The Manufacture of Heavy Ordnance and Armor: Their Ballistics and Resistance *
Mr. Chairman, Members, and Guests:—With the exception of taking a small part in the indecisive Rebates of the Naval Graduates' Association, it has been a great many years since I lifted up my voice in this building; and then it was from yonder gallery where, when a midshipman, as a member of the choir, I joined in the weekly religious services so intimately connected with our future salvation.
To-night I shall sing the praises of the products of mechanical ingenuity which, though seemingly irrelevant for comparison, are equally important for the insurance and protection of our country.
As it will be rather difficult for me to give you within the period usually accorded lecturers the developments that have taken place in guns, gunpowder and armor since the 13th century, I may have to ask your indulgence and trust that I shall not weary you.
After 20 years of indifference to the question of national military defense, the Report of the Gun Foundry Board marked an era of awakened interest, and revived desire to see the United States again take her proper place in the maritime world.
The tremendous strides we have made since that date (February 16, 1884) in the development of war materials have already placed us in the front rank in quality and type (although in quantity we are wanting) and given, in the United States, the production of this class of material a prominence in engineering science which has never before been accorded it.
A glance at the indexes of our societies' transactions will discover such a conspicuous absence of papers referring directly to the manufacture of war material that it would seem to indicate a want of interest in this branch. But, if since May, 1885, when I laid a detailed proposition before the directory of the Bethlehem Iron Company for the erection and equipment of extensive works for the production of war material and transferred to that company the initial machinery and information I had secured for the rapid and successful consummation of my project, the United States Government alone has appropriated $50,000,000 to secure for our ships and fortifications guns, armor and materials of construction, equal, and in some cases superior, to any of their kind made elsewhere; if Great Britain expends $70,000,000 annually for the care and development of her Army and Navy; if France has spent in 20 years $200,000,000 more for her Navy than the three central powers of Europe combined: I need present no further estimates of military expenditure to impress you with the value and present importance of the special branch of Ordnance Engineering. These and many other reasons suggested the thought that you would be interested by a graphic description of the manufacture of some of the heaviest implements of offensive and defensive warfare that annually absorb such vast sums of money and give honorable employment and education to so many thousands of men.
[After citing and illustrating some of the principal engineering accomplishments of the World's Columbian Exposition, and describing the types of ships that made up the Columbian Naval Review, Mr. Jaques explained in detail the construction of, and differences between, the types of modern guns known as "built-up" and "wire-wrapped;" showed what has recently been accomplished in the powders which have increased velocities to nearly 5000 f. s. dwelt upon the advantages of the fluid compression and hydraulic forging of steel in large masses; compared the progress of ocean ship-building and the development of heavy ordnance during the last 50 years; paid a high tribute to Krupp's accomplishment and his remarkable exposition of war material at Chicago; explained shrinkage, the erosion of the bores of guns, gas checking, and the different methods of breech mechanism; the value of alloy in steel for gun and armor making; compared hard and soft armor and showed how they should be attacked to get the greatest efficiency from the modern guns; showed the value of velocity screens placed in the rear of armor to arrive simply at the comparative excellence of armor and projectiles; and closed with a comparison of the two systems of gun construction, built-up and wire-wrapped.
The lecture was illustrated by 250 excellent lantern views, and, although concise, was a thorough exposition of the subject.]
The decrease of the number of parts in guns was a natural sequence of the development of the means in the United States for a certain production of these integers.
Birnie says of the built-up forged steel gun, it is noticeable in its history "that the length of the cylinders surrounding the tube have been steadily increased from the first conception; and its legitimate finality is a gun made, if not of one simple cylinder in each layer, at least so nearly so as to meet the requirements for longitudinal stiffness and minimize the cost of production in pace with increased length of bore.''
Mr. Gledhill (of Whitworth's) has not only advocated the single cylinder in each layer, but has successfully constructed and fired guns thus made.
No great change in the composition of steel for guns has been accepted, although alloys containing manganese, chrome, tungsten, copper, nickel, aluminum, etc., have been tried with the view of securing increased hardness to resist the erosion, or a greater elastic strength to control the pressures that have accompanied the higher velocities.
In connection with the new powders, Captain Sir Andrew Noble, C.B., F.R.S., etc., in conjunction with Sir Frederick Abel, F.R.S., etc., has carried out exhaustive experiments to determine the stability and comparative values of these compounds of nitroglycerin and gun-cotton and the modern brown powders.
