Improvements in Screw Propellers.
Year: 1893

page_text: Date of Application, 4th July, 1893
Complete Specification Left, 4th Apr., 1894-Accepted, 4th Oct., 1894
PROVISIONAL SPECIFICATION.
Improvements in Screw Propellers.
I BENJAMIN WADDY MAUGHAN of 75 Saint James's Road Holloway in the
Parish of Saint Mary Islington in the County of Middlesex, Engineer, do hereby
declare the nature of this invention to be as follows:-
My invention consists of improvements which have been ascertained by
calculations resulting in the advantageous use of certain angles coupled with a
scientific variation in the dimensions of the blade or blades or fan or fans of propellers
or screws rotated or revolved by a motive force and used for propelling or driving
vessels or machines in or upon water.
These improvements consist in the peculiar formation of the back and front of
the blade or blades or fan or fans of my improved propeller by the application of
special angles which I have discovered whereby the recoil of water into a vacuum
is constituted a force for improved speed and motion for vessels and machines in
water and forms the guiding principle of my invention.
The result of my calculations and discoveries is to effect an accelerated speed of
the vessel together with increased power as also a saving of fuel and other
advantages.
The gist of my invention may be briefly summed up as follows:
1. The "nett
"
with a
resistance of the vessel and the force of the motive power
given number of revolutions of the propeller having been ascertained or specified
use angles in the formation of my "improved" blade or blades or fan or fans
based upon experimental data hitherto unknown as to the recoil of water into
vacuum.
2. The speed of the recoil varies at different depths from the surface necessitating
a corresponding variation in the formation of the said angles.
3. I base my design upon the greatest possible speed of the vessel.
4. I base my angles so that the water struck shall recoil upon other surfaces
provided for driving the vessel.
5. I form the blade or blades or fan or fans of my improved propeller so that
when the vessel is moving in a forward or backward direction the water shall strike
the said blade or blades or fan or fans (so devised) so that the action of the water
in so striking the same shall cause an accelerated onward or backward movement
of the vessel as the case may be greater than has hitherto been obtained with the
same motive power.
6. I avail myself of angles both at the front and the back of the blade or blades
or fan or fans of my "improved propeller" whereby the water rushing into vacua
or into spaces (created by the onward or backward progress of the vessel or the
means by which it is propelled) that would otherwise be vacant shall press upon
these certain surfaces both on the front and the back of the said blade or blades or
fan or fans of the propeller increasing thereby its revolutions in number or in
power or both.
In the accompanying drawings
Figure 1 shows the plan of the trailing portion of a helical section at the tip of a
blude or fan of the said propeller constructed according to my invention.
Figure 2 shows the plan of the leading portion of the said section.
Figure 3 shows the plan of the trailing portion and a part of the leading portion
of a helical section of a blade or fan at half the radius of the propeller.
Figure 4 shows the plan of the remainder of the leading portion of the said
section shown in Figure three.

page_text: Figure 5 shows the plan of the trailing portion and part of the leading portion of
a helical section of a blade or fan near the junction of the blade or fan with
the boss.
Figure 6 shows the plan of the remainder of the leading portion of the said
section shown in Figure 5.
Figure 7 is a drawing shewing the back elevation of the said propeller.
Figure 8 is a drawing shewing the side elevation of the said propeller.
Dated the 4th July 1893
B. W. MAUGHAN.
COMPLETE SPECIFICATION.
Improvements in Screw Propellers.
I BENJAMIN WADDY MAUGHAN of 75, St. James' Road Holloway in the Parish
of Saint Mary Islington in the County of Middlesex, Engineer do hereby declare
the nature of this invention and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement:-
My invention consists of improvements, which have been ascertained by
experiments and calculations, resulting in the discovery and advantageous use, of a
series of planes or surfaces, placed at certain special angles relatively one to the
other, and also scientific variation, and increase in the form and dimensions of the
blade or blades, or fan or fans, of propellers or screws, rotated or revolved, by a
motive force, and to be used for propelling or driving vessels or machines in or
upon water, as compared with those now in use, as is hereinafter more fully
explained.
