IMPROVEMENTS PROPELLERS
Year: 1882

page_text: IN SCREW
LETTERS PATENT to Edward Griffith Brewer of 33 Chancery Lane in the
County of Middlesex, for an Invention of "IMPROVEMENTS
PROPELLERS" Communicated to him from abroad by Georg Hoper of
Iserlohn Germany.
PROVISIONAL SPECIFICATION left by the said Edward Griffith Brewer
at the Office of the Commissioners of Patents on the 19th July 1882.
EDWARD GRIFFITH BREWER of 33 Chancery Lane in the County of Middlesex
'IMPROVEMENTS IN SCREW PROPELLERS" (A Communication to me from abroad by
Georg Hoper of Iserlohn Germany)
According to this Invention the blades are cast singly and with prolonged ends
the latter are placed into the mould, by preference chill mould, of the boss the
metal of which is then cast around such ends.
The blades are placed into a frame that gives them their definite position before
the boss is cast, and in this way the blades are firmly secured to the boss. Security
may be increased by dovetailing and bolting the ends of the blades. The fusion of
their surface with the metal of the boss may be facilitated by cutting up or
roughening such surface with a chisel as far as the metal of the boss is allowed
to reach.
The blades may be cast in loam in the ordinary way. The advantages to cast
propellers in the manner described over the casting of propellers in one piece are
the following. First. In the latter the ends of the blades near the boss or the boss
itself near the ends of the blades are exposed to setting and strain which will
occur where castings have their dimensions near bulky ones. Therefore propellers
cast in one piece are unreliable as to the soundness of the metal just in those
parts which are exposed to the severest strains. By the method described above
the metal in those parts is made sound reliable and better controllable. Second.
Blades fastened by casting or by fusion, as described require less bulky bosses
than those fastened mechanically.

page_text: When it is intended to cast the boss of a copper alloy I employ as a core for such
boss a cylinder of iron or steel around which the copper alloy will be tightly fitted
by contraction. The security of such fit may be increased by roughing the outside
of the iron or steel core.
In order to diminish galvanic action that may arise from contact of boss and
core I coat the latter before casting the boss with a material which will militato
against such action say loam or chalk.
I employ the core of iron or steel in bosses of copper alloys for the following
reasons.
When such bosses are in contact with the iron or steel shaft that drives the
propeller the sea water passing between boss and shaft may act as a galvanic
conductor with the tendency to destroy the shaft by decomposition. The arrange-
ment as described brings the shaft into contact with steel or iron only so that
the sea water may pass between boss and shaft without acting as described.
I transfer the contact of iron or steel with the copper alloy to the interior of
the boss where sea water is practically excluded and where besides the generation
of galvanic action is rendered difficult or suspended by the interposition of non-
conducting matter.
The further object of this invention is to produce propeller blades of superior
quality in single pieces, or in compiled sets of pieces.
For this purpose improved patterns or sets of patterns of blades are constructed
the castings from which are forged, or rolled or forged and rolled until they have
the desired hardness, elasticity and resistance as well as dimensions. The blades
are then bent or curved as may be required, and are finished by grinding and
polishing. When the blades consist of more than one piece these are constructed
and compiled as hereafter designed and rivetted bolted or screwed together by
rivets bolts or screws preferably made of copper alloys.
The copper alloys required for carrying out this invention are of a very soft
kind say 94 to 98 per cent of copper and 6 to 2 per cent of Tin and Phosphorus
and which will give blades of indifferent quality when cast as at present, but
which alloys will give blades of a very superior kind when treated according to
this invention.
In order to find the proper dimensions for the construction of the patterns a test
bar is cast of the alloy of which the blade has to consist. By forging or rolling or
pressing the same the proportion is ascertained up to which such alloy may safely
be stretched without annealing and without destroying the cohesion of the grain.
With the alloys mentioned before: ten per cent is a safe average figure for
calculating the practical elongation as it has been found by experiments. By such
mechanical treatment the hardness elasticity and resistance of the alloy are
remarkably increased.
By annealing and repeating the operation, say three times each operation will
somewhat increase the elasticity and resistance. After the last operation the
metal is left unannealed; in spite of its hardness it will retain sufficient ductibility
to bear being bent into such curves as may be required of a propeller blade or
being bent into dovetail ends as hereafter designed.
