DOI Page / Citation link:
https://doi.org/10.11588/diglit.33567#0036
8
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dimensions of the obelisk varying considerably from those given in books, which did not agree; and that it may
have some value for other uses after the obelisk had been erected.
The accompanying drawings (Plates ii and iii) present a front- and a side-view of the structure. The
first shows the obelisk clasped at its centre of gravity in a pair of trunnions ; these rest on steel towers having
masonry foundations. The towers are formed of I beams held in position by screw bolts through angle plates,
flat plates, angle and channel bars. The horizontal steel beams forming the bottom of the structure rest on
wooden beams which lie on the top of the masonry foundations. The wooden beams were designed for
increasing or diminishing the height of the towers to correspond with that of the centre of gravity, which could
not be determined until accurate measurements had been made of the obelisk. The heaviest pieces of the
turning structure are the trunnions ; each one weighs twelve thousand five hundred and seventy pounds ; next
to these are the pillow-blocks, each weighing three thousand seven hundred pounds ; the head-pieces weigh
seventeen hundred and fifty pounds each; and the beams vary from thirteen hundred and sixty to eleven hun-
dred and ninety pounds each.
The device for lifting the obelisk clear of the pedestal and transferring its weight to the turning structure
was a system of screws and turn-buckles. Tie-rods connected the lower edges of the trunnion-plates with
beams under the bottom of the obelisk. Each tie-rod was in two sections, and on each end of each section
there was cut a screw. The two sections were connected by a turn-buckle, and the upper and lower ends of
the rods were held in position through the trunnion-plates and heel-beams by large nuts. As there were four
tie-rods on each side the system comprised thirty-two screws, each with a diameter of three inches, which
were capable of lifting at least double the weight of the obelisk with a large factor of safety.
To prevent the obelisk from slipping through the trunnions after it was horizontal, lips were cast on the
inside vertical edges of the trunnions, to carry heavy iron plates ; these were held in position by three steel
bolts on each side, passing from one trunnion to the other, which also served as additional support.
The trunnions were further held in position by three iron bolts on each side, making twelve in all.
These bolts were not tightened until the obelisk had been lifted clear of its supports and high enough
to allow the heel to swing clear of the pedestal when turning, as it was necessary, in order to lift it, that
it should pass freely through the trunnions.
Although the section of the obelisk through the centre of gravity was found by computation to be strong
enough to support the weight of the ends, with additions of twenty-eight tons suspended at the centre of gravity
of each end, it was determined not to take any risk, in view of the length of time the syenite had been
exposed to atmospheric influences and the possibility of deterioration. The simple device of trussing the ends
of the shaft with steel cables was adopted as being most effective. Thirty tons of the weight of each section
was in this manner transferred to the point of suspension. The truss and verticals are shown on Plate iii.
For lowering the obelisk to the ground after it was horizontal two plans were devised, and. the selection
left to circumstances. One was by means of an inclined plane, the other by means of hydraulic pumps placed
on stacks of timber built up under the ends. The inclined plane would have been adopted if the obelisk had
been transported overland to the port for embarkation ; but as this was not permitted, the plan adopted was
that shown on Plate iii. The hydraulic pumps were fitted with lowering valves, designed by Richard
Dudgeon, of New York, which permitted a descent so gradual that it could not be detected without measure-
ment. When the weight of the obelisk had been transferred from the turning structure to the stacks of tim-
ber, by lifting it with the hydraulic pumps clear of the pillow-blocks on which the trunnions rested, the turning
structure was removed and the descent effected by removing layers of timber alternately from the tops of the
stacks and under the pumps. The obelisk rested on the two top piles of each section while the hydraulic
pumps were being lowered by removing the timber from under them.
There remained only the land transport of the obelisk to provide for to complete my plans for its removal
from Alexandria. For this there were abundant precedents successfully applied in ancient and modern times.
