Page:Aerial Flight - Volume 2 - Aerodonetics - Frederick Lanchester - 1908.djvu/48

 during discharge. The " motive power " is furnished by an india-rubber band, usually composed of about four strands of black "elastic."

The india-rubber is secured to a projecting piece and is guided by two pulleys or spools, one on each side of the runners. The rubber is bound with twine at and about its middle point where it engages with the notch in the after extremity of the backbone of the aerodone. When loaded, the rubber is held in a state of extension by notches near the rear end of the runners, and the discharge is effected by prising it out of the said notches by means of a forked lever.

The length of the free portion of the rubber ordinarily used was 8 feet 4 inches, the weight being ½ lb. and the maximum range of extension employed 11 feet 6 inches.

A plotting of the extension diagram is given in Fig. 22, in which abscissae represent extent of elongation and ordinates the corresponding tensions in pounds. The figures given are loading data, and the loading energy will be given by the area of the curve for the extension employed. It is improbable that the output energy is more than about 75 per cent, of the total.

§ 13. Site and Date of Experiments.—The site of the experiments under discussion was the then residence of the author, "Fairview," St. Bernard's Road, Olton, Warwickshire; the models being projected from a back first floor window facing west; the point of discharge was approximately 15 feet above the ground level, where the general run of the land falls away at a slope of about 1 in 25.

The situation is represented diagrammatically in Figs. 25 and 26, in which are depicted some of the flights made. A plan is given in Fig. 28 showing the general situation, on this also some of the flights have been roughly laid out.

Experiments were made at different dates during June and July, 1894, the models employed being in most part simple aerodones as described in § 11, some half-dozen in all being made