Civil Engineering Reference
In-Depth Information
about horizontally to permit delivery over an area as with the monokōlos. h is
could only be arranged by setting the
dikōlos
on a swivel base, of which there is
neither mention nor depiction. h e
dikōlos
could be constructed more strongly
and on a larger scale than the
monokōlos
and would have been suitable for raising
up heavy blocks to a considerable height for constructing walls. h e blocks could
be set down at one point of the wall under construction and levered along the
subsisting utter bed joint into the required position. h e
dikōlos
would also have
been ef ective in setting columns, including monolithic columns, cf the representa-
tion of this on the relief showing the funerary monument of the Haterii.
h e
monokōlos
and the
dikōlos
are the ancestors of modern cranes, but the evo-
lution into modern cranes which can pick up heavy loads from anywhere within
an extended area and deliver them at great height anywhere else within that area
was tardy and uneven. It was in Late Mediaeval and Early Renaissance times that
rigs were designed to incorporate lateral displacement of a load over an area, and
even to incorporate some mobility (on rails) of the “crane” itself. In this connection
notable contributions were made by Brunelleschi and Leonardo. However such
lit ing devices did not become standard until the Industrial Revolution (cf S. de
Pascale,
Leonardo da Vinci, Engineer and Architect
, Montreal ), 1987, pp. 163-181;
B. Gille, in C. Singer,
A History of Technology
, Vol. 2, pp. 639-661.
h e second group of Hero's devices, the
trikōlos
and the
tetrakōlos
dif er from the
i rst in that their rigging does not depend on guy ropes for its stability. h e wooden
structure is stable in itself. h e
trikōlos
(tripod) is the simplest construction rising
to a height which is inherently stable, and has always been used to mount an object
or attachment (e.g. a pulley) at some height above the ground. h ree long uprights
(legs) are jointed at the summit so that each leg can be moved independently. In
this way by lateral adjustment of the feet it is simple to bring the summit exactly
over any point on the ground. h e limitation of the tripod is that it incorporates
no possibility for horizontal displacement of the load raised up. h us suspended
loads can only be displaced to a limited degree by hauling them aside with another
rope (or tackle). However here it may be added that once upon a time on Middle
East reconstruction sites it was not unknown for experienced operators to “walk”
the tripod with its suspended load a short distance. h e advantage of the tripod is
convient storage and instant erection, together with its strength and stability. On
the other hand although its legs can be of considerable length (e.g. 10 m-12 m), its
working height when mounted is much reduced (e.g. 5 m). In traditional Middle
Eastern restoration work, tripods were used notably for work on smaller columns,
e.g. taking them down and setting them up.
h e term
tetrakōlos
probably can also bear an extended meaning. In the literal
sense it is a parallel to the tripod—a wooden tower of four uprights framed with
horizontals at the top and cross braced for stability at the top and on 2 or 3 sides.
Pulley
rigs
