CHAPTER III.THE LIBERTY ENGINE.

The Liberty engine was America's distinctive contribution to the war in the air, and her chief one. The engine was developed in those first chaotic weeks of preparation of 1917, when our knowledge of planes, instruments, and armament as then known in Europe was still a thing of the future. The manufacture of engines for any aeronautical purpose was one which we might approach with confidence. We possessed in the United States motor engineering talent at least as great as any in Europe, while in facilities for manufacture—in plants which had built our millions of automobile engines—no other part of the world could compare with us. Therefore, while waiting word from Europe as to the best type of wings, fuselages, instruments and the like, we went ahead to produce for ourselves a new, typically American engine which would uphold the prestige of America in actual battle.

Many Americans have doubtless wondered why we built our own engine instead of adopting one or more of the highly developed European engines then at hand; and no doubt our course in this vital matter has sometimes been set down to mere pride in our ability and to an unwillingness to follow the lead of other nations in a science in which we ourselves were preeminent—the science of building light internal-combustion engines. But national pride, aside from giving us confidence that our efforts in this direction would be successful, had little other weight in the decision. There were other reasons, and paramount ones, reasons leading directly from the necessity for the United States to arrive at her maximum aerial effort in a minimum of time, that irresistibly compelled the aircraft production organization to design a standard American engine. Let us examine some of these considerations.

If there was anything to be observed from this side of the Atlantic with respect to the tendencies of aircraft evolution in Europe it was that the horsepowers of the engines were continually increasing, these expansions coming almost from month to month as newer and newer types and sizes of engines were brought out by the European inventors. It was evident to us that there was not a single foreign engine then in use on the western front that was likely to survive the test of time. Each might be expected to have its brief day of supremacy, only to be superseded by something more modern and more powerful.

Yet time was an element to which in this country we must give grave consideration. To produce in quantities such as we were capable of producing would ordinarily require a year of maximum industrial effort to equip our manufacturing plants with the machines, tools, and skilled workmen necessary for the production of parts. The finished articles would under normal circumstances begin coming in quantity during the second year of our program. It would have been fatal to "tool up" our plants for the manufacture of equipment that would be out of date by the time we began producing it a year later.

The obvious course for the United States to adopt, not only with engines but with all sorts of aeronautical equipment, was to come into the manufacturing competition not abreast with European progress but several strides ahead of it, so that when we appeared on the field it would be with equipment a little in advance in type and efficiency of anything the rest of the world had to offer.

This factor of time was a strong element in the decision to produce a standard American engine, since with the possible exception of the Rolls-Royce there was no engine in Europe of sufficient horsepower and proved reliability to guarantee that it would retain its serviceability for the necessary two years upon which we must reckon. There was no other course that we could safely adopt.

But there were other conditions that influenced our conclusion. We believed that we could design and produce an engine much more quickly and with much better results than we could copy and produce any approved foreign model. This proved to be true in actual experience. Along with the production of Liberty engines we went into the quantity manufacture of a number of European engines in this country; and the experience of our engineers and factory executives in this work was anything but pleasant. Among others we produced in American factories the Gnome, the Hispano-Suiza, Le Rhone, and the Bugatti engines.

Now European manufacture of mechanical appliances differs from ours largely in the degree to which the human equation is allowed to enter the shop. In continental practice much of the metallurgical specifications and also of the details of mechanical measurements, limits of requisite accuracy, variations which can be allowed, etc., are not put on paper in detail for the guidance of operators, but are confided to the recollections of the individual workmen. A machine comes in its parts to the assembly room of a foreign factory, and after that it is subject to adjustments on the part of the skilled workmen before its operation is successful. It must be tinkered with before it will go, so to speak. Nothing of the sort is known in an American factory. When standard parts come together for assembly the calibrations must have been so exact that the machine willfunction perfectly when it is brought together; and assembling becomes mere routine. Thus when we came to adopt foreign plans and attempt to adapt them to our practices, we encountered trouble and delay.

Thirteen months were required to adapt the Hispano-Suiza 150-horsepower engine to our factory methods and to get the first engine from production tools, while eight months were similarly spent in producing the Le Rhone 80-horsepower engines. Both of these engines had been in production in European factories for a long time, and we had the advantage of all the assistance which the foreign manufacturers could give us.

