Acrow prop
Encyclopedia
An Acrow prop is a piece of construction
equipment. It is a telescopic tubular steel prop, used as a temporary support.
Acrow props are adjustable for height by a large diameter screw thread
, formed on the outside of the tube itself. The screw thread provides a fine adjustment over a short range. A loose pin through a series of holes in the inner tube gives a wider range of coarse adjustment. Use of a screw thread also allows the props to be tightened when already in place, to adjust the load that each one bears. Props are made in a range of five standard sizes, from 4 feet (1.2 m) to 16 feet (4.9 m). The safe load for each prop is a maximum of 35 kilonewtons (35,000 N), reducing slightly when props are fully extended, or by up to half when the load is not perfectly vertical.
Acrow props are mostly used for shoring
: temporary supports during building repair or alteration work, rather than scaffolding
: access platforms for workers. A typical use is to support an existing horizontal beam whilst its original masonry supports are removed or repaired. When masonry itself is to be supported, holes are first knocked through the brickwork and a strong 'needle' or 'strongboy' is placed through the hole. A pair of Acrow props are then used, one under each end. Existing windows or doorways may also be supported directly, or via needles.
The base and top plate of Acrow props are quite small, so they are suitable for supporting a vertical load but are at risk of toppling if there is any sideways force. In such cases, props should be strutted or 'laced' with scaffolding poles. A recent improvement to Acrow props was to shape this baseplate with notches, allowing pallet
loads of horizontal props to be stacked neatly, rather than randomly piled.
Although the original Acrow prop was only intended for vertical support, the range has since been extended. Shoring 'push and pull' props with swivelling footplates are available and are used to support concrete formwork
. Horizontal strutting props are used for shoring trenchwork. These are similar, but have a 'claw' form to their baseplates.
Acrow props, their size, strength and construction, are now described by a British Standard BS4074: 1982.British Standard BS4074: 1982 A similar lightweight European prop design exists, these have a maximum capacity of only 5 kilonewtons (5,000 N).
Vigier's company was named the Acrow Group, after his solicitor Mr A Crowe. He adopted this name as, like Kodak, it was an easily pronouncable neologism, with the additional advantage of appearing early in alphabetical lists.
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
equipment. It is a telescopic tubular steel prop, used as a temporary support.
Acrow props are adjustable for height by a large diameter screw thread
Screw thread
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...
, formed on the outside of the tube itself. The screw thread provides a fine adjustment over a short range. A loose pin through a series of holes in the inner tube gives a wider range of coarse adjustment. Use of a screw thread also allows the props to be tightened when already in place, to adjust the load that each one bears. Props are made in a range of five standard sizes, from 4 feet (1.2 m) to 16 feet (4.9 m). The safe load for each prop is a maximum of 35 kilonewtons (35,000 N), reducing slightly when props are fully extended, or by up to half when the load is not perfectly vertical.
Acrow props are mostly used for shoring
Shoring
Shoring is a general term used in construction to describe the process of supporting a structure in order to prevent collapse so that construction can proceed. The phrase can also be used as a noun to refer to the materials used in the process....
: temporary supports during building repair or alteration work, rather than scaffolding
Scaffolding
Scaffolding is a temporary structure used to support people and material in the construction or repair of buildings and other large structures. It is usually a modular system of metal pipes or tubes, although it can be from other materials...
: access platforms for workers. A typical use is to support an existing horizontal beam whilst its original masonry supports are removed or repaired. When masonry itself is to be supported, holes are first knocked through the brickwork and a strong 'needle' or 'strongboy' is placed through the hole. A pair of Acrow props are then used, one under each end. Existing windows or doorways may also be supported directly, or via needles.
The base and top plate of Acrow props are quite small, so they are suitable for supporting a vertical load but are at risk of toppling if there is any sideways force. In such cases, props should be strutted or 'laced' with scaffolding poles. A recent improvement to Acrow props was to shape this baseplate with notches, allowing pallet
Pallet
A pallet , sometimes called a skid, is a flat transport structure that supports goods in a stable fashion while being lifted by a forklift, pallet jack, front loader or other jacking device. A pallet is the structural foundation of a unit load which allows handling and storage efficiencies...
loads of horizontal props to be stacked neatly, rather than randomly piled.
Although the original Acrow prop was only intended for vertical support, the range has since been extended. Shoring 'push and pull' props with swivelling footplates are available and are used to support concrete formwork
Formwork
Formwork is the term given to either temporary or permanent molds into which concrete or similar materials are poured. In the context of concrete construction, the falsework supports the shuttering moulds.-Formwork and concrete form types:...
. Horizontal strutting props are used for shoring trenchwork. These are similar, but have a 'claw' form to their baseplates.
Acrow props, their size, strength and construction, are now described by a British Standard BS4074: 1982.British Standard BS4074: 1982 A similar lightweight European prop design exists, these have a maximum capacity of only 5 kilonewtons (5,000 N).
History
The props were invented by Swiss-born William de Vigier, who came to London in 1935. At first traditionalism amongst builders preferred the established timber props, cut to fit for each job. The break for Vigier's adjustable prop's came when they were adopted by a few large builders, including McAlpine. By 1939, over 40,000 Acrow props were in use.Vigier's company was named the Acrow Group, after his solicitor Mr A Crowe. He adopted this name as, like Kodak, it was an easily pronouncable neologism, with the additional advantage of appearing early in alphabetical lists.