This section is from the book "Cement And Concrete", by Louis Carlton Sabin. Also available from Amazon: Cement and Concrete.
The effect of not properly adjusting the briquets in the clip was also investigated. In some cases the briquets were placed in the proper position as nearly as possible. In the other cases they were in a decidedly distorted position, much worse than they would be placed with the most careless manipulation. It was found that if the briquet was so placed in the "Engineers' Standard" clip that the gripping points on one side of the briquet were farther apart than those on the other side, the decrease in-breaking strength was very marked (about 35 per cent.), while if the planes determined by the lines of contact of the gripping points of each clip were parallel, there appeared to be no effect. The reason of this is evident: in the former case the line of force, joining the two pivot points, does not pass through the center of the smallest section of the briquet, and transverse stresses are introduced, while in the latter case the line of force does pass through the center of the smallest section, though not at right angles to its plane. With the Russell and Gimbal clips the distortion seemed to have little effect, provided, that in the case of the former, the clip was itself in its normal position when the briquet was inserted.
1 This clip was devised by the author at the suggestion of Mr. E. S. Wheeler, M. Am. Soc. C. E.
2 Jour. Assoc. Eng. Soc, Vol. vii, p. 212.
 
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