4S2 
Report  on  the  Exhibition  of  Implements 
I),  the  rollers  i,j,  and  the  clock  l ; the  lever  L then  rises,  and  the  pencil  h 
traces  upon  the  sheet  of  papery  a diagram  of  the  power  required  to  work 
the  machine. 
Fig.  2 is  a diagram  to  a reduced  scale  of  the  power  required  by  the 
prize  machine ; the  serrated  or  zigzag  line  on  the  right-hand  side  of  the 
diagram  is  caused  by  irregular  feeding  ; and  to  find  the  average  power , a 
process  has  been  followed,  similar  to  that  adopted  by  the  land  surveyor 
when  measuring  fields  with  crooked  boundaries  ; a mean  line  a,  b is 
carried  through  the  irregularities,  and  the  distances  are  measured  from 
the  base  line  c,  d. 
By  a reference  to  the  diagram  it  will  be  seen  that  the  average  power  is 
41f5  lbs,,  and  this  weight  must  be  considered  as  applied  to  the  lever  L 
(fig.  1)  at  the  end  li. 
The  time  taken  to  thresh  100  sheaves  of  wheat  was  3 minutes  1 second 
= 3-016  minutes,  and  the  counter  indicated  206  revolutions  of  the  shaft  I 
(fig.  1)  during  that  time. 
In  this  experiment,  W = 41*6  lbs. 
T = 3 -016  minutes, 
and  N = 206  revolutions. 
/N\ 
And  the  rule,  I vr,  I x W 
-V  1 J = II  P. 
60142 
Hence 
206 
3-016  X 416 
601-42 
= 473  horses’  power  required  to  work 
the  machine. 
The  time  required  to  thresh  100  sheaves  being  3*016  minutes,  then 
3-016  X 4-73  = 14-26  horses’  power  required  to  thresh  100  sheaves  of 
wheat  in  one  minute. 
Fig.  3 is  a diagram  of  the  4-horse  machine  exhibited  by  Mackelcan ; 
the  average  power  is  51-4  lbs.  ; the  counter  indicated  415  revolutions; 
and  the  time  taken  was  3 minutes  14  seconds,  being  equal  to  10' 99  horses’ 
power  required  to  work  the  machine,  and  35 -49  horses’  power  to  thresh 
100  sheaves  of  wheat  in  one  minute. 
Fig.  4 is  a diagram  of  the  machine,  with  straw-shakers  and  winnowing 
machinery  combined,  exhibited  by  Clayton  and  Shuttleworth,  to  be  worked 
by  steam.  The  average  power  is  60  1 lbs.;  the  counter  indicated  361 
revolutions ; and  the  time  was  5 minutes  40  seconds,  equal  to  6-36  horse- 
power to  work  it,  and  36-03  horses’  power  to  thresh  100  sheaves  of  wheat 
in  one  minute. 
This  diagram  shows  a more  regular  line  than  the  others ; this  may  be 
accounted  for  by  the  fact  that  the  machine  took  above  4£  horses’  power  to 
drive  it  empty,  being  above  two  thirds  of  the  power  it  took  to  drive  it  when 
threshing:  hence  any  little  irregularity  of  feeding  would  increase  the 
resistance  from  this  cause  in  a much  less  ratio  to  the  whole  resistance 
than  a similar  irregularity  would  do  in  another  machine  where  the  power 
required  to  drive  it  empty  is  very  small  in  proportion  to  the  power 
required  to  drive  it  while  working. 
In  designing  a threshing-machine  to  work  by  horses  and  the  minimum 
of  power,  so  far  as  the  gear-work  is  concerned,  care  should  be  taken  to 
have  good  proportions  in  sizing  the  wheels:  thus,  if  all  the  driving  wheels 
were  to  be  laid  on  each  other  (in  the  order  that  they  work)  in  one  heap, 
and  the  pinions  to  be  similarly  placed  in  another,  each  heap  or  pile  should 
form  a regular  cone  in  diameters  and  strengths;  the  only  deviation  from 
this  principle  that  can  be  safely  adopted  would  be  in  the  case  of  the  horse- 
wheel,  which  may  be  as  large  as  convenient. 