According to the above data if the alloys mentioned before were to be employed
in the casting of blades the patterns of such blades must be from ten per cent to
forty per cent thicker and proportionately shorter in those parts that have to be
improved by mechanical treatment as described, than such patterns would be
made if the blades were to be cast at once into definite dimensions, as is now
customary.
As a pattern it is preferred to employ a plain plate or a set of plain plates the
castings from which are repeatedly stretched by rolling as described.
The sheets are then cut to dimensions ground to fit closely arranged and bolted
together, curved by pressure and then fastened to the boss.
When several sheets are employed to make up a blade, they are of various
lengths, the top ends of which are made chisel edged. The bottom end of the
4

page_text: blade as far as it reaches into the boss is made slightly conical downwards in order
to secure a close fit. The large front sheet may be stayed by one or more sheets
to provide for such cases where the propeller is reversed to drive the ship back.
The blade may be fastened into a foot plate by cross bolts or by wedge driven
in between the ends of the plates so as to expand them in the foot plate which is
then secured to the boss in any of the well known ways. If the screw is made
of only one piece it may be fastened in the foot plate by the stem end of it having
a slot cut in it and a wedge driven in so as to expand it or by cross bolts. The
foot plate is cast around a core formed with a tapered or suitable hole for the
end of the blade when expanded by wedge.
For the wedges very hard chilled bronze is preferably employed.
With a large proportion of soft copper alloys a very slight obstruction to
contraction after they have been cast will suffice to make the casting unsound or
even to crack it. In order to counteract this the patterns of the plates may be
made conical, placing the thick end at the bottom of the mould. Such castings
must be hammered beforo they can be rolled.
If the conical casting is of sufficient body to make a blade without the addition
of other plates the piece inay be hammered only and left conical being curved and
polished as described.
The patterns may be moulded in loam in the ordinary way.
It is preferred to cast the bosses and foot plates in chill moulds with or without
conical iron cores to receive the blades.
The remarkable superiority of blades manufactured according to this invention
over those which are cast of copper alloys in the ordinary way as regards resistance
and elasticity offers the advantage that their thickness and weight may be
diminished, the number of revolutions of the propeller may be increased without
increasing the power of the engines which is identical with increasing the speed of
the vessels supplied with blades improved as described.
The blades manufactured of the above mentioned alloys in the manner described,
retain sufficient ductibility to bend, instead of breaking when the blades striko
and they also will bear being hammered straight again. The manner in which
they are constructed and fitted to the boss makes an exchange of blades easy.
The resistance of forged, or rolled copper alloys to oxydation by sea water is
greater than that of mere castings of the same alloys.
In the resistance to repeated flexions or bendings the copper alloys beforo
mentioned when hammered or rolled are superior to wrought iron and to forged
steel as has been ascertained by experiments. The grain of steel and iron will
gradually crystallize by repeated strains and will lose their resistance in the same
degree as the crystallization advances. The above alloys are much less subject to
such crystallization and retain their original resistance very long.
The inventor does not limit himself to the employment of the said alloys but
any copper alloy which is sufficiently soft to bear forging or rolling and whose
resistance is thereby increased, may be employed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edward Griffith Brower in the Great Seal Patent Office on the
19th January 1883.
"
EDWARD GRIFFITH BREWER of 33 Chancery Lane in the County of Middlesex
IMPROVEMENTS IN SCREW PROPELLERS" (A Communication to me from abroad
by Georg Höper of Iserlohn Germany)
According to one part of this invention screw propellers are made as follows.
The boss is formed in a mould and preferably over a metal core say of steel, The
blades are cast singly with a stem which latter is preferably of dovetail form, the
stein is placed in the mould of the boss and the molten metal for the boss run in,
the desired pitch of the blades is given by placing them in a suitable frame before
the boss is cast; by this means the blades are firmly fastened to the boss.
Additional security may be obtained by passing cross bolts through the boss
and stem of blades. The fusion of the stem of the blades with the boss may be
facilitated by grooving or roughening the stem part by cold chisel or other means
before the boss is cast round, when it is intended to form the boss of a copper alloy
it is preferred to use a core in the boss; this core is formed of a tube of iron or
steel preferably the latter, which is an important feature in the Invention around
which the alloy will be firmly fitted by contraction, the security of such fit may
be increased by roughening the outside of the metal tube or core.
