RURAL ENGINEERING. 487 



detailed informatlou concerning a power outfit for boring taprooted stumps for 

 blasting. 



To get the best results when blasting such stumps, the charge must be placed 

 within the taproot. The power outfit consists of one 5-horsepower horizontal 

 gasoline engine, one 3-kilowatt dynamo, two electric drills using IJ-in. augers 

 usually 30 in. in length, and the necessary cables for connecting. The engine 

 and dynamo are mounted upon skids or a wagon and the drills are supplied with 

 current from the dynamo. The total cost for an electric stump boring outfit 

 f. o. b. distribution point is given as $460. 



In a test of such an outfit the dirt was thrown away from one side of the 

 stump to a depth of 12 in. and a hole bored into the stump at least 10 in. below 

 the surface. Of the 100 stumps so blasted 97 were broken off below plow depth 

 while the roots of the remaining 3 were easily cut out low enough to permit 

 cultiA'ation. Slightly less powder was used than where the holes were bored at 

 the surface of the ground and the total average cost for digging, boring, and 

 blasting was 22 cts. per stump. The cost of clearing land with this outfit and 

 the use of nitroglycerin powder will range from $5 to $18 per acre provided 

 the wood from the stumps and roots can be sold for enough to pay for their 

 disposal. 



Scientifi.c tests of a two-cylinder opposed engine, B. Heeb (Gas Engine, 16 

 {1914), No. 3, pp. 137-141, fiffs. 6). — Tests of a two-cylinder opposed engine rated 

 at 10 horsepower are reported. In one and two hour tests at full load, the 

 engine had a mechanical efficiency of 82.67 per cent and a thermal efficiency of 

 23.76 per cent. The heat losses were in the cooling water 47.6, exhaust 11.4, 

 and radiation 17.04 per cent. After a steady 130-hour run at full load the 

 mechanical efficiency was 83.7 per cent and the thermal efficiency 21 per cent. 



Use of ball bearings in agricultural machinery, Hermanns (Jahrb. Dent. 

 Landw. GeselL, 28 (1913), No. 4, pp. 868-891, figs. 26).— The author briefly 

 reviews the history of the ball bearing as regards its origin, manufacture, and 

 use in machinery, and points out its advantageous use in a series of more 

 recent development of agricultural machinery. 



Competitive tests of tractors and other apparatus for mechanical culti- 

 vation, G. D. DE Chassart et al. {Bill Agr. Congo Beige, 4 (.1913), No. 4, PP- 

 799-867, figs. 39). — Tests of a number of steam and internal combustion tractors, 

 motor plows, and motor cultivators are described in detail, and the results 

 reported. 



Out of a maximum of 310 points for construction, operation, and tractive 

 power, the winning steam tractor received a rating of 283 points and out of a 

 maximum of 305 points the winning internal combustion tractor received a 

 rating of 266 points, followed closely by a second at 263 points. For construc- 

 tion and operation, the two leading motor plows were rated at 214 and 212.5 

 points respectively, and the leading motor cultivator at 193 points out of a maxi- 

 mum for all three of 245. 



Mechanical cultivation with windlasses and cables, M. Ringelmann (Ann. 

 Inst. Nat. Agron., 2. ser., 12 (1913), No. 2, pp. 299-343, figs. 12).— The author 

 describes the construction and operation of the roundabout system of windlass 

 and cable plowing, reviews various tests of this system, and reports investiga- 

 tions on the power losses in windlasses, pulleys, and cables, and methods for com- 

 puting them. By use of computations and test data based on these methods, 

 he compares the roundabout system with the windlass and cable systems using 

 one and two tractors. 



The data show that when furnishing a tractive effort of 1,000 kg. the one- 

 tractor, two-tractor, and roundabout systems, have respective mechanical effl- 



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