1®161 RURAL ENGINEERING. 889 



"For the allowable pin pressure it is proposed that for Douglas fir and 

 similar timbers 800 lbs. per square inch be used for cross-bearinK and 1,300 lbs. 

 per square Inch for end bearing. 



" For connections in which the bolts are in single shejir only, as in the case 

 of two timbers bolted together, it is recoiiinieiultHl that the value of tlie bolts be 

 taken at one-half the values given in [thel table. P^or connections In which 

 the bolts bear across the fibers of the timber, it is recommentied that the values 

 of the bolts be talien at six-tenths the values given for all end bearing. 



"The working values recommended are for Douglas fir. For other timbers 

 these values are to be multiplied by the factors following: Long-leaf yellow 

 pine, 1.05; white pine, 0.78; Norway pine. 0.65; white oak, 0.78. All working 

 values herein given are for timber in a dry condition, as for use in the interior 

 of buildings." 



Lag-screwed joints in timber, IT. D. Dewet.l {I'Jnrjin. Nev)S, 76 (/.0/fi). No. 4, 

 pp. 162-164. flsis- 5). — Tests of 14 timber joints fastened by lagscrews, of which 

 4 were on joints in which a 0.5 in. steel plate was fa.stened to a timber block 

 and 10 were on joints in which wooden platen 1.25 to 2 in. in thickness were 

 lagged to an 8 by 8 in. block are reported. 



"The test results show that (1) for loads up to 2,000 Iba. per screw the 

 strength of a 5 in- lag is not appreciably larger than that of a } In. lag; and 

 (2) the working values as given by Kidder correspond to a slip of O.OS in. for 

 the J in. .screw and 0.12 in. for the J in. lagscrew. . . . 



'• On comparing the curves of the lagscrewed all-timber joints with those of 

 tlie bolted joints it is evident that while the ultimate strength of the former is 

 far below that of the latter for the same diameter of lag or bolt, the lag- 

 screwed joints are stilTer for the same load, up to the break in the curve. . . . 

 As in the case of the bolted joints, there seems to be practically no reduction 

 in stiffnc^ for the 5 in. joints, in which the higscrews bore across the fibers of 

 the timber in the main block. This statement holds true only for loads of 

 approximately 2,000 lbs. per lagscrew. In ultimate strength such joints are 

 far below those having all end bearing; the failure Is sudden and due to split- 

 ting of the main timbers. . . . 



" With the criterion of a working strength of one-half the load corresponding 

 to a slip of tV in., the safe resistance of a J by 4i In. lagscrew may be taken 

 as 900 lbs., while that of a J by 5 in. lagscrew may be taken at 1,050 lbs. 

 Similarly for a working slip of 5^ in. the respective resistances are 1.375 lbs. 

 and 1,500 lbs. For joints in which a metal plate is fastened to timbers by 

 means of lagscrews it is believed that the values of 900 lbs. for a J by 5 in. 

 lagscrew and 770 lbs. for a i by 4i in. lagscrew are reiisonable working values 

 and that l.SOO lbs. and 975 lbs., respectively, should be the maximum allowable 

 capacity used. For all-timber lagscrewed joints similar to those te.sted the 

 value of 1,050 lbs. for a J in. lag and 900 lbs. for a } in. lag are recommended 

 for design, with a maximum of 1,500 lbs. and 1,375 lbs., respectively. All 

 working values advocated are for timber in a dry condition and for use in 

 interior building construction." 



Rules for conducting performance tests of power plant apparatus {Amer. 

 Soc. Mech. Engin., Rpt. Power Test Com., Codes of 1915, pp. 215, figs. 27).— This 

 includes, among other thing.s, sections on the testing of pumping machinery, gas 

 and oil engines, and water wheels. 



Directory and specifications of gasoline and oil farm tractors {Farm Ma- 

 chinery, No. 129S (1916), pp. 52, 53, 55, 5G).— This list includes 189 tractors of 

 114 different makes. 



