Compressed air

The compressed air is ambient Air, pressurized with a compressing , generally in the neighborhoods of 10 bars but sometimes until 300 bars.

Industrial use

The compressed air is used in industry as energy to feed from the Moteur S (jacks, serreuses, screw drivers, drilling machines, caster of Dentiste…). It finds also applications in other mediums such as the hospitals (medicinal Air), the diving (respirable Air), etc

Deep-sea diving

In deep-sea diving, the compressed air is used for subaqueous breathing, using bottles generally containing between 12 and 15 liters of compressed air with 200 bars.

Driving energy

The expansion of the compressed air was used very early like energy of propulsion for various vehicles. The Moteur of the vehicle does not emit any noxious gas indeed and is quiet.

One can quote the Locomotive S of mines or the Tramway S like those of the Mékarski system brought into service at Nantes in 1879 and used until in 1917 or on the engines of the Arpajonnais on the Parisian part of the way.

See also: Law of Mariotte, pneumatic Energy, Driving compressed-air, compressed-air Vehicles.

Weapons

Weapons called to " air comprimé" gather all the short gun weapons (Pistolet, Revolver) or length (Carabine, Fusil) using the Détente of a gas in order to propel a Projectile.

The " term; compressed-air " arms; is wrongly used to name the weapons using this principle of relaxation, independently of the real nature of gas. Thus one in general finds two possibilities for propellent gas: - is carbon dioxide (C02) - is Air (mixture of dioxygene 02 (approximately 21%) and of diazotizes N2 (approximately 78%) + other gases (1%))

According to gas used and the mechanism of the weapon, several alternatives are then possible. One thus distinguishes the weapons said to Ressort (piston), with precompressed air, C02

Some of these weapons are used for the Tir of competition, practiced with 10m (target paper) or more (on metal silhouettes).

Spring weapons (piston)

It is the most widespread system, cheapest and, especially, least fragile. A behind assembled piston of the gun is coupled with a spring whose force determines the power of the weapon. A lever, sometimes astutely replaced by the gun itself, makes it possible to compress the spring and to move back the piston: this operation is called “armament of the weapon”.

A pressure on the tail of relaxation releases the piston which then comes to expel the air thus compressed in the room where the projectile was placed.

In fact, one observes a compression then an expansion of the air and not a direct expulsion:

When the piston is released, the projectile requiring an important pressurization of the air to begin its progression in the gun, the gas goes up in pressure as the spring is slackened.
When the pressure reaches a sufficient level to overcome the resistance of the projectile in the room (frictions and partial deformation), the gas undergoes a relaxation as the projectile progresses in the gun, to its exit.

The weapons having a gun fixes and of an additional lever for the armament are famous for their highher degree of accuracy in comparison with those using the gun to compress the spring. Indeed the presence of a gun fixes limit possible displacements of this last during the shooting.

Weapons with precompressed air

These weapons do not have spring to move the piston but comprise a room of precompression placed upstream of the room containing the projectile.

Versions with ATS arming lever

In this version, the ATS arming lever is then used to precompress the air in the room of precompression by direct action on the piston. The support on the tail of relaxation comes to release a valve which lets gas then slacken in the room and propel the projectile

Versions with cartridge

In this version, no ATS arming lever is used. A refillable metal cartridge, placed under the gun of the weapon, contains the precompressed air necessary. The recharging of this cartridge is obtained using a traditional compressor or from a manual pump. It should be noted that the air, with room temperature, cannot be made liquid, with the pressures acceptable for the cartridges, it is thus well in gas form that it is in these last.

More precise than the weapons with ressort+piston, these weapons are also quieter because no part is moving during the shooting itself, which also contributes to their stability. On the other hand, their brittleness is more important because of the mechanism associating the valve and the seals.

Contrary to the generally accepted ideas, the weapons with precompressed air can be more powerful than those with spring. Their only limitation, but which is also that of the weapons with piston+ressort is the speed of expansion of the air. Example of rifle with precompressed air with cartridge (version competition):

Weapons with C02

These weapons use neither piston neither arises, nor ATS arming lever, but a liquid cartridge of C02 for the propulsion of the projectile.

These cartridges of C02 can be disposable or refillable. The disposable cartridges authorize about thirty blows in general whereas the refillable versions exceed the 150 blows. CO2 is stored in liquid form in these cartridges and the gunner must buy news cartridges (disposable version) or reload using a bottle of C02.

Such weapons are less and less used because of the complexity of their recharging (bottle of C02). Example of gun with C02 (version competition):

Use - Performances

ammunition

The compressed-air weapons use in general ammunition of the type Diabolo, out of lead or plastic with head aluminum. There exist also darts for the small gauges, but those Ci are used little because of their weak precision and the risk of damage of the gun.

