26
Molesworth’s pocket-book
.Highest. Tons per sq.inch. Lowest. Tons per sq. inch. Mean. Tons per sq. inch.
Rolled bars .. .30-7 19-9 25-7
Angle-irons .. 28-4 17 24-4
Plates lengthways 28 16-7 22-e
„ cross ways 27 14-5 20-6
Notes on Strength of Materials.
Wet timber is not so strong as dry; in some
cases it is not half the strength of dry.
Crushing weight of a sphere — '26 circumscribed cube.
„ „ roller = '32 „ square.
Cold-blast iron is stronger than hot-blast.
Annealing cast iron diminishes its tensile
strength.
Remelting (up to ten or twelve meltings) or
prolonged fusion increases the strength, and
density of cast iron. Softer irons will beat bear
remelting.
Indirect strains reduce the tensile strength of
east iron. •
Additional strength should be given to cast-
iron girders that take the load on one side of the
bottom flange.
The tenacity of cast iron is only one-third that
of wrought iron, and should not be subjected to
more than one-sixth of the breaking strain.
Tensile strain on wrought iron should not exceed
one-fourth of the breaking weight.