CONTINUOUS RAILWAY BRAKES. 



191 



On a carriage 30 foot long, with a brake cylinder 8 

 inches diameter, 12 inches stroke, the capacity of the 

 cylinder being 600 cubic inches, and capacity of the air 

 vessel 1,800 cubic inches, the train-pipe on each carriage 

 measuring 284 cubic inches, and assuming the piston to 

 travel 6 inches, 884 cubic inches must be discharged for a 

 full application of the brakes. 



Mr. Michael Reynolds, in his work on "Continuous 

 Brakes," supplies these figures. 



A quick air-pump of large capacity is necessary. 



Glass in. {Reservoir Typo.) 

 The " Hardy " Automatic Vacuum Brake. 



In tho " Hardy " brake an ejector on the engine exhausts 

 the air from tho train-pipe, the vacuum reservoir on the 

 engine, and the vacuum reservoirs placed under each car- 

 riage. In addition to the vacuum reservoir, each carriage 

 carries a brake cylinder, whose piston actuates the brake 

 levers. 



When tJio brakes are " off," communication is cut off 

 between tho brake cylinder and the vacuum reservoir by 

 means of a double-seated diaphragm valve, which is main- 

 tained in a condition of unstable equilibrium by the vacuum 

 in the pipe on one side and the vacuum in the reservoir on 

 the other. Tlie brake piston is maintained in sf,ahle equili- 

 brium by a pressure on both sides, the same as that external 

 to the brake cylinder, the brakes being held "off" by the 

 weight of the pistons. 



To apply the brake, the driver admits air to the train- 

 pipe, thereby destroying the vacuum and the equilibrium of 

 the diaphragm valve, which is thrown over, and opens a 

 passage from tho "reservoir" to the brake cylinder, tho 

 air on tho top side of the brake piston expands into the 



P P 



