The Lamar register., 1892-10-29
MAY De BROKEN EASILY.
ships Propelisrs Disabled by Trinina
lansss- -carrosiox, In, xy.a>-


causes-Corroston In Water.
The propeller OF steamer 10 an in.
significant object compared with the
huge body it propels against the COM
bined forces OF wave and wind.
but the Brooklyn Eagle says they
come to grief frequently In .
variety OF ways A few days ago the
RED ID steamer Venezuela. in a calm
sea without a breath of wind almost
suddenly lost one blade OF her screw.
just as suddenly and with as little
cause or notice as overripe fruit drops
from Its parent bough- Around the
dry docks are numbers of gigantic
propellers. all in one stage or another
OF dilapidation- Some are cast in
the solid. that is TO say. the hub
through which the shaft passes and
the fans which extend from 1t are
one solid casting. Others are built
or cast rather in sections; the hub is
one and each fan or blade is another.
which fits into bases made for them
in the hub whcre they are screwed
on by huge bolts that are set in the
hub casting. Where one fan or blade
is broken it is easily replaced. as the
makers retain the molds of all wheels
or propellers as they are Indifferent
ly called which they cast Then the
entire wheel is not rendered useless.
as in the case whom solidly cast pro-
peller. like the Venezuela's comes to
grief. 1t is extraordinary 10 see the
proportion of vessels that arrive hav-
ing received some damage to their
propellers. Occasionally damage is
done by the shaft racing. as it is tech
nicaily called. That is caused by the
steamship plungiDg ahead on into the
trough of big sea and so elevating
the stern and the propeller that it is
completely out of water and being
suddenly rid OF resisting the engine
runs away. so to speak. just as an or
binary engine will do when a driving
belt slips off or breaks. Occasionally
propeller is broken by striking float
ing logs or ice and rarely by striking
a whale or large fish, when it is much
the worse for the fish.
But there is one curious fact alwayt
noticeable about propellers; that is
that the extremities of blades are
eaten away as though by some corro-
sive acid. They are pierced with
holes OF greater or lesser depth. which
weaken the points of the fans so that
they snap oil. These corrosions are
said 10 be caused By the action OF the
water but it seems strange that the
wearing should take tho form OF hon.
eycombing the metal instead of wear
ing it smoothly. as the mere friction
OF striking the water might be sup
posed to do Recently screws or pro-
pellers are made OF different combina-
tions of brass and other metals es-
pecially for steam yachts. and are
very costly. A short timo ago Pier
/ pont Morgan's yacht struck n rock in
I the sound. The force of the blow
smashed one blade clean of, although
I fastened on by eight or ten two-inch
bolts secured BY massive nuts. and
! the second blade was curled up by
| the blow just like sheet of lead.
/ This wheel was only a three -bladed
/ one and yet it cost the comparatively
! enormous sum fs2. 500 1t was made
OF composition metal resembling
! brass in color called Mayanese bronze
! In large ocean steamships. il the pro
7 pellers are not of one solid casting.
I it is usual TO cover the nut and boil
/ points which fasten the fans to the
! hub with n cement, This is SO tena
I cious and becomes so hard wher
once set that it rarely breaks unit
its removal becomes necessary. wher
/ it gives the workmen hard tussle tt
] remoye il