These experiences merely confirmed the opinions of American manufacturers that the preparations for the production of any aviation engine of foreign design—if any such suitable and adequate engine could be found—would require at least as much time as to design and tool up for the production of an American engine. When to this was added the necessity of waiting for several weeks or months for a decision on the part of our aviation authorities, either in the United States or in Europe, as to which of the many types of engines then in use by the allies should be put into production here, procuring and shipping to this country suitable samples, drawings, and specifications, negotiating with foreign owners for rights to manufacture, etc., there was but one answer to be made on this score, and that was to design and build an all-American engine.

Another factor in the decision was that of our distance from France, a fact making it necessary for us to simplify as much as possible the problem of furnishing repair parts. At the time we entered the war the British air service was using or developing 37 different makes of engines, while France had 46. Should we be lured into any such situation it might have disastrous results, if only because of the difficulties of ocean transportation. Germany was practically concentrating upon not more than 8 engines. The obvious thing for us to do was to produce as few types of engines as possible, thus making simpler the problem of manufacturing repair parts and shipping them to the front.

With these considerations in mind, the Equipment Division of the Signal Corps in May of 1917 determined to go ahead with the design and production of a standard engine for the fighting forces of the aviation branch of the Army. In the engineering field two men stood out who combined in themselves experience in designing internal-combustion engines which approached nearest to combat engines, with experience also in large quantity production.

J. G. Vincent, with the engineering staff of the Packard Motor Car Co., had for approximately two years been engaged in research work, developing several types of 12-cylinder aviation engines of approximately 125 to 225 horsepower, which, however, were not suitable for military purposes because of their weight per horsepower. This work had resulted in the acquirement of a large amount of data and information which would be invaluable in the design of such an engine as the one proposed; and also had resulted in the upbuilding of an efficient experimental organization. He had also had wide experience in designing internal-combustion motors for quantity production.

E. J. Hall, of the Hall-Scott Motor Car Co., for eight years had been developing and latterly producing several types of aeronautical engines, which he had delivered into the service of several foreign governments, including Russia, Norway, China, Japan, Australia, Canada, and England. He had also completed and tested a 12-cylinder engine of 300 horsepower, which, however, was of too great weight per horsepower to be suitable in its form at that time for military purposes. He had thus acquired a large experience and fund of information covering the proper areas and materials for engine parts, and proper methods of tests to be applied to such engines, and in addition he had general experience in quantity production. All of this information and experience was of invaluable assistance not only in designing the new engine, but in determining its essential metallurgical and manufacturing specifications.

These two men were thus qualified in talent and in practice to lay down on paper the lines and dimensions of the proposed engine, an engine that would meet the Army's requirements and still be readily capable of prompt quantity production. They had in their hands the power to draw freely upon the past experience and achievement of practically the entire world for any features they might decide to install in the model power plant to be produced. And this applied not only to the patented features of American motors, but also of foreign engines; for each man had exhaustively studied the leading European engines, including the Mercedes upon which Germany largely pinned her faith up to the end of the war.

With respect to American motor patents, an interesting situation had arisen in the automobile industry. The leading producers of motor cars were in an association which had adopted an arrangement known as the cross-licensing agreement. Under this agreement all patents taken out by the various producers (with a few exceptions) were thrown into a pool upon which any producer at will was permitted to draw without payment of royalties.

A similar arrangement was adopted with respect to the Liberty engine, except that the Government pledged itself to pay an agreed royalty for the use of patents. Thus the engineers designing the engine might reach out and take what they pleased regardless of patent rights. The result was likely to be a composite type embracingthe best features of the best engines ever built. Theoretically, at least, a super-engine ought to result from such an effort.

The ideal aviation engine should produce a maximum of power with a minimum of weight; it must run at its maximum power during a large proportion of its operating time, a thing that an automobile motor seldom, if ever, does for more than a few minutes at a time; and it should consume oil and fuel economically to conserve space and weight on the airplane.

Such was the problem, the design of an engine to meet these requirements, that confronted these two engineers when they were called to Washington and asked to undertake the work.

There have been so many versions of the story of how the Liberty engine was designed and produced in its experimental models that it is fitting that the exact history of those memorable weeks should be set down here.

