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 pushing shutters open when the ship 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 ship, 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 bushings 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 ship, 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). Ship 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.
Ship 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 ship 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 battleships 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.
4.5 inches Thickness of cheek 5.8 inches.
50 inches Wheel diameter 58 inches.
6x8x68 inches Axletree 7x9x81 inches.
Heavy siege guns were elevated with quoins, and elevation was restricted to 12 or less, which was about the same as United States siege carriages permitted in 1861. It was considered ample for these flat trajectory pieces.
Both field and siege carriages were pulled over long distances by lifting the trail to a horse-or ox-drawn limber; a hole in the trail transom seated on an iron bolt or pintle on the two-wheeled limber.
Some late eighteenth century field and siege carriages had a second pair of trunnion holes a couple of feet back from the regular holes, and the cannon was shifted to the rear holes where the weight was better distributed for traveling. The United States siege carriage of the 1860"s had no extra trunnion holes, but a "traveling bed" was provided where the gun was cradled in position 2 or 3 feet back of its firing position. A well-drilled gun crew could make the shift very rapidly, using a lifting jack, a few rollers, blocks, and chocks. When there was danger of straining or breaking the gun carriage, however, ma.s.sive block carriages, sling carts, or wagons were used to carry the guns.
Sling wagons were of necessity used for transport in siege operations when the guns were to be mounted on barbette (traversing platform) carriages (fig. 10). Emplacing the barbette carriage called for construction of a ma.s.sive, level subplatform, but it also eliminated the old need for the gunner to chalk the location of his wheels in order to return his gun to the proper firing position after each shot.
The Federal sieges of Forts Pulaski and Sumter were highly complicated engineering operations that involved landing tremendously heavy ordnance (the 300-pounder Parrott weighed 13 tons) through the surf, moving the big guns over very difficult terrain and, in some cases, building roads over the marshes and driving foundation piles for the gun emplacements.
The heavy caliber Parrotts trained on Fort Sumter were in batteries from 1,750 to 4,290 yards distant from their target. They were very accurate, but their endurance was an uncertain factor. The notorious "Swamp Angel," for instance, burst after 36 rounds.
FIELD CANNON
[Ill.u.s.tration: Figure 33--SPANISH 4-POUNDER FIELD CARRIAGE (c. 1788).
This carriage, designed on the "new method," employed a handscrew instead of a wedge for elevating the piece, a--The handspike was inserted through eyebolts in the trail, b--The ammunition locker held the cartridges.]
The field guns were the mobile pieces that could travel with the army and be brought quickly into firing position. They were lighter in weight than any other type of flat trajectory weapon. To achieve this lightness the designers had not only shortened the guns, but thinned down the bore walls. In the eighteenth century, calibers ran from the 3- to the 24-pounder, mounted on comparatively light, two-wheeled carriages. In addition, there was the 1-1/2-pounder (and sometimes the light 3- or 6-pounder) on a "galloper" carriage--a vehicle with its trail shaped into shafts for the horse. The elevating-screw mechanism was early developed for field guns, although the heavier pieces like the 18- and 24-pounders were still elevated by quoins as late as the early 1800"s.
In the Castillo collection are parts of early United States field carriages little different from Spanish carriages that held a score of 4-pounders in the long, continuous earthwork parapet surrounding St.
Augustine in the eighteenth century. The Spanish mounts were a little more complicated in construction than English or American carriages, but not much. Spanish pyramid-headed nails for securing ironwork were not far different from the diamond-and rose-headed nails of the English artificer.
Each piece of hardware on the carriage had its purpose. Gunner"s tools were laid in hooks on the cheeks. There were bolts and rings for the lines when the gun had to be moved by manpower in the field. On the trail transom, pintle plates rimmed the hole that went over the pintle on the limber. Iron reinforced the carriage at weak points or where the wood was subject to wear. Iron axletrees were common by the late 1700"s.
For training the field gun, the crew used a special handspike quite different from the garrison handspike. It was a long, round staff, with an iron handle bolted to its head (fig. 33a). The trail transom of the carriage held two eyebolts, into which the foot of the spike was inserted. A lug fitted into an offset in the larger eyebolt so that the spike could not twist. With the handspike socketed in the eyebolts, lifting the trail and laying the gun was easy.
The single-trail carriage (fig. 13) used so much during the middle 1800"s was a remarkable simplification of carriage design. It was also essential for guns like the Parrott rifles, since the thick reinforce on the breech of an otherwise slender barrel would not fit the older twin-trail carriage. The single, solid "stock" or trail eliminated transoms, for to the sides of the stock itself were bolted short, high cheeks, humped like a camel to cradle the gun so high that great lat.i.tude in elevation was possible. The elevating screw was threaded through a nut in the stock, right under the big reinforce of the gun.
While the larger bore siege Parrotts were not noted for long serviceability, Parrott field rifles had very high endurance. As for performance, see the following table:
_Ranges of Parrott field rifles (1863)_
Caliber Weight Type of Projectile Elevation Range Smoothbore of gun projectile weight of same (pounds) (pounds) caliber
10-pounder 890 Sh.e.l.l 9.75 5 2,000 3-pounder.
do 9.75 20 5,000 20-pounder 1,750 do 18.75 5 2,100 6-pounder.
do 18.75 15 4,400 30-pounder 4,200 do 29.00 15 4,800 9-pounder.
do 29.00 25 6,700 Long sh.e.l.l 101.00 15 4,790 do 101.00 25 6,820 Hollow shot 80.00 25 7,180 do 80.00 35 8,453
Amazingly enough, these ranges were obtained with about the same amount of powder used for the smoothbores of similar caliber: the 10-pounder Parrott used only a pound of powder; the 20-pounder used a two-pound charge; and the 30-pounder, 3-1/4 pounds!