IMPROVE- MENTS IN PROPELLERS FOR SHIPS, BOATS, AND OTHER VESSELS
Year: 1867

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields,
in the County of Middlesex, Gentleman, for the Invention of "IMPROVE-
MENTS IN PROPELLERS FOR SHIPS, BOATS, AND OTHER VESSELS."-A com-
munication from abroad by Auguste Arban and the Marquis Marie
Joseph Antoine Ernest de Learance of Paris in the Empire of France.
COMPLETE
CIF ATION filed by the said John Henry
at the Office of the Commissioners of Patents, with his Petition and
Declaration, on the 8th February 1867, pursuant to the 9th Section of
the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN HENRY
JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex, Gentleman,
send greeting.
WHEREAS I am in. possession of an Invention for "IMPROVEMENTS IN
PROPELLERS FOR SHIPS, BOATS, AND OTHER VESSELS," and have petitioned Her
Majesty to grant unto me, my executors, administrators, and assigns, Her
Royal Letters Patent for the same, and have made solemn Declaration that
the said Invention is communicated to me from abroad by Auguste Arban,
the elder, and the Marquis Marie Joseph Antoine Ernest de Lagrange, of

page_text: Paris, in the Empire of France, and that the same is not in use by any other
person or persons to the best of my knowledge and belief.
NOW KNOW YE, that I, the said John Henry Johnson, do hereby declare
that the following Complete Specification, under my hand and seal, fully
describes and ascertains the nature of the said Invention, and in what manner
the same is to be performed, in and by the following statement, reference
being bad to the accompanying Drawings, and to the letters and figures
marked thereon, that is to say:-
This Invention relates to that class of propellers for ships, boats, and other
vessels wherein a series of fixed floats or paddles attached to reciprocating
rods or frames are caused to enter and leave the water in a perfectly vertical
position, and consists of a peculiar construction, arrangement, and combination
of the mechanism composing such propellers, whereby increased speed is
obtained with considerable economy of fuel.
In order that this Invention may be more readily understood I have
divided the Specification into the following heads:-
1st. The abstract mechanism of the improved propeller applicable to all
dimensions.
2nd. The mathematical formulæ which govern the construction of the said
mechanism.
3rd. The practical mode of substituting the said propelling mechanism for
existing propellers in steam ships, and of applying such propeller to ships
specially constructed for the same..
DESCRIPTION OF THE ABSTRACT MECHANISM.
Commencing with the most simple mechanism (Figures 1 and 2) of the
accompanying Sheets of Drawings, let A be the extremity of the horizontal
crank shaft of the engine of a steam vessel. I secure to this extremity a
crank A, b, which forms an angle of 60° to the left with the horizontal plane
passing through the axis of rotation A; at the end of this crank A, 6, I secure
a crank pin b, b', to the extremity b¹ of which I secure a second crank b, c,
which forms with the first an angle of 30° to the right, and which is of such
a length that its extremity c meets the circumference f, f, f, f, described by
the centre of the crank pin 6 of the crank A, b; I fix to the end of this
second crank a crank pin c, c', of the same length as the first, and at the
end of this second crank pin I adapt a third crank c, d, of equal length with
the second crank, and forming with that crank an angle of 60° to the left; at
the end d of this third crank I fix as before a crank pin d, d', to the extremity
of which I secure a fourth crank d¹,.e, of the same length as the crank A, b,

