China
Africa
Explore chapters and articles related to this topic
Construction engineering
Published in Andrew N. Sherwood, Milorad Nikolic, John W. Humphrey, John P. Oleson, Greek and Roman Technology, 2019
Andrew N. Sherwood, Milorad Nikolic, John W. Humphrey, John P. Oleson
Socket-pieces are affixed to the back faces of the squared timbers at the place where they are spread apart, into which the ends of the windlass are inserted so that the axles may turn easily. Near the ends of the windlass are two holes, arranged in such a way that handspikes can be fitted into them. But to the bottom block are fastened iron pincers, whose prongs are fitted into the stones, which have been bored. When the end of the rope is fastened to the windlass, which is moved by turning the handspikes, the rope is drawn out by winding itself around the windlass, and thus raises the load to the [proper] height and settings for the construction.
Tubular polythene film balloons for load lifting in the construction, mining and recreation industries
Published in Australian Journal of Multi-Disciplinary Engineering, 2022
Lifting loads is one of the most common and energy intensive operations in the construction industry, consuming energy E = Mgh when a load of mass M is lifted through height, h. Traditionally, lifting is achieved with a windlass, i.e. a rope wound around a drum, with the windlass operating as part of a crane in the construction of buildings. The energy used in lifting with a windlass is (M + m/2)gh, where m is the mass of a length, h, of the rope. This is an efficient means of lifting as, usually, m ≪ M. For example the wire rope required to lift a load of 200 tonnes through a height of 1 km has a mass m ~ 12 tonnes (Union Rope 2021), so the energy used to lift the rope is only 3% of the energy to lift the load. Occasionally construction must occur at sites that traverse steep forested slopes, swampy terrain, ravines or gorges that are unsuitable for cranes. In these cases loads are lifted to the sites by helicopter or by constructing a cableway over the site (Figure 7).