These improvements consist in the peculiar or special formation of the back and
front of the blade or blades or fan or fans of my improved propeller or screw, by
the application or use of the said special angles, which I have discovered, whereby
the recoil of water into a vacuum or into a space that would be a vacuum if the
water did not rush in to fill up the said space, is constituted or becomes a motive
force for improved speed and movement of vessels or machines in or upon water,
and forms the guiding principle of my invention in conjunction with details of the
effect of leverage upon the back of the said blade or blades or fan or fans, as is
hereinafter more fully explained. By the term fan I mean screw blade.
The result of my calculations and discoveries is to effect an accelerated speed of
the vessel together with increased power, or they may be used to effect a saving of
fuel, or both the said advantages combined.
The special points of my invention I now proceed to describe as follows:
1. I discover or calculate the "net" resistance of the vessel, and the force of the
motive power or the engine or engines producing or causing a given or specified
number of revolutions of the propeller or propellers.
These said particulars having been ascertained or furnished, together with the
average depth of immersion of the centre or axis of the propeller, I consequently
use planes or surfaces placed at resulting angles in the formation of my improved
blade or blades or fan or fans, based upon experimental data hitherto unknown or
utilised, relating to the recoil of water into a vacuum as aforesaid, and also the
effect of the impact of water upon the back or backs of the blade or blades or fan
or fans, which I so construct or design as to receive the said impact, so that there
is a leverage upon some of the said planes or surfaces in favour of the motive
rpower, as is hereinafter more fully described.
2. The speed of the said recoil of the water into a vacuum, or into a space that
would be a vacuum if the water did not rush into the said space, varies at different
depths from the surface of the water, necessitating a corresponding variation, in
the formation or obtuseness or acuteness of the said angles. The rate of the said
recoil, I have ascertained to be about one half the speed, that would be acquired
by a falling body in vacuo, at any specified depth of immersion.

page_text: 3. I base my design upon the greatest possible speed of the vessel, having regard
to the formation or lines of the hull of the vessel, and the motive power of the
engine or engines, or any other power'in or upon the vessel. I represent in a
drawing, the said greatest speed of the vessel, by drawing first a right angle
triangle, one side or line of which represents the number of feet traversed ahead by
the vessel during a specified period of time; this line, I term hereinafter the
vessel's pitch line, and the other side of which represents the length of the circum-
ference described or traversed by the tip or tips of a blade or fan or the blades or
fans of my improved propeller during the said specified time, this line I term
hereinafter, the circumference at tip line. The hypothenuse of the said right-
angle, equals in length a helical line I term hereinafter, the vessels helical pitch..
line at tip, and the angles of the said planes or surfaces aforesaid are in part
related to or based upon this said helical pitch line at tip.
The said vessels pitch line or vessels helical pitch lines, may be similarly drawn
for any less radius, between the tip of the blade or blades or fan or fans, and the
centre or axis of the propeller, and the angles are similarly related to the vessels
helical pitch lines at any helical or transverse section of a blade or fan, excepting
towards the root of each blade or fan on the front or driving side.
4. I base my said angles upon the said vessels helical pitch lines, so that one of the
angles forming the lines of each inclined surface shall be greater, and the other
shall be less, than the angle or angles of the said vessels helical pitch lives to the
propeller shaft. The said lines forming the said angles represent the relative
angular situation of the said planes or surfaces of my improved propeller blade or
fan at any diameter or radius for which they may be specifically drawn.
I place my said planes or surfaces at such angles, that the water struck by each
leading plane or surface shall recoil, past each contiguous trailing plane or surface
upon the next leading plane or surface provided for driving the vessel ahead or.
astern. In designing or drawing a blade or fan of my improved propeller, I draw ·
as many transverse sections from the tip to the root as may be practically necessary;
these said sections, show the said lines of the said angles, and the inclinations of the
said planes or surfaces one to the other, and their relative positions to the vessels.
helical pitch lines of each transverse section.
