PLAN AT BOTTOM.
Fig. 148.
The volume of water which is used intermittently for the purpose of operating presses—draw-benches for brass and copper tubing and the like is replaced by a pump or pumps which are started and stopped automatically by a connection between the accumulator and the throttle or belt shifter of the pump. The accumulator is used for a double purpose of maintaining a constant pressure and to store up any surplus force of the pumps. The friction loss in the transmission of power by water through mains is very small, as for example: It has been found that water under a pressure of 700 lbs. per square inch may be transmitted through well proportioned mains, one mile with a loss of only two per cent.
The useful work stored in an accumulator may be calculated by the following rule: Multiply the area of ram in square inches by the length of the stroke in inches by the pressure m pounds per square inch divided by 33,000 lbs. the equivalent of one H. P.
This represents the work done by one full stroke of the accumulator ram in descending from its highest position to its lowest.
Example. Required the work done by one stroke of a ram twelve inches in diameter, and a stroke of twenty-two feet, under a pressure of 750 lbs. to the square inch. Area of 12 ram = 113·097 square inches. No. of ins. in 22 ft. = 264. Then
113·097 × 264 × 750
————————– = 678·582 H.P.
33,000
Mr. Tweddel designed the accumulator shown in Figs. 147 and 148 to furnish the varying demand for water where only one appliance of this kind is used in connection with a hydraulic system of shop tools more especially where these tools are numerous.
The ram or spindle A is fixed top and bottom and acts as a guide for the cylinder B which slides up and down upon it.
