206 



SCIENTIFIC AGRICULTURE 



May, 1921. 



DRAFT OF PLOWS 



55% U5c6 lit mtlitig the furrou) sliec 

 3b% Fridion bctiucca plou) & ttw soil 

 lO'^AFT '0^0 Jjifiit^jj & turning the furrou) 



ij \ Plcu) running empty in fhnva> /68/As. . 



It) ^e tofa/ Jra/y 4-76 /As.. 



y iPM mou/cf Aoard remofed 4^^'^/J>3-. 



iSi'/eST' Z66/As. required to eat t/ie f?/rrouf s//ee 



476'-45f-tZ /urn 



given "lead" to the "land". (See Figures lOB and 

 IOC.) When plowing taudem it is 'sometimes neces- 

 sary to give a little "lead" awaj' from tJie land, but 

 it iLsually run.s straight. 



Colters and their Effect on Draft. 



Experiments .liave shown that a colter reduce? the 

 draft from 11 to 25 per cent on the draft. The proper 

 set of this attachment has also been covered. 



Size of Furrow. 



If you refer to Figure 14, you will see that the 

 draft, of the plow can be classified under three main 

 heads. According to Sanborn "the plow shows the 

 light.e.st draft w^ien set to cut the widest furrow." 

 This is pi'obably accounted for by the remarkable 

 results of an experiment at the Utdca trials, which 

 showed that 55 per cent of the draft was used in 

 cutting tlie furrow slice, 35 per cent by the friction 

 of the implement and only 10 per cent was required 

 to lift and turn the furrow. The average draft of 

 a number of plows running in t^e empty furrow 

 was 168 pounds. The total draft was 476 pounds, 

 and the draft with the moldboard removed was 434 

 pounds. The difference between 168 and 434 pounds' 

 was taken to be the draft required for cutting the 

 furrow slice. He states later that 42 per cent of the 

 draft is used by the share and t^e landside, and 

 another writer put the moldboard friction at only 2 

 per cent. This, however, seeuK low. These figures 

 will not hold for all conditions, but even an approx- 

 imate idea of the division of the draft explains many 

 frequently misunderstood fact.s. 



Line of Draft. 



When the depth of plowing is doubled t;ie draft 

 is increased about To per cent, and not twice as much, 

 as might be expected. 



<. Horse W5 111, 



-^ &jccs2ri250- 



// Hw'.IUO- 



>-<-fv ( 



APPARATUS 



for cScmoastnitMui th^ 



Principles of Draft 



IN A MORSE 



F/^/6 



Figure 16. 



"Ocffloiistiutinci I*-' Innucnt? 



LINE OF 

 DRAFT 



/>/?■/}/"/ Of F/i/i/1 

 /1//c/i/^e/iY 



We now come to the chief point which our farmer 

 friends often wish to have discussed. Refer to Figure 

 15 and you will see a diagram representing a wheel 

 and a roadbed. If a spring balance is attached as 

 indicated we find t.iiat; the easiest line of draft is a 

 line parallel to the roadbed. This ideal condition is 

 practically never found in any of our farm imple- 

 ments. It is found on the railroads where the coup- 

 ling.> between the cars are all pulling in a line parallel 

 to the rails. Now, if we move our line of draft to 

 the position AC we are exerting an upward pull as 

 well as a horizontal pull. When the position AD is 

 reached, we are lifting the load entirely. It will 

 be mucji liarder to lift the load than to pull over 

 a smooth roadbed on well-oiled bearings. On the other 

 hand' if we pull through the line AE we are exerting 

 a downward as well as a horizontal pull which will 

 add materially to the total draft of the imijlement. 

 So much for some of t.he underlying principles. 

 Figure 16 shows the effect of the line of the tugs 

 on tJie load it can pull. When the tugs are liorizontal 

 we will assume that it can exert a pull of 1,120 pounds, 

 and when the tugs are at an angle of 22 degrees it 

 can exert a pull of 1,250 pounds. (King's P,hysics 

 of Agriculture.) The reason is that the downward 

 pull helps to give the horse a better foothold, or, in 

 other words, more traction. If you doubt this, con- 

 sider what would be the result if the point of hiU-h 



CHART SHOWiriG LlllE OF DRAFT tor a 

 WALKING PLOWaui 

 C^GIhE PLOW-. 



Figure 15. 



Figure 17. 