In his latest experiments with 6-inch B.L. Rifles of various lengths he has secured enormous energies with 0.4 inch cordite, and found great regularity of burning, stability and freedom from detonation. He says, although its erosive power was slightly greater than that of "brown prismatic", the surface appeared to be pretty smoothly swept away, while the length of the surface eroded was much less. With very long gun, light projectile and high pressure, a velocity of 4980 ft. sec. was obtained.
It seems, therefore, that cordite is the most promising of these so-called smokeless powders, although a product of the United States called the Leonard is now giving gratifying results.
My present conclusions are that the powder question is still a trying one. With the cordite class better ballistics are obtained, and much faith is now placed in its stability, but the destruction it causes to the chamber and commencement of the rifling almost suggests a return to smooth bores.
Unless its temperature can be reduced it may have to be replaced by some other explosive.
In our Leonard powder this factor is said to obtain, but it is a comparative youth in powders, and must yet be subjected to much practical questioning. The early results obtained with it are surely most favorable.
The legal contest in Great Britain over the similarity of ballistite and cordite and priority of invention as a propulsive explosive from nitro-glycerin has resulted in the judicial verdict that there was a substantial difference in kind between ballistite and cordite, and that cordite was a novel invention. The evidence and verdict indicated that cordite had greater propulsive power and more stability and permanence than ballistite.
This wearing of the barrel to which I have referred is at the present time a cause of the greatest anxiety to ordnance engineers and gun makers. Its disastrous effects in ordnance where such enormous powder charges are employed have no doubt greatly influenced some artillerists against the largest calibres, whose racking and smashing powers must be employed to destroy the heaviest armor.
If we do not change the propelling agent I believe we must look to the amount of work put upon the metal and its treatment rather than to the chemistry alone of the metal for the determining agents that will prevent or reduce the amount of erosion; and that the solution of the problem will be found in the mechanical field. This difficulty will probably be best surmounted by carbonizing the bore, which should be highly polished or hardened by mechanical mandreling, in order to secure the smoothness needed to prevent scoring by powder products. The employment, therefore, of any alloy or of any mechanical work that will aid in securing this highly hardened smoothness, without reducing the requisite elastic strength, will greatly assist the solution of this difficult problem. These results cannot be obtained, however, by any sacrifice of attention to the chemistry of gun steel.
If erosion is mainly due to the chemical action of the powder gases and deposits that some powders leave, the powder maker, by changing the mechanical or chemical composition of his products or substituting some other propelling agent, may pass the mechanic in his search for the means of rendering his gun barrel impervious to the destructive action of powder, just as the manufacturers of slow-burning powder outstripped the designers of accelerating guns in securing high velocities.
If we accept the new powders we may have to sacrifice the excellent ballistic results that the erosive ones have given, but if the mechanic succeeds, any kind of powder can probably be used.
If erosion is due to high pressures and temperatures the use of the stronger powders would increase erosion in the proposed short guns; but if it is due to the mechanical work of the non-gaseous (liquid and solid) residue, these new powders, if they can be made reliable, will be a boon.
By cold-rolling the tubes higher elastic strength and greater resistance of erosion will be obtained, and if the life of a gun is limited by its erosion (which is apparently the case) the increased cost to provide the power requisite for this additional mechanical work will be more than compensated by the longer life of the gun. If the addition of an alloy will facilitate this work, so much the better.
The nickel-steel gun forgings made while I was at Bethlehem show an increase of 25 per cent, in elastic strength with but a slight reduction of the contraction of area as compared with plain steel. If we can still further increase these qualities by cold rolling, we will have material that will not only stand the increased pressures demanded but will stand the erosive inroads which so manifestly control the life of our heavy ordnance.
Many examples might be given to show the advance made in the ballistics of heavy ordnance in less than half a century, but the following resume will suffice to show the progress that has been made. Since 1856, the powder charges have increased from 16 to 1000 lbs.; weights of projectiles from 68 to 2613 lbs.; velocities from 1600 to 4980 ft. sec.; while the energies have mounted from 1100 to considerably more than 62,000 ft. tons.
Of the two systems of breech-loading in general use, the American-French interrupted screw and what is now familiarly known as the Krupp wedge, the former is used by both the Army and Navy.