5. I form the blade or blades or fan or fans of my improved propeller as is
hereinbefore and hereinafter more fully described, so that when the vessel is
driven by it in a forward or backward direction, the water shall strike on certain
of the said planes or surfaces of the said blade or blades or fan or fans (so devised)
that the action of the water in striking the same, shall cause an accelerated
onward or backward movement of the vessel or machine as the case may be,
greater than has hitherto been obtained with the same motive power, and without
necessarily increasing the number per minute of time, of the revolutions of the
propeller beyond the revolutions of the ordinary screw propeller, in any specified
case.
6. I avail myself as aforesaid, of angles based upon calculations hereinafter
specified, both at the front and the back of the blade or blades or fan or fans of
my improved propeller, whereby the water rushing into vacua, or into spaces
created by the onward or backward progress of the vessel, or the means by which
it is propelled, that would otherwise be vacant, shall press upon these certain
surfaces, both on the front and back of the said blade or blades or fan or fans of
my improved propeller, increasing thereby its revolutions in number or if not
increased in number, then in power, by increase of surface or pitch or both, and by
the said rush and pressure of the water.
7. The said angles differ one from the other, both as to their number of degrees,
and as to the relative lengths of the two lines forming each angle from the tip to
the root of the back of each blade or fan of my improved propeller; and also from
the tip to near the motive power radius (which term is defined in page 5 of the
Specification) of the front of each blade or fan of my improved propeller. Also in
the case of two vessels differing one from the other in the lines of the hulls, and the
4

page_text: relative motive force or number of revolutions of the propeller per minute, or in
any other important particular, the said angles of my improved propellers, will
differ one from the other in each case. I have discovered the method of
ascertaining and drawing the correct angles of my improved propeller for any
specified vessel, which said method I now proceed to describe, after first defining
the terms I find it necessary to make use of.
In the accompanying drawings,
Figure 1. shows the plan of the trailing portion of a helical section at the tip of
a blade or fan of the said propeller constructed according to my invention, with
increasing angles from the trailing point to the centre of the section.
Figure 2. shows the plan of the leading portion of the said section, with
decreasing angles from the centre to the leading point of the section.
Figure 3. shows the plan of the trailing portion of a helical section, aud a part
of the leading portion, of a blade or fan, at half the radius of the propeller with
increasing angles from the trailing point, to the centre of the section.
Figure 4. shows the plan of the remainder of the leading portion of the said
section shown in Figure three, with decreasing angles to the leading point.
Figure 5. shows the plan of the trailing portion and part of the leading portion
of a helical section of a blade or fan near the junction of the blade or fan with the
boss, with increasing angles from the trailing point to the centre on the back, but
without angles on the front.
Figure 6. shows the plan of the remainder of the leading portion of the said
section shown in Figure five, with decreasing angles on the back to the leading
point, and without angles on the front..
Figure 7. is a drawing showing the back elevation of the said propeller, in
perspective.
Figure 8. is a drawing showing the side elevation of the said propeller in
perspective, showing flanges on the front sides of the blades or fans.
Figure 9. shows the vessels helical pitch line at tip V P, as herein described.
Figure 10. shows the leverage pitch line at tip L P, as herein described.
Figure 11. shows the back vacuum line at tip V B, and the front vacuum line at
tip VF, as herein described.
Figure 12. shows the central pitch line at tip V R, as herein described.
Figure 13. shows the balance pitch line at tip B P, and the slip pitch line at
tip S P, as herein described.
Figure 14. shows the transverse or helical section at the tip of one of my improved
blades or fans.
In constructing my improved blade or fan I wrap a section of the form shown
upon a cylinder of suitable diameter and thus obtain a series of points corre-
sponding with the apices of the angles of the section. I then wrap a similar section
round a cylinder of larger or smaller diameters and thus obtain another series of
points, and by connecting such points by lines proceeding to the boss, I obtain the
required surfaces for my blade or fan. This method of construction explains what
I mean by the term helical section.
