AN IMPROVED APPARATUS FOR PROPELLING SMALL CRAFT
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Joseph Bohanna, junior, at the Office
of the Commissioners of Patents on the 18th May 1880.
JOSEPH BOHANNA, junior, of Manchester, in the County of Lancaster, Clerk,
"AN IMPROVED APPARATUS FOR PROPELLING SMALL CRAFT."
My said Invention consists of improved means for the propulsion of rowing
boats, skiffs, and other small craft propelled manually by means of oars, sculls, or
sweeps. Under the present system the distance between the oarsman's hand and
the rowlock is considerably less than from the rowlock to the effective portion of
the oar blade. The oar is thus practically a lever, the shorter and less powerful
end of which is grasped by the operator. By means of my Invention I propose
to overcome this disadvantageous leverage by the employment of intermediate
apparatus, which will permit the oarsman to operate the sculls under more
favourable and less fatiguing conditions, while at the same time increasing the
speed of the boat. In pursuance of this object I pivot an oar blade or scull upon
a bracket projecting from each side of the boat, and preferably in advance of the
seat. An arm or outrigger is also secured to the sides in the ordinary position, and
at the end of each arm or outrigger is a pivot or fulcrum upon which is centred a
lever, which takes the place of the ordinary oar and is grasped by the occupant of
the boat. This lever is prolonged sufficiently past the pivot to engage with and
operate another lever centred at some distance back on the arm or outrigger.
By observing a due proportion between the distance from the oarsman's hand to
the fulcrum, as compared with the distance from the fulcrum to the outer end of
the lever, greatly increased power may be exercised and transmitted to the sculls.
The bereinbefore referred to secondary lever is provided at its inner end with a
toothed segment, which gears with a similar segment on a lever centred still
further back on the outrigger, so that when the first referred to primary lever is
moved to and fro the two secondary levers are oscillated horizontally in opposite
directions to each other. A rod extends from the inner secondary lever to a
rocking arm centred on the side of the boat, and another rod extends from thence
to the inner end of the pivotted scull, which is thus caused to move backwards and
forwards. The scull or paddle is attached to its pivot by a rod upon which it is
free to swivel, so as to execute a feathering motion on the back stroke, and this rod
being prolonged rides during the sculling stroke upon a cam fixed to the boat side,
and so shaped as to cant the scull downwards, causing it to dip into and remain

page_text: under the surface of the water. At the end of the stroke a spring fixed to the
bracket draws down the prolonged end of the scull axial rod and causes it to pass
beneath the cam, thus raising the blade above the water, while at the same time
the forward pressure of the herein before referred to connecting rods turns the scull
on its axial rod so as to feather it. On arriving at the end of the back stroke the
rod passes from under and releases a spring piece, which trips the rod and causes
it again to mount the cam and dip the paddle vertically into the water ready for
the forward sculling stroke. The different parts of the apparatus may be made
adjustable, and in lieu of the toothed segments, knuckle, or other suitable joints
may be used to connect the levers on the outriggers. Stops may be arranged to
limit the stroke if desired, and the whole apparatus may be mounted so as to be
easily removable in case it should be wished to employ the ordinary oars or
sculls.
Although I have described the foregoing apparatus as applicable chiefly to the
propulsion of small craft, it will readily be understood that it could also be used as
a propellor for a larger class of vessel, in which case it might be operated by steam
power.