The engine was put on paper in the rooms occupied by Col. E. A. Deeds at the Willard Hotel in Washington. Col. Deeds had been the man of broad vision who, by taking into consideration the elements of the problems enumerated above, determined that America could best make her contribution to the aviation program by producing her typically own engine. He had proposed the plan to his associate, Col. S. D. Waldon, who had thereupon studied the matter and agreed entirely with the plan. The two officers persuaded Messrs. Hall and Vincent to forego further efforts on their individual developments and to devote their combined skill and experience to the creation of an all-American engine. The project was further taken up with the European authorities in Washington, and it was supported unanimously.

In these conferences it was decided to design two lines of combat engines. Each should have a cylinder diameter of 5 inches and a piston stroke 7 inches long; but one type should have 8 cylinders and the other 12. The 8-cylinder engine should develop 225 horsepower, as all the experts believed then, in May, 1917, that such a motor would anticipate the power requirements as of the spring of 1918, while the 12-cylinder engine should develop 330 horsepower, as it was believed that this would be the equal of any other engine developed through 1919 and 1920. Every foreign representative in Washington with aeronautical experience agreed that the 8-cylinder 225-horsepower engine would be the peer of anything in use in the spring of 1918; yet, so rapidly was aviation history moving that inside of 90 days it became equally clear that it was the 12-cylinder engine of 330 horsepower, and not the 8-cylinder engine, upon which we should concentrate for the spring of 1918.

With these considerations in mind Messrs. Hall and Vincent set to work to lay out the designs on paper. With them were Col. Deedsand Col. Waldon, the officers to insist that nothing untried or experimental be incorporated in the engines, the engineers to direct their technical knowledge by this sine qua non. The size of the cylinders, 5 by 7 inches, was adopted not only because the Curtiss and the Hall-Scott Companies, the largest producers of aviation engines in the United States, had had experience with engines of this size, but also because a new and promising French engine, the Lorraine-Dietrich, had just made its appearance in experimental form, and it was an engine approximately of that size.

On May 29, 1917, Messrs. Vincent and Hall set to work. Within two or three days they had outlined the important characteristics of the engine sufficiently to secure—on June 4—the approval of the Aircraft Production Board and of the Joint Army and Navy Technical Board to build five experimental models each of the 8 cylinder and the 12 cylinder sizes.

The detail and manufacturing drawings of the two engines were made partly by the staff of the Packard Motor Car Co., under Mr. O. E. Hunt, and partly by an organization recruited from various automobile factories and put to work under Mr. Vincent at the Bureau of Standards at Washington. Due credit must here be given to Dr. S. W. Stratton, the director of that important governmental scientific bureau. The Liberty engine pioneers woke him up at midnight and told him of their needs. He promptly tendered all the facilities of the Bureau of Standards, turning over to the work an entire building for use the following morning. Thereafter Dr. Stratton gave the closest cooperation of himself and his assistants to the work.

While the detail drawings were being made, the parts for the 10 engines were at once started through the tool rooms and experimental shops of various motor car companies. This work centered in the plant of the Packard Co., which gave to it its entire energy and wonderful faculties.

Every feature in the design of these engines was based on thoroughly proven practice of the past. That the engine was a composite is shown by the origin of its various parts:

Cylinders: The Liberty engine derived its type of cylinders from the German Mercedes, the English Rolls-Royce, the French Lorraine-Dietrich, and others produced both before and during the war. The cylinders were steel inner shells surrounded by pressed-steel water jackets. The Packard Co. had developed a practical production method of welding together the several parts of a steel cylinder.

Cam shafts and valve mechanism above cylinder heads: The design of these was based on the general arrangement of the Mercedes and Rolls-Royce, and improved by the Packard Motor Car Co. for automatic lubrication without wasting oil.

Cam-shaft drive: The general type as used on the Hall-Scott, Mercedes, Hispano-Suiza, Rolls-Royce, Renault, Fiat, and others.

WELDING JACKET ON CYLINDER FOR LIBERTY ENGINE. CADILLAC MOTOR CAR CO., DETROIT, MICH.

DRILLING CYLINDER FLANGES WITH MULTIPLE DRILL. PACKARD MOTOR CAR CO.

MACHINING THE CONNECTING RODS FOR THE LIBERTY ENGINE. CADILLAC MOTOR CO.

GAUGING VALVES AND PISTONS FOR THE LIBERTY ENGINE. LINCOLN MOTOR CO.

