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The authors advance for discussion some important problems in the construction of airplanes for military use in this country. The functions of military airplanes designed for strategical and tactical reconnaissance, control of artillery fire and for pursuit are outlined. Problems in construction with reference to the two-propeller system, methods of reducing vibration, application of starting motors, details of the gasoline supply-system, metal construction for airplanes, flexible piping, desirable characteristics of mufflers, shock absorbers, landing gear, fire safety-devices, control of cooling-water temperature, variable camber wings, variable pitch propellers and propeller stresses, are all given consideration. The paper is concluded with suggestions for improvement in design relating to the use of bearing shims, the rigidity of crankcase castings, interchangeability of parts and better detail construction in the oiling, ignition, fuel supply and cooling systems.

It is the purpose of the author to analyze some of the factors that have influenced tractor development. He reviews a number of factors on which the usefulness of tractors depends, showing what the farmer is interested in when buying tractors and how the design should be worked out to secure the greatest general efficiency. The paper then mentions certain general specifications that are required by tractor engines. The author finds that the conditions on about 90 per cent of all farms require a four-cylinder engine of between 16 and 40 hp., operating on the four-stroke cycle. The disadvantages of the two-cylinder horizontal-opposed engine are summarized. An empirical formula is given that can be used to calculate the most satisfactory operating speed of an engine. In concluding the paper a number of the most important general themes of design are outlined. Particular mention is made of the lubrication system and of the special provisions required for kerosene burning engines.

The author states as his object a review of what has been done and what must be done to make tractors successful in operating on low-grade fuels, especially kerosene. He takes up in order the four principal methods in common use of applying heat to vaporize kerosene, pointing out the advantages and disadvantages of each method and of its modifications. The author then cites various experiments with different types of carbureters in burning kerosene, drawing at length upon his own experience in this connection. He cites difficulties with gas distribution, manifold condensation, pistons and spark-plugs and points out that carbureter design is inseparable from considerations of tractor engine and manifold design. That better progress has not been made in the past in developing kerosene-burning tractor engines is stated to be largely owing to the fact that there has not been sufficient cooperation between engine and carbureter manufacturers.

The title of this paper fully indicates its scope. The author presents an intimate picture of conditions prevailing at the war front which affect the operation and maintenance of war trucks, and these two factors in turn indicate the trend that design should take. The training of the mechanical transport personnel of the Army is also gone into at some length. The English and American trucks used earlier in the war consisted of about nineteen different makes and forty-two totally different models, resulting in a very serious problem of providing spare parts and maintenance in general. In the British Army transportation comes under an Army Service Corps officer called the Director of Transport and Supplies. At the outbreak of the war these officers had had little mechanical experience, horses being employed principally. In the French Army motor vehicles were used to a greater extent before the war, under the artillery command.