Of these the most ingenious is the method devised by Count Carburi, who was employed under the name of
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dimensions of the obelisk varying considerably from those given in books, which did not agree; and that it may
have some value for other uses after the obelisk had been erected.
The accompanying drawings (Plates ii and iii) present a front- and a side-view of the structure. The
first shows the obelisk clasped at its centre of gravity in a pair of trunnions ; these rest on steel towers having
masonry foundations. The towers are formed of I beams held in position by screw bolts through angle plates,
flat plates, angle and channel bars. The horizontal steel beams forming the bottom of the structure rest on
wooden beams which lie on the top of the masonry foundations. The wooden beams were designed for
increasing or diminishing the height of the towers to correspond with that of the centre of gravity, which could
not be determined until accurate measurements had been made of the obelisk. The heaviest pieces of the
turning structure are the trunnions ; each one weighs twelve thousand five hundred and seventy pounds ; next
to these are the pillow-blocks, each weighing three thousand seven hundred pounds ; the head-pieces weigh
seventeen hundred and fifty pounds each; and the beams vary from thirteen hundred and sixty to eleven hun-
dred and ninety pounds each.
The device for lifting the obelisk clear of the pedestal and transferring its weight to the turning structure
was a system of screws and turn-buckles. Tie-rods connected the lower edges of the trunnion-plates with
beams under the bottom of the obelisk. Each tie-rod was in two sections, and on each end of each section
there was cut a screw. The two sections were connected by a turn-buckle, and the upper and lower ends of
the rods were held in position through the trunnion-plates and heel-beams by large nuts. As there were four
tie-rods on each side the system comprised thirty-two screws, each with a diameter of three inches, which
were capable of lifting at least double the weight of the obelisk with a large factor of safety.
To prevent the obelisk from slipping through the trunnions after it was horizontal, lips were cast on the
inside vertical edges of the trunnions, to carry heavy iron plates ; these were held in position by three steel
bolts on each side, passing from one trunnion to the other, which also served as additional support.
The trunnions were further held in position by three iron bolts on each side, making twelve in all.
These bolts were not tightened until the obelisk had been lifted clear of its supports and high enough
to allow the heel to swing clear of the pedestal when turning, as it was necessary, in order to lift it, that
it should pass freely through the trunnions.
Although the section of the obelisk through the centre of gravity was found by computation to be strong
enough to support the weight of the ends, with additions of twenty-eight tons suspended at the centre of gravity
of each end, it was determined not to take any risk, in view of the length of time the syenite had been
exposed to atmospheric influences and the possibility of deterioration. The simple device of trussing the ends
of the shaft with steel cables was adopted as being most effective. Thirty tons of the weight of each section
was in this manner transferred to the point of suspension. The truss and verticals are shown on Plate iii.
For lowering the obelisk to the ground after it was horizontal two plans were devised, and. the selection
left to circumstances. One was by means of an inclined plane, the other by means of hydraulic pumps placed
on stacks of timber built up under the ends. The inclined plane would have been adopted if the obelisk had
been transported overland to the port for embarkation ; but as this was not permitted, the plan adopted was
that shown on Plate iii. The hydraulic pumps were fitted with lowering valves, designed by Richard
Dudgeon, of New York, which permitted a descent so gradual that it could not be detected without measure-
ment. When the weight of the obelisk had been transferred from the turning structure to the stacks of tim-
ber, by lifting it with the hydraulic pumps clear of the pillow-blocks on which the trunnions rested, the turning
structure was removed and the descent effected by removing layers of timber alternately from the tops of the
stacks and under the pumps. The obelisk rested on the two top piles of each section while the hydraulic
pumps were being lowered by removing the timber from under them.
There remained only the land transport of the obelisk to provide for to complete my plans for its removal
from Alexandria. For this there were abundant precedents successfully applied in ancient and modern times.
Of these the most ingenious is the method devised by Count Carburi, who was employed under the name of