Figure 1 shows in side elevation and Figure 2 in sectional elevation or partial
sectional back view the boss of a propeller with blades attached made in the
manner just described according to the first part of this Invention, a is the tubular
steel core, b is the boss ccc the propeller blades.
The advantages to be obtained by forming propellers as described over casting
them in one piece are the following:-First-In the latter the ends of the blades
near the boss, or the boss, itself near the ends of the blades are exposed to settling or
under contraction and strain, which will occur where castings have thin dimensions
near bulky ones. Second-Blades fastened as described require less bulky bosses
(a considerable advantage) than where they are fastened by bolts or screws in the
usual way.
In order to diminish galvanic action that may arise from contact of boss and
core, the latter is coated before casting the boss with a material which will militate
against such action, such as loam or chalk. The advantages obtained by using a
core or tube of steel in bosses cast from copper alloys are as follows. When bosses
formed of copper alloys are in direct contact with the iron or steel propeller shaft
the sea water passing between boss and shaft may act as a galvanic conductor
with the tendency to destroy the shaft by decomposition. By the use of a metallic
core such as described in the boss into which the propeller shaft is fitted, this
injurious result is prevented.
Another part of this Invention refers to the alloys for manufacturing propeller
blades from and the mode of treating such alloys.
The alloys preferred to be used are of a very soft kind say 94 to 98 per cent
copper and 6 to 2 per cent tin and phosphorus: Blades cast from such an alloy
as this in the usual way will be of very inferior quality but when treated according
to this invention will be of very superior quality. An alternative alloy might
be 95 per cent copper 2 per cent tin and 2 per cent zinc but without limiting the
proportions or to the use of an equivalent alloy or material.
The method of treatment is as follows:-
After the blade has been cast in the usual way the same is subjected to forging
or rolling or both so as to extend the size in all directions without destroying the
cohesion of the grain of the alloy; with the alloys mentioned an extension of ten
per cent may be calculated or expected to be obtained and then in spite of its
hardness it will bear being bent into the necessary curves for propeller blades.
The blades are then finished by grinding and polishing.

page_text: Another part of this invention consists in forming the blades of propellers of
several sheets of metal treated as before described of various lengths or in sets of
various lengths ground to fit closely and bolted together by rivets or screws made
from suitable copper alloys. The desired curves for the blades may be given to
the plates before being bolted together or afterwards. When several plates of
different lengths are used to make up a blade the top ends should be chamfered off
to a chisel edge. The bottom ends of the plates are secured in a boss by cross
bolts.
Figures 3 and 4 shew propellers the blades of which are made as just described
of several plates rivetted together and fastened in boss by cross bolts & d¹.
Another mode of securing the blades to the boss is by expanding the ends by
means of a wedge driven in between the plates. When this latter mode is used, it
is necessary to employ a foot plate having a suitably tapered hole into which the
end of the blade is inserted before being expanded by wedge; the welge can be
secured from moving by a cross bolt. After the blade is attached as described the
foot plate is fastened to the boss by bolts or screws or otherwise.
Figure 5 shows in sectional elevation this mode of fastening propeller blade in
foot plate that is by expanding the stem end of the blade by means of wedge; o is
foot plate, wedge; g cross bolt for securing wedge.
When the blade is made of a single plate, extended and hardened as before
described, instead of being fastened in the boss by moulding the boss round the
stem, it can be fastened by cutting a slot in the stem and expanding the same in
a foot plate by means of a wedge and fastening the foot plate to the boss by screws
or bolts.
Figure 6 shows a sectional elevation and Figure 7 an end view of this mode of
fastening. In order to relieve the bolts from strain, the stem end of the blade or
blades may be compressed by wedges at the part where it or they emerge or
emerges from the boss or foot plate as shown at W Figure 8.
When propellers of comparatively small diameter say for fish torpedoes are made
according to this Invention they may be manufactured from one piece of hardened
sheathing of a soft copper alloy. The space required between the blades is cut out.
The thickness of the latter is then reduced towards the edge by for example
planing grinding or otherwise until the longitudinal diagonal and cross section of
a blade assumes such a form as that shown at Figure 9.
