Page 392 - (DK) The Ultimate Visual Dictionary 2nd Ed.

SEA AND AIR
Paddle wheels and propellers

THE INVENTION OF THE STEAM ENGINE IN THE 18TH CENTURY made mechanically driven ships fitted with
paddle wheels or propellers a viable alternative to sails. Paddle wheels have fixed or feathered floats, and the
model shown below features both types. Feathered floats give more propulsive power than fixed floats because
they are almost upright at all times in the water. Paddle wheels were superseded by the propeller on oceangoing
vessels in the mid-19th century. Propellers are more efficient, work better in rough water,
SHIP’S WHEEL and are less vulnerable in collisions. The first propellers were two-bladed but later three-
and four-bladed versions are more powerful; the shape and pitch of blades have also been
King spoke
handle refined over the years. At the beginning of the 18th century, tillers were superseded on
many larger ships by the ship’s wheel as a means of steering.
Handle PADDLE WHEEL
WITH FIXED FLOATS
Spoke Slip eccentric
for slide valve
Rim plate OSCILLATING
Wrist pin STEAM ENGINE Ahead/astern
controls
Felloe
(rim section) Limb Slide valve
Main crank
Maker’s name
Fixed float
Nave plate
Hub
Nave
Deck
beam

THREE-BLADED PROPELLER

Blade

Tapered
shaft
hole
Hub

Strut
Frame
Piston rod (tail rod)
Stuffing box

Keyway Oscillating cylinder
Pitch
Propeller blade Bottom plate
tip trace (bedplate)
Propeller
Blade diameter
Slide valve rod
PROPELLER
ACTION Control
Propeller hub trace platform
Hub

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