88 EXPERIMENT STATION EECOED. 



load without any appreciable bending and the test load is to be applied at the 

 exact center of this top bearing. The frames for top and bottom bearings are 

 to be of sufhciently heavy timber to avoid any bending by side pressure. The 

 test load is to be applied continuously and gradually without shock or disturb- 

 ance to the tile and no considerable time is to elapse between load additions. 

 The bearing strength is taken equal to the total top load plus, the weight of the 

 frame and bearing timbers, sand, etc., plus five-eighths the weight of the pipe. 

 This load is to be divided by the length of the pipe in feet to give the bearing 

 strength in pounds per foot. 

 The modulus of rupture in pounds per square inch is then calculated by the 



formula F——2-, in which 6=bearing strength per linear inch, r=the mean 



radius of the tile in inches, and /=the minimum thickness of the tile at the top 

 and bottom in inches. 



A method of making tests on drain tile, A. N. Talbot and D. A. Abrams 

 (Engin. Rec, 65 (1912), No. U, pp. 38^, 885, figs. 2).— This is a paper read 

 before the Eighth Annual Convention of the National Association of Cement 

 Users. It points out the need for inexpensive adjustable, portable, and accurate 

 testing machines for definite and important qualities of drain tile, and describes 

 and gives tabulated results of 3 series of tests of tile with such a machine. 



The machine consists essentially of a simple framework and a lever for 

 applying the load by means of dead weight. The framework is adjustable and 

 can hold any diameter of tile up to 42 in. The top and bottom loading blocks 

 are 4 by 6 in. material and provided with bearing edges and rubber hose 

 cushions for distributing the load uniformly over the length of the tile. The 

 lever is 4 ft. 6 in. long and the dead load is applied to its end. The machine 

 weighs 225 lbs. and the authors claim that it should not cost more than $18. 



In using the machine, the tile is rolled into place on the bottom loading 

 block which has 2 half round strips 2 in. apart for rest and the framework is 

 adjusted to the size of the tile. The top loading block is placed on the top of 

 the tile, the lever fitted into place, and the dead load is applied at the lever's end. 



Whatever the method of test may be, it is necessary finally to determine the 

 relation between the strength of the piece tested and the strength needed in the 

 structure. The method of loading along a line at the top and bottom of the 

 tile is selected because of its simplicity, and because it gives simple, direct, and 

 fairly uniform results for varying conditions of tile. The bending moment 

 developed, the modulus of rupture, and the load per foot of length of pipe of 

 given size can be determined by these tests. The authors give as the expression 

 for bending moment the formula 0.16 Qd, in which Q is the concentrated load 

 applied to the ci'own, and d the mean diameter. The formula for modulus of 

 rupture is given as /=0.96 Qd If, in which I is the length of tile and t the 

 thickness along the top and bottom elements. 



Preserving good roads, L. W. Page (Sci. Amer. 8up., 13 (1912), No. 1892, 

 p. 210). — The use of motor-truck trains in the maintenance of trunk highways 

 is discussed and the necessary equipment noted. 



An automobile equipment is suggested which will include all the apparatus 

 and facilities necessax-y to employ efliciently a repair gang of 8 men in the 

 maintenance of the road surface over 100 miles of roadway or more. Three 

 significant requisites mentioned are that the cost of the equipment should be 

 kept consistently low and within the range of customary expenditures, that 

 novel or si>ecially constructed apparatus should be avoided, and that the outfit 

 should be so flexible in its makeup as to serve readily a variety of utility or 

 lend itself to peculiar requirements under varying conditions. An approximate 

 estimate of the total equipment is as follows: Machine with steel dumping 