Angle between cylinders: In the Liberty the included angle between the cylinders is 45°. This angle was adopted to save head resistance, to give greater strength to the crank case, and to reduce periodic vibration. This decision was based on the experience of the Renault and Packard engines.

Electric generator and ignition: The Delco system was adopted, but specially designed for the Liberty to provide a reliable double ignition.

Pistons: The die-cast aluminum-alloy pistons of the Liberty were based on development work by the Hall-Scott Co. under service conditions.

Connecting rods: These were of the forked or straddle type as used on the DeDion and Cadillac automobile motors and also on the Hispano-Suiza and other aviation engines.

Crank shaft: A design of standard practice, every crank pin operating between two main bearings, as in the Mercedes, Rolls-Royce, Hall-Scott, Curtiss, and Renault.

Crank case: A box section carrying the shaft in bearings clamped between the top and bottom halves by means of long through bolts, as in the Mercedes and Hispano-Suiza.

Lubrication: The system of lubrication was changed, this being the only change of design made in the Liberty after it was first put down on paper. The original system combined the features of a dry crank case, such as in the Rolls-Royce, with pressure feed to the main crank-shaft bearings and scupper feed to the crank-pin bearings, as in the Hall-Scott and certain foreign engines. The system subsequently adopted added pressure-feed to the crank-pin bearings, as in the Rolls-Royce, Hispano-Suiza, and other engines.

Propeller hub: Designed after the practice followed by such well-known engines as the Hispano-Suiza and Mercedes.

Water pump: The conventional centrifugal type was adapted to the Liberty.

Carburetor: The Zenith type was adapted to the engine.

As the detailed and manufacturing drawings were completed in Washington and Detroit they were taken to various factories where the parts for the first engine were built.

The General Aluminum & Brass Manufacturing Co., of Detroit, made the bronze-back, babbitt-lined bearings.

The Cadillac Motor Car Co., of Detroit, made the connecting rods, the connecting-rod upper-end bushings, the connecting-rod bolts, and the rocker-arm assemblies.

The L. O. Gordon Manufacturing Co., of Muskegon, Mich., made the cam shafts.

The Park Drop Forge Co., of Cleveland, made the crank-shaft forgings. These forgings, completely heat treated, were turned outin three days, because Mr. Hall gave the Cleveland concern permission to use the Hall-Scott dies.

The Packard Motor Car Co. machined the crank shafts and all parts not furnished or finished elsewhere.

The Hall-Scott Motor Car Co., of Berkeley, Calif., made all the bevel gears.

The Hess-Bright Manufacturing Co., of Philadelphia, made the ball bearings.

The Burd High-Compression Ring Co., of Rockford, Ill., made the piston rings.

The Aluminum Castings Co., of Cleveland, made the die-cast alloy pistons and machined them up to grinding.

The Rich Tool Co., of Chicago, made the valves.

The Gibson Co., of Muskegon, Mich., made the springs.

The Packard Co. made all the patterns for the aluminum castings, which were produced by the General Aluminum & Brass Manufacturing Co., of Detroit.

The Packard Motor Car Co. used many of its own dies in order to obtain suitable drop forgings speedily, and also made all necessary new dies not made elsewhere.

As these various parts were turned out they were hurried to the tool room of the Packard Co., where the assembling of the model engines was in progress.

Before the models were built, however, extraordinary precautions had been taken to insure that the mechanism would be as perfect as American engineering skill could make it. The plans as developed were submitted to H. M. Crane, the engineer of the Simplex Motor Car Co. and of the Wright-Martin Aircraft Corporation, who had made a special study of aviation engines in Europe, and who for upward of a year had been working on the production of the Hispano-Suiza 150-horsepower engine in this country. He looked the plans over, and so did David Fergusson, chief engineer of the Pierce-Arrow Motor Car Co. Many other of the best experts in the country in the production of internal-combustion motors constructively criticized the plans, these including such men as Henry M. Leland and George H. Layng, of the Cadillac Motor Car Co., and F. F. Beall and Edward Roberts, of the Packard Car Co.

When the engineers were through, the practical production men were given their turn. The plane and engine builders examined the plans to make sure that each minute part was so designed as to make it most adaptable to quantity production. The scrutiny of the Liberty plans went back in the production scale even farther than this; for the actual builders of machine tools were called in to examine the specifications and to suggest modifications, if necessary, that would make the production of parts most feasible in machine tools either of existing types or of easiest manufacture.