page_text: and forming with the third, crank an angle of 30° to the right; finally,.
secure to this fourth crank a journale, e', the end of which rests in a bearing e¹
in the same way that the extremity o, A, of the crank shaft rests upon a
bearing A. All the parts are securely held together, consequently the
mechanism o, A, b; b, c, c, d, d¹, e, e¹, forms one rigid whole. In projecting
this mechanism against a vertical plane (Figure 1) it will be seen that the
two cranks b', c, and c, d, are nothing more than the two sides of an equilateral
triangle inscribed within the circle f, f, f, the radius of which is the crank
A, b, or d', e; these two cranks being both of the same length the two bearings
A and e¹ are therefore situate on the same horizontal plane, and the bearing e¹
is strictly in the prolongation or axial centre line of the crank shaft o, A.
The mechanism o, A, b, b, c, c, d, d, e, e'; is thus capable of rotating. easily
without any dead centre whilst resting upon the two bearings A and e', and the.
movement will be such that the crank pins b, b, c, c¹, and d, d', will exactly.
describe the circumference f,f,f, which has for its radius the radius. of the
propeller; the projection of this mechanism upon a horizontal plane (Figure 2).
produces, as will be seen between the bearings A and el, a total width m, n,
which is rather greater than the sum of the lengths of the crank pins b, b, c, c¹,
d, d, and which constitutes as will be seen hereiu-after the width of the field of
evolution of the propeller, or, which amounts to the same, the width of the
paddle box of the vessel. I designate the crank A, b, the leading crank, the.
one d', 'e, the frame crank, & the two cranks b¹; c, and c, d, the connecting
cranks. If now at a certain distance from the axis of rotation AI mount on
the same horizontal plane, and parallel to the first shaft or axis, a second.
axis A (Figures 3 and 4) and repeat exactly upon this axis the several
cranks secured to the first one, I shall obtain two exactly similar and symetrical
pieces of mechanism o, A, b, b, c, c, d, d, e, e¹, and o, A', g, g, h, h', i, d²; j,j',
the four bearings A, A', e¹ and j', all being on the same horizontal plane, and
connecting two and two the crank pins b, b', 9, 9', c, c', h, h¹, and d, d'; i, i¹, by
the connecting rods B, C, D, E, and F, G. By rotating the crank shaft o, A, of
the prime mover the two mechanisms will be caused to revolve simultaneously
forward or backward and parallel to each other, the connecting rods main-
taining constantly their respective positions horizontally, each point in these
rods strictly describing the circumference f, f,f,f, or that marked f',f,f,f
which is the same.
If I fix to each one of the connecting rods B, C, D, E, F, G, a certain
number of fixed floats, three for example, 1, 2, 3, 4, 5, 6, 7, 8; and 9 (Figures
3 and 4), which floats remain constantly in a vertical positon, since they are
rigidly secured in a perpendicular position on the horizontal connecting rods,

page_text: and if I admit that the bearings A, A¹, e¹, j, are separated from the line of
floatation by a vertical distance equal to the length of the leading crank A, b,
it will follow that the surface of the water will be parallel to the plane of the
bearings, and tangential to the circumference of evolution of the propeller, and
that on moving it in one direction or the other each connecting rod will simul-
taneously submerge the whole of the floats secured thereto, and will effect in
the direction of an arc of the circumference already given a power of propul-
sion in proportion to the speed of working, the size of the floats, and the
radius of the circumference of evolution. It further follows that the
connecting rods will succeed each other regularly in the same order, and that
if the height of the floats be properly calculated, a propeller on the most sound
principles will have been constructed. If now on the two sides of a vessel I
adapt two propellers similar to that shewn in Figure 4, and mount them
symetrically as in Figure 5; I shall have advantageously replaced the paddle
wheels and all other known propellers that could be applied to this vessel.
The position of the propeller is of little importance; it may be applied in.
duplicate on the sides, amidship, or astern, or engaged wholly or partially in
the hull of the vessel, or placed singly at the stern or in a well in the longi-
tudinal axis of the vessel, or after the fashion of the American steamboats, or
otherwise disposed. The number of connecting or float bearing rods, as I
shall presently show, is not restricted to three, in fact, in several cases a
greater number may be applied according to the radius adopted, the draught
of water, the working of the engines, and the desired speed of the vessel.
Supposing it is desired to construct a propeller composed of more than three
float-bearing rods, it will be as easy to connect 4, 5, 6, or more rods with
cranks of such a length and mounted in such a manner that they shall form
the sides of a square, pentagon, regular bexagon, or other polygonal figure
described within a circle, the radius of which is equal to the radius of propeller
or length of crank decided upon, as it is to connect three rods by the aid of
the sides of an equilateral triangle described in the same circle as shewn in
Figures 1 and 2; thus there will be as many connecting rods as there are
equal divisions of the circle described by the leading crank pin, and in
principle there will be as many connecting cranks less one as there are
divisions in the said circle or sides to the polygon inscribed therein, therefore
the radius of the crank remaining the same, the length of the connecting
cranks diminishes in proportion as the number of float-bearing rods increases.
I shall herein-after point out the relations existing between these cranks,
the length of the float-bearing rods, and the height of the floats themselves.
Figures 6, 7, 8, and 9 (Sheet 2 of the Drawings), represent in four