Although there have been many modifications of the original designs, the numerous broad claims of the Canet-Whitworth patents seem to cover them all. As far as simple mechanics are concerned, Messrs. Canet and Gledhill (Whitworth) are masters.
The de Bange gas check is universally used in the United States, and its pre-eminence as an effective obturator has been proved by long series of the most exacting tests.
While the Whitworth plant was only indirectly represented at the World's Columbian Exposition by the products of the fluid compression and hydraulic forging presses which I purchased of that firm, and transferred to Bethlehem, Krupp installed in a separate pavilion one of the most unique and interesting collections of preparatory and finished war material ever exhibited. It would be impossible to praise too highly the enterprise with which the risks of transportation and difficulties of installation of this remarkable collection of products were met, the masterly conception and accomplishment, and the liberality with which it was effected. It was a veritable exposition in itself.
In wire gun construction, a large amount of experimentation has been carried on, but until recently few practical results have been obtained. Wire has been so extensively used in other engineering work, that it is remarkable its employment for guns and shafting has been so long delayed.
In bridges its graceful value is especially emphasized, and I see no reason why wire guns and wire shafting should not attain the same eminence in their respective branches as the Brooklyn bridge has in bridge construction.
Placing the supply of naval ordnance in the hands of the British Admiralty has greatly improved their naval armaments; but in all navies a mistake is made in not replacing obsolete with modern ordnance of higher ballistics, even in those ships which are considered obsolete themselves. If they are useful enough to be retained in service, they would be more efficient if they had modern batteries. While the general tendency is not to exceed 67-ton guns of 13-inch caliber, case hardened armor will require larger calibers and greater energies. This has led to a revival, particularly in England and Russia, of wire wrapped ordnance, and in the former country alone, large numbers of this type, of calibers varying from 6 to 12 inches, are being manufactured. While the guest of Dr. Anderson, Director-General of Ordnance Factories, in December last, he spoke to me with great satisfaction of the results that have been obtained and the progress made in this direction. I was glad to learn from Mr. Longridge that the British Government had at last recognized his work by giving him a pension. He was naturally gratified that guns of a type so long cherished by him should now be manufactured as service guns. Since my return I have received a letter from him saying that the 12–inch wire-gun had behaved perfectly under trial, and that a muzzle velocity of over 2500 ft. sec. had been obtained, or an energy of 30,000 ft. tons.
Elswick's present position on the "wire question" has been presented through Lloyd and Hadcock in their 1893 publication on "Artillery." It states that "between the years 1875 and 1879, Elswick successfully built over 40 wire guns, the largest being of 10-inch caliber," and that "Elswick did not pursue the wire construction between 1879 and 1892 because, guns built in the usual manner having ample strength, there appeared to be no reason to accept disadvantages and especially higher cost, for the sake of obtaining what really was not necessary. The introduction of cordite and the higher pressures consequent thereupon has, however, put a somewhat new complexion on the matter, and wire will probably, to a limited extent, find its place in gun-construction of the future."
While in conclusion this extensive book of 463 pages (apparently written solely in the interest of Elswick's methods and products) states:—"Greater circumferential strength can be obtained at the expense of weakness longitudinally, higher cost, delay in construction, and slightly greater vulnerability of attack," it devotes nearly a page to the advantages of the system.
The Departments of the United States have not prosecuted this branch of gun-construction with much activity.
The Woodbridge, Crozier and Brown types constitute our principal experimentation in wire wrapped ordnance. Other systems and types have been suggested, but difficulties of various kinds have prevented their completion. A comparison of the methods of construction of the three guns here presented, the Brown, Crozier, and Woodbridge discovers that the Brown utilizes to the greatest extent the high elastic properties obtained in the segments and wire.
Birnie's criticism is that it is an uneconomical construction, because in making a gun of so many parts, it has been necessary to use metal of far higher physical qualities than would be required to secure the same tangential resistance in a less complicated way.
Dr. Woodbridge's present adaptation consists of a continuous steel tube, overlaid throughout its rear half with a cylinder of closely fitted steel staves, the whole wound with wire of either square or flat cross-section, tinned or coated with a metal of low fusibility capable of being used as a solder. The whole length of the gun is divided into three sections by steel rings or bands, and forward of the staves the wire is wound directly upon the steel tube. The splices are made by a lapping joint, brazed with silver solder, the wire being cut in a milling machine with special cutters, producing an interlocking serration of the joined surfaces. The strength of the joint was carried above the highest tension of winding by subsequent swagging in a press.