Thus scrutinized and criticized, the plans of the engine were the best from every point of view which American industrial genius could produce in the time which was available. It was due to this exhaustive preliminary study that no radical changes were ever made in the original design. The Liberty engine was not the materialization of magic nor the product of any single individual or company, but it was a well-considered and carefully prepared design based on large practical aviation-engine experience.

On July 4, 1917, the first 8-cylinder liberty engine was delivered in Washington. This was less than six weeks after Messrs. Hall and Vincent drew the first line of their plans. The same procedure was even then being repeated in the case of the 12-cylinder engine. By the 25th day of August the model 12-cylinder liberty had successfully passed its 50-hour test. In this test its power ranged from 301 to 320 horsepower.

As an achievement in speed in the development of a successful new engine this performance has never been equaled in the motor history of any country. No successful American automobile motor was ever put in production in anything under a year of trial and experimentation. We may well believe that in the third year of war the European aviation designers were working at top speed to improve the motive power of airplanes; yet in 1917 the British war cabinet report contains the following language:

Experience shows that as a rule, from the date of the conception and design of an aero engine, to the delivery of the first engine in series by the manufacturer, more than a year elapses.

But America designed and produced experimentally a good engine in six weeks and a great one in three months, and began delivering it in series in five months. This was due to the fact that we could employ our best engineering talent without stint, to the further fact that there were no restrictions upon our use of designs and patents proved successful by actual experience, and to the fact that the original engine design produced under such conditions stood every expert criticism and test that could be put upon it and emerged from the trial without substantial modification.

As soon as the first Liberty models had passed their official tests plans were at once made to put them in manufacture.

The members of the Aircraft Production Board chose for the chief of the engine production department Harold H. Emmons, an attorney and manufacturer of Detroit, Mich., who, as a lieutenant in the Naval Reserve Force, was just being called by the Navy Department into active service.

The production of all aviation engines, for both Army and Navy, was in his hands throughout the rest of the war. He placed orders for 100,993 aviation engines of all types, which involvedthe expenditure of $450,000,000 and more of Government funds. Of these 31,814 were delivered ready for service before the signing of the armistice. The United States reached a daily engine production greater than that of England and France combined.

In August, 1917, it was intended to manufacture both engines, the 8-cylinder and the 12-cylinder, and an agreement was reached with the Ford Motor Co. of Detroit to produce 8-cylinder Liberty engines to the number of 10,000. But before this contract could be signed the increasing powers of the newest European air engines indicated to our commission abroad that we should concentrate our manufacturing efforts upon the 12 alone, that being the engine of a power then distinctly in advance in the rapid evolution of aviation engines. The engine production department, therefore, entered into contracts for the construction of 22,500 of the 12-cylinder Liberties, and the first of these contracts was signed in August, a few days after the endurance tests had demonstrated that the 12-cylinder engine was a success.

Of this number of Liberty engines the Packard Motor Car Co. contracted to build 6,000; the Lincoln Motor Co., 6,000; the Ford Motor Co., 5,000; Nordyke & Marmon, 3,000; the General Motors Corporation (Buick and Cadillac plants), 2,000; while an additional contract of 500 engines was let to the Trego Motors Corporation.

Early in the liberty engine project it became apparent that one of the great stumbling blocks to volume production would be the steel cylinder, if it were necessary to machine it out of a solid or partially pierced forging such as is used for shell making. This problem was laid before Henry Ford and the engineering organization of the Ford Motor Co., at Detroit, and they developed the unique method of making the cylinders out of steel tubing. One end of the tube was cut obliquely, heated, and in successive operations closed over and then expanded into the shape of the combustion chamber, with all bosses in place on the dome. The lower end was then heated and upset in a bulldozer until the holding-down flange had been extruded from the barrel at the right place. By this method a production of 2,000 rough cylinders a day was reached.

The final forging was so near to the shape desired that millions of pounds of scrap were saved over other methods, to say nothing of an enormous amount of labor thus done away with. The development of this cylinder-making method was one of the important contributions to the quantity production of Liberty engines.

EXPERIMENTAL WORK ON NEW IDEAS FOR LIBERTY ENGINE.

TEST CYLINDERS FOR THE LIBERTY ENGINE AT THE PLANT OF NORDYKE & MARMON, INDIANAPOLIS, IND.