page_text: principal positions upon the circumference. the propelling mechanism provided
with 3, 4, 5, and 6 float-bearing rods. I have not considered it necessary
to further extend the examples, as those I have given will suffice for all
practical purposes.
With reference to the relations and mathematical formula which govern
the construction of the improved propeller, I may observe that the polygonal
mechanisms upon which are mounted the float-bearing rods are subjected to
the theory of regular inscribed polygons. Having decided upon the radius.
of the propeller, or, in other words, on the radius of the circumscribed circle,
and on the number of float-bearing rods to be employed, the problem will
be solved by the following rules, each nechanism being considered as void of
width and thickness, and projected on a vertical plane. The rules as regards
the angular elements are,---
1. The polygon to be inscribed in the circle having for radius the radius
of the propeller will have as many sides as there are float-bearing rods to be
adapted thereto.
2. The angle of the first connecting crank with the leading crank will be
the half of the internal angle of the regular polygon inscribed.
3. The angle formed between the connecting cranks will be equal to the
internal angle of the said polygon..
4. The angle of the last connecting crank with the frame crank or outer
one of the set will be equal to the angle of the leading crank with the first
connecting crank, that is to say, equal to the half of the internal angle of the
inscribed polygon.
5. The angle of the leading crank with the frame crank will be equal to
the angle at the centre of the regular inscribed polygon. The rules which
bear upon the lineal elements are,-
6. The length of the side of the inscribed polygon, or, in other words, of
the connecting crank, will be equal to the double sine of the demi angle at the
centre, which in the function of a radius obviously amounts to,-
For an equilateral triangle
و"
-
R X 1.78
RX 1.412
:
:
a square
a
"
regular pentagon
"
a regular hexagon -
and so on..
-
R x 1.17
R x 1.00
In place of adopting as the connecting cranks the sides of the polygon
inscribed in a circle having for radius the crank adopted, there may be
imparted to these cranks the form and developement of the arc which they
subtend; in this case nothing will be changed in the other formula, for in

page_text: connecting the crank pins. by straight lines a regular polygon will still be
produced.
The same applies to the leading cranks and to the frame cranks, which
may be forged in the form of an S, or of any other form, even that of a fly
wheel. I only give these variations as examples of the different modes of
applying the principle upon which this Invention is based; in practice, of
course, the most simple, strong, least heavy, and compact forms only will be
selected, and in this respect straight cranks will be preferable to circular
cranks. It is not considered advisable to load the shafts with fly wheels,
which are obstacles to the change in the direction of motion, and add nothing
to the movement but weight; neither will it be useful to mount the float-
bearing rods on more than two sets of polygonally disposed cranks, in other
words, on more than two axles, a greater number entailing additional space,
weight, and friction.
.
7. The distance between the axes or shafts or the length of the float-
bearing rods will be double the length of the connecting crank, increased by a
certain amount, which will vary from about 18" to 8 feet; this amount
however is not absolute as will be presently shewn. As an explanation of
this rule I may observe that above all things in good construction it is necessary
to endeavour to obtain a solid compact and light mechanism; the movement
moreover should be so organised as to be contained within itself as it were,
and approaching the circumference as much as possible in its entirety, the
object of the Inventors is therefore to construct a propeller as short and
narrow as the principles of its construction and the object to be attained will
admit; this being established it will be seen at once (on referring to Figure 5)
that the floats a, a¹, a¹¹, a¹¹¹, a, a, situate near the ends of the rods A, B,
C, D, E, F, must, during their evolutions, pass between the cranks m, m³, n, n',
0, 0, p, p¹; it is necessary therefore that these floats should be of a length less
than the width between the sides of the cranks. The same does not apply to
the floats 6, 6, 6", which are situate towards the middle of the connecting
rods, and at a certain distance from the orbit of the crank pins, hence they
do not encounter the cranks, and provided their width be a trifle less than the
distance between the connecting rods themselves, or between the connecting
rods and the side of the ship, or of the paddle box, they will perform their
evolutions without any obstruction. On referring to Figure 10, and supposing
the two equilateral mechanisms to be in the respective positions o, A, B, C,
and o¹, A, B, C, it will be seen that the connecting rod A, A', is enclosed
laterally to a certain extent by the connecting crank A, B, hence all floats
fitted to this portion A, B, will pass a connecting crank during their evolutions.

