So you have one of those 15,000 pound 10-inch columbiads or 9,000 pound 8-inch columbiads mounted (which was no small feat to begin with). The enemy fleet is threatening to sail up the channel. How the heck to you point that big gun on the target?
The Bellona 8-inch Columbiad at Fort Darling is a good study to answer that question.
Pointing1 the gun required two variables – traverse and elevation. The gun crew positioned the gun in traverse – the horizontal direction to point the gun – by turning the carriage itself. The Fort Darling gun sits on a center pivot barbette carriage. Handspikes fixed to sockets on the rear of the carriage rails allowed the crew to turn the gun 360°. For front pivot barbette carriage, the crew worked with a reduced traverse, but the concept was the same. While the crew had to exert themselves to move the weight of gun and carriage, if well maintained, the wheels and rollers allowed free movement. Traverse of the large columbiads differed little from the smaller seacoast guns on similar carriages.
The horizontal angle, or elevation, however involved movement of the piece against the trunnions. In the case of smaller guns, an elevating screw worked against the bottom of the breech, to raise or lower the back end of the gun. Excess weight, or preponderance, on the back end of the gun ensured the piece laid on the head of the elevating screw. This mechanism worked fine for weapons ranging from field artillery and seacoast guns, which were not elevated beyond 5°. For columbiads, where elevations might reach 40°, the breech elevation screw would be too long for practical use.
So for columbiads, the Ordnance Department figured out a different, more elaborate, means to elevate the piece. Joseph Robert’s Hand-book of Artillery explained this system in detail:
The elevating arrangement consist[s] of an elevating-screw, working into a screw-bed, which slides in a vertical box, and carries on top of it a movable pawl to fit into the notches cut in the breech of the gun, in order to give considerable elevations. For the purpose of transferring the pawl from one notch to the next, it has a slit in it, through which the elevating bar is passed, and the gun supported by making use of the edge of the elevating-box as a fulcrum. This arrangement is over the rear transom.2
The mechanism used four components – elevating screw, elevating box, a pawl (or finger), and an elevating bar. Three of those four are seen below on the Fort Darling columbiad.
The elevating screw, at the bottom of this view, worked inside the elevating box. The box also housed the pawl, which sat on top of the elevating screw. As the crew worked the elevating screw, the pawl moved up and down within the elevating box.
The movement of the pawl would apply or relieve pressure on the breech of the columbiad. To provide the pawl a purchase against the breech, the pawl fit into a series of notches or ratchets in the breech. This was of course fine to elevate the gun through about 5°, but the mechanism needed more play to work the required 40°. That’s where the handle on the back of the pawl came into play.
When more than 5° of elevation were required, the crew placed the elevating bar (what we might call a pry bar today) against the breech. The channel on the top of the elevating box provided a fulcrum for the elevating bar, which was also fed through the open eye in the pawl. This allowed the crew to relieve pressure on the pawl. One of the crew would then remove the pawl from the ratchet by using the handle (note the hinge at the base of the pawl seen inthe view above). If needed, the elevating screw worked to reposition the pawl height. Then the crew-man would set the pawl into the appropriate ratchet.
For operation, here’s how the Instruction for Heavy Artillery (1850) described the process for elevating a columbiad:
The gunner withdraws the priming-wire; inserts the pawl of the elevating machine in the proper notch by means of the elevating bar, and with the breech-sight gives the required elevation; No. 4 [crew-man] turning the handle of the screw according to his direction.
The moment the piece is correctly pointed he rises on the left leg, and gives the word READY, making a signal with both hands….3
The setup at Fort Darling is a bit “over elevated.” While this allowed me to photograph the details, the arrangement is not how the mechanism would appear in action. To better appreciate the setup, consider this wartime photo of a 10-inch Columbiad at Fort Darling.
If you look close, there is an elevating bar to the left of the elevating box. The pawl is set against the bottom ratchet, which is the right position for point blank firing.
So all that work would allow the gunner a view something like this:
Busy work for a gun crew in the heat of battle, don’t you think? Keep in mind that for every shot, the crew would return the gun between zero and 5° elevation to facilitate reloading. Worse yet, since the columbiad elevation system still required preponderance to seat the gun against the pawl, the crew had a lot of weight to deal with. For an 8-inch that was 635 pounds. For a 10-inch that was 740 pounds.4 Not a trivial matter.
Early Rodman Guns used the same elevation system, with some reduction of preponderance. For the first batches of 8-inch Rodmans, the preponderance stood at 350 pounds. The 10-inch Rodman prototypes had a 519 pound preponderance. However, the 15-inch Rodman prototype, the most favored anti-ship weapon in the arsenal, strained the muscles of the crew with its 1,200 pound preponderance.5 Clearly the system had reached its physical limitations. So the Ordnance Department devised an alternative. I’ll turn to that next.
- The verb “pointing” appears in most pre-war and wartime manuals. Pointing implied the gun was oriented towards a target, as was the case with fire control practices of the time. The verb “aiming” came into wider use for artillery towards the end of the 19th century, as gunners would use reference points to predict and direct the shot onto a target.
- Joseph Roberts, The Hand-book of Artillery: For the Service of the United States (Army and Militia) (New York: D.Van Nostrand, 1860), page 137.
- Instruction for Heavy Artillery (Washington: Government Printing Office, 1862), pages 70-71.
- The Ordnance Manual for the Use of the Officers of the United States Army, edited by Theodore T. S. Laidley (Philadelphia: J.B. Lippincott & Co., 1862), page 20.
- The Ordnance Manual for the Use of the Officers of the United States Army, edited by Theodore T. S. Laidley (Philadelphia: J.B. Lippincott & Co., 1862), page 18.