Scaf′fold.
1. (
Building.) A platform temporarily erected during the progress of a structure, for the support of workmen and material.
The ordinary bricklayer's scaffold consists of upright poles called
standards, supporting the horizontal poles which are lashed thereto and called
ledgers; these support the outer ends of the
putlogs, the other ends resting in holes in the wall.
The scaffold boards rest on the putlogs.
Square timber-scaffolding with a traveling-crane was introduced into
England at the building of Euston Station of the
Northwestern Railway.
London, and subsequently was used at the raising of the
Nelson Column, Trafalgar Square,
London, and the new Houses of Parliament,
Westminster.
See over-head-crane; traveling-crane.
The square timber-scaffolding was, however, used on the
Cologne Cathedral from the commencement of its building, A. D. 1248, and probably will be for several hundred years to come on the same structure, in the rebuilding and extension which seem to be progressing simultaneously.
A precedent for the
Nelson Column erection is found in the more complex and difficult work of raising the
Egyptian Obelisk in the Plaza of
St. Peter's at
Rome, by Domenic Fontano, A. D. 1586.
The Arc de l'etoile and the
Eglise de la Madeleine are triumphs of the first
Napoleon.
on which the same style of scaffolding was used.
The tendency in the
United States is to the use of the derrickcrane, whose simplicity and efficiency leave little to be desired.
The extension of the
Treasury Building in
Washington, under the conduct of
A. B. Mullet, was made by colossal stones; its monolithic character is said to be second only to the
Church of St. Isaac's at
St Petersburg, Russia.
The derrick-crane was used on this building, and on the
Capitol Extension also.
Fig. 4648 represents a hanging scaffold contrived by
Perronet for the workmen employed in dressing and pointing the masonry of the arches of the bridge at
Orleans.
It was suspended from a frame which straddled the parapet, and was rolled from place to
[
2048]
place as required.
The platform could be raised and lowered and held at any desired hight.
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Hanging scaffold. |
Curious turning scaffolds have been used in domes.
See
Cresy.
From the numerous varieties, three representative examples may be shown: —
a. Suspended from spars or upright timbers.
The uprights have base supports and braces at their lower ends.
The platform is connecting to sliding frames which are raised by ropes passing over sheaves at the tops of the uprights and wound by windlasses attached to the frames.
b. Propped against the building.
In the example, the platform is sustained against the wall by the extensible props reaching from the ground to the inner angle between its horizontal and vertical parts.
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Builders' suspended scaffold. |
c. Suspended from
trestles. The platform is balanced by ropes passing over pulleys secured to the upper cross-pieces of the trestleframe, the said ropes having a weight attached to one end. The platform is sustained in any fixed position by bars, which are passed through holes in the uprights of the trestle.
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Propped scaffold. |
2. (
Mining.) A platform affording a temporary resting-place for an ascending or descending load.
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Suspended scaffold. |