page_text: If the same mechanism be brought into the position o, a, b, c, and o, a', b', c',
the rod A, A', situate at a, a', is enclosed laterally along the entire length of
the crank a', 6', the same as A, B; the distance B, 61, is then the only portion
wherein a float can be adapted, which on turning will not encounter a crank.
It is for this reason that it is advisable to make the float-bearing or connecting
rods somewhat longer than double the length of the connecting cranks, this
space being restricted to the space necessary for fixing the float and its fittings.
If the crank pins were made longer, so as to allow of sufficiently wide floats
working between the sides of the cranks, then the width of the paddle boxes
would be inconveniently great, and the machinery itself would be less firm
and compact.
8. The number of floats on each connecting rod will usually be three.
Now admitting what has been already stated, namely, that at the middle of
each float-bearing rod a wide float is to be mounted, it will be readily under-
stood that the other and narrower floats, whatever may be their number,
situate in line in front or behind, will only exert a relatively small power, all
the floats being submerged together, the total force obtained from the several
floats in front of the large float may be measured almost by the isolated power
exerted by such large float, because in turning "a-head" the front floats do
little more than follow the water, which is rapidly displaced in order to supply
the vacant space formed by the hind floats, and these only follow in the wake
produced by the large float. In reality the front floats produce a certain
effect, inasmuch as their speed is greater than that of the liquid which flows
before them; but it is more advisable only to calculate as submerged float
surface rather more than the surface of the middle float, that is to say, it is
better to arrange that this float be comparatively wide. One float only might
be used, but independently of the small supplementary effect due to the other
floats they reduce to a certain extent the strain upon the large float, which
ought to be made very strong. It is therefore sufficient to employ three floats-
on each rod, but this number nevertheless is by no means absolute, as in case
of using very long rods a greater number of floats may be usefully applied,
whereas in other cases one or two floats may suffice. In all cases it is
advisable that the distance between the floats shall be about equal to the
traverse of such floats through the water, or rather more than the length of
one of the connecting cranks.
.
9. The height of the floats should be equal to one and a half times the
difference between the cosine of the demi angle in the centre and the radius,
or one and a half times the difference between the apothem of the inscribed
polygon and the radius of the circle, of which the leading crank is the radius;

page_text: or one and a half times the rise of an are, of which the connecting crank is
the cord; or, lastly, taking the radius as a function,―
For an equilateral triangle
"
"
"
square
regular pentagon
"
"
hexagon
R x 0.75
R x 0.44
R x 0.29
R x 0.20
and so on.
Now supposing, in Figure 11, the position of the mechanism o, A, B, C,
be such that the two rods mounted on the crank pins A and B being on the
same horizontal plane aro partly enclosed by the cranks, the third rod C, K,
will be at the summit of its course, and admitting that at a certain distance
from the crank pins A, B, and C are fitted the floats m, n, o, of a height
equal to the length of the rise of the arc subtended by the connecting crank
A, B, or by the side A, B, of the equilateral triangle A, B, C. Supposing,
also, the surface of the water to be tangential to the circles described by the
crank pins, the movement of the propeller being from left to right, as shewn
by the arrows, it will be seen that the float m fixed to the rod A, I, is on the
point of being immersed, whilst the float n fixed to the rod B, J, is leaving
the water. The edge of each of these floats touches the water, but the float m
has not yet entered, and the float n will no longer enter the water; no effort
will therefore be produced, and the propeller will meet with no resistance.
If the mechanism be brought into the new position o, A, B, C, the float m
having travelled the half of its course in the water, will be found in the
position m', m³, and will be entirely immersed. At this period the propeller
will meet with its maximum resistance; hence an irregular action is pro-
duced in the apparatus varying from nil or minimum in the position o, A, B, C,
to the maximum resistance in the position o, A¹, B¹, C¹. It is true that,
considering the speed of revolution the periods of minimum and maximum
resistance are infinitely short, but they nevertheless exist, and must be taken
into consideration. In symetrically mounting on each side of a vessel a
propeller fitted with floats of the height of those before referred to this
irregularity of working will produce a very perceptible pitching motion which
will be alike injurious to the propeller itself and to the hull of the vessel.
By mounting on the contrary this propeller in opposite positions on each
side of the vessel so as to ensure that on one side a series of floats shall be
completely immersed, whilst on the other side the corresponding series of
floats shall be at the same time completely out of the water, a serpentine
movement will be produced which will develope a disagreeable rolling of the
vessel. I may here remark that in the previous case the effective course