The said section shown in the drawing is the above described helical section
extended and drawn upon a flat surface, or plane.
The angles are formed at the back by the leverage pitch line at tip L P and the
back vacuum line at tip V B, and lines parallel to them, also shows the angles
formed at the front, by the slip pitch line at tip S P, and the front vacuum line at
tip V F as herein described.
Figure 15. shows a transverse or helical section at the tip of one of my improved
blades or fans with more angles than in Fig. 14, but formed by the same method as
aforesaid, and as is herein described.
8. The vessels helical pitch line at tip of the blade or fan as herein before
described, is shown in Fig. 9, by the line V P, the vessels pitch line is the
line V C.
The circumference at tip line is the line C P. The leverage pitch line or lines,

page_text: I so term, because they represent a plane or surface or planes or surfaces, at the
back of the blade or fan of my improved propeller, which, when the vessel is being
driven ahead, is forced against the water, and assists by means of leverage, the
motive power.
Its angle in any transverse section of my blade or fan to the vessels helical pitch
line is ascertained as follows:-
to one.
As the tip of a propeller blade or fan is usually four times the radius of the
crank or gearing on the propeller shaft, hereinafter termed the motive power
radius, it follows that a power or pressure at the tip of the blade or fan of a
propeller assisting its revolutions, is in such case, multiplied by a leverage of four
In my improved propeller I do not coufine myself to the said proportion
of four to one, 1 adopt an increased proportion when it is practicable to do so.
In Fig. 10, the triangle V C P Fig. 9, is exactly repeated, and in each case
represents developing angles at the tip of my improved blade or fan. The leverage
being specified as four to one, 1 divide the line CP into five parts always one
more than the leverage. I measure the length of one of these parts along the
line C V, to the point X. I join the points X and P by a right line X P. Assume
water to be pressing on the back surface of the blade or fan represented or
indicated by the line XP, then the effect of four parts of the pressure or force is in
the direction C to X, but owing to the rigidity of the blade or fan, there is no
leverage assisting this force, which I term hereinafter the fore to aft force. The
effect of one part of the said five parts of the pressure or force is in the direction C
to P. Having regard to the impossibility of movement of the propeller in any
other direction than around its axis, this force has a leverage of four to one,
assisting the motive power, and I term it hereinafter the circumferential force at
tip. It follows that as both the said forces are represented by the co-efficient four,
that they are equal.
The fore to aft force retarding the progress of the vessel, the circumferential
force equally assisting, therefore this line XD Fig. 10, is of no value, as and for the
purposes specified, but it serves as a basis to discover the most valuable and
powerful line as follows:
I
I bisect the part of the line XV Fig. 10, at L and join by a right line the
points L and P which line LP I term the leverage pitch line at tip. If we
assume that the part CL of the line CV, is one third of the length of the
line CP, it will follow by parity of reasoning, that the co-efficient of the fore to
aft force is two, and the co-efficient of the circumferential force is four, that is, one
multiplied by the aforesaid leverage four; the assistance to the progress of the
vessel being in this case, one hundred per cent. greater than the resistance.
term the line L P the leverage pitch line at tip. If the vessels pitch line CV is
increased in length while the circumferential line CP remains as drawn, the
proportion of the part of the line XV to the line C V, will be greater than shown
in the drawing Fig. 10, the vessels helical pitch line would then be at a coarser pitch.
If on the contrary, the line C P is lengthened, and the length of the line CV is
unaltered, then the proportionate length of the part XV of the line CV is
decreased, and the vessel's helical pitch line V P would then be at a finer pitch.
The position of the line VP is dependent upon the proportion between the
number of revolutions of the propeller to the length of the distance the vessel is
propelled thereby in equal times.
The pitch of the line V P is altered therefore and will vary with almost every
vessel.