There are two features in the construction which Dr. Woodbridge considers important: To so machine and shape the longitudinal staves as to obtain a condition that will allow the employment of the whole contractile effort of the wire in opposition to the interior pressure, instead of having the resistance of the staves taking a share in it; and to winding wire with a curvature in order to reduce its tendency to unwind if cut. The accomplishment of the former would be accompanied by many mechanical difficulties, while the latter would scarcely seem to meet all the conditions of protection needed against the attack of heavy rapid-fire guns. Dr. Woodbridge states, however, that in practice the former was easily accomplished, and that he has much faith in the efficiency of the latter.
The Crozier gun, called the Ordnance wire-wound gun, being made from designs of the Ordnance Department, consists of a steel tube overlaid from breech to muzzle with steel wire wound in layers, with a jacket enveloping the wire over the reinforce, and a continuous layer of steel hoops covering the wire from the trunnion band forward to the muzzle. The coils of wire are electrically welded end to end, so that the gun is wound with a continuous strand of wire. The breech-mechanism is of the usual service type. Captain Crozier advocates the use of castings for the jackets, but in this particular gun the jacket is a forging. The general idea of the type is to have the wire as little interrupted as possible by hoops, etc., between breech and muzzle; to have the jacket take the longitudinal strain; and to so arrange the general construction that no part except the tube need be of expensive material, without any sacrifice of strength thereby.
As described by the company's engineer, "The Brown Wire Gun consists essentially of a segmental core wound with wire under such tension that the compression between the longitudinal segments of the core induced thereby will be more than sufficient to resist all ordinary powder pressure. The longitudinal segments are primarily held together by a breech and muzzle nut screwed on hot, with the proper degree of shrinkage, so that the tension of the nut and adjoining wire will be the same after winding. The wire is wound between the nuts under a high degree of tension, and anchored by a special device.
The trunnions are not attached to the core or body of the gun, but to an outer trunnion jacket, which jacket is attached to the gun proper by means of the breech nut. By this means the recoil is transmitted to the trunnions through the breech nut and jacket, and the core or body of the gun is thus relieved from the major part of the longitudinal thrust due to powder pressure upon the bottom of the bore. The gun itself is free to expand longitudinally within this jacket, which is attached only to the breech nut. The essential feature of the gun is, of course, the segmental core. This core consists of a number of longitudinal steel segments, the number being so regulated that the maximum thickness of a segment shall not exceed one-half inch materially. The chase jacket consists of a series of interlocking hoops shrunk on over the wire, extending from just in advance of the trunnions to the muzzle, the entire jacket being held in place by a muzzle nut, the thickness of which and the amount of shrinkage being so adjusted that when completed the compression produced by the building-up muzzle nut will be the same as that produced by the wire and chase rings."
During the progress of the work, which has been extended over a period of three years, mechanical difficulties and the results of the trials of experimental cylinders representing sections of the powder chamber gave reason for decreasing the number and increasing the size of the longitudinal segments and the necessity for the insertion of a lining tube to prevent the entrance of the powder gas between the segments, which, in the case of one of the experimental cylinders, was so great as to cause marked discoloration at the joints. The lining tube was inserted under initial tension and extended to about five or six calibers in advance of the front end of the chamber. This tube can be removed and replaced by a new one whenever it becomes too much eroded for service.
Mr. Brown claims that the fundamental principle of his gun lies in the segmental tube and not in the wire wrapping. He has never asserted that he was the inventor of the wire gun, nor that the use of the segmental tube was new; but he believes that the idea of sub-dividing a core for the purpose of obtaining special elasticity is original with himself, and that thereby it is possible to set up such a high degree of initial compression that even under the highest powder pressure the compression at the surface of the bore will not be reduced to zero.
If the segments compressed by the full elastic strength of the wire present an interior surface that can withstand the erosive action of the powder products, we must admit that Mr. Brown has supplied a method of forming the bore of the gun which has decided advantages; but if recourse has to be had to a liner to resist erosion we return to a core that will not sustain the full elastic strength of the wire, and it probably will be more economical to use a steel tube of suitable dimensions than a combination of segments and thin liners, unless these liners like the segments, are cold drawn, and thus by a great amount of mechanical work rendered impervious to the serious ravages of the powder products.
