KURAL ENGINEERING. 389 



Analysis of Expense of Motor Truck and Horse Equipment ; The Invaluable 

 Tractor; The Inevitable Tractor; What Size of Tractor? The Problem of tlie 

 Small Tractor; Power-Plowing in Small Fields; The Tractor in the Corn Belt; 

 The Tractor on the Fruit Farm; Raising Wheat with a Big Tractor; Tractors 

 and Dry-Farming; and The Future of the Tractor. 



[The traction gear] {Gas Etir/ine, 15 {1913), No. /,, pp. 186, 187, fig. 1).— 

 A tractor gear is described which is designed to draw from 2 to 6 plows and 

 to which it is claimed practically any small stationary engine may be adapted. 

 The gear may be obtained equipped with any particular make of engine pre- 

 ferred or any small stationary engine in present use on the farm may be 

 mouuted on it. 



Results and measurements are given in tabular form from a series of tests 

 on this tractor gear equipped with various engines, conducted by W. T. Ma- 

 gruder of the Ohio State University, and which indicate that the gear tested 

 was of high efficiency. 



The pulling' power of slack belts, R. T. Kent (Indus. Engin. and Engin. 

 Digest, 13 {1913), No. 5, pp. 203-207, figs. 9).— Experiments were conducted 

 with the object of determining the relative pulling power of treated and un- 

 treated belts at different arcs of contact on the pulley and at varying tensions 

 on the belt and to investigate the effect of varying the tension on the slack 

 side. 



The results, which are graphically presented, are in favor of the treated 

 belts. The value of the treated belt apparently lies in the fact that the ten- 

 sion on the slack side of the belt may, owing to its greater coefficient of fric- 

 tion, be decreased to a much lower value than for the untreated belt before slip 

 occurs. This decrease in the value of the tension on the slack side of the belt 

 is accompanied by an increase in the length of the belt, thereby giving it a 

 greater wrap or arc of contact on the pulley, both of which 2 factors, it is 

 shown, tend to increase the pulling power of the treated belt over that of the 

 untreated belt in an increasing ratio. 



The indicator for steam traction eng-ine testing, E. R. Wiggins {Thresher- 

 men's Rev., 22 {1913), No. 5, pp. 7, 8, J,0, 41, figs. S).— This article discusses 

 several sets of tests of steam tractors using the steam engiae indicator. These 

 point to the importance of perfecting the design and operation of the steam 

 tractor and for further development of investigations of the power required for 

 the various draft and belt work on the farm, the power losses in gearing, and 

 the tractive efficiency. 



Calculating speeds, F. N. G. Kkanich {Amer. Thresherman, 15 {1913), No. 

 12, pp. IS, 19, figs. 2). — Two types of speed indicator are described and methods 

 are outlined whereby one may calculate the speeds, pulley diameters, and cog 

 wheel sizes necessary in driving different kinds of power-driven farm machinery. 



Cost of pulling small trees with a traction engine, F. Hutchinson {Engin. 

 and Cantract., 39 {1913), No. 19, p. 513). — A report is given of experimental 

 work in tree pulling with a 45 brake h. p. gasoline-kerosene engine. 



It was found that in pulling trees up to 3 in. in diameter the best method was 

 to hitch to as many trees in a straight line as the length of a 30 ft. |-in. chain 

 would permit. In pulling ti'ees from 4 to 8 in. in diameter a single pull was 

 taken at each tree, with a hitch made from 3 to 5 ft. above the ground and a 

 heavy block of wood on the ground next to the tree to act as a fulcrum. The 

 most efficient procedure was found to consist in running the engine at full 

 speed and to bring the tractor against the load slowly until the pulling chain 

 became taut, then suddenly to bring the full power of the engine against the 

 pull by means of the friction clutch. 



