Civil Engineering Reference
In-Depth Information
h is objection is augmented by the fact that the
dikōlos
crane must be stayed
by securely i xed guy roping. Here Taylor makes the reasonable observation that
such guy ropes must be continued down to the ground for secure attachment, and
as a result can be ca 100 m long. h e upshot of this is that although the use of
two legger cranes may have been quite in order for building at ground level, they
do not appear suitable for use at the higher levels of construction. h is is testii ed
to by Taylor's i ne drawings of the cranes at work: his i g 82 showing the cranes
at work on the ground is convincing, his i g 96 showing the cranes installed at the
uppermost level of construction appears improbable. Moreover because of the grand
dimensions of the Colosseum cranes would require a long jib (Taylor mentions
20 m) and a two legged crane with such a jib would be a massive contraption to
rig up in a cramped, insecure location. h ere is also a further consideration here.
h e speed with which the Colosseum was built would only be achieved by mul-
tiple simultaneous operations. Now since in most operations more than one crane
was required to work conjointly, then the total number of these cranes required
on the job must have been very considerable indeed. All this suggests that other
arrangements were made for setting the ashlar masonry at higher levels. h is, in
fact, was the use of what is referred to in the ancient mechanical treatises as the
tetrakōlos
.
It has been noted that the term
tetrakōlos
in the literal sense signii es the
square / rectangular tower scaf olding built up around an isolated structure (v
supra
,
pp. 80, 81); and in this sense it would apply to arrangements for hoisting into
position the monolithic columns forming the colonnade around the uppermost
level of seating, nearly 50 m above pavement level. On the other hand the term can
well apply to any run of independent standing scaf olding since such scaf olding
is composed of successive units formed by four uprights. In this fashion it could
apply to the arrangements made for setting the masonry of the ashlar walls. If the
“access” scaf olding to the wall faces were made robust, it could also serve as the
frame for hoisting blocks into position with the pulley block units mounted on
the horizontal timbers at the top of the scaf olding. Horizontal motion is af orded
by several pulley blocks installed at dif erent positions, so that the resultant of
their dif erential activation can position the load as desired (v
supra
, pp. 81, 82).
If necessary where a heavy block is to be hoisted, the scaf olding can be reinforced
by adding members.
When the walling is carried up to the rooi ng level the robust scaf olding can
stand as the basis for the centering and shuttering of the vaulted roof. When this
vaulting has become competent, the supporting scaf olding can be dismantled and
erected on the l oor of the next higher level. h e scaf olding against the external
wall face of the monument, of course, must rise uninterruptedly from pavement
level, a formidable construction. Such a process requires ingenious adjustment but
h e Col-
osseum
400