page_text: m, n, of the float in the water is nearly equal to the length of the connecting
crank, and that this course increases in proportion as the height of the float
increases (Figure 12); it will therefore be necessary to give to the floats a
height greater than the rise of the arc subtended by the connecting crank, and
therefore it is preferred to make it equal to one and a half times this rise,
whereby the best results are obtained.
On reference to Figure 12, the mechanism being o, A, B, C, and the float
m, m, of a length equal to one and a half times the rise of the arc subtended
by the connecting crank A, B, touching the water, in this condition the
float n, n, mounted on the rod B, b, is still in active operation, and is immersed
to two-thirds of its height. If now the mechanism be brought into the
position o, A, B, C, the two rods A', a', and B1, 61, will be on the same
horizontal plane; the float m, m, being brought to m', m', has immersed
one-third its height in the water, and the float n, n, having arrived at the
position n', n', is also immersed one-third its height; total two-thirds. Lastly,
by bringing the propeller into the position o, A", B", C", the float m, m,
having arrived at m", m, is at the middle of its circular course m, K, and
will be entirely immersed; the same demonstration with regard to an equi-
lateral triangle applies equally to all regular inscribed polygons. Figure 12 bis
represents the same applied to a square or four cranks; the difference between
the maximum and minimum resistance is therefore only about one-third, and
this difference is not sufficiently marked to produce the least disturbance in
the proper working of the engine nor in the hull, especially if due care be
taken to mount the two propellers symetrically on each side of the boat.
It may further be remarked that with this height of floats the useful course
of each float in the water is relatively great, and approaches very nearly the
small diameter of the propeller; thus for a triangle this course is equal to
twenty-three twenty-fifths the diameter; for a square four-fifths the diameter;
for a pentagon, seven-tenths the diameter; and for a hexagon three-fifths the
diameter.
10. As regards the width of floats, this will vary according to the draught of
water, the power of the engines, and the speed to be attained, so as to produce
an equilibrium of resistance between the mid-ship frame and the immersed
float surface.
With regard to the application of the propeller to existing vessels or to
vessels specially built to receive it, I may observe that the improved propeller
may be applied to existing paddle-wheel boats without interfering with their
engines or altering any part except the propeller, whereby the speed will be
increased by one-fifth to one-fourth, and a proportionate economy of fuel effected.

page_text: In adopting the new propeller, I select as the radius of the propeller the
distance from the paddle shaft to the inner edges of the floats, or, in other
words, the internal radius of the paddle wheel, or which is a better rule still,
considering that the radius of the paddle wheels may have been badly selected
in the first instance, or the radial length of floats incorrect, I take as the
radius of the new propeller the vertical distance between the centre of the
crank shaft and the line of floatation when the ship is light; the result is that
when the shaft is laden the float-bearing rods will be immersed, which fact
will present no obstacle to the construction of the rods, as will be explained
herein-after, but will, on the other hand, permit of those portions of the floats
contained within the mounts or fittings of such rods to have a useful effect.
Supposing the interior diameter of the paddle wheels to have been well
chosen, and that this diameter has been fixed upon as the diameter of the new
propeller, bearing in mind also, on the other hand, that the mean radius of the
paddle wheel is that which is taken when calculating the mean speed of the
floats, and for comparing this speed with the linear speed of the ship, it follows
that the radius of the improved propeller will be rather smaller than the mean
radius of the original paddle wheel, and that, if the relation between the mean
circumferential speed of the floats and the linear speed of the ship were the
same for the improved propeller as for the paddle wheel in question, an
increased speed of revolution will be required to produce the same speed in the
ship. But it must not be forgotten that the force exerted by the floats of the
improved propeller being infinitely more efficacious than the ordinary floats,
since those do not strictly speaking work with full effect excepting during the
instant they are in a vertical position, whilst the vertical position of the
improved arrangement of floats is their normal condition, the speed of the ship
will be greatly increased up to the point where it will be very nearly equal to
the circumferential speed of the propeller. It is evident, on the other hand,
that the inner motive power expended in a proper manner will tend to impart
increased speed to the ship. The arrangement of the improved propeller
permits of a higher rotatory speed being imparted to it, with an equal radius,
if too high a speed be imparted to an ordinary paddle wheel, the water is not
renewed sufficiently fast in front of the floats; these do not become fairly
immersed, and the coefficient of relative speed is considerably diminished,
whilst at the same time the loss of power increases in the same proportion;
the improved propeller, on the contrary, acts upon the water in 3, 4, 5, or
more parallel and distinct lines, and acts always on comparatively dead water,
and even whilst working at double the ordinary speed imparts a uniform
movement to the ship.-

