Improved Instrument for Measuring the Pitch of Screw Propellers.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improved Instrument for Measuring the Pitch of Screw Propellers.
JAMES WILLIAM PETERSON, Engineer, Granton Square, Edinburgh, JAMES
SUTHERLAND, Engineer, Richmond Villa, Edinburgh, do hereby declare the nature.
of this invention to be as follows:-
The invention relates to the measuring of pitches or angles of screw propeller
blades and arriving at the true result without calculation. The instrument con-
sists of two arms or bars, the one being twelve inches and the other eighteen
inches or thereby in length, placed accurately at ninety degrees the one to the
other, the longer arm being free to work up and down in a slot in the shorter
and capable of being held fast by a set pin at any desired position.
On the sliding bar is marked the pitch in feet and inches also their relative
diameters.
arm,
In applying this instrument the shorter arm is placed so that it lies parallel
to the face of the propeller boss, the end of the arm being allowed to rest on the
blade, then by releasing the set screw the longer or graduated arm drops down
until the end of it touches the blade, then after tightening the set screw, the
instrument may be 'removed and the reading from the end of the graduated to the
under side of the shorter arm is the pitch of the blade at the point where
the instrument was applied.
Dated this 16th da
1000
JAMES W. PETERSON,
JAMES
SUTHERLAND.
COMPLETE SPECIFICATION.
Improved Instrument for Measuring the Pitch of Screw Propellers.
JAMES WILLIAM PETERSON, Engineer, Granton Square, Edinburgh; and JAMES
SUTHERLAND, Richmond Villa, Edinburgh, also 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:-
:—
This invention relates to the measuring of angles or pitches of screw propeller
blades and arriving at the true result without calculation.
Fig. 1 of the accompanying drawings shews the instrument in elevation.
Fig. 2 shews the instrument applied to a propeller blade, the blade being in
sectional elevation.

page_text: Fig. 3, shews the instrument and propeller blade in plan according to our in-
vention.
A is the vertical arm or bar.
B is the horizontal arm or bar, having a slotted boss at one end through which
the arm or bar A freely moves at right angles to arm or bar B.
C is a set screw for binding the two arms or bars of this instrument together.
D is a section of propeller blade.
E is the propeller boss or centre.
F is a plan of propeller blade.
G is a plan of propeller boss or centre.
Hare arcs drawn from centre of the boss of propeller.
On arm or bar A is graduated the angle or pitch in feet and proportions thereof,
also their relative diameters. In applying this instrument to find the angle or
pitch of a propeller blade it is necessary to draw an arc or arcs H across the blade
at any desired distance from the centre of the boss. Then arm or bar B is placed
so that it lies parallel to the boss or centre E the end of which touches the blade
on are H, then by releasing set screw C the arm or bar A is allowed to drop until
the end of it also touches the blade on arc H. The set screw C is then tightened
and the instrument removed. The angle or pitch is then taken by noting the
diameter of are H at which the instrument was applied. Then by referring to
the corresponding diameter on the graduated arm or bar A the reading from end
of graduated arm or bar A to underside of horizontal arm or bar B is the pitch
or angle of the blade at that particular diameter.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, we declare that what
we claim is :-
:-
Instrument composed of two arms or bars for measuring the pitches or angles
of screw propellers.