Midst Toil And Tribulation – Snippet 37
Seamount had initially proposed designating rifled guns by the weight of their solid shot while changing the designations for smoothbores to the diameter of their bores, since it was primarily the increase in projectile weight which presented the technical challenges he had to solve. In the end, however, he’d decided it would cause too much confusion. Every officer of the Imperial Charisian Navy knew exactly what a “thirty-pounder” meant right now, so he’d chosen to label the new guns using the new nomenclature rather than confuse the issue by making everyone learn yet another new one. Besides, the guns were all going to be firing more than one weight of projectile in the very near future, anyway. The thirty-pounder’s solid shot actually weighed almost thirty-two pounds, but its shell — with fifty-five cubic inches less iron and a roughly two-pound bursting charge — weighed less than eighteen. The six-inch rifle’s solid shot, on the other hand, weighed over a hundred pounds, and the standard shell carried an eleven-pound bursting charge and weighed sixty-seven pounds. And at the moment, Merlin knew, Seamount and Rahzwail were working on heavy shells for attacking armor and masonry. The thicker walls of the new shell’s central cavity would reduce the bursting charge to no more than three or four pounds but increase overall shell weight by thirty-five percent, which would give it much greater striking power and penetration.
It would also increase the bore pressures and recoil forces still further, of course. Still, the same basic design for a recuperator — effectively, a hydro-pneumatic recoil system — ought to work equally well for the thirty-pounder and the six-inch, although he understood Seamount’s reservations about applying their current design to the much heavier eight-inch and ten-inch rifles Edwyrd Howsmyn was currently designing. It ought to work, but until they positively proved it would, they couldn’t approve a final design for the new guns’ mounts.
The original concept had Mahndrayn’s, although Rahzwail had taken the dead commander’s original rough sketches and, along with Hainai, turned them into a practical proposition. Essentially, it was simply a pair of large, sealed cylinders, one filled with oil and the other with compressed air. The gun was rigidly attached to a piston inside the oil-filled cylinder; when it fired, recoil pulled the piston towards the rear, forcing the oil through a small opening into the second cylinder. The second cylinder’s free-floating piston separated the oil from a confined volume of compressed air, and as the floating piston was pressed forward, it compressed the air even further. The result was to absorb the recoil progressively, braking it smoothly as the internal air pressure rose, and at the end of recoil, that increased air pressure generated a back pressure that returned the gun forward to its original position.
It was only one of several approaches from Mahndrayn’s fertile imagination, including the pivoting slide carriage the Navy had adopted while it waited for the hydro-pneumatic system to be worked out. The current carriage, just being introduced, would have been called a “Marsilly carriage” back on Old Earth, and it was a major improvement on even the “new model” carriages one Merlin Athrawes had introduced only five years earlier. There had been some resistance to it, since it required iron or steel slides, but its advantages had quickly become evident. Pivoted at the front end of the carriage, it could be quickly moved to new angles of train. Two men with roller-ended handspikes could train it quite easily on its eccentric axles, and since it used the friction between the metal slide and the transom of the piece to damp recoil, its recoil path was much shorter, which meant it could be loaded and fired much more rapidly. It had already been tested satisfactorily with thirty-pounders, and it could be fitted with compressor screws to increase the friction for still heavier guns, if needed.
The Mahndrayan carriage was more practical than some of his other ideas, although his spring-driven recoil mechanism would probably work for lighter pieces. (Another design, for coastal artillery, using counterweights in a deep pit under the gun platform had proved practical even for the heaviest cannon, although the system would have been totally unworkable for a naval mounting.) As far as the recuperator was concerned, however, Rahzwail had profited in his development of Mahndrayn’s original sketches by consulting with the Royal College. Doctor Mahklyn had been able to nudge him gently past a couple of obstacles, but the vast majority of the work was his and Hainai’s original work, with substantial contributions from the College’s Doctor Vyrnyr. Merlin had found himself tempted to step in and push the project more than once, but Rahzwail and Hainai were doing exactly what he needed Safeholdians to learn to do, and so he’d let them run with it.
, he thought now, we do have a few advantages Ahlfryd and the others don’t know about. For example, I feel strangely confident that Ehdwyrd’s artificers will solve that leakage problem before too much longer. I believe “Doctor Owl” will have a little something to say about that!
“If — or, rather, when — we get the leak problem licked, we’ll have an effective recoil absorbing system,” Seamount continued, “and if we can manage that, I feel confident we’ll be able to produce the ‘pedestal mounts’ at least for lighter pieces.” He glanced at Merlin with a half smile as he used the term Merlin had coined. “For the heavier pieces, we’re still going to need something more massive, but I think the pivot mounts Fhranklyn and Master Howsmyn have been working on should prove practical. Frankly, one of the things that’s bothered me the most has been the need to integrate some sort of capture mechanism to latch the gun in the fully recoiled position for loading. It works fine with Urvyn’s counterweight system for the shore batteries, but I’m less comfortable with it for the recuperator. It’s an added complication and another potential failure point in the entire system, not to mention significantly increasing strain — or, at least, the period of maximum stress — on the pneumatic cylinder. But we have to bring the muzzle back inboard and keep it there if we’re going to reload it. Or” — he looked back up from his notes suddenly, his eyes sharp — “that’s been our working assumption from the time Urvyn and I started on the project. Now, however, Ahldahs and Fhranklyn have come up with a completely new suggestion.”
“New suggestion?” Rock Point cocked his head at Seamount and Rahzwail. “They do seem to come rather fast and furious around your lot, Ahlfryd. Is this another one I’d rather not get too close to on the proving ground?”
“It should work fine, Sir,” Seamount said reassuringly. “In theory, at least.”
“I could’ve gone all month without that little qualifier,” Rock Point said dryly. “I seem to remember a few other qualifiers which led to loud, noisy explosions.”
“But most of them’ve worked out in the end, Sir.”
“Including that flamethrower notion of yours? Or the liquid incendiary shell fillings?” Rock Point inquired just a bit tartly.
“I did say most, not all, Sir.”
Rock Point eyed him coldly for a moment, then snorted.
“Yes, you did. And, yes, most of them have worked out . . . so far. So what has Captain Rahzwail come up with this time?”
“Ahldahs?” Seamount looked across the table at his assistant, and Captain Rahzwail squared his shoulders.
“The idea actually came to me from another of Commander Mahndrayn’s sketches, My Lord. When he was looking at ways to seal the breach of his rifle, he considered the possibility of using a threaded plug, one that would screw in and out and produce a tight seal that way. He adopted the solution he finally chose because it would take much longer to screw a breech plug all the way in and out, and also because he was concerned fouling would cement the plug in place. But the notion of a threaded breech plug or block stuck in my brain, and it occurred to me that the plug didn’t have to be completely threaded.”
“I beg your pardon?” Rock Point frowned, his expression intent.
“If we were to cut away a part of the threads, My Lord, so that the plug could slide all the way into position, then rotate through a half-turn or so and lock solidly into place, it would greatly reduce the time between shots.”