Agricultural  Kngines. 
197 
the  piston  rod.  The  cross  head,  guides,  and  crank  are  all 
enclosed,  and  lubrication  to  these  is  hy  sj)lash  from  the  crank 
chamber.  Below  the  front  half  of  cylinder  and  in  the  casting 
forming  the  base  is  an  air  box  through  which  the  charge 
of  air  and  vapour  of  petrol  is  sucked  into  the  forward  half  of 
cylinder  by  the  receding  piston,  and  in  which  it  is  slightly 
compressed  when  the  piston  again  advances.  At  the  forward 
end  of  its  stroke  the  piston  first  uncovers  the  exhaust  port  and 
immediately  afterwards  the  admission  j)ort  from  the  air  box. 
The  slightly  compressed  charge,  rushing  into  the  cylinder  under 
a suitable  deflecting  ])late  upon  the  rear  end  of  the  piston, 
sweeps  out  the  remaining  j)roducts  of  combustion  and  fills 
the  after  end  of  the  cylinder.  The  charge  is  then  compressed 
by  the  returning  piston.  Passing  through  the  centre  of  the 
back  end  cylinder  cover  is  an  insulating  bushing  through 
which  passes  a long  straight  firing  pin  held  forward  to  its 
proper  position  by  a spiral  spring.  This  pin  can  be  almost 
instantly  removed  and  replaced. 
One  wire  of  the  electric  firing  circuit  is  attached  to  this 
])in  and  the  other  wire  to  the  engine  frame.  The  piston  at  the 
back  end  of  its  stroke  comes  in  contact  with  this  pin,  pushing 
it  slightly  backwards  and  completing  the  electric  circuit.  As 
the  piston  advances  the  circuit  is  again  broken  and  firing  of 
the  charge  takes  place.  The  amount  of  the  charge  drawn  into 
the  cylinder  can  be  regulated  by  a valve  placed  between  the 
air  box  and  the  cylinder.  The  ])etrol  tank  is  a shallow 
rectangular  box  placed  in  front  of  the  air  box  under  the 
cro.ss  head  guides.  The  object  aimed  at  by  the  makers  has 
been  to  provide  the  most  simple  engine  })ossible  ; and  it 
j)romises  to  be  a very  satisfactory  motor  for  small  power 
where  high  efficiency  is  not  of  much  inij)ortance. 
Articles  fi78  and  (!79. — Messrs.  Ruston,  Proctor  d'  Co.,  Ltd., 
Sheaf  Iron  Works,  Lincoln.  “Oil  Engines  for  Orude  Oil, 
8 B.H.P.”  Price  178k  ; 2.5  B.H.P.,  dOo/. — The  difficulties  of 
using  crude  oil  in  an  oil  engine  in  consequence  of  the  vaporiser 
fouling  with  the  deposits  of  carbon  are  well  known.  It  is 
claimed  that  with  the  new  design  of  vaporiser  used  in  this 
engine  cleaning  is  only  re(piired  about  once  a month  instead 
of  almost  daily,  as  is  usually  the  case.  Any  kind  of  oil  from 
benzene  and  kerosene  to  crude  oil,  whether  from  Texas  or 
Russia,  may  be  used.  The  arrangement  of  the  vaporiser  is 
shown  in  the  illustration  (Pig.  10),  which  gives  various  sections. 
(a)  is  an  extension  of  the  combustion  chamber  of  the  cylinder. 
