In non-professional sources (newspapers, magazines, fiction, movies, and even some military publications) this detonator is usually called "fuse cord". However, as a rule, the application of the name "fuse cord" to a modern means of transmitting a firing impulse to a detonator cap is inappropriate and erroneous in principle. With the same right, you can call a car a carriage, a pistol a revolver, an apartment building, a hut, a magazine, a newspaper, a booklet, a book, etc.
The only thing in common between the modern “fuse” and the old “fuse-cord” is that they have the same purpose - to transmit force of fire to the detonator cap or powder charge, some similarity in design and appearance.
Before talking about the design and differences between both types of cords, it is worth delving into the history a little, consider the background.
In general, subversive or mine work appeared almost simultaneously with the invention of gunpowder. It can even be said that the subversive business appeared before firearms. The history of the discovery of gunpowder is not described reliably enough in historical sources. As one of the versions, there is a version of the discovery of gunpowder by the inhabitants of northern Africa, where there were exits to the surface of saltpeter. The cattle breeders made fires, after which the coals remained. The rains moistened the earth, dissolved saltpeter, which soaked charcoal in the solution (remnants of fires). Thus, a natural gunpowder was obtained. When attempting to re-build a fire on such coals, this natural gunpowder exploded. Someone paid attention to this. So gunpowder appeared. However, this is only a version. There are no reliable written sources about the invention of gunpowder.
It is reliably known that in the late Middle Ages, gunpowder was used not only in firearms, but also to blow up the walls and towers of castles. In the Russian army in the 16th century, there were special units for the production of explosions. The subversive specialists were called “gorokopi” (from the word “forge” - an underground cavity for placing a powder charge in it). During the siege of Kazan in 1552, Russian mountain diggers made several undermines under the walls of the fortress and made several explosions. So on September 4 they blew up the Muraleev gates of the Kazan Kremlin, on October 2 they blew up the junction of the Kremlin wall and the fortress between the Atalykov and Tyumen gates of the Kremlin, on October 2 the wall near Lake Guzeeva and on October 3 the wall between the Nogai and Spassky gates of the fortress. The Tatars could not hold the defense in the breaches and Kazan fell. Black powder was used as an explosive, and the flame was transferred along a powder track poured from the charge for safe removal.
However, with the development of military affairs and the increasingly widespread use of mine and blasting operations, this method of blasting could not meet the needs. In underground passages, it is usually quite damp, it is not always possible to fill in a continuous path of gunpowder (for example, due to the stepped development), drafts could blow off parts of the path. The method of installing a burning candle on the charge was also unreliable (the candle could be blown out) and extremely dangerous (a spark, a smoldering remnant of the wick that fell down could cause a premature explosion).
The first attempt to improve the fire method of detonation (then the only one) was the invention of a leather sleeve. A long tube was sewn from the skin, which was stuffed with gunpowder. It can be considered the forerunner of the fuse-cord.
Promotional video:
Somewhat later, the so-called "stopin" was proposed, a thin cord impregnated with a mixture of saltpeter and gunpowder. Stopin has also found wide application in the lighting of palaces and theaters. Before the start of the performances, balls, it was required to simultaneously light a large number of candles, and even those placed on high suspended chandeliers. In such cases, the wicks of all candles were connected to each other with a thin stop, and the end of the stop was lowered down. It was enough to set it on fire, as the flame ran around all the candles, setting them on fire.
However, for all these inventions, the common disadvantage was the availability of moisture to gunpowder and saltpeter. Saltpeter quite actively absorbs water from the air and loses the ability to ignite. Reliability and sleeves with gunpowder and stopin were unsatisfactory. In addition, the stopin gave out a rather weak force of the flame.
The English engineer D. Bickford in the second half of the 19th century proposed combining the stopin with a powder sleeve, replacing the leather with a textile braid, and impregnating the braid with asphalt to protect it from moisture. Thus the fuse-cord was born. The figure schematically shows the construction of a fuse-cord cord (without observing the scale and proportions). Stopin ensured the stability of the combustion of the cord, the powder pulp, sufficient flame force, double braid, flexibility and core integrity, asphalt protection from moisture. Asphalt was proposed by Bickford for another reason. When the fire goes far from the beginning of the cord, then there may not be enough oxygen to maintain combustion (the resulting propellant gases block the access of oxygen from the outside). Asphalt melting and burning out from high temperatures loses its strength, which allows the powder gases to break out,and oxygen to enter the combustion area.
The Bickford cord was used in subversive activities until the outbreak of World War II. The massive use of demolition work during the war, especially by poorly trained personnel, clearly revealed the previously inconspicuous, but very significant shortcomings of the fuse-cord:
1. The cord goes out under water due to lack of oxygen.
2. The burning rate of the cord is unstable due to the peculiarities of the powder pulp (different degrees of moisture in different areas, different density of different areas), which makes it difficult to calculate the length of the cord for detonating the charge after a given period of time).
3. The open ends of the cord must be protected from moisture, otherwise the cord may fail when ignited.
4. Asphalt cracks at low temperatures and does not provide the cord tightness and protection from moisture.
5. In the cords made during the war, due to a decrease in quality, cases of the so-called "lumbago" have sharply increased. instantaneous transmission of the flame to some part of the cord, which led to premature explosions of explosive charges.
Already in the second half of the war, these significant shortcomings of the fuse cord prompted engineers to create a new type of cord for the firing method of detonation. As a result of first partial changes in the design, and then more radical changes, a new type of cord appeared, which was named "Fire-conducting cord".
First of all, they abandoned the powder pulp. It was replaced by a pyrotechnic composition based on nitroglycerin powder. In the process of burning the composition, oxygen is generated, which ensures stable combustion of the cord even under water at depths of up to 5 meters (realistically and at much greater depths). The stopin was replaced with a guide thread, twisted from three cotton threads, each with a different impregnation. This ensures a sufficiently accurate control of the burning speed of the cord, prevents combustion attenuation and prevents the lumbago phenomenon. The type of braiding has changed from radial to diagonal, and the adjacent layers of the braid have different weaving directions, which provides higher strength and flexibility of the cord. The number of layers of the braid has become not two, but three or five. Asphalt began to cover not only the top layer of the braid, but also the intermediate ones. Cord,having five layers of sheath became known as "double paving cord". Somewhat later, in the mid-fifties, the outer layer of asphalt was replaced with plastic.
The fuse cannot be extinguished until the integrity of the guide thread is broken, unlike the fuse cord. This is impossible in principle.
In the USSR (and now in Russia), a fuse is produced in three main types:
* OSHA - asphalted fire-line with cotton braid. Its color is dark gray. Burning speed 1cm. per second (plus minus 7%). Diameter 4.8-5.8 mm. Supplied in coils 10m long.
* OShDA - double asphalt fire-conducting cord with cotton braid. Its color is dark gray. Burning speed 1cm. per second (plus minus 7%). Diameter 5-6 mm. Supplied in coils 10m long, it is recommended for use in damp places and under water.
* OShP - a fire-conducting cord in a plastic sheath. Its color is white. Burning speed 1cm. per second (plus or minus 5%). Diameter 5.0 mm. Supplied in coils 10m long. Recommended for all occasions. Its modification is also produced with a burning rate of 0.278 cm per second. This cord has a blue sheath color.
