1946 



MACHINERY 



In Fie 2202 is illustnitM a ooiiiinon typo of ()iso- 

 harrow onll.xl the fuU-bhultxl typo, rho ;liumolor of 

 the .liscs u=<ually varios fn^n 12 to 21) inol.os a.ul tho 

 harrow wi.lth usually covers from 4 to 10 feet llu 

 depth of penetration of the .lisos is gove^u^^ chiefly by 



2261. Common tyvu oi ununid harrow with metal tooth bars. 



the curvature and shari)ness of the discs, the angle of 

 the eanes, and the woifjht of the harrow. 



The disc-harrow bearings are visually of wood, oU- 

 soaked maple being proforr«?. Tho friction between 

 wood and iron is less than botwoon '^V" I'-^'^^'^^ » 'roii 

 hence the value of woo.lon bearmgs. The end thrust 

 of each gang is usuallv taken care of mainly by the 

 bumpers between the gangs. The couplings between the 

 main frame and the boaring-box ousting are usually so 

 arranged that the bumiH-rs will come together with 



2263. Curved-knife harrow or clort-crusher 



2264. Spring-tooth harrow, with frame. 



2262. Common type of disc-harrow, showing bearmgs 

 and scraper. 



the angUng levers in any position. The individual discs 

 are usuallv set about 6 inches apart. The scraper for 

 cleaning the discs may be made stationary or to be 

 operat<?l by the driver. .\ special type of disc-harrow 

 for use in orchards has the disc-gangs widely separate<l 

 so as to disc under trees without injuring the_ branches 

 The cutaway disc-harrow differs from the full-bladed 

 tv-pe in that notches are cut out of the discs to permit 

 d'eeper penetration. It has been found, hovvever, that 

 the pulverization is not so complete with this type as 



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

 arlvantage in that the discs arc difficult to shan>en 

 since ea<;h di.sc must be removed and ground Its 

 principal use seems to be for renovating hay land and 



"A^'type'^of'curvefi-knife harrow or pulverizer is illus- 

 traterJ in Fig. 2263. This is often calle<] the Acme har- 



MACHINERY 



row Tho slanting curved knives are elTective in crusli- 

 iii" clods, leveling tho surface, destroying small weeds, 

 aiid in ]iroducnig llio uuirorm soil structure so desirable 

 i'or a sood-bod. Soiuo of those iiuploinonts have a set 

 of rako-tooth following tho knives, tho inu'iioso of which 

 is to conii)loto tho inilvoriznig and smoothing process. 

 The so-called siiring-toothod harrow illustrated in 

 Figs 221)4, 2205, while in one sense- a harrow, is really 

 a cuitivato'r. It is an imi)loiiiont which has boon in more 

 general use in Kuropo than in this country. The long 

 spring tooth when striking a stdiio or root are easily 

 released, thus making this iiniiloniont ofioctive in bad 

 ground. It eft'ccts considerable pulverization but is 

 said to have a rather excessive draft. 



The wceder. 



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 weals, 

 particularly the 

 latter. 



Special weeder 

 implements are, 

 however, in use. 

 These usually 

 combine surface- 

 cultivation with 

 the destroying of 

 weeds. One tynie 

 used on seed-beds 



has a large nuni- , 



ber of rather long teeth with flattened and curved 

 points which tear out and destroy weeds and pulverize 

 or scarify the surface soil. t . i „„^ 



A second type, used between the rows of truck and 

 root crops, is in reality a combination horse-drawri 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 iiow 

 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 sou 

 is desirable, the loose mellow seed-bed shoii d 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 w-ay of 

 smashing clods. The smooth surface left by the roller, 

 however while desirable from the standpoint of mow- 

 ers bind'ors, an.l so on, permits excessive surface evap- 

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

 dition is remedio.1 somewhat by following the roller 

 immediately with a 

 harrow, thus produc- 

 ing a surface mulch 



and breaking up 



evaporation. 



Tho roller jiulvor- 



izer or pulvori/.or- 



packor (Fig. 2267) 



may perhaps bo 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. 



