The Locomotive - Lighthouse Survival Blog

1901.] Til E LOCOMOT I Y E. ^g
The plate being 13.51" wide and 0.53" thick (on an average), with a tensile strength
of 59,680 pounds per square inch, the total strength of the whole solid plate was
13.51" x0.53"x59,G80 = 427,327 lbs.
If tlie joint had withstood a stress of 427,327 pounds before breaking, its efficiency
would have been 100 per cent. Since, however, it actually did fail when the pull became
201,700 pounds, the efficiency, according to the method of calculation adopted by
the Watertown authorities, was
201,700-427,327=47.2 per cent.
(The Watertown report gives the efficiency 47.1 per cent. The difference is unimpor-
tant.)
This method of calculation does not appear to us to be entirely fair, because the joint
tested is not an integral number of "units" in width. The total width is four times
the pitch, it is true ; but in an actual double riveted joint in a boiler there would be
eight rivets in a section four units wide instead of only seven, as there were in the joint
here described. The width of the specimen, in order to correspond to seven rivets,
ought to be 3£ units instead of 4. That is, the total width of the plate ouo-ht to be
3iX3%" = 11 ]|". The strength of the solid plate would then be
then be
llif" x 0.53" x 59,680 = 373,634 lbs.
The efficiency of the joint, according to this amended mode of calculation, would
201 , 700 + 37 J,634 =54.0' per cent.
,
which agrees perfectly, (as it should,) with the efficiency of this same joint as calculated
by the first of the methods given above.
We trust that we have established, to the satisfaction of anyone who may be inter-
ested, the fact that the criticism upon our method of computing the efficiency of riv-
eted joints has no just foundation. This is not a case where the doctors disaqree, as
Mr. Dixon phrases it. In view of the errors that he made in setting down the data
which led to his comparison, it would be more accurate to say that this is a case where
the patient refused to take the medicine that the doctor prescribed.
The year 1889 marked a revolution in the aluminum industry. Castner and Netto,
by new and ingenious processes, had made metallic sodium (the reducing agent of
Deville's process) at a greatly reduced cost, and had thereby largely reduced the cost
of jn'oducing aluminum. New life had thus been put into the industry, and the yearly
output had increased to 71 tons, while the selling price of the pure metal had decreased
to less than $5.00 per pound. In fact, that very year it fell to about half that figure.
Besides tins, the electric processes of Cowles Bros, and of Ileroult were furnishing
aluminum in copper and iron alloys (but not the pure metal) at even lower prices. The
last year of the century finds the industry upon an entirely different basis. From an
aunual production of 70 tons it has risen to the relatively enormous figure of 7,000
tons; and the price has fallen from nearly $5.00 a pound to the almost incredible figure
of 30 cents. The seeds jof this revolution were already germinating in 1889, for in that
year pure aluminum, made electrolytically (by Hall in America and by Heroult in Europe)
began to undersell the product of the sodium processes, and two years later the sodium
processes were distanced and driven out of the business. The pure sodium exhibited
at Paris in 1889 was all made by the sodium process; while that shown in 1900 was all
made electrolytically.— Prop. J. W. Richards, in The Journal of the Franklin Institute.