"Are you going to hit someone?!look at it!!" Bobby was startled by the shouts outside the car, and he waved his hand at the worker in the white canvas overalls, who was almost run over by the tractor's tracks, and nodded his head in apology. Pen & Fun & Pavilion www.biquge.info

Be brave, Bobby, be brave, he silently admonished himself in his heart.

Just then, Bobby saw a tractor driven by a co-worker heading towards him. The tractor was exactly the same as the one he was driving, with the only difference being a huge "French horn" mounted on the roof.

That's right, the round, curved pale gold pipe is very similar to the French horn that Bobby saw at the New Year's party at the border station, but it is several times larger, and it occupies almost the entire top of the tractor, no...... The flare is also a little different from the shape of the French horn, and it sticks out a long way towards the front of the tractor.

Next to the huge horn, there was even a shelf welded, and the battle mage in a light gray robe was standing in that shelf, holding the handle of the giant horn, turning the direction from side to side.

Bobby didn't know what the French Horn was, but he knew that the tracked tractor he was driving would soon be fitted with a French Horn, because he was tasked with driving the tractor to the tuning factory.

On the concrete walls, Sam's gaze was also fixed on the strange "French horn". Of course, Sam wouldn't be as confused as Bobby, who knew everything about the French horn.

It is a 42mm caliber nitrogen cannon, using 0.7 kg alloy shells and liquid nitrogen as a propellant at ultra-low temperatures.

Nitrogen was chosen as the propellant because of its membrane resistance limit of 270 atmospheres at room temperature, which is the highest among common gases;

Another reason is that the high temperature and high pressure generated by the combustion (explosion) of the compound will penetrate into hyperspace within a very short time at the moment of the reaction (the concept of "virtual" has been officially named hyperspace in the monthly journal of Truth), and even cause the "hyperspace barrier" (the new term, that is, the confinement effect of the three-dimensional film itself) to temporarily fail, so that the pressure decreases rapidly.

In the process of liquid nitrogen heating from ultra-low temperature to normal temperature, it can always maintain a pressure of 270 atmospheres, and as long as the gun diameter is long enough, it can push the alloy shell to an extremely high speed.

Of course, the problem of how to solve the problem of the difficulty of installing too long gun paths bothered Donner for a long time, until he saw a horn at the New Year's concert of Coennas.

Because the alloy shell has a slow speed in the first half, and the alloy properties of this world are surprisingly perverted, it is completely possible to design the barrel to look like a French horn. The initial acceleration of the shells in boiling nitrogen is completed in a roundly curved barrel.

Therefore, the total length of nearly 7 meters of the Mithril Secret Copper alloy barrel, 4.8 meters is bent in a radius of 1.2 meters in a circle, only 2.8 meters of barrel and tangent to the circle, the entire barrel inner diameter of 41mm, the outer diameter of 120mm, because of a small amount of secret copper mixed and light gold, from the color and shape are very similar to a giant horn, the large brake of the barrel mouth, is deliberately designed to resemble the shape of a French horn.

Because a small amount of mythril was added to the alloy just now, experiments have proved that as long as you don't cast more than level 8 magic on the barrel, the secret copper component in the barrel will not produce fatal deformation.

The design of the "French Trumpeter" type nitrogen cannon was brain-wrenching, but it was not difficult to manufacture, and even the Fog City factory, which was much behind the Avery Machinery Factory, had the capacity for mass production.

However, the cannonballs used by the horn player were far more simple.

First of all, the liquefied nitrogen needs to be produced by Air Liquide, and secondly, it is a remarkable feat to inject 0.11 kg of liquefied nitrogen into the tail of the alloy shell.

Donner's solution was to make the cannonball from an alloy with the lowest possible thermal conductivity, and bury a 2.8mm diameter and 7mm long water-based bronze totem pole into the empty sac at the tail of the cannonball, leaving a small hole at the back end of the cannonball, and then place the cannonball upside down in liquid nitrogen and soak it for a while. After that, when the alloy shell is removed from the liquid nitrogen, the small hole in the tail of the empty sac will automatically close due to the cold shrinkage effect.

After the alloy shell comes down from the assembly line of the liquid nitrogen factory, under artificial control, it heats up to 20 degrees Celsius in 24 hours, and in the whole process, the small hole closed after cold shrinkage will open and relieve pressure from time to time due to excessive pressure in the empty sac, like a capillary pressure relief hole, and the small hole will be closed again after the pressure is completely balanced. After that, the malleability effect of the metal will completely seal the empty sac.

Finally, the low temperature created by the Secret Copper Pillar of the water system can keep the liquid nitrogen below the boiling point, but the entire alloy cannonball will also continue to cool down (the entropy drop process is caused by the secret copper totem pole of the water system), and if stored in the natural state, the cannonball will become a large lump of ice after a few hours, and it will not be usable at all.

The solution is also very simple, the standard storage box of liquid nitrogen shells has a fire totem pole to balance this cooling process at all times, and when a box of 80 shells is stored, the temperature can be kept at room temperature.

Just as the magic light bulb regulates the temperature by shielding the totem pole with a mythical copper cover, there is also an adjustment lever on the cannonball storage box, which is divided into full, sixty, forty, twenty, and empty five gears to adjust the efficiency of the fire totem pole.

However, in the empty box, even if the lever is facing the empty space, the fire totem pole cannot be completely covered by the secret copper cover, and the entire box is still hot, at least a fire magic apprentice can only carry it with his bare hands.

Such a set of liquid nitrogen alloy shells and storage systems can be produced anywhere else in the world except in the Avery Industrial Zone.

Compared with its extremely complex production and storage processes, the use of liquid nitrogen alloy shells is extremely simple.

As long as the firing pin driven by the clockwork battery hits the tail of the cannonball, the fragile secret copper totem pole will be destroyed, and the heat generated by the high-speed impact and the mixing of room temperature air after the destruction of the empty sac wall will immediately cause the liquid nitrogen to heat up, boil, and produce high pressure, pushing the alloy cannonball forward in the barrel, at this time, the high temperature generated by the shell rubbing the barrel will greatly increase the boiling speed of liquid nitrogen, and in an extreme time, the extreme pressure of 270 atmospheres can be reached in the barrel, and the whole process will continue until the cannon is ejected.

During the design of the horner's liquid nitrogen cannon, in order to control the recoil within an acceptable range, Donner not only had a brake at the muzzle, but also left numerous exhaust holes in the rear compartment of the breech.

The starting point of this design is that when liquid nitrogen boils rapidly, the ultimate pressure will be immediately reached in the confined space, and there will always be a certain amount of nitrogen to break through the hyperspace barrier, and instead of letting this nitrogen leak into the hyperspace, it is better to let it be ejected through the rear exhaust hole, and by the way, it can also reduce the recoil.

Two years ago, when Sam first witnessed the power of the horn player's liquid nitrogen cannon, he almost felt a sense of the uselessness of magic.

However, for Donner, it took so much effort to design this weapon entirely because the magic crystal resources were too precious. You know, one orange crystal can only be fired four times by a level 7 magic crossbow array, and if you fight a slightly larger war, Donner's magic crystal reserves will be depleted - you know, the latter is a non-renewable resource.