CRANK-SHAFT DIE FOR THE LIBERTY ENGINE. BUICK ENGINE CO., DETROIT.

ACCEPTED LIBERTY ENGINES BEING BOXED FOR SHIPMENT.

It was evident that in the actual production of the Liberty engine there would continually arise practical questions of manufacturing policy that might entail modifications of the manufacturing methods, while our aviation authorities in Europe could be expected to advance suggestions from time to time that might need to be embodied in the mechanism. Consequently it was necessary to create a permanent development and standardization administration for the Liberty engine. Nor could this supervision be located in Washington, because of the extreme need for haste, but it must exist in the vicinity of the plants doing the manufacturing.

For this reason the production of the Liberty engine was centered in the Detroit manufacturing district, since in this district was located the principal motor manufacturing plant capacity of the United States. James G. Heaslet, formerly general manager of the Studebaker Corporation and an engineer and manufacturer of wide experience, was installed as district manager. The problems incident to the inspection and production of the Liberty engine were placed in charge of a committee consisting of Maj. Heaslet (chairman); Lieut. Col. Hall, one of the designers of the engine; Henry M. Leland; C. Harold Wills, of the Ford Motor Co.; and Messrs F. F. Beall and Edward Roberts, of the Packard Motor Car Co. With them were also associated D. McCall White, the engineer of the Cadillac Motor Co., and Walter Chrysler, of the Buick Co.

The creation of this committee virtually made a single manufacturing concern of the several, previously rival, motor companies engaged in producing the Liberty engine. To these meetings the experts without reservation brought the trade secrets and shop processes developed in their own establishments during the preceding years of competition. Such cooperation was without parallel in the history of American industry, and only a great emergency such as the war with Germany could have brought it about. But the circumstance aided wonderfully in the development and production of the Liberty engine.

Moreover, the Government drew heavily upon the talent of these great manufacturing organizations for meeting the special problems presented by the necessity of filling in the briefest possible time the largest aviation engine order ever known. Short-cuts that these firms might have applied effectively to their own private advantage were devised for the Liberty engine and freely turned over to the Government. The Packard Co. gave a great share of its equipment and personnel to the development. The most conspicuous success in the science of quantity production in the world was the Ford Motor Co., which devoted its organization to the task of speeding up the output of Liberty engines. In addition to the unique and wonderfully efficient method of making rough engine cylinders out of steel tubing, the Ford organization also perfected for the Liberty a new method of producing more durable and satisfactory bearings. Messrs. H. M. and W. C. Leland, whose names were indissolubly linked with the Cadillac automobile, organized and erected the enormous plant ofthe Lincoln Motor Co. and equipped it for the production of the Liberty, at a total expense of approximately $8,000,000.

Balanced against these advantages brought by highly trained technical skill and unselfish cooperation were handicaps such as perhaps no other great American industrial venture had ever known. In the first place, an internal-combustion engine with cylinders of a 5-inch bore and pistons of a 7-inch stroke—the Liberty measurements—was larger than the automobile engines then in use in this country. This meant that while we apparently had an enormous plant—the combined American automobile factories—ready for the production of Liberty engines, actually the machinery in these plants was not large enough for the new work, so that new machinery therefore must be built to handle this particular work. In some cases machinery had to be designed anew for the special purpose.

To produce every part of one Liberty engine something between 2,500 and 3,000 small jigs, tools, and fixtures are employed. For large outputs much of this equipment must be duplicated over and over again. To provide the whole joint workshop with this equipment was one of the unseen jobs incidental to the construction of Liberty engines—unseen by the general public, that is—yet it required the United States to commandeer the capacity of all available tool shops east of the Mississippi River and devote it to the production of jigs and tools for the Liberty engine factories.

Then there was the question of mechanical skill in the factories. It soon developed that an automobile motor is a simple mechanism compared with an intricate aviation engine. The machinists in ordinary automobile plants did not have the skill to produce the Liberty engine parts successfully. Consequently it became necessary to educate thousands of mechanics, men and women alike, to do this new work.

