Nearly 30,000 northern troops surrounded the city of Zhenzhou, and it was a little strange that the defenders in the city did not appear particularly flustered, but the city gate was closed, seemingly preparing to hold on for a long time, and there was no intention of surrender.

They were confident in Zhenzhou's defenses, which really annoyed Li Qi.

Immediately, the armies were ordered to send men to cut down trees on both sides of the valley, and then, under the guidance of craftsmen, to make siege equipment in the battalion.

There was no difference between the building carts, the siege ladders, and the siege engines, and Li Qi summoned several of the main craftsmen to his tent in the camp of the Chinese army, and explained to them in detail the techniques of making trebuchets and ballistas. The main ones are the counterweight trebuchets that the Mughurs brought back from the West, and the other is the ballista that uses rails to throw stones similar to the slingshot.

The heavy trebuchet in the Tang Dynasty was mainly pulled by manpower or animal power, and the principle of leverage was also used, the problem was that each trebuchet needed to be equipped with more than 150 to 200 personnel to pull the trebuchet, and it was not easy to coordinate, and the waste of manpower was too much.

Li Qi's improvement according to the principle of the Mengwu trebuchet is actually very simple, that is, to install a counterweight stone on the end that was originally pulled by manpower, so that as long as the other end of the lever is pulled down with a pulley group, the cannon stone is loaded, and the cannon stone can be automatically launched after the rope is released with the machine bracket. In this case, each trebuchet would only need to be equipped with a maximum of twenty soldiers.

The reason is very simple, and it is actually the method used by the Mongols more than 250 years later.

The only thing that was difficult was the making of the pulley block.

Pulleys appeared in the pre-Qin period, but strangely enough, the principle of pulley blocks, which can save more effort by combining several pulleys, has not been discovered. The reason for this is that Li Jiqi thinks that the status of craftsmen may be very low, because it is not cheap to make a pulley, and the thinking of those craftsmen who have some status and status has been rigid. The craftsmanship of the craftsmen of this era is still quite admirable, and only axes, saws, chisels and planers can be used to make some very delicate wooden accessories.

For later generations of junior high school students who knew the principles of levers and mechanics, the principle of this counterweight cantilever trebuchet was very simple.

A counterweight cantilever catapult is the kind of counterweight box that is attached to one end, and then the cantilever is extended at the other end, and then a leather pocket is installed on the cantilever to hold the cantilever stone. As soon as you press down the cantilever, place the rounded cannon stone in the leather pocket, and finally release the cable, the weight box will naturally lift the extension arm upwards by its own weight. When the open leather pocket is thrown to the highest point, the raised arm suddenly stops, and the cobblestone contained in the leather pocket will naturally be thrown out.

In general, the longer the raised arm, the farther the stone is thrown.

Li Qi knew how much damage it would do to the Central Plains people who were now weakened by the war at the end of the Tang Dynasty if this thing was learned by the Khitans on the grassland. Therefore, before making the trebuchet, he asked all the personnel involved in the production and operation of the trebuchet to be brought back to Jinyang and placed in the military camp near Taiyuan.

This request seemed very unreasonable, but after Li Qi explained it slightly, Yuan Xingqin immediately understood.

When Li Qi set out on the expedition, considering that he was going to attack the city, he actually brought a lot of iron accessories, and all the craftsmen in the camp needed to do was to cut down the wood, and then make large structural parts such as brackets and levers.

It took only three days for two crude cantilever trebuchets to be built.

A group of generals from the original army rushed to the edge of the Hutuo River to watch the first test of the trebuchet.

The cantilever was pulled down, and then two fixed hemp ropes were tied to the bracket. Yuan Ren personally commanded the four soldiers to put a cobblestone of about 100 catties into their leather pockets, and everyone was eager to see how far this trebuchet, which seemed to be less than half, could throw the boulder.

The head craftsman Zheng Sheng is a disciple of Luda, who originally made and operated trebuchets, so he was in charge of commanding, and some of Shi Kang's subordinates operated them.

Shi Dang held a sharp knife in his hand, inserted it into the rope, and then said to the soldier operating on the other side: "After hearing the order to shout, let's cut the hemp rope together!" ”

The soldier nodded, but Li Qi asked all irrelevant people to stay away from the trebuchet, who knew what would happen if such a large stone was thrown out......

"Ready...... Put! Zheng Sheng shouted loudly.

Shi Dang and the soldier on the other side twitched their knives almost simultaneously, cutting the hemp rope that held the top of the boom in place, only to hear a creaking sound, and the heavy weight box quickly pressed the boom up.

"Bang!"

The weight box landed on the seat frame with a loud bang, and with a bang, the huge cobblestone in the leather pocket that swirled along with it flew out. The cobblestone made an arc in mid-air, flew about five hundred paces, and then slammed into the woods on the edge of the riverbank, breaking two bowl-thick birch trees with an astonishing sound.

The first test launch was a great success!

There was a cheer from the spectators, and the trials of the other two trebuchets were successful, with the only problem being that the distances of the trebuchets were not quite the same. Several generals are also eager to try, and finally joined the ranks of the trial investment, it seems that the heart is not small, as if they have seen a fresh toy, and their childlike innocence is still alive.

After watching the effect, Yuan Xingqin swallowed his saliva and said, "Very good, this thing can directly smash the anti-arrow chest wall and wooden shield at the head of the city!" ”

Another siege weapon commanded by Li Qi was the ballista!

It's something like a bed crossbow, a large slingshot, and a trebuchet mixed together, a kind of siege machine that combines these three siege machines. It's kind of like a large slingshot or a catapult, but with rails attached.

Ballistae actually appeared in the Spring and Autumn Period, but because the accuracy and range were not enough, and they were not even as good as trebuchets, many people didn't like it very much, so there was a tendency to be eliminated. Li Qi's improvement on the ballista is the addition of a grooved rail, which will make it much more accurate to shoot.

The important thing about this thing is the cannon, which must be very sleek to achieve a greater killing effect.

More than ten days later, dozens of various siege equipment had been made, and then they began to be assembled about five hundred steps away from the eastern city of Zhenzhou.

There are heavy guards of the Northern Army, and the defenders at the head of the city are staring at the Northern Army when they see the siege equipment being assembled, and they are helpless.

……