1920] RURAL ENGINEERING. 89 



cuolinfi. A formula 1\)r radiator sizinir and recoiinnondations for water circula- 

 tion, air velocity, and fan details are given. 



Tractor friction transmissions, C. A. Trask (Trnn.s. Soc. Aiitoiiiotirc Enyin., 

 13 {lfU8), pt. 1, pp. 320-330, figs. 9).— Graphic data and formulas on power 

 transniittinji capacity, pressure application, slippage, operating speeds, and 

 design and installation are given, and difficulties in practical application are 

 discussed. Under friction transmission types the application of the friction 

 t>iie to a number of ti'actors is explained and illustrated. 



Lubrication of tractor engines, W. G. Clark (Trans. Soc. Autouwtive 

 h'Uf/iu.. 13 {1918), pt. 1, pp. 4J,5-J,5Jt).—The author deals with the relation of 

 lubrication to carburetion and ignition and with the importance of the proper 

 selection of oil. It is stated that when apparently suitable oils have been 

 selected they should be subjected to occasional laboratory and field tests. An 

 explanation of tlie cold friction and power tests is given. 



Standardizing tractor parts, G. T. Strite (Trans. Soc. Automotive Engin., 

 12 (1917). pt. 2, pp. 193-197).— The standardization of tractor parts is dis- 

 cussed, and some features of the standardization methods adoi)ted by the 

 Society of Autontotive Engineers are pointed out, with particular reference to 

 the size of tractor engines in relation to number of plows pulled. 



The farm tractor in Iowa, E. V. Collins (Iowa Sta. Circ. 63 (1919), pp. 8, 

 fig. 1). — This circular sunuuarizes 228 reports covering the 1918 operating 

 season for tractors in Iowa., Thirty-nine reports were secured by personal 

 visits to farms and the remainder by mail. Data are also included on 44 

 tractors discarded or sold. 



It was found that between 85 and 90 per cent of the tractors investigated 

 are considered by their owners to be paying investments. The principal reason 

 for failure of those that do not pay are lack of experience or patience on the 

 part of the operator or the use of a tractor which is unreliable in construction 

 or unsuited to the conditions. The tractors best adapted to field work in Iowa 

 are the 2 and 3 plow outfits. Two-plow outfits should have a working speed 

 of at least 2i miles per hour. The average 2-plow outfit has the advantage on 

 soft ground due to its lighter weight. For belt work, especially on small 

 thrashers and silage cutters, the average 3-plow outfit has an advantage. A kero- 

 sene-burning tractor is desirable from the standpoint of economy, but requires 

 more skill on the part of the operator. Depreciation is usually the largest single 

 item in the cost of operation and is controlled largely by careful selection and 

 operation of the tractor. 



Building a small track-laying tractor, F. H. Colvin (Amer. Mach., 52 

 (1920), Xo. 8. pp. Jf07--'fl0, figs. 11). — This article describes some of the meth- 

 ods used in manufacturing a small track-laying agricultural tractor, special 

 attention being given to convenience in handling the various parts. The 

 illu.strations include drilling, milling, and grinding operations together with 

 special fixtures. 



Use of artillery tractors on Salmon Lake Dam construction, Okanogan 

 project. Wash., L. V. Branch (Redan}. L'ec. [U. S.], 11 (1920), No. 3, pp. 

 131-133, fig. 1). — Experience with three 10-ton artillery tractors of the cater- 

 pillar type equipped with engines developing 55 h. p. at 600 r. p. m. on hauling 

 and elevating grader work in connection with irrigation dam construction is 

 reported. Under normal conditions the tractors easily handled three 3-yard wagon 

 trailers, but under adverse conditions of wet ground and grades they could 

 handle only two. The tractors were found to be excellent stump and brush 

 pullers, using a 3-in. steel cable. 



On the basis of this experience the opinion is expressed that the.se tractors 

 when used for transporting earth will show greater economy, as compared with 



