Monday, December 03, 2007

The windbüchse of Prostl - Part 4
A fictional account of the development of an early airgun

by Tom Gaylord

Part 1
Part 2
Part 3

The butt of the piece was intended to hold the condensed wind, and must therefore allow none of it to escape. He fashioned it from thick sheet iron, which he folded into a long hollow triangular shape that was locked together at the seam on the bottom with a special mechanical lip and shelf. The butt plate was similarly attached, then brazed with hot brass around its seam to prevent leaks. After two dozen iron rivets had been installed to prevent the long seam on the bottom of the butt from weakening under pressure, it was similarly brazed for integrity. It took no small skill to braze that long seam accurately, but such skill was part of what made the old man the master he was. Now fashioned, the butt was ready to contain the real secret of the gun. Bidderman's special wind-lock valve.

In his dreams about the gun, the master had seen that wind, like all natural forces, moves according to rules that never change. Once, when shooting the prototype gun from the Low Countries, he had chanced a second shot and found it to be nearly as strong as the first. That started him thinking that if the wind was allowed to exit the gun through a portal that remained open for only an incredibly short amount of time, there might be enough remaining in the butt for a second shot. Perhaps even more. He began to think of the wind as he did the water that powered the village mill. It was controlled by the width of the millrace and therefore was always moving the mill wheel with the same force, regardless of how high the stream was.

From his clockmaking, old August knew that force was the result of both opportunity and desire. The wind in the butt had a great desire to escape, but it didn't have the opportunity until the valve provided it. By allowing only a small opening to pass the escape hole for a brief moment in time, he could control how much wind was expelled with each shot, thereby leaving some for the next shot.

He made many of the valve parts from brass, for he knew that metal best of all. It would work tirelessly for years without lubrication. It could work at great pressure, so it was perfect for a part that would reside in the butt, where the pressure would sometimes be extreme. But best of all, brass would not corrode like iron and even steel. This was important for a part subjected to the heating of the condensing syringe and the cooling caused by sudden release at firing. Yes, brass was perfect for this job.

To seal the opening at the tip of the valve, he selected material from the fresh horn of a bull. When cut to size and fitted to the steel rod that passed through the brass valve head, a ring made from bull-horn stopped the flow of air almost perfectly. But almost was not good enough for August Bidderman. He desired a vessel which, when filled with condensed wind, would retain all of it for a full day or even longer. So he turned the steel rod tipped with bull-horn against the brass end of the valve, adding common chalk for lubrication, until the valve screeched like a vixen in the spring. This was the sound that announced a perfect mating of horn to metal. When oiled with a small amount of sperm oil, the valve would contain the wind tightly. Bidderman pronounced the work good, but he did one more thing before moving on.

He removed the brass valve from the iron butt and smeared grease on the walls inside the butt. Now, when dirt particles made their way into the butt from the condensing syringe, they would stick to the grease instead of getting into the smooth valve parts to disrupt the seal. The gun from the Low Countries had been treated in this way, and he could see the value when he examined it. Before returning that piece, he had cleaned out the old grease and applied fresh in its place. Such a job might be expected to last for up to five years, depending on the goodness of the grease, how many times the butt was filled and how quickly the grease aged. Except for a covering, the butt was now complete.

The cover was fashioned from the skin of a shark! Bidderman cut the leather to fit, then artfully stitched the seam with the finest deer tendon fiber. Then he slid the covering on the butt and immersed it in water for a day. When it was removed and dried in the sun, it tightened like any leather would, adding strength to the butt. This material, known as shagreen, was not common in Bidderman’s day, but it would become the most popular kind of covering for wind gun reservoirs within the next 50 years.

For the lock and all its working parts, only forge-hammered steel would do. Bidderman carefully heated each part of his lock in the forge then skillfully hammered them into the proper shapes. Files did the finish work, of course, but he wanted to get as close as possible with the forged part to retain the integrity of the metal's own living grain.

One part that almost stumped the old master was the powerful spring to drive the hammer. An ordinary snaphance or flintlock hammer simply causes flint to strike steel with force, but Bidderman's lock required the hammer to push the valve lever through a determined arc against the force of wind trying to escape the butt. That was how the marvelous valve he designed worked. It had to be pushed both open and then be allowed to close by the two-way action of the lever, which was made to operate by the unique shape of the hammer.

To do all that work required a spring that had never before been constructed. Oh, far larger and more powerful springs existed for a long time before this. Coaches had them, as did a number of large mechanical devices. Even large clocks had them. But never before had the power required for Bidderman's lock been made into a spring small enough to fit within the lock he designed. He had to experiment until he got what he wanted.

Weeks went by as the old master labored to fashion that which he had never seen. A few times he lost confidence and had to do other work until his mind had cleared once more. One full year and a part of the next had passed since the Baron had given his word to proceed and still the promised gun did not exist. And, unless he could fashion a spring to power it, it never would.

He tried new shapes and sizes but nothing was to any practical avail. The closest he got was a huge spring that was too outsized for any gun. By tying his gun to the workbench and leaving the lockplate off, he could mount this spring and get off a shot of wind from the butt before the spring jumped out of position.

What he needed was a spring with the strength of this huge one, yet its size had to be more like that of a firelock spring. He made one that was so thick it stuck out to the side of the lock, but it did remain on when he shot the gun and the whole thing did work. But this fat spring was too ungainly for him to put on anything that bore his own precious name, so back he went to figure something new.

All this power was causing the outside of his comely lock to triple in size. No longer was its elegance visible behind the huge outer housing needed to contain both the huge hammer spring and the trigger spring.

He needed the mass of a large spring to fit into the space of a small one. One day, for no reason he could discern, he remembered his youth as an apprentice sawyer, before he had impressed the father of his current patron with his great talents for metal work. As a young apprentice, he was the one who got all the worst work, so of course he was the man down in the pit who pulled on the bottom of the saw.

The pit man had the dirtiest job at the mill, for the sawdust fell straight down on him with every downward stroke of the blade. There was no breeze in the musty pit, so in minutes, he was covered with sawdust from head to toe. Even though he took three dunkings a day in the stream, he still had sawdust in every crevasse of his body. It was why, to this day, old August would only used riven planks to make anything. It was his contribution to the pit men of the world, to keep the demand for sawn planks to a minimum.

For several years, though, he had been aware of a new machine that eliminated the man in the pits, by allowing the top man to do all the work by himself. Because of his experience as a youth, he paid keen attention to how that machine was constructed, since it paroled so many young men from a purgatory of filth and bad health. The interesting thing about that machine is that it multiplied the force of the one sawyer by extending his arms through levers. An especially long lever of iron, called a pitman arm, did the work that a man formerly had to do. The pitman arm was attached to a powerful spring, and since the entire mechanism was too ungainly to fit into the pit, it was constructed in such a way as to remain outside. The machine was therefore much larger than the workplace, and had to be built outside it. Could the same be done for the spring of his lock?


Post a Comment

<< Home