The leverage pitch line for any other part of the radius of the blade or fan,
between the motive power radius and the tip may be similarly ascertained and
drawn. At and near the motive power radius, the leverage pitch line is superseded
in power, by a line I term the central pitch line.
In Fig. 12, let V Y be the vessel's helical pitch line at the motive power radius,
let VD be a line at an angle of 45° to the fore and aft line of the vessel or the
propeller shaft, then a pressure of water upon the line V D will be one half in a

page_text: fore to aft or resisting direction, and one half in a circumferential or assisting
direction; therefore, this line VD, (the slight leverage in its favour being
excepted), is of no value as and for the purposes specified, but it serves as a basis
to discover, for this part of my blade or fan, the most valuable and powerful line
as follows:
I bisect the part YD of the line CP at R, and join the points V and R
by a right line, this right line I term the central pitch line of the motive
power radius.
The central pitch line for any part of the radius of the blade, between the root
and near to where the vessels helical pitch line is at an angle of 45° to the fore and
aft line of the vessel, may be similarly ascertained.
The back vacuum line at tip V B is shown in Fig. 11. The dotted line V P
shows the said vessel's helical pitch line at tip, of a blade or fau of my improved
propeller. The rate per second at which the tip of the propeller blade or fan
moves along the said helical line when the vessel is being driven by my said
improved propeller at full speed having been calculated or ascertained, is herein-
after termed the helical rate at tip. The rate per second the water rushes into a
vacuum, or into a space that would be a vacuum if the water did not rush into it,
at the average depth of immersion of the axis of the propeller being calculated or
ascertained, is hereinafter termed the vacuum rate. Then if the length of the
dotted line VP, is assumed to represent to any scale the distance traversed by the
tip of a blade or fan through one helical revolution during the space of one second
of time, and the vacuum rate is assumed to be one third of the said helical rate,
then the line P B, drawn from the point P, at right angles to the line VP aud one
third of the length of the line V P will represent the said vacuum rate, and a right
line drawn from the point P, to the point B, is the line I term the back vacuum
line at tip, the use of which line I hereinafter more fully describe.
The back vacuum line can be similarly ascertained for any other part of the
blade or fan between the tip and the root.
The front vacuum line at tip, is formed from an equal extension of the right
line BP, to F, and joining by a right line the points P and F. This line can be
similarly ascertained for any other part. of the blade or fan.
The balance pitch line at tip, is a line B P, Fig. 13, forming an angle with the
vessels helical pitch line at tip V P, on the front side, equal or nearly equal in its
number of degrees, to that formed by the leverage pitch line at tip LP, with the
vessels helical pitch line at tip VP on the back side.
This balance pitch line can be similarly ascertained for any other part of the
blade or fan. From the balance pitch line at tip, the increased pitch of the slip
pitch line at tip S P, is calculated. The pitch of the slip pitch line at tip; is a
pitch which being adopted from the tip to near the motive power radius upon the
front of each blade or fan of my improved propeller, is calculated or ascertained, to
utilise at the maximum number of revolutions of my said propeller, the entire force
of the engine or engines or motive power employed to revolve it.
The object of determining the slip pitch line, is to obtain a suitable angle for the
propelling surfaces shown at A Figs. 14 & 15.
The 45° pitch line Fig. 12, is a pitch line I describe as follows. With the length
of the vessels pitch line C V, I measure from the point C along the circumference
at tip line CP to the point D. I join by a right line the points V and D. As
the lines CV and C D are equal one to the other & form together an angle of 90°
the hypothenuse V D must be at an angle of 45° to the vessels pitch line C V this
line hereinafter term the 45° pitch line.