It was surprising to what extent unfriendly influence in the United States, much of it probably of a pro-German character, cut a figure in the situation. This was particularly true in the supply factories furnishing tools to the Liberty engine plants. Approximately 85 per cent of the tools first delivered for this work were found to be inaccurate and incorrect. These had to be remade before they could be used. Such tools as were delivered to the Liberty plants would mysteriously disappear, or vital equipment would be injured in unusual ways; in several instances cans of explosives were found in the coal at power plants; fire-extinguishing apparatus was discovered to be rendered useless by acts of depredation; and from numerous other evidences the builders of Liberty engines were aware that the enemy had his agents in their plants.

Difficulty was also experienced in the production of metals for the new engines. The materials demanded were frequently of a much higher grade than the corresponding materials used in ordinary automobile motors. Here was another unseen phase of development which had to be worked out patiently by the producers of raw materials.

LIBERTY ENGINE READY FOR TEST AT THE LINCOLN MOTOR CO., DETROIT, MICH.

LIBERTY ENGINE ON INSTRUCTION STAND, WILBUR WRIGHT FIELD.

VIEW SHOWING LIBERTY ENGINE WITH PROPELLER HUB ATTACHED.

TEST SHED AND STAND WITH LIBERTY ENGINE MOUNTED WITH TEST PROPELLER. PACKARD MOTOR CAR CO.

Difficulties in transportation during the winter of 1917-18 added their share to the perplexing problems of the engine builders, while at times the scarcity of coal threatened the complete shutdown of some of the plants.

Under such obstacles the engine-production department forced the manufacture of the Liberty engine at a speed never before known in the automotive industry. In December, 1917, the Government received the first 22 Liberty engines of the 12-cylinder type, durable and dependable, a standardized, concrete product, only seven months after the Liberty engine existed merely as an idea in the brains of two engineers. These first engines developed a strength of approximately 330 horsepower, and this was true also of the first 300 Liberty engines delivered, these deliveries being completed in the early spring of 1918.

When the Liberty engine was designed our aviation experts believed that 330 horsepower was so far in advance of the development of aero engines in Europe that we could safely go ahead with the production of this type on a quantity basis. But again we reckoned without an accurate prophetic knowledge of the course of engine development abroad. We were building the first 300 Liberty engines at 330 horsepower when our aviation reports informed us from overseas that an even higher horsepower would be desirable. Therefore our engineers "stepped up" the power of the Liberty 12-cylinder engine to 375 horsepower. Several hundred motors of this power were in process of completion when again our observers in France advised us that we could add another 25 horsepower to the Liberty, making it 400 horsepower in strength, and be sure of leading all of the combatant nations in size and power of aviation engines during 1918 and 1919. This last step, we were assured, was the final, definite one. But to anticipate possible extraordinary development of engines by other nations, our engineers went even further than the mark advised by our overseas observers and raised the power of the Liberty engine to something in excess of 400 horsepower.

This enormous increase over the original power of the Liberty engine required changes in the construction, notably in increasing the strength of practically all of the working parts, including the crank shaft, the connecting rods, and the bearings. The change also resulted in making scrap iron of a large quantity of the jigs and special tools employed in making the lighter engines. A still further change had to come in the character of some of the steel used in some of the parts, and this went back to the smelting plants, where new and better methods of producing steel and aluminum for the Liberty engine had to be developed.

Thus while there were no fundamental changes in the design of the engine, the increase of its power required a considerable readjustment in the engine plants. Yet so rapidly were these changes made that on the first anniversary of the day when the design of the Liberty engine was begun—May 29, 1918—the Signal Corps had received 1,243 Liberty engines. In this achievement motor history was written in this country as it had never been written before.

From a popular standpoint it may seem that the Liberty engine was radically changed after its inception, but such an assertion is entirely unwarranted; for in the fundamental thing, the design, there was but one change made after the engine was laid down on paper in May, 1917, namely, in the oiling system. The original Liberty engine was partially fed with oil by the so-called scupper system, whereas this later was changed to a forced feed under compression. The scupper feed worked successfully, but the forced feed is foolproof and was therefore installed upon the advice of the preponderance of expert criticism.

It is also true that in working out certain practical manufacturing processes some of the original measurements were altered. But this is a common experience in the manufacture of any internal-combustion engine, and alterations made for factory expediency are not regarded as design changes, nor are they important.

The delivery of 22 motors in December of 1917 was followed by the completion of 40 in January, 1918. In February the delivery was 70. In March this jumped to 122; then a leap in April to 415; while in May deliveries amounted to 620.