page_text: It is not intended to be meant by this that it is better to gain speed by
increasing the number of revolutions of the propeller than by the developement
of the circumference; it is the opposite which is the truth, but in certain cases
and to a certain extent (provided that the mean speed of the pistons of, say,
four feet per second be not exceeded) there need be no fear as regards the
speed of the engines, which permits of the use of smaller and less ponderous
engines, propellers, and paddle boxes. On the whole the same applies to the
radius of the improved propeller as to the radius of a paddle wheel; this radius
is governed by various circumstances, and what in practice holds good with
regard to the one is equally applicable to the other, bearing in mind, as I
before stated, that the radius of the improved propeller should be shorter
than the paddle wheel by the amount of the height of the floats thereon, or
generally by one-third or one-fourth of the radius of the paddle wheels of
river steamboats, and by a still larger amount for sea-going steam ships.
This relative diminution of the radius enables, as I have already stated, the
height of the paddle boxes for a correspondingly sized paddle wheel to be
reduced by the radial height of one of the floats of such wheel.
The radius of the improved propeller having been determined, the height of
the floats should next be decided upon, the number of float-bearing rods to be
employed depending upon this height.
The height of the floats depends upon the draught of the ship; for flat-
bottomed ships the tops of floats should not in their evolutions pass beyond
the water line, on the contrary they should lie a little above this line; for a keel
ship the margin is greater, but there are nevertheless certain heights of floats
which should not be exceeded, and therefore I prefer to restrict the height of
the largest floats to from four to five feet. The height of the floats having been
approximately fixed it will be necessary to consider to what particular arrange-
ment of cranks or polygonal mechanism this height corresponds, which is
easily effected, since it is simply necessary to divide the given - height of
float by the radius adopted, and to compare the quotient with the numbers
herein-before given under rule 9; opposite the number which approaches
nearest to the said quotient will be found the particular form of polygon
to be adopted, and consequently the number of float-bearing rods to be
employed.
As an example supposing the radius of the propeller decided upon is 1m 50
and 0 65 is the height of the float, the quotient of 0.65 by 1.50=0.4333;
this number (see rule 9) approximates very nearly to 0.44 wbich corresponds
to a square, therefore four float-bearing rods will be required. Again take a

page_text: radius of 30 Eeight of float decided upon 090 = 0.30; this
corresponds to a pentagon. Again say R 1 20 height of float 0:90
0.90
1.20
=0 75 which corresponds to a triangle. In most cases it will be found
that by preference either a triangle or a square will be adopted.
The other rules herein-before given are equally simple in their application
with that of rule 9. I may, however, repeat that the results arrived at by
these rules are not strictly absolute, and that they may be slightly modified as
circumstances may require without diminishing the advantages obtained; this
should not however be taken as applying to the rules with reference to tho
length of the connecting cranks and to the angles at which they are mounted;
these rules are immutable.
I recommend moreover that no great variation be made from any of the
data given above, and that the floats be made, if anything, rather higher but
never lower than the proportions given.
In order to facilitate the carrying out of the said Invention I will now
proceed to give an example of the application of the rules herein-before
mentioned. In the case, say, of adapting the improved propeller to a steam
boat in substitution for the ordinary paddle wheels, suppose the paddle wheels
to be 5 in external diameter (say 16 feet), provided with floats 0 60 (say
2 feet) in radial height and of a length of 2m (6 feet 6 inches), also that these
wheels revolve at a height of 0 30 above the water line, and that the light
draught of water of the ship is 0.90, the width of the midship frame being
given at, say, 450, the midship section will be 0m 90 x 4" 50=4.05 square
metres, and the immersed float surface of the paddle wheels 0 60 x
2×2 2 40 square metres. The interior diameter of the paddle wheels
being 5-120-380 the internal radius of the wheel 190 will be the radius
of the improved propeller, and without passing the water line a height of
0 85 may be given to the floats of the new propeller. From these data the
number of float-bearing rods may be arrived at by the aid of the rule 9 herein-
before referred to, thus 85. =0.44 about, which number indicates that the
arrangement of cranks to be adopted is that of a square, and consequently four
float-bearing rods will be required. The length of the connecting crank of
this mechanism will be R x 1412, that is to say, the radius 1" 90x1™ 412=
.2m 683.
1.90
The length of the float-bearing, rods is 2m 683 +2 683 = 5 37 +.0° 50
about, for the reception of the middle float with its mountings:
5 37, or,
say in round numbers, 6 0. There will be three floats on each rod.

