1892.] 



by Friction in the Bores of Rifled Guns. 



419 



Table VII. Result of Experiment with Driving Rings of 

 Section "F." 



From these two tables it will be seen that the loss of velocity 

 due to the uniform and parabolic rifling is, in Table VI, 12 ft.-secs. 

 and 64 ft.-secs. respectively ; and in Table VII, 18 ft.-secs. and 36 ft.- 

 secs. respectively ; these velocities corresponding to losses of energy 

 of 12 ft.-tons and 22 ft.-tons due to the uniform twist, and 41 ft.-tons 

 and 42 ft.-tons, or about 3 per cent., due to the parabolic rifling. 

 Calculated as before from the uniform rifling, the coeflicients of fric- 

 tion are respectively O114 and O208. 



Examining now with respect to the uniform rifling the whole of the 

 series I have described, and observing that with this rifling the 

 particular form or width of the driving ring would have but a very 

 slight, if any, effect upon the loss of energy due to friction, it will 

 be seen, from Table VIII, that the mean loss of energy amounts to 1*52 

 per cent, of the total energy corresponding to a mean coefficient of 

 friction of 0'203, or, say, 0'2. 



If, as I have pointed out, the loss of energy in the parabolic rifling 

 was proportional to the pressure on the driving surfaces, the additional 

 loss due to that rifling would be 0*74 per cent. . The actual additional 

 loss is, on the mean of the whole of the experiments, about three times 

 as great, the mean loss due to parabolic rifling being, as shown by 

 Table VIII, 3' 78 per cent., and this considerable increment may be 

 ascribed to the causes I have mentioned. 