The quantity production of Liberties may be said to have started in June, 1918, one year after the engine's conception in Washington. In that month 1,102 motors of the most powerful type were delivered to the service. In July the figure was 1,589; in August, 2,297; in September, 2,362. Then in October came an enormous increase to the total of 3,878 Liberty engines. During the month before the armistice was signed the engine factories were producing 150 engines a day.

In all, up to November 29, 1918, 15,572 Liberty engines were produced in the United States. In the disposal of them the American Navy received 3,742 for its seaplanes; the plants manufacturing airplanes in this country took 5,323 of them; 907 were sent to various aviation fields for training purposes; to the American Expeditionary Forces in France, in addition to the engines which went over installed in their planes, we sent 4,511 Liberty engines; while 1,089 went to the British, French, and Italian air services.

Some of the earliest Liberties were sent to Europe. In January, 1918, we shipped 3 to our own forces in France. In March we sent 10 to the British, 6 to the French, and 5 to the Italians. By June 7 the English tests had convinced the British air minister that the Liberty engine was in the first line of high powered aviation engines and a most valuable contribution to the allied aviation program. The British air minister so cabled to Lord Reading, the British ambassador in Washington. Again on September 26 the British air ministry reported that in identical airplanes the Liberty engine performed at least as well as the Rolls-Royce engine. Birkight, who designed the Hispano-Suiza engine in France, declared that the Liberty engine was superior to any high-powered aviation engine then developed on the Continent of Europe.

INSTALLING LIBERTY ENGINE IN THE LEPERE FUSELAGE AT PACKARD PLANT, SHOWING PROGRESSIVE ASSEMBLY.

Figure 14.Liberty Engines Produced Each Month During 1918.Jan.▍ 40Feb.▋ 70Mar.█ 122Apr.████ 415May.██████ 620June.███████████ 1102July.████████████████ 1589Aug.██████████████████████ 2297Sept.███████████████████████ 2362Oct.████████████████████████████████████ 3678Nov.██████████████████████████████ 3056Dec.████████████████████████ 2437

A more concrete evidence of the esteem in which this American creation was held by the European expert lies in the size of the orders which the various allied Governments placed with the United Statesfor Liberty engines. The British took 1,000 of them immediately and declared that they wished to increase this order to 5,500 to be delivered by December 31, 1918. The French directed inquiries as to the possibility of taking one-fifth of our complete output of Liberty engines. The Italians also indicated their intention of purchasing heavily for immediate delivery.

This increased demand for the engine had not been anticipated in our original plans, as we had no idea that the allied Governments would turn from their own highly developed engines to ask for Liberty engines in such quantities. The original program of 22,500 engines was only sufficient for our own Army and Navy requirements. As soon as the foreign Governments, however, came in with their demands we immediately increased the orders placed with all the existing Liberty engine builders, and in addition contracted to take the entire manufacturing facilities of the Willys-Overland Co. at its plants in Toledo and Elyria, Ohio, and Elmira, N. Y. We also engaged the entire capacity of the Olds Motor plant at Lansing, Mich. In addition we had subsequently contracted for the production of 8,000 of the 8-cylinder engines. Thus the number of engines which would have been delivered under contract, if peace had not cut short the production, would have been 56,100 engines of the 12-cylinder type and 8,000 of the 8's.

The foreign Governments associated with us in the war against Germany showered their demands upon us for great numbers of the American engines, not only altogether because of the excellence of the Liberty, but because partially their plane production exceeded their output of engines. Mr. John D. Ryan, Director of Aircraft Production, verbally agreed to deliver to the French 1,500 Liberty engines by December 31, and further agreed to deliver motors to the French at the rate of 750 per month during the first six months of 1919. The British had already received 1,000 Liberty motors, and this order was increased with Mr. Ryan personally by several thousand additional engines to be delivered in the early part of 1919. When the armistice was signed the Liberty engine was being produced at a rate which promised to make it the dominant motive power of the war in the air before many months had passed.

The engine was originally named the "United States Standard 12-cylinder Aviation Engine." In view of the service which it promised to render to the cause of civilization, Admiral D. W. Taylor, the chief construction officer of the Navy, suggested during the early part of the period of production that the original prosaic name be discarded and that the engine be rechristened the "Liberty." Under this name the engine has taken its place in the history of the war as one of the most efficient agencies which was developed and employed by this country.

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