INTO THE STRENGTH OF WROUGHT-IRON PLATES. 
695 
The system of double riveting- exhibits several remarkable properties as regards 
strength, and the plates appear to retain their position under strain much better than 
single-riveted joints. These circumstances have induced a comparison of the results 
of the preceding experiments with those contained in Tables VII., VlIL, IX. and X. 
The experiments in Tables VII. and VIII. give indications of increased strength by a 
slight enlargement of the lap and the introduction of a single rivet to keep down the 
end of the plate. In those experiments it was found that the additional rivet gave an 
increase of 26 per cent, over those obtained from the single rivets ; a circumstance 
which suggested a further extension of the experiments, accompanied with a minute 
investigation of the parts, in order to ascertain their relative strengths, and the 
strongest form of joint. 
The mean breaking weights of equal sections of single-riveted joints, as given in 
Table VI. and taken from nine experiments, are respectively as follows 
lbs. 
23 , 127 ^ 
16,107 
18,982 
19,147. 
■ Mean . 
18,590 
giving a mean of 18,590 lbs. for the strength of single-riveted joints. Now in the 
second and third experiments. Table VII., with the rivets inserted in the shape of an 
isosceles triangle (which in fact is double riveting), and of equal sections to the speci- 
mens in Table VI., the mean breaking' weight is 23,035, which gives an excess of 4445, 
or a ratio of 10 : 8 in favour of the experiments recorded in Table VII. 
In the experiments (Table X.), the area of the section, taken through the line of the 
rivet-holes, is '44 inch, or precisely equal to the section of the specimens experimented 
upon in Table VI., in which the mean breaking weight is 18,590 lbs. In these expe- 
riments the breaking weight is 23,707 lbs., which is rather more than that in Table IX., 
where the material had a smaller section, but having its dimensions exactly corre- 
sponding with the proportions given above. It therefore follows that in plates jointed 
with single rivets, the ratio of the strength of the single rivets is to that of the double- 
riveted joints as 8 to 10, the latter being one-fourth stronger. 
It has been ascertained that it required a weight of 23,707 lbs. to tear asunder 
double-riveted plates, 3^ inches wide and '22 inches thick, with a flush joint, having 
a plate on the back and held together by five f-inch rivets on each side ; the quantity 
of metal between the holes, in a direct line across the plate, being •2X‘22='44 inch, 
which is the same transverse section as those operated upon in the first Table. 
Now if we take the mean breaking weights of the riveted joints in Tables X. and 
VI. and compare them with the section of the plate itself as given in Table I., the 
areas being the same, we have for the tensile strength of plates — 
Section of iron torn asunder. 
lbs. 
In Table I., solid plate 
... -44 
25,400 
In Table X., double-riveted joints . 
... -44 
23,707 
In Table VI., single-riveted joints . 
... -44 
18,590 
