1946 



MACHINERY 



MACHINERY 



In Fig. 2262 is illustrated a common type of disc- 

 harrow called the full-bladed type. The diameter of 

 the discs usually varies from 12 to 20 inches and the 

 harrow width usually covers from 4 to 10 feet. The 

 depth of penetration of the discs is governed chiefly by 



2261. Common type of toothed harrow with metal tooth bars. 



the curvature and sharpness of the discs, the angle of 

 the gangs, and the weight of the harrow. 



The disc-harrow bearings are usually of wood, oil- 

 soaked maple being preferred. The friction between 

 wood and iron is less than between two pieces of iron, 

 hence the value of wooden bearings. The end thrust 

 of each gang is usually taken care of mainly by the 

 bumpers between the gangs. The couplings between the 

 main frame and the bearing-box casting are usually so 

 arranged that the bumpers will come together with 



2262. Common type of disc-harrow, showing bearings 

 and scraper. 



the angling levers in any position. The individual discs 

 are usually set about 6 inches apart. The scraper for 

 cleaning the discs may be made stationary or to be 

 operated by the driver. A special type of disc-harrow 

 for use in orchards has the disc-gangs widely separated 

 so as to disc under trees without injuring the branches. 

 The cutaway disc-harrow differs from the full-bladed 

 type in that notches are cut out of the discs to permit 

 deeper penetration. It has been found, however, that 

 the pulverization is not so complete with this type as 



2263. Curved-knife harrow or clod-crusher. 



with the full-bladed disc-harrow. It has a further dis- 

 advantage in that the discs are difficult to sharpen 

 since each disc must be removed and ground. Its 

 principal use seems to be for renovating hay land and 

 old pastures. 



A type of curved-knife harrow or pulverizer is illus- 

 trated in Fig. 2263. This is often called the Acme har- 



2264. Spring-tooth harrow, with frame. 



row. The slanting curved knives are effective in crush- 

 ing clods, leveling the surface, destroying small weeds, 

 and in producing the uniform soil structure so desirable 

 for a seed-bed. Some of these implements have a set 

 of rake-teeth following the knives, the purpose of which 

 is to complete the pulverizing and smoothing process. 

 The so-called spring-toothed harrow illustrated in 

 Figs. 2264, 2265, while in one sense a harrow, is really 

 a cultivator. It is an implement which has been in more 

 general use in Europe than in this country. The long 

 spring teeth when striking a stone or root are easily 

 released, thus making this implement effective in bad 

 ground. It effects considerable pulverization but is 

 said to have a rather excessive draft. 



The weeder. 



Weeds in a seed-bed or between crop-rows have been 

 found to use up considerable moisture and plant-food. 

 The plow and har- 

 row serve to de- 

 stroy many weeds, 

 particularly the 

 latter. 



Special weeder 

 implements are, 

 however, in use. 

 These usually 

 combine surface- 

 cultivation with 

 the destroying of 

 weeds. One type 

 used on seed-beds 

 has a large num- 

 ber of rather long teeth with flattened and curved 

 points which tear out and destroy weeds and pulverize 

 or scarify the surface soil. 



A second type, used between the rows of truck and 

 root crops, is in reality a combination horse-drawn hoe, 

 weeder, and cultivator. The hoes are broad and flat 

 and by passing almost horizontally just beneath the 

 surface of the soil, cut off and destroy weeds and at the 

 same time form more or less of a surface mulch. 



The roller, or packer and planker. 



The roller as originally used was a tree-log. This, 

 however, did not operate satisfactorily. Wrought- and 

 cast-iron rollers succeeded the wood and they are now 

 also made of concrete in some cases. Like the disc- 

 harrow, rollers and packers usually have wooden 

 bearings to reduce the friction. 



While fairly deep general pulverization of the soil 

 is desirable, the loose mellow seed-bed should be rather 

 shallow and the plowed soil below be well packed to 

 conserve moisture. 



The iron roller (Fig. 2266) not only compacts the 

 soil but effects considerable pulverization in the way of 

 smashing clods. The smooth surface left by the roller, 

 however, while desirable from the standpoint of mow- 

 ers, binders, and so on, permits excessive surface evap- 

 oration and consequent loss of soil-moisture. This con- 

 dition is remedied somewhat by following the roller 

 immediately with a 

 harrow, thus produc- 

 ing a surface mulch 

 and breaking up 

 evaporation. 



The roller pulver- 

 i z e r or pulverizer- 

 packer (Fig. 2267) 

 may perhaps be used 

 to better advantage 

 than the smooth 

 roller. This type of 

 roller compacts the 



subsurface soil and 2265. Another form of spring-tooth 

 pulverizes the surface harrow. 



