Part 6 (1/2)
For a four-wheeled English carriage of 1750, height of the cheek was 4-2/3 diameters of the shot, unless some change in height had to be made to fit a gun port or embrasure. To prevent cannon from pus.h.i.+ng shutters open when the s.h.i.+p rolled in a storm, lower tier carriages let the muzzle of the gun, when fully elevated, b.u.t.t against the sill over the gun port.
On the eighteenth century Spanish garrison carriage (fig. 28), no bolts were threaded; all were held either by a key run through a slot in the foot of the bolt, or by bradding the foot over a decorative washer. Compared with American mounts of the same type (figs. 30 and 31), the Spanish carriage was considerably more complicated, due partly to the greater amount of decorative ironwork and partly to the design of the wooden parts which, with their carefully worked mortises, required a craftsman's skill. The cheek of the Spanish carriage was a single great plank. English and American construction called for a built-up cheek of several planks, cleverly jogged or mortised together to prevent starting under the strain of firing.
[Ill.u.s.tration: Figure 30--ENGLISH GARRISON CARRIAGE (1756). By subst.i.tuting wooden wheels for the cast-iron ones, this carriage became a standard naval gun carriage.]
Muller furnished specifications for building truck (four-wheeled) carriages for 3- to 42-pounders. Aboard s.h.i.+p, of course, the truck carriage was standard for almost everything except the little swivel guns and the mortars.
Carriage trucks (wheels), unless they were made of cast iron, had iron thimbles or bus.h.i.+ngs driven into the hole of the hub, and to save the wood of the axletree, the spindle on which the wheel revolved was partly protected by metal. The British put copper on the _bottom_ of the spindle; Spanish and French designers put copper on the _top_, then set iron ”axletree bars” into the bottom. These bars strengthened the axletree and resisted wear at the spindle.
A 24-pounder fore truck was 18 inches in diameter. Rear trucks were 16 inches. The difference in size compensated for the slope in the gun platform or deck--a slope which helped to check recoil. Aboard s.h.i.+p, where recoil s.p.a.ce was limited, the ”kick” of the gun was checked by a heavy rope called a breeching, shackled to the side of the vessel (see fig. 11). s.h.i.+p carriages of the two-or four-wheel type (fig. 31), were used through the War between the States, and there was no great change until the advent of automatic recoil mechanisms made a stationary mount possible.
[Ill.u.s.tration: Figure 31--U. S. NAVAL TRUCK CARRIAGE (1866).]
With garrison carriages, however, changes came much earlier. In 1743, Fort William on the Georgia coast had a pair of 18-pounders mounted upon ”curious moving Platforms” which were probably similar to the traversing platforms standardized by Gribeauval in the latter part of the century. United States forts of the early 1800's used casemate and barbette carriages (fig. 10) of the Gribeauval type, and the traversing platforms of these mounts made training (aiming the gun right or left) comparatively easy.
Training the old truck carriage had been heavy work for the handspikemen, who also helped to elevate or depress the gun. Maximum elevation or depression was about 15 each way--about the same as naval guns used during the Civil War. If one quoin was not enough to secure proper depression, a block or a second quoin was placed below the first. But before the gunner depressed a smoothbore below zero elevation, he had to put either a wad or a grommet over the ball to keep it from rolling out.
s.h.i.+p and garrison cannon were not moved around on their carriages. If the gun had to be taken any distance, it was dismounted and chained under a sling wagon or on a ”block carriage,” the big wheels of which easily rolled over difficult terrain. It was not hard to dismount a gun: the keys locking the cap squares were removed, and then the gin was rigged and the gun hoisted clear of the carriage.
A typical garrison or s.h.i.+p cannon could fire any kind of projectile, but solid shot, hot shot, bombs, grape, and canister were in widest use. These guns were flat trajectory weapons, with a point-blank range of about 300 yards. They were effective--that is, fairly accurate--up to about half a mile, although the maximum range of guns like the Columbiad of the nineteenth century, when elevation was not restricted by gun port confines, approached the 4-mile range claimed by the Spanish for the sixteenth century culverin. The following ranges of United States ordnance in the 1800's are not far different from comparable guns of earlier date.
_Ranges of United States smoothbore garrison guns of 1861_
Caliber Elevation Range in yards
18-pounder siege and garrison 5 0” 1,592 24-pounder siege and garrison 5 0” 1,901 32-pounder seacoast 5 0” 1,922 42-pounder seacoast 5 0” 1,955 8-inch Columbiad 2730” 4,812 10-inch Columbiad 3915” 5,654 12-inch Columbiad 39 0” 5,506
_Ranges of United States naval smoothbores of 1866_
Caliber Point-blank range Elevation Range in yards in yards 32-pounder of 42 cwt 313 5 1,756 8-inch of 63 cwt 330 5 1,770 IX-inch sh.e.l.l gun 350 15 3,450 X-inch sh.e.l.l gun 340 11 3,000 XI-inch sh.e.l.l gun 295 15 2,650 XV-inch sh.e.l.l gun 300 7 2,100
_Ranges of United States naval rifles in 1866_
Caliber Elevation Range in yards
20-pounder Parrott 15 4,400 30-pounder Parrott 25 6,700 100-pounder Parrott 25 7,180
In accuracy and range the rifle of the 1860's far surpa.s.sed the smoothbores, but such tremendous advances were made in the next few decades with the introduction of new propellants and steel guns that the performances of the old rifles no longer seem remarkable. In the eighteenth century, a 24-pounder smoothbore could develop a muzzle velocity of about 1,700 feet per second. The 12-inch rifled cannon of the late 1800's had a muzzle velocity of 2,300 foot-seconds. In 1900, the Secretary of the Navy proudly reported that the new 12-inch guns for _Maine_-cla.s.s battles.h.i.+ps produced a muzzle velocity of 2,854 foot-seconds, using an 850-pound projectile and a charge of 360 pounds of smokeless powder. Such statistics elicit a chuckle from today's artilleryman.
SIEGE CANNON
Field counterpart of the garrison cannon was the siege gun--the ”battering cannon” of the old days, mounted upon a two-wheeled siege or ”traveling” carriage that could be moved about in field terrain.
Whereas the purpose of the garrison cannon was to destroy the attacker and his materiel, the siege cannon was intended to destroy the fort.
Calibers ranged from 3- to 42-pounders in eighteenth century English tables, but the 18- and 24-pounders seem to have been the most widely used for siege operations.
[Ill.u.s.tration: Figure 32--SPANISH EIGHTEENTH CENTURY SIEGE CARRIAGE.]
The siege carriage closely resembled the field gun carriage, but was much more ma.s.sive, as may be seen from these comparative figures drawn from eighteenth century English specifications:
24-pounder 24-pounder field carriage siege carriage
9 feet long Length of cheek 13 feet.