THE HYDRAULIC BRAKE 



787 



5 feet. Protection against excessive load is provided by a relief valve 

 loaded to 1,000 Ibs. per square inch at the back end of the cylinder. 



Recoil Cylinders for Guns. In the case of a 6-inch quick-firing gun 

 having a weight of recoiling parts equal to 14,800 Ibs., when firing a 

 cordite charge of 13 Ibs. and giving a muzzle velocity of 2,150 feet per 

 second to a projectile weighing 100 Ibs., the velocity of recoil is found to 

 be approximately equal to 17*5 feet per second. The energy of recoil is 

 about 70,500 foot Ibs., and is absorbed by a buffer of 12-inch stroke and 

 7J inches internal diameter. 



For such a purpose a tension buffer is commonly used, and Fig. 396 

 illustrates such an one as fitted to a 6-inch gun. The liquid, escaping 

 from left to right through the valve V on the working stroke, passes 



FIG. 396. Tension Kecoil Cylinder for 6-in. Gun. 



through the annular passage O, whose area depends on the position of 

 the piston relative to the central taper spindle T. The piston is returned 

 by springs, whose action is buffered near the end of the stroke by the 

 resistance to the flow of liquid from the space S through the holes 

 at D. 



Fig. 397 shows a type of compression buffer without tail rod, as 

 fitted to the Canet quick-firing guns. Here the fact that the displace- 

 ment increases throughout the stroke has been utilized to give a return 

 device. In this buffer, when the piston A is pressed home, the displaced 

 fluid passes through the pipe P and forces home the piston S, in the 

 auxiliary cylinder B, against the resistance of the spring T. When the 

 recoil has been absorbed this spring forces back the piston S, and 

 increases the pressure in the main cylinder to an extent which depends on 

 the strength of this spring. This pressure, acting on the unbalanced area 

 of the piston rod, forces the main piston forward to the end of the 

 cylinder. In this buffer the orifices are of constant area. 



3 B 2 



