﻿OF 
  SINGLE-ACTING 
  EXPANSIVE 
  STEAM-ENGINES. 
  199 
  

  

  The 
  data 
  respecting 
  the 
  dimensions 
  and 
  load 
  of 
  the 
  engine, 
  which 
  are 
  constant 
  

   throughout 
  the 
  experiments, 
  are 
  the 
  following 
  : 
  — 
  

  

  Area 
  of 
  piston, 
  . 
  . 
  . 
  A 
  =34-854 
  square 
  feet. 
  

   Stroke, 
  / 
  =10 
  feet. 
  

  

  Cubic 
  space 
  traversed 
  by 
  piston 
  during 
  one 
  down 
  stroke, 
  = 
  A 
  ^=348-54 
  cubic 
  feet. 
  

   Clearance 
  and 
  valve-boxes, 
  18*00 
  

  

  Sum, 
  . 
  366-54 
  

   Therefore, 
  c=0-05 
  

  

  R= 
  useful 
  load 
  of 
  piston, 
  . 
  . 
  . 
  =1597' 
  lb. 
  per 
  square 
  foot. 
  

  

  F= 
  additional 
  resistance, 
  = 
  266-6 
  

  

  R 
  + 
  F 
  = 
  total 
  mean 
  pressure 
  on 
  piston, 
  =1863-6 
  

  

  The 
  mode 
  of 
  calculation 
  is 
  the 
  following 
  : 
  — 
  

  

  l' 
  

   Mr 
  Wicksteed 
  states 
  the 
  fraction 
  j 
  of 
  the 
  stroke 
  performed 
  at 
  full 
  pressure 
  in 
  

  

  each 
  experiment. 
  From 
  this 
  the 
  ratio 
  of 
  expansion 
  s 
  is 
  computed 
  by 
  equation 
  

   (b), 
  giving 
  in 
  this 
  case 
  

  

  1 
  = 
  0-95^ 
  + 
  0-05 
  

   s 
  I 
  

  

  The 
  value 
  of 
  Z 
  corresponding 
  to 
  s 
  is 
  then 
  found 
  by 
  means 
  of 
  the 
  third 
  column 
  

   of 
  Table 
  second 
  ; 
  that 
  column 
  being 
  selected 
  because 
  the 
  initial 
  pressures 
  were 
  all 
  

   below 
  four 
  atmospheres. 
  This 
  affords 
  the 
  means 
  of 
  determining 
  the 
  initial 
  pressure 
  

   of 
  the 
  steam 
  by 
  equation 
  (59), 
  viz. 
  : 
  — 
  

  

  P 
  1= 
  |- 
  (R 
  + 
  F) 
  = 
  1863-6 
  -i- 
  

  

  By 
  using 
  Table 
  first 
  according 
  to 
  the 
  directions 
  prefixed 
  to 
  it, 
  the 
  volume 
  of 
  

   one 
  pound 
  of 
  steam 
  at 
  the 
  pressure 
  P 
  t 
  , 
  in 
  cubic 
  feet, 
  is 
  calculated, 
  and 
  thence, 
  by 
  

   equation 
  (60), 
  the 
  weight 
  of 
  steam 
  per 
  stroke, 
  according 
  to 
  theory, 
  which 
  is 
  com- 
  

   pared 
  with 
  the 
  weight 
  as 
  ascertained 
  by 
  experiment. 
  

  

  Further 
  to 
  illustrate 
  the 
  subject, 
  the 
  useful 
  effect, 
  or 
  duty 
  of 
  a 
  pound 
  of 
  steam, 
  

   is 
  computed 
  according 
  to 
  the 
  theory 
  and 
  the 
  experiments 
  respectively, 
  and 
  the 
  

   results 
  compared. 
  

  

  The 
  following 
  Table 
  exhibits 
  the 
  results. 
  

  

  VOL. 
  XX. 
  PART 
  II. 
  3 
  G 
  

  

  