Although the Woodbridge and Brown guns have developed defects, the i62d shot of the latter (5-inch Brown) with 30 lbs. of Leonard smokeless powder, gave a muzzle velocity of 3240 ft. sec. to a 63 lb. projectile, and stood a pressure of 65,300 lbs. per square inch. The Crozier has not yet been tried.
The wire-wrapped type, a 9. 2-inch B. L. rifle had the honor of firing the "Jubilee Round" at Shoeburyness, April 16, 1888. This 22-ton gun fired a 380 lb. projectile with 270 lbs. of powder, at a muzzle velocity of 2360 ft. sec, the range being 12.4 miles, and the height of trajectory 17,000 ft. when fired at 45 degrees elevation.
Comparing the velocity, however, with a more recent 6-inch quick-firing gun (hooped), a velocity of no less than 4928 feet has been realized with a 19 ½ pound charge of cordite.
As to the comparative value of the two systems, there is now such abundant evidence in favor of each, that the choice may be governed, like a lady's toilet, by a caprice of authority.
Between the best examples of the two types, there appears to be so little difference that a mistake could hardly be made by the selection of either.
Birnie's conclusions are "that on the whole there is little to be gained in attempting to make wire guns to be professedly stronger tangentially than the forged guns. And if equal strength only is aimed at, then the forged gun has the advantage of being inherently the more solid and stiffer construction."
In relation to armor, the United States is not the only nation successfully producing hard armor, nor is the method employed by Mr. Harvey the only one the gun has to meet. Hadfield's manganese plates, the Schneider gas-hardened type, St. Chamond's nickel-chrome products, and Krupp's special type have all scored "touch-downs," and others are in training.
The views which I shall show you will give you a much better idea of the behavior of the plates than any detailed description I could give you. The failure of some of the thicker case-hardened plates has caused much doubt as to the thickness which will be improved by the so-called "Harvey'' process. 13-inch, 12-inch, and even 10-inch armor-piercing shells, attacking at service energies, have cracked them; and although increasing the number of bolts may keep the cracked pieces in position, we find ourselves back again to the old discussion as to which is least objectionable, considerable penetration or cracks. No matter what future tests may decide, one thing is certain, the calibers and energies of guns must be increased, not diminished.
The complicated shapes and varying sections of armor demanded by the naval architect add seriously to the risk of manufacture and treatment of steel plates. They are now required to be shaped as if they were mahogany, and naval architects have not reached their ambition of complexity, although one might suppose the ram Katahdin was rich enough in graceful curves.
The value of velocity screens behind plates in testing armor and projectiles demands a moment's notice. The suggestion to employ velocity screens behind plates in testing armor has, I believe, been more specifically recommended by Captain Orde Browne and myself than by others.
Very little has been done in this direction, although much valuable data could be obtained by their use to replace assumed arbitrary conditions, and to lessen the demand upon the Greek alphabet, which is so copiously drawn upon to represent the unknown quantities of ballistic equations. Not only is this true in determining the comparative resistance of plates, but equally so in grading projectiles, which in many cases fired with high velocities are either lost or not discovered until one of the approximate elements of value—heal—has disappeared.
In closing, I cannot refrain from saying a few words in relation to the arguments which are so frequently set forth by representatives who cannot see beyond the environs of their own cities or states and are, therefore, too narrow to understand the value even to themselves, of an adequate coast defense. They protest that such preparation is uncivilized; that no country will ever attack us; that we have no dangers to fear from the outside world; they want us to submit everything to arbitration.
All history, however, recalls the dangers of vast acquisitions of wealth without adequate protection. The United States is rapidly overreaching other nations in the vastness and variety of what is supposed to constitute wealth. Labor has been as favored as capital.
An insurance of some sort is absolutely necessary upon this nation's wealth and the people who have been induced by our wise laws to acquire it. Why then should we hesitate to apply almost any amount of money for the development of our various lines of defenses, when the amount ($126,377,800) recommended by the most ambitious board ever appointed—the board on fortifications or other defenses—would require a tax rate of less than one-fourth of what we pay for the insurance of our property against fire.''
* Ilustratred by lantern views and specimens of material.