Environmental Engineering Reference
In-Depth Information
7.3 (a) Large vertical capstan powered by workers pulling a
gold wire through a die. (b) Great wheel used to turn a metal-
working lathe. From Diderot and D'Alembert (1751-1772).
made it possible to choose many gear ratios, and the mo-
mentum of a large flywheel smoothed the variation of
human muscle power that was used to turn it and made
it easier to maintain even revolutions during spells of
higher or lower power need. Powering the wheel was a
hard task when machining hard metals. In 1813, when
George Stephenson's workers operated a great wheel
while making parts for his first steam locomotive, they
had to rest every five minutes (Burstall 1968).
Treadwheels provide more power than windlasses or
capstans, and efficient transmission of their rotation via
gearwheels brought a wide variety of final uses (fig. 7.4).
The similarity of action with cycling, the most efficient
form of human locomotion, is obvious as powerful leg,
abdominal, and back muscles, supported by stationary
arms, do nearly all the work. Landels (1980) described a
well-designed treadwheel as a highly efficient mechanical
device and, given the monotony of the work, one of the
most comfortable for the operator (many of whom were
prisoners, often treading, side by side, a long cylindrical
wheel). Internal vertical treadwheels were used widely
in water pumping (fig. 7.4), and in preindustrial Europe
they also powered large construction and dock cranes.
Pieter Bruegel the Elder's painting of the Tower of Babel
(1563) depicts a crane powered by six to eight men to lift
large stones (Klein 1978). The same work was needed
for one of the last treadwheel cranes (4.8 m diameter
and 2.7 m wide) that operated on London docks during
the nineteenth century.
Much less common, external vertical wheels maxi-
mized torque (when treading was on a level with the
axle) and made it easy to adjust the pull on the hoisting
ropes of cranes simply by shifting the operator's position
higher on the wheel. Horizontal treadwheels were fairly
popular in Europe, and inclined treadwheels were also
in use (fig. 7.4). Drumlike devices could be rolled on
