Wednesday, November 28, 2007

The windbüchse of Prostl - Part 3
A fictional account of the development of an early airgun

Part 1
Part 2

by Tom Gaylord

The next day, old August Bidderman went to work in his shop with renewed vigor. He needed a powerful screw, and he needed to attach to it a long lever—the kind with which Aristotle might have moved the world. Together, they might just provide the mighty force required to bend the solid steel lock while it was still as cold as stone.

He knew that printers had large screws to run their presses. But the force he required went so far beyond any printing press in existence that the comparison was only in kind. He needed a much larger screw than any printing press.

His answer might lie in the university. They had a machine that generated huge forces by means of a mechanical screw. Could he "borrow" just the screw? No, he could not. It was embedded within a complex press that was too valuable to be dismantled, no matter how skilled the craftsman.

Then, could he use the press? Perhaps. First, the regent would have to be informed of the complete nature of the intended experiment, and of course the university would somehow have to be compensated for the use of their valuable machine. Bidderman knew the regent wanted money for himself, but he thought he could disguise his work sufficiently to get it past him without comment. The Baron could take care of the fee. But when the price was named, it proved too large to even approach his patron.

That left him to his own devices. He would have to construct a press to generate huge forces that were beyond imagination. If only steel weren't so very hard! But that was what made it steel—after all. If only it could be hard under some circumstances and soft under others. On this point, he pondered at length, which gave him an idea. If anyone knew all the properties of steel, it had to be the very same Spaniards from whom his supply of the metal had originally come. He had to talk to one of them who knew how to work the metal. But where would he find such a man? In Vienna, of course.

The city of Vienna was famous as one of the continent's busiest crossroads, even in the early 18th century. Bidderman traveled there by coach, paid for by his patron, who knew as well as he the value of the knowledge he sought. If August said there was something he had to learn before proceeding on the gun, nothing could be allowed to hinder him.

Once in the city, he paid an agent to arrange a meeting with the right people who, as it turned out, were in permanent residence. They had been commissioned by the city fathers to construct a wondrous new clock, whose train of steel-shod gears would last a millennium or more. Their knowledge of the metal was encyclopedic, as it had to be, for they were many weeks journey from the source of metal and the legendary foundries of Toledo. Still, they managed quite well with what looked to the uninformed to be a well-provisioned blacksmith's shop. That was where the master of Prostl met with them and that was where the new knowledge was imparted.

“You see, Herr Bidderman, steel is a most complex substance." his tutors counciled. "It's nothing at all like the iron from which it is made. Even though the two metals resemble one another closely and both are known to attract the needle of a compass, steel is by far the better material. For strength and durability, it has no equal.

“Now, as to bending it—that is where the nature of the metal is to your advantage. If you are a careful worker, and we know beyond the shadow of a doubt that you are, you can bend the steel as easily as you can iron, yet still retain all the properties of the stronger metal."

With that pronouncement, the Spaniard showed August how, by controlling the temperature of the metal through observation of its color when heated, one could bend it as easily as iron, yet still retain all the precious carbon that gave it its character. No matter how large the piece, as long as the heat was even and controlled and did not go too high, the steel would bend.

Bidderman remained in the city a fortnight, learning all that his funds entitled him to, then he secured passage on the first coach going near his village. Within a week of returning, old August had built the special forge he required to control the temperature precisely. Like the object he was crafting, the secret of the forge was also forced wind. Another two weeks were required to fashion the powerful screw he required, together with the mechanism in which it would operate. Built mostly from iron, he used some of his precious steel to strengthen the parts that would take the largest strain.

As it turned out, the screw he needed wasn’t nearly as large as he originally imagined it would have to be. The secret of heating the steel allowed the use of much less force. That was a blessing, because even at its reduced size, making the screw proved a daunting task for the clockmaker. Its scale was beyond what he was used to.

After performing several trials to see that his new apparatus worked as intended, he finally heated the steel lock and bent it to precisely the angle he required. Because of the subtle angle put into the lock, the butt of the gun would rest squarely on the shooter's shoulder while the barrel would point naturally in the direction of the target. The bend was so trivial that August could only see it if he concentrated very hard. He had to use a straightedge to demonstrate its deflection for the casual observer, but since the gun was a secret, the only one he showed it to was the Baron. Still, it was this bend—the very whisper of a curve—that gave his weapon the grace of the ages, instead of looking like something a tinsmith had put together.

For a barrel, Bidderman selected a slender brass bar, which he had also obtained while in Vienna. This he heated and stretched by working it over an iron mandrel until it stretched three times its original length. The mandrel left a smooth bore that he could simply freshen with a small cutter, but the master was far from finished with his innovations on this gun. Instead of just reaming out a straight smooth hole as any competent gunsmith would have done, he made a tiny cutter to insert into the barrel. By following a carefully made gearing mechanism on the outside of the work, the cutter proceeded to cut a shallow spiral down the inside of the brass tube.

The cutting machine was based on one he used for clock gears, so it was little trouble to index the cutter again and again until the inside of the tube contained an even dozen scratches, all parallel to each other and all spiraling down to the muzzle. These scratches, when properly deepened by repeated cutting, were called rifling, the effects of which had been discovered by the Flemish a century before.

The original thought was that the rifling imparted a spin to the ball, which made it impossible for demons to sit astride and steer it off its course. No one believed such a myth in the 18th century, however. They had deduced that a spinning ball must act like a child's top, and be better balanced through its flight. Whatever the science, the spinning ball was proven many times more likely to strike the target than one that flew free.

Again and again, Bidderman fed his tiny cutter down each scratch. It was at this point that the precise indexing of his machine paid off, for his eyes could discern none of the grooves yet. Pass after pass of the cutter was made, deepening each groove in turn until it was finally possible to see them all. When he noticed this, he pushed a ball through the barrel and saw it come out the muzzle with the perfect impression of the rifling engraved on its sides. The Baron would have no trouble hitting what he shot at with this gun! The borrowed wind gun from the Low Countries had a smooth barrel, so already he had kept his promise to make this one better.

3 Comments:

At 11:14 PM, Blogger Kevin said...

Tom,
Please excuse this if you have already gotten the question. (I am having trouble with blogger tonight.)
I noticed on Dr. Beeman's site in the Girandoni articles, a comment from him that intrigued me, "Girandoni military air rifle that the discharge sound is quite audible, though by no means as loud as a similar large bore flintlock firearm. However, the fact the guns discharge without smoke or muzzle/pan flash does make locating the position of someone firing such a gun much more difficult. (Modern note: Powerful, modern, silenced, 9mm PCP airguns are being used by U.S. Seals in Iraq to snipe at insurgents. Firing an M-16 at dawn or dusk could attract a lot of return fire to the flash point.)"

What are our guys using in Iraq, and how are they silenced, etc...
Best regards,
Kevin

 
At 8:04 PM, Blogger TSBrat2002 said...

Kevin,

That would sound like the Shin Sung rifles to me.

Tom,

I decided to re-read the originals you posted and see which I could pick as my favorite of them. Couldn't do it, it was basically a tie. Andy & Squirrel Boy. If I had to give an edge, Squirrel Boy would have it, for the expression on his face in the picture, but just barely.

 
At 10:05 PM, Blogger rimugu said...

Wow, now I will have to be waiting for the next part.

 

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