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. [Illustration: VERTICAL SECTION. FIG. 149.] This cylinder is loaded with weights marked to indicate the pressure which the accumulator will balance with those weights in use. The water is pumped into the bottom through the pipe _C_, and fills the annular space around the spindle. The entire weight of cylinder is raised by the pressure of water acting only on the area of the end of brass sleeve _D D_, which is only 1/2 inch thick all around the center spindle, and extends down through the bottom packing in cylinder, as shown in sectional view. Fig. 149. A compact arrangement is thus gained and any reasonable, required cubical capacity may be reached by lengthening the stroke. The accumulator is supplied by two pumps having plungers 1-3/8″ diam. by 3-1/2″ stroke, speed 100 to 120 rev. per minute. When the loaded cylinder _B_ reaches the top of its stroke, by means of a small chain it closes the suction cock _E_, which shuts off the water supply of the pumps. To put in a new bottom packing, the cylinder is let down to rest on the wooden blocks _G_, and the spindle is lifted out of its tapered seat at the bottom by a tackle hooked into the eye-bolt at the top. To renew the top leather the bracket holding the top end of spindle _A_, has to be removed. This accumulator (having only a small area) falls quickly when the water is withdrawn, thus producing a combined blow and squeeze, which is of great advantage in hydraulic riveting. _The Hydraulic Intensifier_ is a cylinder having two diameters, in principle very like the tandem compound engine. It is used for increasing the pressure of water in hydraulic mains, pipes, or machines, using only the energy of the pressure water to effect the change. But for this distinction a steam pump would be an intensifier. An intensifier worked the reverse way is a “diminisher” as a hydraulic pump usually is, giving a reduced pressure. _The intensifier is in some respects analogous to the electric transformer._