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. Deeds and 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.