page_text: 0
67+ the necessary
about. The height
30 above the deck,
The course of the floats in the water will be about 3m 0, the total length of
the float-bearing rod being 6" 0, the distance between each of the three floats
will be about 275, the width of the middle float in order to obtain the same
amount of immersed surface, as in the paddle wheel, should be 1" 40, without
counting as immersed surface more than the surface of this float only, and
110 when causing the surfaces of the supplementary floats to enter to the
extent of one-fourth the surface of the principal float, the total length of
the paddle box will be 5m 87 +1 90 + 1m 90 = 9
clearance for the free working of the cranks, or, say, 10m
of the paddle box, supposing the axis of rotation be 0
will be 1 90+ 0.30 = 2.20 +0.80 about, for thickness of material and for
clearance in working, or 2 50 about. It will thus be seen that the paddle
box will be longer but not so high as when intended for the paddle wheels,
yet this length may be reduced as well as the height of the floats by selecting,
as the polygonal arrangement of cranks, either a pentagon or hexagon, in lieu
of a square, and by following the rules which apply to such forms. As regards
the width of the paddle boxes it does not follow that the internal width should
be equal to as many times the width of the main float as there are float-
bearing rods, as these floats may be made to overlap each other considerably,
as shewn clearly in Figures 4, 5, 14, and 15, and therefore the width will
not generally exceed that required for equivalent paddle wheels, for example;
in the present case, applicable to a fast river steamer of from one hundred
and twenty to one hundred and fifty horse-power, with paddle box, will not be
wider than 2 75, say 9 ft.
In the case of adapting the new propeller to a screw steamer the alterations
will be more extensive, for independently of the change of position of the
propeller shaft, and the alteration in the mode of applying the power, it will
frequently be necessary to change the position of the engines, or to substitute
others, it is necessary therefore to compare this case with the following.
The application of the improved propeller to ships to be built presents no
difficulty, and is based on the rules herein-before laid down, the radius of the
propeller and height of float having been first determined. The selection of
the radius is naturally of the greatest importance, for on it depends the
speed of the propeller and of the ship, and consequently the speed of the
engines and the consumption of fuel. In order to obtain a high speed of
revolution it is necessary to have comparatively short cylinders, and in this
case the cylinders requiring to be more often renewed, and the expansion
being less advantageously used than in the case of long cylinders the

page_text: consumption of fuel is increased. It will therefore be economical to employ
propellers of large radius, pistons of long stroke, and a relatively low speed
of revolution. On the other hand it cannot be denied that a large radius
of propeller involves the use of long connecting cranks and float-bearing rods,
also a larger number of these rods, and hence increased space, weight, friction,
and other objections are entailed, which must be obviated in order to secure
strength and steadiness in the machinery. There exists therefore a medium
course which will result in speed combined with relative economy of fuel,
and solidity and lightness combined with compactness. In general it will
be advisable never to exceed a radius of 2 0 (say, 6 ft. 6 in.); as regards
the engines 100 to 120 strokes per minute will be sufficient. The circum-
ferential course travelled by the pin of the leading crank of 2 0 radius, and
making 60 revolutions per minute, will be equal to nearly 28 statute miles
per hour, which, after making the necessary deductions, gives a speed of
headway never before attained. If, without regard to great economy in
working, it is desired to construct a steam vessel specially adapted for
exceptional speed such as a mail packet, for example, then the radius of
the propeller may be reduced and the speed of working increased; this
reduction of the radius will be rendered necessary in such a case in order to
secure the stability of the mechanism. From what has been already stated
it will be seen that in most cases where new ships are built the main shaft
or axis of rotation of the improved propeller will be placed rather lower than
the same shaft if intended for ordinary paddle wheels, and that the engines
will be worked at a higher speed than is usual with paddle-wheel engines.
It will also be seen that the improved propeller is applicable both to ocean
and inland navigation, and may be disposed in duplicate on each side of and
beyond the hull, or continued more or less within the sides of the vessel, or
it may be situate amidships or towards the bows or stern, or be employed
singly in the longitudinal axis of the vessel after the manner of the paddle
wheel of American steam boats, or near the bows or stern.
Another mode of applying the improved propeller which will be well
adapted for sea-going vessels if the draught of water be not too great, consists
in mounting it in a well situate in the longitudinal axis of the vessel, and near
the middle thereof; this well should be of rectangular form with vertical sides
inclosing the propelling mechanism; the height of the propeller shaft and
the radius adopted should be so arranged that the crank pins in revolving
shall pass tangentially to the horizontal plane of the keel. By this arrange-
ment the floats will be entirely submerged beneath the keel line, and will

