The New York herald., 1876-12-27
THE EAST RIVER BRIDGE.


THE MANUFACTURE AND TESTS OF CABLE
wIRE-oPINIoN OF PROFESSOR THUnsToN,
+ OF THE STEVENS INSTITUTE OF TECHNOLOGY.
The discussion in columns OF the above subject
has brought forth the following communication from
Professor r. H. Thurston the head of the department.
OF mechanical engineering director Of the mechan
ca laboratory Of the Stevens Institute OF Technology,
at Hoboken, N.J:-
HoRoKEs, N j., Dec. 90 1915.
To THE EDITOR OF THE HERALD
My attention has been called TO the discussion IN the
columns OF the HERALD OF the characteristics OF good
steel bridge wire proposed 10 be used In the East
River Bridge, and am asked by your reporter whether
rything more should bo demanded than compliance
with much OF the specification as covers the quail
l ity and method OF test Of the wire The spcciflca-
/ lions for the wire to be furnished under tho
| contract about 10 be made are, in my opin-
and, although probably certain give the successful
| bidder trouble and considerable annoyance they
will as certainly secure OF good material and
the safety OF the largest OF its class de-
signed Assuming arthmetical accuracy In us details
ana that tho responsible engineer VIII DO aoie 70 re.
move apparent Inconsistencies affecting TO q certain
/ extent the position OF the line TO he drawn bctweon
metal TO be accepted and metal 70 be rejected, have
never seen It's equal, and consider II TO constitute
long first step tho direction OF Improvement II,
therefore, is OF importance and has interest alike to
members OF the engineering profession and to that pub
lie which is benefited SO greatly by every advance in
the arts subsidiary that profession we'll by tho
red to. Specifications OF such stringent character and
SO minute in detail tend TO create valuable improve
i
/ work which have permanent value aud which are Of
advantage TO the world IN thousand ways
HOW FAILURE MAY ARISE.
Tho only liability 10 failure under specifications OF
this class will from certain possible ,rrcguary
OF prOduct, which may be consequence oi peculari-
ties in method OF manufacture, which no specification
| wholly provide against or from variations IN
quality OF stock used in Manufacture which are equally
| beyond the range OF specification. Even here, how
ever these specifications cover tho case so lar us II
be covered by the proviso-paragraph 6-that the
inspector shall have opportunity to satisfy himself
that the wire made OF suitable steel prepared from
uniform stock.
| The specifics acations-paragraphs 10 and 11-provido
for testing piece Of wire sixty feet long from the end
ring every orty, OF six ieot OF wire from the
end OF one ring IN hye Of sixteen inches end
OF each ling. and Of one loot by bending test from
the end OF zach ring furnished Tho "ringsn OF wire
weigh abou, sixty pounds each II these end peces pass
inspection the whoc ring passes inspection The only
uncertainty therefore arises out OF the possibility that
the Of tho ring may oe good while the rest, or
cepled not great hen the makers of the wire
skllul and experienced, and engineers do no, hesitate
available but good engineer neglccts to take every
precautlon such uniformity in stock and IN
method OF as well as In quality, as Is de-
tcrmned by the specified tests
IRREGULARITIES UNAyOIDADLE
certain rregularIty OF quality unavoidable, Is
shown by tho fact developed in these very tesis-of
which tue cords under my hand-of wire offered
the Bridge Company by bidders n which the average
that of larger number OF tests Of the same wire,
varying from nearly 1000 pounds for a halt
double that number OF tests defect may thus oc.
cur the quality may be bad in any one piece. and
remain undiscovered If the defect or tho low quality
does not happen exist in tho end piece tested This
risk OF passing low quality wire is greater With some
methods than with othors, and Is least
where uniformly good stock used The latter rcGui
site is readily secured and the engineer then ceds
simply study metnois OF manufacture 10 make the
80 STEEL PROCESSES
Steel Is made by several processes but by far tho
greatest part the steel in markets 10 made by
either that known as the csucble process or by the
Besscmer process. third method, known us the sie-
| Mar IN. N n
especially in Great Britain where its distiu-
iroduced 1t. or these processes the crucibe pro-
cess has formerly been distinctively tool-sce pro-
very .'ow steel, such as is used for rails and tho
Semens process has been exceptionally valuable in
wsaT aso az p!oaucea ow steel The steel re
quired py the builders OF the East River Bridge eau be
made by either method In the Bessemer process cast
iron carefully for purity and richness in silicon
and carbon, Is melted and poured into vessel called
converter in quantities Of usually about i've tons TO
until the sincon ana carbon have been burned out,
and there romans almost pure wrought ron Sufcient
CARTON is added TO make OF It the required grade
OF steel Finally the molten steel is poured into ingot
mouds large enough contain several hundred pounds
weight cach metal, and when solidaed it is rolled
into w,re rodsn drawn out wire. The rings Of
woigh about sixty pounds, and each ingot makes
several rings OF which ono IS from the top one from
the bottom and The others from intermediate parts OF
ngot In tho Semens several tons OF cast
iron melted on the hearh OF reverberatine fur
nace and the carbon removed partly by The oxidizing
OF the flame and partly by dlution with scrap
or other wrought iron Samples taken out and
then and tho metal is tapped of into ingots when in
spec,ion shows proper grade have been obtained
The iueots similar TO those just described and are
In tho crucible process. formerly exclusively
practscd selected "blister stecl' Of which the quail
ity was absolutely certainly kncwn, melted down
in cruc,bes and cast Into comparatively small ingots
weighing 10 TO loo pounds each. These ingots were
broken, inspected and assorted into lots, In oach OF
which all the steel was adapted to specific class OF
| work.
cruc!be presence Of the necessary qrantty OF
bon manganese and lux, and the steel thus obtained
BEsssMER UNCERTAINTIES.
Some uncertainty as TO quality OF product exists in
the Bessemcr process in consequence of the difficulty
met with in adjusting the proportions OF carbon and
consequence oil the difficulty OF sampling accurately
where such large masses nre handled The skill
markablc, and n mistake rarely occurs IN making
stock for the purposes for which the metal is most
used.
The Siemens- Martin process is less we'll fitted
TO produce large quantities OF metal but the oppor
molten in the furnace and for correcting any defect
in grade adspts u TO uses for which Bcssemer metal
only be obtained by unusual skill in manufacture
or in selection The makers OF crucible steel have
very great advantages in being able 10 select their
almost absolute uniformity IN mixture, and in deaL
ing with such small ingots that the quahty Of the
mass is ndexed accurately by that oi ,ne surfaces OF
The skill of old makers OF crucble steel In selecting
and grading the metal is simply wonderful They
dctccI glance differences OF composition which the
most careful study by the unpractsed eye would not
| lead others to suspect
CRrciBLR STEEL ADvANTAGEa
On the records OF the Mechanical Laboratory OF the
Stevens Institute of Technology to be found the
suits OF the Of twelve distinct grades Of crucbe
steel winch differ by less than tenth Of per
cent in proportions OF carbon and which were selected
by the eye, and without single mistake The power
OF selection thus Indicated Will be appreciated when It
that tho chemist cannot by the best methods
OF analysis grade steel with equal certainty and
tratn n n
recording testing machine of laboratory, confirm
this evidence OF the remarkable power Of tho trained
eye OF the experienced siecmaker In citing steel
for any important work the engineer usually prefers
| to throughout metal made OF the same ores, the
| same stock and by the same process.
Either of the above described methods can be mado
The Of The ciQcafinua