Screw Propellers.
Year: 1887

page_text: Date of Application, 23rd Apr., 1887
Complete Left, 23rd Jan., 1888
Complete Accepted, 24th Feb., 1888
Screw Propellers.
We, WALTER STODDART CUMMING, of 23 Abington Street, Glasgow, Lanarkshire,
and DONALD CRAWFORD of Glenrosa, Arran, Buteshire, Marine Engineers, do hereby
declare the nature of our invention to be as follows:
--
This Invention has reference to and comprises a new or improved construction of
portable instrument for use in taking the pitch and angles of screw propellers, or their
blades, at any part of their diameter, and which will be suitable also for patternmakers or
moulders in verifying the pitch of screw propeller blades at their various diameters or
circumferential segmental lines, and be more simple and universally applicable, than
any of the instruments heretofore used for that purpose.
The nature and novelty of the Invention, or construction of the instrument consist
all as follows:-Under one modification it would consist of two parallel thin blades,
preferably of steel, to bend, of from an inch to an inch and a half broad, both jointed
close over each other at one end by a centre screw stud and gripping thumb screw
with broad friction head, and washer at one side; while a small quadrant sextant or
protractor may be formed on the back limb, or similarly gripped by a thumb screw
on the opposite side of the centre screw. These two blades would preferably be made
each two feet long and divided on one side as a four-feet rule into inches, and have
centre lines strongly marked or cut up both sides of each blade coinciding with the
axial centre of joint; these two limbs are for being opened out and set to the angle
of the propeller blade at any radial point on it desired, and fix them there by the
thumb screw as hereinafter explained. The outer side of the front blade, which is
hereinafter termed the radial diameter blade, is divided from the centre joint into a
scale of divisional parts of say a quarter of an inch to the foot, of from one foot up to
twenty-four feet in diameter, corresponding to the circumferences of these diameter
divisions of from 1 to 24; that is to say 18" is divided into 24 parts representing
feet in diameter from 1 to 24 feet for or equivalent to circumferences on a scale of
quarter inch to a foot for these respective diameters. This radial diameter blade has a
level secured by a screw stud and thumb screw nut on its lower front end below the
said scale. A loose separate T-square is used as another member of the instrument for

page_text: sliding up and down the left hand edge of this radial blade, at right angles to or
tangential to any of the said diameter divisions for taking the pitch as hereinafter
stated. The blade of this T-square is divided off on a scale also of quarter inch to the
foot, from a line on it near the stock, coinciding with the centre line of the radial
blade, to form one to thirty-five feet, that is, having eight and three quarter inches
divided into thirty five parts representing feet in pitch on that scale for each revolution
of any circumference, or diameter, as from 1 to 24 on the radial diameter blade with
the centre line on the angle blade when this is opened out and set to the angle of the
propeller blade at any desired diameter on the blade of which the pitch is desired
to be obtained.
The instrument is set and used as follows to obtain the pitch and angle of a propeller
blade, at any radial diameter on it ;-thus the inner edge of the radial blade is laid
vertically on the turned end of the boss of the propeller, preferably the after end, and
should the axis of the shaft not be lying level or horizontal in the longitudinal
direction, this can at once be tested by the level on the lower end of the blade, and
which can then be shifted and set level, which will enable the radial blade to be
removed out to any radius or diameter on the blade of the propeller, and set by the
level parallel to the boss at any point or radius or diameter on the propeller blado
where it is desired to take the angle or pitch. Then the angle blade will be shifted
out to coincide with the angle of the blade, at right angles on either side to this radial
line on the blade of the propeller or where the blades are curved away from the radial
line and the angle cannot well be taken at right angles to this as stated, the angled
blade of the instrument being thin can be bent to the circumferential line from the
said tangential line and radial line on the propeller and the thumb screw nut fixed to
secure the blade at this angle as so taken and set which might be any angle; and the
angle taken can at once be seen and read off on the sextant or protractor of the back
blade agreeing to this diameter of the propeller blado which say in this case was
twenty two and half degrees. While to get the pitch the set squaro is placed with
either edge in line with the number on the radial diameter blade, agreeing to the
radial line and diameter where the angle was taken on the propeller; that is if the
angle was taken at a four feet radius, the square would be set at eight agreeing to this
diameter, and the number on the blade of the T-square opposite the centre line on the
angled blade read off would give the pitch for that diameter, which say was ten, this
would be ten feet pitch for the eight feet diameter propeller blade which would give
five feet pitch for four feet diameter, and fifteen feet pitch for twelve feet diameter,
and twenty feet pitch for sixteen feet diameter and twenty five feet pitch for twenty
feet diameter and thirty feet pitch for twenty four feet diameter; and the angle would
be for these pitches and diameters twenty two and one half degrees. The diameters or
radial lines could be easily measured off on the propeller by the blades as a rule of
four feet; and the T-square might have a hole in its extreme end, and be attached
to the instrument by one of the thumb screws, and the whole thus made compact and
portable for being packed in a caso or otherwise when not required for use.
Dated this 23rd day of April 1887.