page_text: produce as powerful an effect as though they were placed at the sides. The
arrangement of floats or paddles working below the keel will not be dangerous
in deep water; it is, however, indispensable when using a well, since if the
propelling effect were exerted within the well, the water agitated and thrown
against the sides of the well by the action of the floats would not be able to
escape freely, hence an immense loss of power would result. Thus situate
and protected on the "larboard" and "starboard," and in front and "astern
by the hull itself of the ship, the improved propeller would be better guarded
than the screw from accidents of all kinds, and especially from those resulting
from pitching or heaving, and from cannon shot.
"
I shall now proceed to make a few observations on the principal arrange-
ments, and the materials to be employed in constructing the improved propeller.
As this propeller requires a paddle box of more than ordinary length, and as
certain parts of the mechanism are out of perpendicular with the bearings,
there is a tendency to vibration. It is therefore necessary that the parts be
all very strong, constructed of the best iron, and put together with the greatest
care. The sustaining axes should pass completely through the vessel. The
cranks should have ribs or webs forge ou their faces in order to stiffen them.
The joints and couplings of the float-bearing rods and also the crank pins
should be case hardened, or subjected to the process of cementation, for the
purpose of rendering such parts more durable; these joints will not require
oil cups as the water itself will be a sufficient lubricant. The keys should all
be secured by other keys driven through them transversely. The float-bearing
rods should by preference be composed each of two wrought-iron plates or
bars secured at suitable intervals by distance pieces or stays interposed
between them. The floats, which may be made of wood or sheet metal, but
by preference of metal, should be arranged so as to slide in frames or supports
securely rivetted to the two plates or bars composing the connecting rods.
By causing the floats to slide in their frames the amount of immersed surface
may be varied or adjusted as may be found requisite. When four or more.
float-bearing rods are used it will be advisable for the sake of stability to
employ an intermediate longitudinal support in the centre of the paddle box
with intermediate bearings, as shewn in Figure 14.
These observations apply more particularly when the propeller is adapted to
the outsides of a vessel as in a paddle wheel steamer, but when it is applie:1
on the longitudinal axis or more or less enclosed within the sides of the ship,
the question of solidity and stability will be more simplified. Further comment
o the details of construction is unnecessary; the description herein-before

page_text: given will enable the practical engineer to apply the improved propeller in any
case which may present itself.
Figures 13, 14, and 15 represent in elevation, plan, and section a propeller
having a radius of 1 50 or about five feet, provided with four float-bearing
rods, and intermediate bearings applicable to a river steamer of one hundred
and twenty horse-power, and drawing at light draught from 2' 6" inches to
2' 8" inches of water.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried
into effect, I would observe in conclusion that what I consider to be novel and
original, and therefore claim as the Invention secured to me by the herein-
before in part recited Letters Patent is, the peculiar construction and
arrangement of propellers for steamboats and vessels of all sizes, and the
modes of applying the same, substantially in the manner herein-before
described and illustrated by the Drawings hereunto annexed.
In witness whereof, I, the said John Henry Johnson, have to this my
Specification set my hand and seal, the Seventh day of February,
One thousand eight hundred and sixty-seven.
J. HENRY JOHNSON. (L.S.)