Barbette or Casemate?

On several occasions I’ve mentioned barbette and casemate carriages.  In the 19th century, seacoast fortifications used both mountings for their main armaments.   To maximize the firepower on each facing of the fort, engineers stacked tiers, each supported by strong arch structures.   This cutaway model display at Fort Pulaski provides a good visual reference.

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Cutaway of Fort Pulaski

On top, the model has pads and fixtures for front pivot guns.  Manuals of the period identified these as “barbette”. The guns mounted there fired over the parapet, mounted on tall barbette carriages.   A good example of such supports a 32-pdr seacoast gun at Fort Moultrie, South Carolina today.

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32-pdr Seacoast Gun on Barbette Carriage, Fort Moultrie

The gun sits on a truck, formed by an angle brace, sort of a triangle, which slides upon a bed.  The bed consisted of two side rails and a center rail.  Most pre-war (1840s or earlier) featured a large “wheel” for handling.  This allowed the crew to roll the truck forward on the supporting Later examples, particularly for the columbiads, used handspikes for running the gun out.

“Eccentric” axles, which were slightly off true center axis, baffled the recoil when the gun was fired.  As anyone who has experienced an out of balance tire on their car knows, such off-center wheels tend to reduce speeds.  When running the truck forward, a leaver lifted the gun and truck up to “true center” axis, so the crew didn’t have to work as hard.  But crews had to engage the eccentrics before the gun was fired, else the recoil was dangerous.  (And some will recall that failure to engage the eccentrics caused some damage to guns at Fort Sumter in April 1861.)

By the late 1850s, wrought iron replaced wood in many situations (although iron did not replace wood during the Civil War).  Located a few yards away from the 32-pdr at Fort Moultrie is a pair of 15-inch Rodmans on front pintle iron barbette mounts.

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15-inch Rodman on Barbette Carriage, Fort Moultrie

Generally similar in layout with the wooden carriages, the iron versions relied on two side rails and dispensed with the center rail.  Regardless of wood or iron, the design of barbette carriages allowed the guns to stand over the parapet, and also afforded higher angles of elevation.  Because of this, the heaviest, longest-range guns in a seacoast fort usually sat on the barbette tier.  Of course, the height of the carriage profiled the gun and crew who had no overhead cover.

Looking back to the Fort Pulaski model, below the covered way are a series of arches, between which are more pads and fixtures for front pivot guns.  These form a gallery of casemates.  The casemate guns fired through an embrasure (seen to the right of the model).  An example of a gun on a casemate carriage greets visitors to Fort Sumter today.

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42-pdr Seacoast Gun on Casemate Carriage, Fort Sumter

Ordnance officers designed the casemate carriage with the cramped space of the gallery in mind.  Instead of a tall triangle truck, the casemate guns sat on a truck very similar in profile to navy carriages.  The casemate crews used handspikes to work a small wheel when running the gun out.

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Banded and Rifled 42-pdr, Fort Sumter

Like the barbette carriage, the casemates relied upon an eccentric to reduce recoil force.  One of those eccentric rollers is at the back of the truck in the view above.   Also in this view, note the slots for the handspikes in the wheel on the left of the carriage.

As with the barbette carriages, the Army began using wrought iron carriages just before the Civil War.  Several excellent examples of such carriages sit just a few yards away from the 42-pdrs at Fort Sumter.

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6.4-inch Parrott on Iron Casemate Carriage, Fort Sumter

Following similar evolutions to the barbette carriages, the iron casemates featured only two side rails.  Ordnance officers did not intend the casemate guns to fire at elevation, as the embrasure limited the angle of fire.  But the gunners were protected behind the fort’s structure.  Shutters (in some cases spring-loaded iron types) closed the embrasure when the gun ran back.  This gave the casemate gun crew much more protection than those exposed on the barbette.

Keep in mind that carriages allowed mounting even the largest guns on either the barbette or casemate tiers.  In operation, the Army left the employment to the opinions of the fort’s commander.  During peaceful times, many commanders kept the guns and equipment in the casemates to reduce exposure to the elements.

Not all American seacoast forts featured casemate tiers, but the major forts did.  Fort Sumter had two casemate tiers in addition to the barbette level.  In April 1861, Major Robert Anderson, considering the risks of manning the barbette tier of Fort Sumter, confined his crews to the casemate guns.  While better protecting the men, this also meant Fort Sumter’s guns were unable to effectively reply to the Confederate bombardment.  Yet, a few years later Confederate gunners sat in the relative safety of the casemates while responding, and damaging, Federal ironclads attacking Fort Sumter.

Each mounting had advantages and disadvantages, which the commander on the ground had to consider against the tactical situation.

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