Lawrence Hargrave was firmly committed to sharing the fruits of his research, even though he conducted his experiments in Australia, far from the bustle of European and American aeronautics. He regularly communicated with the Royal Society of New South Wales and through that group (of which he was a member) to the rest of the world. He didn't patent the ground-breaking results of his research, believing that whatever he could do to promote the development of flying machines would be reward enough. Hargrave was also an historian, and remarked that the inventor of a new mode of transportation had never been made rich by that invention, patented or not. Octave Chanute certainly knew of Hargrave and appreciated the importance of what Hargrave was then doing. One of Hargrave's earliest achievements was to demonstrate that for a wing to lift and move through air efficiently, the center of pressure ought to be located at about 25% of the chord length of the wing section. This was an understanding of great significance and to ensure that it would find application by any aerial experimenters so interested, Hargrave published his discovery. It seems quite likely that Chanute had a hand in Hargrave's donation of his No. 14 (which made a flight of 312 feet in 19 seconds, powered by compressed air driving flapping-wing-type propellers which he termed "Trochoided planes") to the Field Columbian Museum in Chicago, Illinois, during 1894.
Hargrave's experiments with a series of powered experimental model flying machines were of great interest to people then involved with aeronautics and aerial research. Chanute's now-classic 1894 book "Progress In Flying Machine" devoted more than thirteen pages to Hargrave's work. Chanute opened his section on Hargrave by writing:
|"'If there be one man, more than another, who deserves to succeed in flying through the air, that man is Mr. Lawrence Hargrave, of Sydney, New South Wales. He has now constructed with his own hands no less than 18 flying machines of increasing size, all of which fly, and as a result of his many experiments (of which an account is about to be given) he now says, in a private letter to the writer, that : 'I know that success is dead sure to come.'"|
The full quote from Hargrave's private letter to Chanute reads
|"The people of Sydney who can speak of my work without a smile are very scarce ; it is doubtless the same with American workers. I know that success is dead sure to come, and therefore do not waste time and words in trying to convince unbelievers." "|
Chanute seemed particularly impressed with the fact that Hargrave kept and maintained detailed notes and logs of his work "... so that a stranger, if an expert, could come into his shop, study his notes and drawings, pick up his tools and continue his work, and thus no portion of it would be lost." Hargrave and Chanute shared an unshakable and deep belief that aeronautical work would progress only through the continuity of labor and research of a number of people over time, which had, after all, been Chanute's motivation for writing "Progress In Flying Machines." Hargrave's series of experiments began with some 50 "Trochoided plane" model flying machines which sought to reproduce the propelling motions of birds and fish. Some of these models were powered by clockwork mechanisms. Using data derived from these experiments, Hargrave derived the average of the most successful of them and used those averages to design the next series of machines, using stretched (not twisted) rubber bands as power. He built and tested about 10 of these models.
The first of Hargrave's models to be powered by compressed air driving "Trocoided Planes" was #10, which flew a remarkable 368 feet in 1890. Hargrave #10 weighed a little over 2 1/2 pounds, had a length of slightly over 4 feet, its compressed air engine weighed in at only 6 1/2 ounces, and its wings were made of paper. That same year Hargrave built model #12, a development of #10, which, while heavier, nonetheless flew 343 feet. He powered his #15 with a chemical-reaction "explosion" engine which did not succeed, while his #17 and #18 machines were powered by lightweight yet powerful steam engines (which caused him considerable trouble).
Hargrave is most remembered, however, not for his numerous remarkable model flying machines but for his series of "cellular kites." He invented the box-kite, a lightweight yet very strong configuration of lifting surfaces which defined most aeronautical design prior to The Great War, WWI. Alberto Santos-Dumont's biplane No. 14-bis which flew in 1906 was the embodiment of Hargrave's box-kite, an inspiration which Santos-Dumont acknowledged. Gabriel Voisin first advertised his famous Voisin biplanes as "Hargrave" machines. The Herring and Chanute biplane and triplane gliding machines of 1896-1898 were based on Hargrave's box-kite, as, indeed, were the Wright Flyers and the biplanes produced by Glenn Curtiss, as well as the Voisin and Farman biplanes. It's difficult to imagine the pre-WWI period of aviation without the incorporation of the Hargrave's box-kite design, so dominent was the cellular structure on biplane and triplane aeroplanes. Hargrave introduced the design in a paper read at the great International Aerial Navigation Congress held during August of 1893 in Chicago, Illinois. Of particular note in Hargrave's 1893 paper is the comparison made to the lifting ability of the box-kites illustrated below, "E" and "F." Although they were virtually identical in all respects, save one, Hargrave box-kite "E" generated almost twice the lift of box-kite "F." The difference, which was noted with great interest at the time, was that the horizontal surfaces of box-kite "E" were curved in section while those of "F" were flat. Lawrence Hargrave was not one to claim credit where it was not deserved and he duly noted that it had been Francis Herbert Wenham in 1866 who first suggested superimposing lifting surfaces in his classic paper "Aerial Locomotion."
Hargrave sought to preserve his models for further study. After failing to find any other institution which he thought would be up to that task, in February of 1910 he donated 176 of his model flying machines to the Deutsches Museum in Munich. Allied bombing of Germany in WWII destroyed all but 25 of Hargrave's flying machines. The remaining Hargrave models were later transferred to Sydney, Australia's Powerhouse Museum, where they form the central exhibit of Hargrave's work.