Vermont phÅ“nix. [volume] (Brattleboro, Vt.) 1834-1955, 1896-12-18
Strength Testing Machines.
The Most Dangerous Tests Are Those
Made on Blocks of stone.

One of the most interesting places in the
city of Boston to one of a mechanical turn
of mind is the engineering building of the
Massachusetts, Institute of Technology, and
especially that part of 1t where the tests of
the strength of different materials are made.
The testing plant is one of the best of its
kind in the country, aud the test of the
strength of about anything, from twine TO
iron columns can be made. II is not gen
orally known, but it is a fact that ii was at
this pant that the first tests of large beams,
columns, etc, for buildings were made, and
as a result of the discoveries which were
made by these tests the building laws all
over the world were changed.
The most interesting discoveries were
made with regard to the strength Of wood
en- beams. Previous TO these tests the
strength of beams had been figured by test
ing small pieces of the same kind of wood
and then calculating the strength Of the
beam from the strength shown by these
small sections. In making these calcula-
tions the small pieces which were tested
were taken perfectly clear and free of
knots, and allowance was made for the
weakening of the beams by the imperfec-
tons in them. As result of the tests
made at the institute on entire beams IL
was shown that this allowance was not
nearly large enough, and that for some
time beams had been figured on TO carry
loads which would bring them dangerously
near their breaking point.
The most imposing figure In the testing
plant at present is the big machine which
is used for crushing and tensile tests. The
machine is an Emery patent and is on just
the same principle as the one at the Wa
tertown arsenal, although it is not so pow
erful, the latter being the biggest in the
world The institutes machine has a
strength of only 300,0 pounds, but this
is enough for any tests which are made
there, and, in fact, for the large majority
of the tests which are made at the arsenal.
This machine will crush great iron col
umn together endwise in its powerful grasp
or will pull it apart as a confectioner pulls
molasses candy.
More spectacular than such tests as
these are those made on wood beams,
when the great timbers, after resisting TO
their utmost, bend upward and then break
with a tremendous, rending crash. The
most dangerous tests are those made on
blocks of stone, granite especially. A
block of granite will resist almost to its
breaking point without giving any sign,
and when it goes II goes with report like
small cannon, and Is reduced almost 10
powder. The small fragments fly with
tremendous velocity, and it is necessary in
making a test of this kind to cover the OBJ
ject with thick layers of cloth, to prevent
the wounding of the students.
Over in the corner of the basement is the
tortion machine, one of the most interest
ing in the whole plant. 1t is powerful
enough to twist a three-inch bar of the
finest wrought steel an unlimited number
of times. 1t is surprising the extent to
which bar of good material will twist be-
fore breaking. There are at the institute
some bars of Norway iron which have
been twisted round and round twenty times
in length of six feet, and the pitch is as
even as though 1t had been cut with a ma
chine. Domestic iron, on the contrary,
will stand hardly any twist without break.
ing. The means by which the twist Is
measured is remarkably interesting. Two
telescopes are mounted on the bar before
the twisting process is begun, and these
are sighted on a graduated scale on the
wall across on the other side of the shop
and by this means the slightest movement
of the bar can be read with the create i
distinctness. 1t seems almost incredible
but it is possible for a man to take hold
of the bar when II has been clamped into
the machine, and by twisting II with one
hand to produce movement which IL
= discernble on the scale on the wall-BOs
= ton Transcript