Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1900-08-07
pRopelLER SHAFTS.

or course there ID go0dly minority
among Newspaper readers who know ex-
actly what ID meant by steamer break
Ing her shaft, bat for the benefit OF the
majority who do not know, it may. be
necessary, In order to show how the GO
cident 10 brought about, 70 give . few
words OF explanation ~ simply - may
b. Nearly al steamers have their en-
ginee ct considerable distance from the
propeller, the four bladed and three
bladed screw, which, according ~ 1t 10
turned, thrusts the hull forward or
draws Il backward.
The connection between the engines
and the propeller ID made by means Of
solid cylinder Of steel passing through
bearings lined with gun metal generally
and kept cool by stream OF water
flowing over them outside and liberal
supply of some lubricant, usually tallow,
inside. Now, It does not need much wit
TO understand that the twisting stress
upon these long shafts OF steel 10 ct ell
times very great, needing them to be of
the most hawless composition, In order
that they shall be dependable.
Such 10 the care taken 10 their manu-
facture that It may safely be said that
II they were only subjected TO the
steady, eQuable strain OF the engines
upon them there would scarcely ever be
q case Of shaft fracture heard OF. But
such state of things Is unthinkable 1t
sea. Out on the ocean the frequent oc-
currence Of gales Of wind and conse-
quent heavy seas bring about such an
alteration Of the conditions Of service
OF the shaft that II IL marvellous how
few, relatively, Of these accidents do
occur.
When even the heavily laden steam
ship, with her propeller so far beneath
the surface Of the sea a. TO be out of
sight, meets with . heavy gale ahead,
raising q succession OF confronting
waves, she must Of necessity pitch and
dive tremendously. And Ia so doing It
IL Inevitable that she will occasionally
llft her propeller out Of the water sud-
denly, while the full drive Of the engines
IL being exerted upon II. What that
means to every part Of the machinery
can only be imagined by Q lsyman %
non-engineer). The sudden leap from the
solid resistance Of the water Into the
non-resistsnce Of the air IL change OF
condition so great that not even the
most cunningly devised governor can
do more than attempt 70 modify Its
severity.
II Is instantly followed by return to
the former strain with . wrench that
seems sufficient to strip the mighty
blades OF metal from the propeller as II
they were feathers In q shuttlecock.
The governor mentioned comes to the
relief Of the sorely tried mechanism by
automatically shutting of the supply
of steam with the cessation OF strain,
and turning 1t on again as the propeller
plunges into its proper element. But
the changes are so instantaneous, the
treasures are 90 enormous, that a tiny
Hsw, = slight weakness, IL almost sure
to be fatal. Perhaps not In that gale,
but In the next.
And II this be go In loaded steamer,
how much more Ia IL so In light one.
Experts are at one 10 considering that
from this cause alone, although there
are others that cannot now be touched
upon, an underlosded steamer 10 quite rs
uuseaworthy a. m overloaded one.
How often does one pass large steam
ship coming down channel bound over
seas, and notice that even Id the smooth
est water nearly half Of her propeller
IL Idly beating the air. just . little
hesd sea gets up, and that vessels en-
gines, shaft and propeller are immedi-
ately subjected to q succession OF shocks
that made their escape from damage
almost miracle.
Then Il Ia that the engineers lot,
never light one, becomes truly terrible
10 its burden. He knows In his Inner
most fibre sll that IL going on, the po-
tentislities of disaster there are 10 every
plunge OF the ships stern, from It's high
polse on the back Of the sea down Into
the weltering valley between-knows,
TOO, what lies before him and his trusty
helpers II the shaft should break, II the
engines should 60 TO smash.
No warrior In the deadly breach ever
showed more perfect courage or reached
4 higher plane OF self-sscrlAce than does
the marine engineer, and that not ~
mere episode of his calling, but almost
continually. What apparent miracles
have been wrought by these sons OF steel
at the call OF duty, and under the most
terrible circumstances, we need an en-
gineer's roll Of honor 10 teach us-not
that any public recognition OF their
worth could possibly add to the fidelity
and heroism continually manifested BY
them.
One word In conclusion, on an uufa-
vorable comparison which was drawn
between men-o,war and merchant
steamers, unisvorable to the latter on
account Of the almost complete immu-
nifty from shaft breskage Of the former.
The comparison Is unfair, and should
never have been made. The losdline OF
a warship Is almost fixed quantity.
This has, perhaps, more to do with
shaft fracture than aught else.-London
Graphic.