THE HYDBAULIC BKAKE 785 



has a travel of 3 feet 6 inches, and is a plain disc, 9f| inches 

 diameter, with two waterways 3 inches wide by J J inches deep working 

 over two feathers running from end to end of the cylinder. These 

 feathers are 3 inches wide, and are 1% inches thick at the back 

 tapering to J inch at the front end, the area of the waterways varying 

 from 6 square inches at the back to zero at the front end of the cylinder. 

 The clearance between cylinder and piston is equivalent to a further 

 constant area of '25 square inch. The covers are provided with two 

 screwed glands, the inside gland of cast iron holding the hat leathers in 

 position, while the outer glands of brass, which are merely intended as a 

 stand-by, are packed slackly with hemp. A rubber pad 1J inches thick is 

 inserted at the back end of the cylinder as a final cushion. 



To bring the buffer forward after being pushed in a series of three 

 counter weights are attached to the tail rod of the piston through chains 

 working over pulleys at the front end. These weights must be put in 

 motion gradually to prevent breakage of the chains by shock, and to this 

 end the centre weight is divided into a main weight and a jockey weight, 

 the latter being suspended from a 6-inch pulley working in guides and 

 riding on the centre chain. The jockey weight is then supported on the 

 slack of the chain when the buffer is in the forward position, and when 

 the buffer is driven in is lifted before the main weight, thus taking up 

 the first shock on the chain. For the same reason the side weights are 

 mounted on spring hangers. 



The cylinder is automatically fed with water by gravitation through a 

 small pipe fitted with a non-return valve, while a small valve attached to 

 the top of the cylinder is provided for the escape of any air which may 

 accumulate, and for convenience in filling. 



A similar brake, described by Mr. Langley, has a 3|-inch piston rod 

 and a piston 12-inch diameter and 4 -feet stroke. 



The total area of the connecting passages varies from 7'18 square inches 

 at the front to '38 square inch at the back end. After being driven 

 home the piston is returned by means of counterweights. With this 

 brake a maximum pressure of 800 Ibs. per square inch was obtained 

 when stopping a train weighing about 200 tons, and moving at 8 miles 

 per hour. 1 



In a somewhat similar brake at Strasbourg 2 the piston diameter is 16 

 inches, and its travel 8'2 feet. A train of 200 tons moving at 8 miles per 



1 " Proc. Inst. Mech. Eng.," 1886, p. 105. 



2 " Proc. last. C. E.," vol. 119, p. 419. 



H.A. 3 B 



