ON A CONSTANT INDICATOR FOR STEAM-ENGINES. 



323 



FoRMULiE FOR DETERMINING THE WoRK OF AN EnGINE BY MEANS OF THE 



Indicator. 



The following are the values of the constants which enter into the general 

 equation in its application to the indicator constructed by the Committee. 



Radius of the integrating wheel . . . = p = 2'99 in. 



Radius of the piston of the indicator = r* = I "125 in. 



Radius of the pulley measuring to the centre of the cord = R = 3 in. 



Angle at apex of cone = 2j = 90°. 



Friction of piston, of integrating wheel on cone, &c. &c., mean value = F 

 = 1-2074 lb. 



Additional deflection of springs due to each f gPJ^IJJS JJ*^' J' = *JJ^^ 

 additional pound of pressure on piston of< = A P""S °* ^- ~ . j?, ^ 

 indicator. pring o. J. _ 1115 



1^ Sprmg No. 4. = -0489. 



Substituting the above values of p, r, R, i in equations (2.) and (3.), we ob- 

 tain for double acting engines, 



U= 1-67052 (— W-iF.L (4.) 



for single acting Cornish engines, 



U = 1-67052 (—\ N - i A -f -1\ F . L (5.) 



If in these equations we substitute the values of A for the different systems 

 of springs, and also the mean value of F, which is 1-25 lb., we ^hall obtain 

 for spring No. 1, A = -028 in. 



U = 59-6614 m N — -3018 L (common engine). 



U = 59-6614 tmN- -3018 



(-1) 



L (Cornish engine). 



"•■ The radius of the piston is so taken that its area may equal exactly four square inches. 



t2 



