An Improved Double Slide Rule for Calculating Displacement, Register Tonnage, Indicated Horse Power, and Speed of Ships.
Year: 1894

page_text: Date of Application, 22nd May, 1894
Complete Specification Left, 21st Feb., 1895-Accepted. 18th May, 1895
An
PROVISIONAL SPECIFICATION.
An Improved Double Slide Rule for Calculating Displacement,
Register Tonnage, Indicated Horse Power, and Speed of Ships.
THOMAS HENRY WATSON 10 Neville Street, Newcastle upon Tyne, Naval
Architect. I do hereby declare the nature of this invention to be as follows:-
n.easy and quick method of calculating on a double slide rule the displacement
and register tonnage of ships from the principal dimensions and “coefficient of
fineness," also the indicated horse power and speed from the displacement and a
suitable "constant.' The rule to be made of wood, or some other suitable material,
and consisting of two moveable slides worked in separate grooves. One slide used
for register tonnage and displacement and the other for indicated horse power and
speed.
"
1007

page_text: .
1000 feet and on the same slide at the right hand end is the number of tons. On
the lower part of the side, i.e., A₁ of fixed piece A Ai are the coefficients of
fineness. Those for displacement tonnage are placed at the right hand side of the
mark which mark is placed about midway in the length of the rule, and those
coefficients for tonnage at the left hand side of the same mark.
For finding the displacement in tons of a ship having the length, beam, draft of
water and coefficient of fineness. The "length" of the vessel is found on the
slide B and is placed directly opposite to the "beam" of the vessel which is found
on the fixed part A and the figure on the slide B opposite the "depth" of the
vessel, which stands for draft of water, is moved back to the mark ↑ on the fixed
part A, then the displacement in tons on the slide B which stands opposite to the
suitable "coefficient for displacement" is the displacement in tons of the vessel, or
the displacement on the slide B gives the coefficient of displacement of the vessel
on the fixed part A₁.
To find the register tonnage the "length" of the vessel is found on the slide B
and is placed opposite to the "beam" of the vessel which is found on the fixed
part A and the figure on the slide B opposite to the "depth" of the vessel on the
fixed part A which must be depth of the hold in this case, is moved to the mark ↑
on the fixed part A, then the register tonnage is that which stands on the left hand
side of the mark ↑ on the fixed part A, opposite to a suitable "coefficient for
tonnage." The coefficient for under deck tonnage will be different to that for the
gross tonnage, but no further movement is required, the respective tonnages being
read opposite their suitable coefficients. Also 13% and 32% of the gross tonnage
may be found at the same time, the points of 13 % and 32 % being marked on the
fixed part A, and the tonnage being that on the slide B standing opposite to the
percentages.
To find the equipped weight of a vessel the "length" of the vessel is found on
the slide B and placed opposite to the "beam" of the vessel which is found on the
fixed part A and the figure on the slide B opposite to the "depth" of the vessel on
the fixed part A which must be " depth" moulded in this case, is moved to the
mark on the fixed part A, then the equipped weight of the vessel is that which is
directly opposite on the slide B to a suitable coefficient on the fixed part A, on the
left hand side of the mark t..
Fig. 2, is a full sized sketch of the speed scale on the opposite side of the rule to
that given in Fig. 1. shewing a separate slide D working in the other side of the
fixed part of the rule and marked A, and Ag.
"
The speed in knots from 5 to 22 is set off along the fixed part marked A,.
The indicated horse power is set off along the upper part of the slide D from
100 to 24000 horse power. The displacement in tons from 10 to 13000 is set off
along the lower part of the slide D. The " constants are set off on the fixed
part A, from 100 to 400. To find the indicated horse power necessary to drive a
ship at a certain speed or the speed which a fixed indicated horse power would give,
place the displacement in tons of the vessel to be found on the slide D opposite a
suitable constant on the fixed part A, and read off on the upper part of the slide D
opposite the arranged speed which is on the fixed part A, the indicated horse power
necessary, or read off on the fixed part A, the speed which a fixed indicated horse
power would give by noting what speed on a fixed part A, stands opposite to your
indicated horse power.
Fig. 3 is a cross section through rule at C. E of Fig. 1 and 2.
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
*7

page_text: Secondly. The rule working up to large tonnages and indicated horse power and
speed.
Dated this 10th of Fabmiar 1905
THOMAS H. WATSON,
Applicant.