"Boom!"

An orange-red flame burst out on an unnamed island about twenty miles from Nagasaki, and the bow of the "Aurora" suddenly fell silent.

On the third day after Chu Fan's visit to Tsunasaburo, a bed crossbow composed of three bows was sent over and installed at the bow and stern of the "Dawn".

The Kato family hired six of the best carpenters in Nagasaki for Chu Fan, but just like that, it took two whole days to install - in order to make the bed crossbow turn and pitch up and down, Chu Fan and the carpenters experimented with many new components.

In the end, the problem of rotation was solved by means of a bearing-like structure - a round wooden rail was installed on the foredeck of the "Aurora", in which a circle of wooden rollers was attached, and then a large disc containing the bed crossbow was placed on the wooden rail, which was fixed by a wooden latch when fired.

The problem of pitching is much simpler - two rows of wooden columns are erected on the large disc, and the bed crossbow is installed on the column, and the pitching of the bed crossbow can be realized by adjusting the wooden bolts on the front and rear columns.

In fact, in Chu Fan's opinion, the steering machine is fine, but this high and low machine is too crude, and according to his temperament, the precise positioning of the high and low machine can be achieved through metal gears.

However, even such a crude device had already made those carpenters of the Wa Kingdom admire Chu Fan to the ground.

Can you really make a big, bulky bed crossbow spin freely? At the beginning, the carpenters were skeptical, but as their imagination became reality step by step, after they pondered the principle, they all bowed to Chu Fan - he could think of such an ingenious method!

Even more ecstatic was Tsunazaburo Kato. On the very day that the two bed crossbows were installed, he rushed over, and after experiencing the thrill of "pointing and fighting", Tsunazaburo's eyes were red - even a layman knew too well what a rotating bed crossbow meant to a warship.

After a lot of coaxing and scaring the carpenters who kowtowed like garlic, he finally threw out a sentence "If you can't learn, you should all apologize for your seppuku" and walked away, frightening the carpenters into white faces.

Compared with the carpenters, the three blacksmiths who arrived a day later were much less stressed, they only needed to beat the wrought iron into thin sheets, and then roll it into a hollow conical shape according to Chu Fan's instructions, and then make a slightly thicker circular base, without much technical content.

The only trouble was that Chu Fan asked them to draw the threads at the bottom of the hollow cone and the corresponding positions on the thick base to facilitate the fixation after the charge - wrought iron was relatively soft, and the three blacksmiths quickly found a much harder pig iron as a knife to draw the threads, and after this technical problem was solved, Chu Fan's ideal hollow ballista "cannonball" was completed.

The volume of the "cannonball" is about half a liter, and it can be filled with two catties of black fire*. In order to increase the power of the black fire* medicine, Chu Fan was going to add some copper oxide to it, but how to get copper oxide became a problem.

Fortunately, Chu Fan's thread-bound notebooks full of all kinds of modern knowledge he carried with him, and after flipping through them for a long time, Chu Fan found a useful chemical formula: "4NaHCO3+2CuSO4=Cu2(OH)2CO3+2Na2SO4+3CO2+H2O"

Sodium bicarbonate is baking soda, copper sulfate is alum, are easy to find raw materials in this era, and the basic copper carbonate produced by the reaction of the two can be obtained by simple calcination.

Of course, Chu Fan definitely couldn't let Tsunazaburo know this secret, so Chu Fan had to do it himself, got a lot of bottles and cans, and worked in the west courtyard as a warehouse for an afternoon, and finally got more than ten catties of black copper oxide.

In order to achieve a better effect, Chu Fan even re-ground the ** that had been granulated, mixed it with copper oxide and granulated it again, so angry that Yan Ruxue, who had been helping him for a long time, rolled his eyes again and again, saying that he was purely full.

All the hard work was in vain, and when the first ballista exploded on an uninhabited desert island about a hundred and eighty paces away, everyone was stunned by the unusually loud noise and the extraordinarily huge fireball.

"Brother Yixian, how can such a light of gunpowder explode with such power?"

Of course, Tsunazaburo Kato would not miss the test firing of this ballista, at this moment he was holding a thick crossbow arrow more than three feet long in his hand, repeatedly looked at the iron arrow that did not look big, and shook his head again and again to express his puzzlement.

"Well," Chu Fan said perfunctorily while watching Zhu Zi and Zhao Hai wind up the bed crossbow, "Fan has his own magic method." ”

Kato Tsunazaburo understood as soon as he heard it - just like the fairy grass cigarette, this Ming Guoxiu just added ingredients to the black fire * medicine again, but what kind of ingredients did he add? Tsunazaburo can figure it out with his toes, and Chu Fan will never tell him.

This Chu Fan is simply as cunning as a ghost!

Tsunasaburo's face was blue and white for a while, and he cursed fiercely in his heart, but he was helpless, and he held back for a long time before he burst out with a sentence, "Brother Yixian, you can make a price, how much is this black fire * medicine a catty?" ”

Only then did Chu Fan take his eyes off the pillars and turn to Tsunasaburo's face and said, "San Lang, I'm still experimenting with this black fire potion, and I'll sell it to you when I find the most powerful recipe...... I'm an honest businessman, and I started selling it without trying it out, so isn't that a fake? ”

Tsunazaburo's face looked a little better, and he insisted again, "What is the approximate price?" I'll let my uncle know. ”

"Don't worry, it's not too expensive." Chu Fan smiled and comforted Tsunasaburo. But his next sentence made Tsunazaburo almost vomit blood, "At most, it's three times the market price...... Do you Kato family still care about this little money? ”

Tsunasaburo has a feeling of being stripped naked and thrown on the board waiting to be slaughtered - listen, Chu Xiucai has tripled the price with a few words, but he still has to rush to buy it!

There was no way, if the Master Matsusada, who was in charge of training the monks, knew that there was such a good black fire medicine and the Kato family ignored it...... Tsunazaburo hurriedly shook his head, that is an unforgiving master!

He was still thinking about adding black fire* powder, and Chu Fan had already paced to the ballista that was winding.

The three-bow bed crossbow is extremely powerful, but it is rarely used except to defend the city, because in addition to being bulky and difficult to move, it is also extremely difficult to wind.

Now there are eight people who wind the crossbow on the bed—one on the left and one on the right, four on each side—and these eight people are all strong men with infinite strength like Zhu Zi and Zhao Hai, but now the eight of them are all sucking, and the thick bowstring is still slowly pulling back like a snail crawling.

Finally, the eight of them finally pulled the bowstring into place, but they were all so tired that they sat down on the deck and rubbed their arms.

Well, it looks like this ballista needs to be overhauled!

In Chu Fan's heart, he already had a way.

PS: Bow and thank Jiang Xuanjing for his great support, the crab can't be repaid, and a more chapter will be added tomorrow :)