The angles are formed and drawn so that their interior apices either coincide
with the vessels helical pitch lines or with lines parallel thereto. On the back of
each blade or fan one line of each angle is parallel to the leverage pitch lines or
the central pitch lines as aforesaid the other line of each angle is parallel to the
aforesaid back vacuum line. From the tip of each of my said blades or fans to the
45° pitch line V D Fig. 12, one line of each angle is drawn parallel to the leverage

page_text: pitch line as aforesaid. From the 45° pitch line V D to the root of my said blade
or fan the other line of each of the angles is drawn parallel to the central pitch line
as hereinbefore described. On the front of each blade or fan one line of each angle
is parallel to the aforesaid slip pitch lines and the other line of each angle is
parallel to the front vacuum lines. Figures 1, 2, 3, 4, 5, 6, 14, & 15, show examples
of the said angles drawn as described. The line or edge of the tip of each of my
blades or fans coincides with the helical line described by it when my propeller is
propelling the vessel at its maximum speed. I place one or more flanges upon the
said line or edge at right angles to the helical radius of the blade or fan projecting
over the back surface or surfaces as well as the front.
The lines of the angles parallel to the aforesaid vacuum lines or the planes or
surfaces they represent, are so drawn or constructed, that the fluid struck away by
the preceding or leading line, or plane or surface the line represents, shall return
upon the following leading line, or plane or surface, parallel to the other lines, both
on the back and front of my propeller. It does not necessarily follow, that the
same molecules of water struck by a leading surface, should return upon the
following leading line or plane or surface. The general body of fluid in which
the propeller is revolving, supplying the recoiling force. The vacuum line or
plane or surface I draw or construct, so that it shall agree with the rate of the said
recoil. In the construction of my propeller I purposely avoid all curves excepting
those arising from the helix, my reason being that water invariably moves in curves,
and the most powerful surface to strike it, is a surface that is not curved. I am
also aware, that it is immaterial in what manner water is struck by a plane or
helical plane surface, or what direction the water takes after it is struck. In any
and every case, the resulting mechanical force is in a direction square to the surface.
As fluid always moves along the line of least resistance the aforesaid angles would
cause the water to take a centrifugal course, therefore I use the aforesaid flange or
flanges so that the line of least resistance may be along the transverse or helical
sections of my blade or fan. Owing to the incompressibility of water, the flange
or flanges at the tip herein before described is or are sufficient to place the line of
least resistance along the transverse or helical sections of each blade or fan of my
improved propeller.
I adopt for this final Specification the five sheets of drawings lodged with my
Provisional Specification together with the additional two sheets of drawings filed
with this final Specification as hereinbefore described.
I do not confine myself to any specified number of blades for my improved
propeller.
I may use one blade consisting of or representing one complete revolution of the
helix or may divide one complete revolution into two, three, four, or more, equal or
unequal parts. Each part constituting a blade or fan and so fixed upon a boss or
hub, that they revolve around the propeller axis in distinct helical planes.
Assuming that there are two blades of equal area and as aforesaid, then the
line CP Figs. 14 or 15, may represent the half instead of the whole of the aforesaid
circumference at tip, and the line CV will represent one half of the pitch of the
propeller. Similarly, assuming there are three blades of equal area and as
aforesaid, then the line CP Figs. 14 or 15, may represent one third instead of the
whole of the aforesaid circumference at tip, and the line CV will represent one
third of the pitch of the propeller. The above reasoning applies similarly to four
or more divisions of the said helix. I wish it to be understood however, that I do
not confine myself to the utilisation of one entire revolution of the helix in the
design and construction of my improved propeller.
In the foregoing description of my invention I have given my method of
ascertaining the exact angles I use in specified cases and the extent of surface of
the propeller. I do not confine myself to the exact angles or surface or surfaces
herein explained as it is obvious that a departure not too great from the said angles
or surface or surfaces might be made and yet include advantages beyond the screw
propellers at present in use.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is―
1. The use of the angles herein before described either upon the front or back or
both upon the front and back of the blade or blades or fan or fans of my improved
propeller.
2. The use of the flange or flanges aforesaid extending over the back as well as
the front or over the back or front of the blade or blades or fan or fans of my
improved propeller.
B. W. MAUGHAN.