The gauge of the compressed-air weapons is rather variable, although certain values are definitely more widespread. Let us quote for example gauge .177 (4.5mm), the .22 (5.5mm), the 6.35mm, but still the .50 for largest.

give rhythm shooting

The compressed-air weapons using a piston+ressort do not authorize the shooting repeated without manual rearmament by action on the lever. The rate of shooting varies then according to the skill of the gunner, from 2 to 3 shootings per minute up to 8-10 shootings per minute.

The versions with air precompressed with bottle or C02 allow a semi-automatic operation since no external energy is necessary to their operation. It is then possible to connect the shootings (shooting speed), which gave rise to the shooting from speed to 10 meters, to the gun and the rifle. The rates of fire reach the 1 then shooting a second, but the number of shootings remains limited according to the capacity of the cartridge…

power - range - precision

Power of the weapons known as " compressed-air " hardly vary some Joules until several hundreds of Joules according to their version and their mechanism.

All the weapons of this type are limited by the velocity emission of the projectile, which cannot exceed that of relaxation of propellent gas. The propellent gas being maintained at temperatures close to ambient (20°C in general), the speed of relaxation cannot be very high. In general one obtains speeds of projectiles reaching 300-350m/s maximum.

The power (abusive term, since it acts in fact kinetic of energy) of the weapon is expressed by the formula

$E= \ begin {matrix} \ frac {1} {2} \ end {matrix} M_ {projectile} V {projectile} ^2$

Where M is the mass (in kg) and V the velocity emission (in m/s)

This formula does not take account of the rotation imposed on the projectile by the stripes of the gun and giving a term of additional energy of rotation, because this effect remains negligible for these ammunition, except for their stability in vol.

Since speed is limited, it is on the mass of the projectile that one can play to increase the power.

Thus certain versions of compressed-air weapons have sometimes enormous gauges (.58 for example, is approximately 14.7mm!) to increase their power. Such weapons are used for hunting for big game in the United States for example (in France hunting for the compressed-air weapons is prohibited).

The range of the compressed-air weapons depends on their power and the type of projectile used. In general, the range does not exceed 100 meters, except for the largest gauges.

For the gauge 4.5mm, the ranges are about:

8 to 30 meters in effective range (maximum distance from which the speed of the projectile decreases appreciably)
30 to 100 meters in useful range (maximum distance from which the speed is considered to be too low to preserve a sufficient effectiveness (precision, to be able of penetration)
100 to 200 meters in stray bullet (total loss of precision)

The capacity of perforation remains limited, especially in hard materials, even for the ammunition with reinforced head (aluminum), because of their weak swiftness in comparison with other ammunition. However the dangerosity of such weapons is far from êtr negligible; as example a weapon firing a ammunition from gauge 4.5mm to 340m/s makes it possible without problem to cross 1cm of fir tree to 25 meters.

The precision of the compressed-air weapons is one of highest, with the short distances from shooting. Combined with an instrumentation of very precise aiming on certain models intended for the competition, this one authorizes groupings of impact out of target sometimes hardly believable. It is indeed not rare to obtain only one hole whereas several blows were drawn. Thus the rifles and guns known as of competition allow the shooting on targets of size very reduced 10 meters.

Example of target of shooting to 10 meters (version rifle - real size):

Legislation

In France weapons called to " air comprimé" , whatever their exact type, are classified in 7th category. When they develop less than 10 Joules at exit of the gun they are on sale free to the major people. When it develop more than 10 Joules at exit of gun their acquisition must be done on presentation of the license of shooting or hunting permit of the purchaser. Once acquired it must be the subject of a declaration in prefecture.

In Belgium, the weapons with air, whatever their type and developed energy are on sale and completely free detention for the major people.

Whatever their category, these weapons are not authorized with the sale with the minors. However, a blur exists concerning the " software ball" , version toy of the compressed-air weapons, drawing from the plastic balls at a rather reduced speed. Such toys are not really any more when their power exceeds certain levels (danger to the eyes in particular). These toys very often escape the rules from trade and are likely to about worry the forces by their resemblance sometimes very succeeded to real weapons.

Anecdote - History

As opposed to what one could believe, the compressed-air weapons are not recent and several arms manufacturers contributed to their current development.

The first compressed-air weapons, then called " weapons with vent" appeared in the neighborhoods of the XVIIIe century. Provided with a kind of balloon metal being used as tank, they required the repeated action of a lever actuating a pump to assemble to a few tens even hundreds of Bars for most powerful. They were thus weapons with precompressed air!

The projectile used was then relatively heavy because of a important Caliber (about a few centimetres).

Relatively precise and authorizing shootings at rather important distances to the wire of their development, these weapons found their use on the battle fields for the snipers, aiming at the officers of the opposing side.

External bonds

French-speaking Forum reference of the compressed-air weapons
History of the railway vehicles compressed-air
MDI, compressed-air cars
K' Airmobiles - compressed-air vehicles
Glossary the compressed air

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