The blades are then bent or pressed into the desired curves. The pressing may
be accomplished in a metal mould or in sets of moulds. The central part which
might if desired represent the boss, is in that case left uncurved and is then
fastened to the shaft in manner before described or in any other suitable and
convenient manner. Boss and blades may be stayed, when required, by collars such
as in Figure 15 with or without the short arms hereinbefore described in
reference to Figure 11:
The blades of these pressed propellers decrease in thickness lengthwise as well
as from back to edge and such blades instead of forming one piece with the boss
may also be made separately and may be fastened to the boss by wedges and bolts
with or without the slot all as before described.
Another mode of forming screw propellers according to this Invention is to form
short projecting arms or short blades from the boss, onto which are bolted or
rivetted various sheets of metal to make up the blades.
Figures 10 and 11 shew in side elevation and partly in section respectively a
screw propeller the blades of which are rivetted onto a short blade or arm formed
on the boss, a is the steel core, b the boss, h the short blade or arm to which the
full blade or series of blades is or are rivetted.
The blade may be stayed by a collar at the stem, if required.
It is preferred to employ sheets which are rolled conically i.e. diminishing in
thickness towards the edge of the blade such a series of rolled plates forming a
blade is shown in vertical longitudinal section at Figure 12.
In building up the blades it is preferred to employ the sheets in sets of one pair

page_text: each, one such pair being added to the front of the central sheet or sheets, whilst
the other corresponding one is added to the back side as shown at Figure 8. And
this is continued until the blade has reached the desired thickness. The blade
will thus be equally well stayed, whether the screw be turned forward or be
reversed. The stem end of the blade may be slit as shown at S Figure 13 which
will make it easier to bend it into the desired curve.
The rivetting of the sheets may be limited to their edges see Figure 13. When
sheets of even thickness are employed it is preferred to cut their outlines as shown
at Figure 14 in order to diminish the thickness of the blade towards the edge.
But at the stem end all sheets should be of equal width which will facilitate their
⚫ being fastened to the boss all as shown with reference to Figure 14.
Figures 15 and 16 show boss composed of hammered or rolled plates which are
arranged in sets as shown. The central sets C, C, C, C, are elongated so as to form
two or more short arms to which the blades may be fastened. These arms C are
curved to correspond with the curve of the blade, whereas that part of the plates
which represents the boss proper may be left uncurved, i.c. in rectangular position
towards the axis of the shaft, bosses so composed, especially when made of
malleable copper alloys can be made lighter than when cast of the same metal.
The circumference of the sheets composing these blades is by preference not a
straight line but parabolical or curved as shown.
Having now described the nature of the said Invention and in what manner the
.same is to be carried out I am aware that it has heretofore been proposed to make
.screw propeller blades of more than one piece rivetted together and I am also
aware that it has been proposed to fasten propeller blades in the boss by casting
the boss round the stem end of such blades but what I claim as the aforesaid
Improvements in screw propellers is :-
First: The use of a tubular core in the boss made of a different metal to the
boss as and for the purpose set forth.
Second-The construction of propeller blades of plates of various lengths or in
sets of various lengths rivetted together substantially as hereinbefore described and
.shewn with reference to Figures, 3, 4, 5, 8, 10, 11, 12, 13, 14, 15 and 16 of the
accompanying drawings.
Third-The mode of fastening propeller blades in foot plates by expanding the
stem ends of same by means of wedge with or without counter-wedges substantially
as herein before described and shewn with reference to Figures 5, 6, 7 and 8 of the
accompanying drawings..
Fourth- The construction of propellers with bosses having short blades or arms
formed thereon to be cast in one piece or bosses composed of hammered or rolled
plates part of which are elongated into short blades for the purpose of bolting or
rivetting thereto the propeller blade or blades substantially as shown and described
with reference to Figures 10, 11, 15 and 16 of the accompanying drawings.
Fifth In a screw propeller the manufacture thereof from one piece of sheathing
.of the described alloys and with or without stays or collars substantially as and
for the purposes described and particularly with reference to Figure 9 of the
accompanying drawings.
Sixth: As applied to the manufacture of screw propeller blades the employment
of the combined process for treating a soft alloy substantially as and for the
purposes herein before described.
In Witness whereof I the said Edward Griffith Brewer have hereunto set
my hand and seal this Eighteenth day of January in the year of our Lord
One thousand eight hundred and eighty three:
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