When the speed is given by S in m/h (miles an hour) the factor 550 is replaced by 375, which is 33,000 88, as 1 mile an hour is 88 feet per minute. .35 FIG. 2. If the weight to be lifted is m times the weight of the motor, the motor must weigh so that at S 40 m/h, say Q = 60 f/s, and with n = 5, m = 2, as in Maxim's machine, the motor must weigh the figure given by Maxim; and Herbert Spencer and Clifford could tell the aeronaut with certainty that his ideal must await the motor which could be brought down to this weight, 11 lb/I.H.P., and lower still, before his machine could fly. The petrol motor had not come to any perfection in the day of Maxim's experiment, 1895, and so he was obliged to carry a boiler up with his engine. This implied a great increase in size all round, so that Maxim's machine (Fig. 3) weighed close on four tons, quite unmanageable in the light of modern experience. An aviator is akin to the imperfect orator, as his chief difficulty arises when he wants to get down; and the shock of landing of four tons rather abruptly would be terrifying, with a boiler close by full of steam at 275 lb/inch2. FIG. 3. A modern locomotive will weigh complete about 80 tons, and will indicate 1,000 H.P. at 50 to 60 m/h; the H.P./ton is then 12.5, and the lb/H.P. = 2,270 = 180, so that no locomotive can be expected to fly, still less a marine engine, with its additional weight of condenser. This simple arithmetical calculation, of Herbert Spencer and Clifford, it can hardly be called mathematical, is enough to show why mankind was compelled to await the advent of the light petrol motor; and man might still be waiting, but for the previous development of the motor car. A list is given here of the chief dimensions of the early pioneering machines; the list can be added to, and brought up to date with each successive pattern and development. |