places required quite accurate machining. Orville Wright's diary of 1904 has the entry, "Took old engine apart to get measurements for making new engine." Finally, no Wright drawings of the original engine have been seen by anyone connected with the history or with the Wright estate. In the estate were two drawings (now at the Franklin Institute), on heavy brown wrapping paper, relating to one of the two very similar later engines built in 1904; one is of a cylinder and connecting rod, the other is an end view of the engine. Thus even if the very ingenious drafting board now in the Wright Museum at Carillon Park was available at the time there is no indication that it was used to produce what could properly be called drawings of the first engine.

There are in existence, however, two complete sets of drawings, both of which purport to represent the 1903 flight engine. One set was made in England for the Science Museum in the two years 1928 and 1939. The 1928 drawings were made on receipt of the engine, which was not disassembled, but in 1939 the engine was removed from the airplane, disassembled, the original 1928 drawings were corrected and added to, and the whole was made into one very complete and usable set. The other set was prepared in Dayton, Ohio, for Educational and Musical Arts, Inc.,[6] and was donated to the Smithsonian Institution. This latter set was started under the direction of Orville Wright, who died shortly after the work had been commenced.

The two sets of drawings, that is, the one of the Science Museum and that made in Dayton for the Smithsonian Institution, cannot be reconciled in the matter of details. Hardly any single dimension is exactly the same and essentially every part differs in some respect. Many of the forms of construction differ and even the firing order of the two engines is not the same, so that in effect the drawings show two different engines.

Figure 1.—First flight engine, 1903, valve side. (Photo courtesy Science Museum, London.)

The primary trouble is, of course, that the exact engine which flew in 1903 is no longer in existence, and since no original drawings of it exist, there is considerable doubt about its details. The engine had its crankcase broken in an accident to the airframe (this was caused by a strong wind gust immediately following the last of the first series of flights at Kitty Hawk), and when it was brought back to Dayton it was for some inexplicable reason completely laid aside, even though it presumably contained many usable parts. When the engine was disassembled to obtain measurements for constructing the 1904 engines, again apparently no drawings were made. In February 1906 Orville Wright wrote that all the parts of the engine were still in existence except the crankcase; but shortly after this the crankshaft and flywheel were loaned for exhibition purposes and were never recovered. In 1926 the engine was reassembled for an exhibition and in 1928 it was again reassembled for shipment to England. The only parts of this particular engine whose complete history is definitely known are the crankshaft and flywheel, which were taken from the 1904-1905 flight engine. This latter engine, now in the restored 1905 airplane in the Carillon Park Museum in Dayton, does not contain a crankshaft, and in its place incorporates a length of round bar stock.

Figure 2.—First flight engine, 1903, underside and flywheel end. (Photo courtesy Science Museum, London.)

In late 1947 work on the Educational and Musical Arts drawings was initiated under the direction of Louis P. Christman and carried through to completion by him. Christman has stated that Orville Wright was critical of the Science Museum drawings but just what he thought incorrect is not known. Whatever his reasons, he did encourage Christman to undertake the major task of duplication. Christman worked directly with Orville Wright for a period of six weeks and had access to all the records and parts the Wrights had preserved. The resultant drawings are also very complete and, regardless of the differences between these two primary sets, both give a sufficiently accurate picture of the first engine for all purposes except that of exact reproduction in every detail.

There exists a still unsolved puzzle in connection with what seems to be yet another set of drawings of the first engine. In December 1943, in writing to the Science Museum telling of his decision to have the airplane and engine brought back to the United States, Orville Wright stated, "I have complete and accurate drawings of the engine. I shall be glad to furnish them if you decide to make a replica."[7] No trace of these particular drawings can be found in any of the museums, institutions, or other repositories that normally should have acquired them and the executors of Orville Wright's estate have no record or knowledge of them. The date of his letter is four years before the Dayton drawings were commenced; and when Christman was working on these with Orville Wright they had copies of the Science Museum drawings, with complete knowledge of their origin, yet Christman has no knowledge of the drawings referred to in Orville's letter to the Museum. Finally, the evidence is quite conclusive that there were no reproducible or permanent drawings made at the time the first engine was constructed, and, of course, the reconstructed engine itself was sent to England in 1928 and not returned to this country until 1948.[8]

The Engine of the First Flight, 1903

In commencing the design of the first engine, the first important decision arrived at was that of the number and size of the cylinders to be employed and the form in which they would be combined, although it is unlikely that this presented any serious problem. In a similar situation Manly, when he was working on the engine for the Langley Aerodrome,[9] was somewhat perturbed because he did not have access to the most advanced technical knowledge, since the automobile people who were at that time the leaders in the development of the internal combustion engine, tended for competitive reasons to be rather secretive about their latest advancements and designs. But although the standard textbooks may not have been very helpful to him, there were available such volumes as W. Worby Beaumont's Motor Vehicles and Motors which contained in considerable detail descriptions and illustrations of the best of the current automobile engines. The situations of Manly and the Wrights differed, however, in that whereas the Wrights' objective