HYDRAULIC BRAKE.

150

transversely across the front end of tlie cylinders, two over andtwo under the piston-rod, and connected together by a loosegirder through which the rod passes. The cylinder B is shownin sectional plan by fig. 5. It is 4 feet inches long, cast witha flange on each end, and hored out to 12 inches diameter, with2£ inches thickness of metal. Covers are bolted to both flanges,and are fitted with hydraulic glands, with cup leather packing,for the piston-rod, which passes through both ends of thecylinder. An india-rubher ring 1 inch thick is fixed round therod 011 each side of the piston, to form a cushion between thepiston and the cylinder ends, the piston being turned to an easyfit. The constant eircumferential clearance between the cylinderand the piston is 0'38 of a' square inch. In addition to thisconstant space, a gradually diminishing area of passage has beencontrived, whereby a uniform resistance is maintained through-out the stroke. This is accomplished by a wrought iron Strip C,three inches wide, fastened by stud-screws along each inner sideof the cylinder. They project of an inch into the cylinder atthe commencement of the stroke, and taper up to lx^ inch atthe rear end. This wrought iron strip fits into a correspond-ing slot inch deep, which is cut out in each side of thepiston.

"VVhen an impact takes place, the piston is forced backwards.The clear space between the tapering strips and the slots inthe piston becomes less and less, as shown by the diminishingareas of the waterway (the thin rectangular strip with thehatching) in sections GFE and D, so that, notwithstanding thediminishing speed, an equal amount of resistance is maintaineduntil the train is at rest. The waterway of G is 496 squareinches, of F is 318 square inches, of E is T40 square inch, andof D is 0’08 of a square inch. By means of adjusting screws,applied to gauge plates, the proper sizes of the openings throughthe pistons were determined by experiment. The cylinder iskept constantly filled with water by a supply pipe H fixed tothe front of it. When released, the piston is drawn forwardagain into its original position by the action of a counter-