This will be Mike and Tracy's first mortar build, so we are asking for a little help from those of you who have built mortars before. This mortar will not be duplicated by us. One is going to be enough, we believe. The object of this build is to launch a heavy, solid concrete projectile weighing approx. 180 lbs. from a mortar set at 60 deg. elevation to a distance of at least 100 yards accurately and SAFELY, and perhaps have a 300 yard maximum range. We think that 1 lb. of 1 Fg BP should get us to 100 yards and maybe 2 lbs. should be adequate for 300, so our chamber size should hold 2 lbs. until range experiments prove otherwise.
An initial design sketch is almost done and we will post it in a day or two and you experienced builders can rip it to shreds. 
We expect at least two or three rounds of revisions before an effective and SAFE design can be decided upon. The photo below shows a 5 Gallon water jug flanked by a 4" cannonball and a 15" Beach Ball for scale.
If you are interested, a brief bio on Col. Paixhans and the testing and battle use of the Monster Mortar is also included below.
Regards,
Tracy and Mike
Henri-Joseph Paixhans, 1783-1854 was a French artillery officer and ordnance inventor. He graduated from the distinguished technical university, Ecole Polytechnique and fought in the Napoleonic Wars.
In 1823, he invented the first shell guns, which came to be called Paixhans guns (or "canon obusiers" in the French Navy). Paixhans guns became the first naval guns to combine explosive shells and a flat trajectory, thereby triggering the demise of wooden ships, and the iron hull revolution in boat building. Paixhans also invented a "Mortier monstre" ("Monster Mortar"), using 500 kg bombs, which was used to terrible effect in the Siege of Antwerp in 1832.
"Paixhans had so far satisfied naval men of the power of shell guns as to obtain their admission on shipboard; but by unduly developing the explosive element, he had sacrificed accuracy and range.... The difference between the system of Paixhans and my own was simply that Paixhans guns were strictly shell guns, and were not designed for shot, nor for great penetration or accuracy at long ranges. They were, therefore, auxiliary to, or associates of, the shot-guns. This made a mixed armament, was objectionable as such, and never was adopted to any extent in France... My idea was, to have a gun that should generally throw shells far and accurately, with the capacity to fire solid shot when needed. Also to compose the whole battery entirely of such guns."
—Admiral John A. Dahlgren.[1]
The United States Navy adopted the Paixhans Shell Gun design, and equipped several ships with 8-inch guns of 63 and 55 cwt. in 1845, and later a 10-inch shell gun of 86 cwt. Paixhans guns were used on the Constitution know as "Old Ironsides," a wooden-hulled, three-masted frigate of the United States Navy.... (4 Paixhans guns) in 1842, under the command of Foxhall A. Parker, Sr., and were also present onboard the Mississippi (1841), (10 Paixhans guns), and the USS Susquehanna (1847), a sidewheel steamer which was the first ship of the United States Navy to be named for a river and carried (6 Paixhans guns) during Commodore Perry's mission to open Japan in 1853.
Legacy
Ironclad warships
Wooden boats became so vulnerable that the only possible response could come with the introduction of the iron-hulled Warship.
The first of them was the French La Gloire, soon followed by the HMS Warrior (1860).
HMS Warrior was the world's first ocean-going iron-hulled armored battleship.
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The Celebrated Mortar.— It having been announced that an experiment would be made on the 24-inch (English) mortar on the heath of Braeschaet, a number of generals and officers of all arms proceeded to that village. The previous experiments made at Liege had not succeeded, either from some defect in the shell, or in the mode of firing. It had been tried with the usual wooden sabot, as well as with a wad of twisted straw ; but, with one or two exceptions, the projectile burst at the moment of quitting the piece. This was attributed to a want of thickness in the shell, particularly of the culot or part coming in contact with the charge, which, from the great diameter of the cavity, had not sufficient thickness to resist the shock of the powder and concussion of the air. Fresh shells were subsequently directed to be cast.
The first eight or ten experiments were made with the dead shell filled with its proper weight in sand, and fired with various charges, from six to twelve pounds, gradually increasing. No accident occurred. The artillery officers being satisfied with these trials, the shell was loaded to a third, and so on to its full charge, upwards of a barrel and a quarter. One shell alone burst out of six, at the mouth of the piece; the remainder fell near the target, and exploded with a fierce detonation, tearing up many cubic feet of earth, and scattering splinters to the distance of 450 yards. The shells were hoisted to a level with the mouth of the cylinder by means of a chevalet supporting a swivel bar, on the one end of which were suspended two chains with hooks to catch the rings of the shell, and on the other a weight nearly equalling that of the projectile ; it was easily raised by this means, and then lowered without any jar into the chamber. A straw-twisted wad was employed as a sabot. The operation of loading required an average of 37 minutes to 50. The vent was fitted with a spring detonator, and the man who fired stood behind a traverse and pulled the spring with a long cord.
The experiment having succeeded, it was resolved to bring the mortar into Antwerp, and preparations were made to place it in battery on the covered way of the bastion of the city, between the re-entering place of arms of Montebello and the Malines gate. Eight horses were required to draw the carriage on which it was placed, and eight others to draw the carriage containing the bed. The weight of the empty shells being nearly 1,000 lbs. it is easy to calculate the number of these projectiles that could be moved in any ordinary ammunition wagon. The weight of the bed, which is of timber, is not given in the scale, but it may be taken as at somewhat more than the mortar itself, making altogether about 30,000lbs.; add to this 110 shells for 100 rounds at 1,000 lbs. each, and 110 barrels of 90 lbs. each, and it gives the enormous dead weight of 70 tons, exclusive of gins, triangle, chevalet, carriage, and sundries. The name of Monster-mortar seems to have been well selected, for it is scarcely possible to conceive a more ugly or unwieldy implement. With the exception of the mortar at Moscow, which has thirty-six inches in diameter at the mouth of the cylinder, and was, if ever used, employed for projecting masses of granite, the monster- mortar exceeds any other weapon of the kind hitherto known. The original conception is due to Colonel Paixhans ; it was executed under the direction of Baron Evain, and cast at the Belgian royal foundery at Liege.
Firing.—At midnight, the twenty-four-inch mortar was loaded with twelve and a half pounds of powder, and the first discharge took place. The huge projectile, of which the internal charge was fifty-four pounds of powder and combustibles, was watched with anxiety as it made its parabola, and a look-out person stationed on the tower of St. Andre reported that it had fallen and exploded near the great powder magazine at the gorge of bastion Fernando. The success of the experiment was thus demonstrated. At the second shot, which took place nearly an hour later, the shell burst on issuing from the mouth of the mortar, not by explosion from the fuze, hut from the weakness of the projectile itself. Great care was therefore ordered to be taken in selecting others, of which the culots were thicker.
The dimensions are as follows:
Calibre massive, 23.62 in.
Thickness, exclusive of culot .. 2 in ,,
Weight of empty shell 9l6 lbs. ,,
Powder contained in shell .... 99 lbs. „
Weight of Shell, full charge ..1015 lbs. „
Weight of mortar (metal) 14,700 lbs. „
Weight of bed (wood) 16,000 lbs. „
Powder in Chamber (full) 30 lbs. ..
The French weight has been preserved purposely for the sake of greater accuracy.
