.S.) is a device used to make a loud sound as a warning signal to train drivers. The detonator is the size of a large coin with two lead straps, one on each side. The detonator is placed on the top of the rail and the straps are used to secure it. When the wheel of the train passes over, it explodes emitting a loud bang.

[edit] Uses

Typical uses of detonators include:

• a warning of a caution or stop signal aspect in dense fog, when signals are difficult to see
• a warning of a train stopped on the line ahead by an incident or accident – the train's personnel are usually responsible for placing the detonators
• a warning of permanent way works ahead
• when a signaller or other railway employee requires to stop approaching trains in an emergency

On a line with a high line speed, detonators may require to be placed on both running rails.

As with all explosives, detonators can become unstable after a period of time and therefore they must be replaced regularly.

[edit] In the United States

Upon hearing the noise of a torpedo exploding, the engineer would reduce speed to 20 mph or less; the train could not resume its original speed until it had travelled at least 2 miles beyond where it encountered the device. Traditionally used in pairs to ensure that the sound registered with train crews, torpedoes in the U.S. today are essentially obsolete as a modern locomotive cab's soundproof construction renders the devices useless.

Quoting from the terminology book of the Brotherhood of Railroad Signalmen:

A torpedo is a device which is strapped to the top of a rail. When a train drives over the torpedo, it emits a very loud "bang" which can be heard over the noise of the engine, and signals the engineer to stop immediately. Torpedoes are generally placed by the flagman when protecting a train ahead. Torpedoes are about 2" x 2", red, about 3/4" high, and have two lead straps attached which hold it to a rail. The torpedo has discs inside and are filled with detonating powder. The Torpedo was invented about 1874.

[edit] In the United Kingdom

The Manufacturer of the Clayton “Certainty” range of Warning Signals (generally known as Fog Signals was a spin off from Karrier Motors based in Huddersfield. By the early 1900s Karriers offered a range of heavy vehicles from buses to lorries and had depots throughout the UK and oversees at Melbourne, Sydney, Hobart, Christchurch, Cape Town, Bombay, Buenos Aires, Hesingfors, Leiben and Athans.

The main Karriers works was staffed by over 1000 people manufacturing all the major components which were fully equipped with state of the art machine tools (all belt driven) and had the benefit of an in-house foundry and forge shop.

There were several spin offs from the main works, one of which was the design and manufacture of the “Certainty” range of Warning Signals (generally known as Fog Signals), a stand alone audible warning device employing Black Powder, and used within the railway industry. The signal is placed on a railway line and held in place by two lead clips, a train travelling along the line will crush the signal igniting the internal percussion cap causing a loud “Bang”. Initially the manufacturing took place within the Karrier Works, however with the works being located in the Heart of a large town like Huddersfield, concern was expressed since the process required having large stocks of Black Powder. It was therefore decided to form a subsidiary company and to relocate out of town. A site was found in Penistone & Production of the signals commenced at Penistone along with Bird Warning Devices. A further semi-auto range of signals were introduced which allowed remote insertion onto the line, normally near signal boxes, and deployed when thick fog blanked out the Arm Signal (illumined by gas or oil lamps). The mechanical apparatus required to install the signal was also deigned and built at Penistone.

Having developed an Electric Trolley Bus in 1933 Karrier Motors was sold to the Rootes Group (then the Singer/Humber/Hillman group now part of General Motors) however the Clayton Penistone business continued in the hands of the Clayton family.

During the war years Claytons turned its production over to ammunitions, for which it received a commendation from Lord Melchett in May 1943 on the behalf of the Ministry of Supply. The commendation states that during the whole production period, not one item of manufacture had been rejected.

The next major step was in 1952 when the company purchased the land housing its factory at Penistone followed by the construction of the Penistone Bypass which gave improved access to the works.

With very little change the company has continued to manufacture the Warning Device which today plays an integral part in the safety of personnel working and travelling on the railways.

[edit] Detonator placer

Many mechanical signal boxes in the UK were fitted with detonator placers, which automatically placed a number of detonators on a running line when a lever was operated in the signal box. The levers were painted a striking white and black chevron pattern – pointing upwards for the "Up" line or pointing downwards for the "Down" line. In some cases, the placers were fed from a cartridge holding a number of detonators.

[edit] References

• BRS 72 - Brotherhood of Railroad Signalmen - Railroad Terminology, Slang, Definitions, quoted with permission.

[edit] External links

• Detonator use images