page_text: A New or Improved Instrument for Taking the Pitch and Angles o
Screw Propellers.
We, WALTER STODDART CUMMING, of 23 Abington Street, Glasgow, Lanarkshire,
and DONALD CRAWFORD, of Glenrosa, Arran, Buteshire, Marine Engineers, do hereby
declare the nature of our invention and in what manner the same is to be performed,
to bo párticularly described and ascertained in and by the following statement in
writing, reference being had to the accompanying Sheet of Drawings, and to the
letters and figures marked thereon, that is to say:
Our said Invention has reference to and comprises a new or improved construction
of portable instrument for use in taking the pitch and angles of screw propellers, or
their blades, at any part of their diameter, and which will be suitable also for pattern
makers or moulders in verifying the pitch of screw propeller blades at their various
diameters or circumferential segmental lines, and be more simple and universally
applicable than any of the instruments heretofore used for that purpose.
And in order that our said Invention, and the manner of performing or carrying
the same into effect or pratice may be properly understood, we have hereunto
appended an explanatory sheet of Drawings, in which the same reference letters are
used to indicate corresponding parts in all the figures where shown. Figures 1 and 2
represent a front elevation and edge view respectively of our new or improved
instrument for taking the pitch and angles of screw propellers and their accompanying
fittings. Figure 3 is a stern end view of a screw propeller showing the boss B and
two opposite blades A, A. Figures 4 and 5 represent sectional views of the opposite
blades of the propeller as taken at the dotted lines a, and a², respectively, showing
the instrument as applied for taking the pitch and angles.
Referring to the modification shown in these Figures, the nature and novelty of
the invention consist all as follows:-In constructing the instrument of two parallel
thin blades C, D, preferably of steel, to bend, of froin an inch to an inch and a half
broad, both jointed close over each other at one end by a centre screw stud c and
gripping thumb screw with broad friction head, or washer c', on the front side, with
a small quadrant sextant E, preferably gripped by a thumb scrow on the opposite
side of the centre screw. These two blades C, D, are preferably each made two feet
long and divided on one side (the back side or side opposite to that shown in the
Drawings) as a four-feet rule into inches, and have centre lines c, e, and c, e¹, strongly
marked or cut up both sides of each blade coinciding with the axial centro c of joint;
these two limbs C, D, are for being opened out and set to the angle of the propeller
blade A or A, as at a or a', or any other radial point on it desired, as indicated by the
dotted lines a and a", and fixed there by the thumb screw c', as hereinafter explained,
which may be done very firmly by a small portable screw-key F, carried on the
instrument and shown in Figures 1 and 2. The outer side of the front blade C, which
is hereinafter termed the "radial diameter blade," is divided from the centre joint into
a scale of divisional parts of say a quarter of an inch to the foot, of from one foot
up to twenty-four feet in diameter, as shown by the figures 1 to 24 on the blade C, in
the Drawings, corresponding to the circumferences of these diameter divisions of

