The following computation of the head in feet, necessary to force the water through the pipes, valves and condenser tubes at the velocity corresponding to sixty strokes of the pump per minute, made previous to the experiment, according to the laws of hydraulics as laid down in Rankine's Civil Engineering, serves to check the accuracy of the experiment, and to show that the power necessary to work a circulating pump on ship board can be very approximately computed when the arrangement of pipes is known : Assumed velocity of pump, 60 strokes per minute. in which F is a factor depending upon the form and material or the To overcome resistance in bends, being an amount depending upon the number and abruptness of bends, h2 =1·1664. To overcome resistance of springs on back of valves: Area of rubber disc, 50 square inches. Strength of spring, 45 lbs. Estimated lift, & inch. Press per square inch, lbs. This error probably arises from the valves not lifting as much as inches, and therefore the springs on the backs of the receiving and delivery valves not offering the resistance stated. TEST TRIAL OF THE LYNN PUMPING ENGINE. SECOND REPORT OF THE BOARD OF ENGINEERS, TO THE PUBLIC WATER BOARD OF LYNN, MASS. [Continued from Vol. lxviii, page 414.] MEASURES OF CAPACITY OF PUMP. The overflow from the stand-pipe at the reservoir was conveyed by a wooden trunk into a weir box 15 feet long, 6 feet wide and 4 feet 6 inches deep. The weir was at the opposite extremity from the trunk. Its crest was 2.113 feet above the bottom of the box, and 3.73 feet wide, and placed centrally in the end of the box. That the water should approach the weir with as uniform flow as possible, two racks covered with wire cloth were placed between the trunk and the weir. The arrangement of weir and mode of taking heights of water were like those adopted by Mr. Francis in his "Lowell Hydraulic Experiments." The readings were every 2 minutes, and as the heights varied but little they have been averaged as giving a result sufficiently The discharges have been calculated by Mr. Francis' Tables and the correction for velocity of approach from his formula. near. The readings were taken from 3 P. M. to 6 P. M., December 10, and from 3 P. M. to 6 P. M., December 11. Readings would have been taken the 12th, but the filling of the reservoir by the pumping disturbed the supports of the weir box. The average height on the 10th was... 66 66 66 11th was........... 0.743 0.739 Discharge from 3 P. M. to 6 P. M., December 10th..........................7·666 cubic feet per second. 11th..........7.606 66 ...0.0092 " 66 66 66 10th, 3,303. Leak of weir measured and estimated................ Capacity of pump by weir, measured December 10th....... 186.68 = = .9601. Loss of action of pump as given in the first report, 4 per cent. |