212 



AGRICULTURAL ENGINEERING 



which permits the teeth to be held in a perpendicular position 

 when drawn in one direction or in an inclined position when 

 drawn in the opposite direction. The harrow is reversed by 

 changing the evener from one side of the harrow to the other. 

 All harrows may at first seem alike, yet there is much 

 difference in their construction. There is no doubt but that 

 some harrows are made as cheaply as possible to sell for a 

 low price. Of course there are conditions where the soil is 

 easily cultivated and a light harrow is desirable; yet, as a rule, 

 the amount of cultivation performed is in proportion to the 

 weight and number of teeth in the harrow. Stony ground 

 will require a heavier construction than would otherwise be 

 necessary. 



Construction of the Smoothing Harrow. The tooth 

 bars are commonly made of the so-called U bar or pipe. The 

 former seems to be the stronger for the weight of metal 

 used. The teeth may be had in two sizes, one-half or five- 

 eighths inch square, the 

 larger, of course, being 

 adapted to heavy serv- 

 ice. All the teeth 

 should have large heads 

 to prevent loss should a 

 fastener become loos- 

 ened. The number of 

 teeth varies from six to 

 eight per foot of width. It stands to reason that the greater 

 number of teeth will do more in pulverizing the soil. 



For use in orchards, the harrow with protected tooth 

 bars has a decided advantage, since the bars will not do 

 much damage by catching upon the trees. As a smoothing 

 harrow is too wide to pass through the average farm gate, it 

 should be convenient for dissembling and assembling. 



Fig. 120. A pipe-bar smoothing har- 

 row. Common methods of fastening 

 teeth are illustrated. 