page_text: from 1 to 24; that is to say, 18 inches is divided into 24 parts representing feet in
diameter from 1 to 24 feet, for or equivalent to circumferences on a scale of quarter
inch to a foot for these respective diameters. This radial diameter blade C, has a
level C¹, secured by a screw stud and thumb screw nut C³, on its lower front end
below the said scale. A loose separate T-square d, d', is used as another member of
the instrument for sliding up and down the left hand edge of this radial blade C, at
right angles to or tangential to any of the said diameter divisions for taking the pitch
as hereinafter stated, and as shown placed at the twenty-third division in Figuro 1.
The blade d' of this T-square d, is divided off on a scale also of quarter inch to the
foot, from a zero line on it near the stock d, coinciding with the centre line C₂ e of
the radial blade C, to from one to thirty-five feet, that is, having eight and thres
quarter inches divided into thirty-five parts representing feet in pitch on that scale
for each revolution of any circumference, or diameter, as from 1 to 24 on the radial
diameter blade C, with the centre line on the angle blade D, when this is opened out and
set to the angle of the propeller blade A or A¹, at any desired diameter on the blade at
which the pitch is desired to be obtained, the T-square d being set to agree with
23 feet diameter on the blade C, agreeing with the 24th division of the blade
the squaro mecting the centre lino of the angled blade D.
of
The instrument is set and used as follows, to obtain the pitch and angle of a
propeller blade A or A', at any radial diameter on it, as say, a on the blade A; thus
the inner edge of the radial blade C is laid vertically on the turned end B₁ of the
boss B of the propeller, preferably the after end, and should the axis of the shaft not
be lying level or horizontal in the longitudinal direction this can at once be tested by
the level C on the lower end of the blade C, and which can then be shifted and set
level, and thus enable the radial blade to be removed out to any radius or diameter,
as a, a, on the blude A of the propeller, seen in Figures 3 and 4, and set by the
level parallel to the boss B at any point or radius or diameter on the propeller
blade A where it is desired to take the angle or pitch. Then the angle blade D will
be shifted out to coincide with the angle of the blade at right angles on either side of
this radial or circumferential lino a on the blade A of the propeller; or otherwise where
the blades are curved away from the radial line 1--1 as is frequently done from the
leading edge of the blade, as shown on the right hand side of Diagram end or face
view of the propeller blade of this character in Figure 6, and the angle cannot well
be taken at right angles to the centre line 1---1 as stated; the angled blade D of
the instrument being thin can be bent to the circumferential line a-a, from the said
tangential or perpendicular line, and radial line 1---1 on the propeller, and the
thumb screw nut c' fixed by the screw key before stated to secure the blade D at this
angle as so taken and set, which might be any angle to agree to the propeller blade;
and the angle taken can at onco be seen and read off on the sextant or protractor E of
the back blado agreeing to this diameter of the propeller blade, which say in this case
was twenty-two and a half degrees. While to get the pitch the set-square d, d',
placed with either edge of the blade d' in line with the number on the radial diameter
blade C, agreeing to tho radial line and diameter where the angle was taken on the
propeller; that is, if the angle was taken at a four feet radius, as a-a, the square d, d
would be set at eight agreeing to this diameter, and the number on the blade d of the
T-square d opposite the centre line on the angled blade D read off would give the
pitch for that diameter, which say was ten, this would be ten feet pitch for the eight
feet diameter propeller blade, which would give five feet pitch for four feet diameter,
and fifteen feet pitch for twelve feet diameter, and twenty feet pitch for sixteen feet
diameter, and twenty-five feet pitch for twenty feet diameter, and thirty feet pitch for
twenty-four feet diameter; and the angle would be for these pitches and diameters
twenty-two and one half degrees, all as indicated by the dotted perpendicular lines
at 4, 8, 16, 20 and 24 of the blade C, meeting the dotted angled line e, e, and
indicating the centre line of the blade D for this anglo of 22 degrees and these
respective pitches 5, 10, 15, 20, 25 and 30 for the said diameters of blades. The
diameters or radial lines could be easily measured off on the propeller by the blades
as a rule of four feet and the Ṭ-square might have a hole in its extreme end; and be
is

page_text: attached to the instrument by one of the thumb screws as dotted in in Figure 1, and
the whole thus made compact and portable for being packed in a carrying case or
otherwise when not required for use.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what we
claim is :-
First. The construction, or arrangement and combination of the parts of an
instrument and its fittings for taking the pitch and angles of screw propellers and
their blades, substantially as herein described, in reference to and shown in the
accompanying Drawings.
Second. An instrument for taking the pitches, and the angles, of screw propellers
and their blades, comprising two thin spring steel or other metallic blades jointed at
their one end, and marked with an indicating scale on the radial blade, with a Ṭ-square
having its blade divided to give the pitches proportional to the divisions on the radial
blade, all substantially as herein described in reference to and shown in the accom-
panying Drawings.
Third. In an instrument for taking the pitches and the angles of screw propellers
and their blades, the fitting of a spirit level on the radial blade, for enabling the true
angle to be taken although the propeller shaft may be out of level, substantially as
herein described in reference to and shown in the accompanying Drawings.
Dated this 23rd day of January 1887