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Government Experts Decide That Practical Type Should Be Lever- Controlled From Ship's Bridge—Mechanism Must Be Simple tained in the model tank at the navy yard, Washington, during ex- periments made to determine whether or not it was feasible to design and install a brake on the side of a merchant vessel to assist in stopping a steamer when in danger of collision or grounding. The question of installing such a brake is a financial one and is dependent upon the lessened insurance. demanded and _ the advertisement of such an appliance to increase the passenger list. It is not one for the naval architect or marine engi- neer to solve and is not brought up for discussion on that point. In the spring of 1910, a set of trials was made on the: -U;..S. $) Ine DIANA off Delaware Var breakwater to de- ‘termine the effect of the Lacoste ship brake. Due to a lack of preliminary investigation, this trial showed very little either for or against the brake and it was some time after that the writer was requested by personal friends to take up the study with a view to de- signing a practical brake. After the loss of Tiranic, interest was awakened to such an extent that a syndicate was formed and the permission of the navy department was obtained to make a se- ries of trials in the model tank, the results of these trials being available through the courtesy of the Lacoste Shipbrake Syndicate. The Wm. Cramp & Sons Ship & En- gine Building Co. was kind enough to furnish the lines of St. Louis, and a model of this vessel was constructed. Three runs were made to determine the curve of speed and power before fitting any brakes, and the successive ten runs were made with different areas and set- tings of the brake to determine the re- sistances and pressures per square foot. Sr. Louris is 536 feet in length, 62 feet 9 inches beam, and the draught at load line was 28 feet for model experiments, Peis ix ne data have been ob- From a paper read at the Twenty-third gen- eral peecuig of the Society of Naval Architects and Marine Engineers, New York, Nov. 18 and 19, 1915. the displacement being about 17,230 tons. The following deductions were made: The stopping power varies directly as the projected area opposed at 90 degrees to the fore-and-aft line. One pair of brakes is more efficient than two, as shown by a test run in which the combined area is 624 square feet for the two brakes, and the stopping power or resistance opposed is not in the same proportion as that of the pair 12 feet by 14 feet, giving 168 square feet. The pressure per square foot practically de- creases as the width of the brake is reduced and, by plotting curves of DESIGN OF SHIP BRAKE USED IN. MODEL TESTS pressures at various speeds for different widths of brake, it is found that after a certain width is passed the pressure per square foot is not increased. The model was also fitted with a pair of brakes of 11 feet 834 inches projected area, by 14 feet deep, fitted so as to be tripped and thrown out from the travel- ing carriage of thé model tank. A set of guides was fitted so as to keep the model in position under the carriage, yet allow it to advance freely when the carriage was stopped. The foot-way along the tank was marked off in equal distances from a certain point far enough from the starting point to allow the car- riage to reach the proper speeds. The model was then brought up to speed, the carriage stopped at the determined point, the model released with the _ brakes thrown out, and the times marked by stop-watches at each marked distance until the model was brought to rest or the limit of the tank reached. Interesting data showing the instan- taneous stopping effect of a pair of brakes of different sizes were compiled, 25 By Capt. Wm. Strother Smith, U.S. N. as shown in the accompanying table. The experiments conducted on In- DIANA showed very little. The vessel was entirely unsuitable, owing to the fact that there is not a straight line in any part of her hull and the brake had to be fitted on by means of a molded frame. There were no accurate means of determining the total instantaneous indicated horsepower nor the exact speed. When the subject was revised, the model tank was considered by far the most accurate method of determining the data to be used in designating a brake. To satisfy the ideas of many concerned, va- rious forms of the brake were consid- ered, principally with the idea of controlling the brake by power so as to open and close at will, the vessel going at full speed. The four plans were as fol- lows: Long hydraulic cylinders are in- stalled athwartship on a stiffened bulk- head to work con- necting rods attached tothe brakes. This involved an additional weight of about 190 tons, including 33 tons of contained water. In order to reduce weights, especially that of contained water, a toggle joint arrangement was studied to reduce the power required and to reduce the peak © load when the brakes were to be started in. This involved a stress of 340,000 pounds on each of three principal con- necting rods and 320,000 pounds on each of three lesser members. A rack and pinion arrangement, allow- ing very little contained water was de- signed. The diameter of the vertical shaft working the pinions and the width of the gear needed rendered this scheme out of consideration. Another plan was adopted with the idea of push- ing the brake out to 35 degrees to assist the rudder. This required too much machinery to develop the power necessary, about 500 estimated horse- power for a pair of brakes 9 by 13 feet. Many other schemes were studied out, but the weights and power required ine einen titi i i a il hl a a og eS Soe