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Pulley Block Factory (Portsmouth Block Mills) and machinery
Block Mills, Portsmouth Dockyard, Portsmouth, Hampshire, UK
Pulley Block Factory (Portsmouth Block Mills) and machinery
associated engineer
Sir Marc Isambard Brunel
Henry Maudslay
date  1802 - 1808
UK era  Georgian  |  category  Machinery, industrial  |  reference  SU627008
ICE reference number  HEW 890
photo  by Comlay (own work) CC BY-SA 3.0, via Wikimedia Commons
The Georgian era Royal Navy required a constant supply of timber pulley blocks, a vital element in the rigging of sailing ships. A big step forward in the Industrial Revolution was made by the development of machinery for the automated production of the blocks, installed in a factory at Portsmouth Naval Dockyard. This was the world's first steam-powered production line. The factory still stands, though disused, and some of the machinery can be seen at Portsmouth and in London's Science Museum.
A pulley block is a shaped block of timber drilled out to enable it to contain one or more pulleys (sheaves). In use, ropes are threaded through the pulleys with the aim of making haulage easier — for the control of sails and operation of other other bits of rigging. An arrangement of two or more blocks, one of which is fixed in place, is linked by a rope called a tackle, hence the phrase 'block and tackle’.
A single 74-gun ship of the period required between 1,000 and 1,400 pulley blocks, and replacements were also needed as they were often were damaged at sea. Until the mid-18th century, the blocks were handmade by craftsmen, which was not only expensive but led to inconsistencies in manufacture and quality. Over time, a faulty block could saw through a rope or set it alight through friction, with disastrous consequences.
Many different sizes of pulley blocks were needed. Those over 450mm long were made up of several pieces of timber bolted together. The cost of handmade blocks purchased by the Navy in 1791 ranged from 8d (3.3p) for a 100mm single-pulley block to more than eight guineas (£8.40) for a 965mm triple-pulley one. By 1798, prices had risen 20 percent.
In the run-up to the Napoleonic Wars (1803-15), the Admiralty set about modernising its dockyards. In 1795, Brigadier General Sir Samuel Bentham (1757-1831) began working at Portsmouth Dockyard, was appointed Inspector General of Naval Works in 1796, and as part of upgrading Portsmouth’s facilities championed the installation of a mass production line for pulley blocks.
In 1799-1802, the former Upper Wet Dock (constructed 1691-8), which, from 1777, had been used as a reservoir to drain Dry Dock No.4 and No.5, was covered over by two brick vaults. The lower vault remained a reservoir (extant), the upper vault was used for storage, and the roof — level with the surrounding ground — provided much-needed space for expansion.
A single storey engine house to the north east of Basin No.1 (formerly Lower Wet Dock) held a 8.95kW steam pumping engine designed by James Sadler (1753-1828), installed in 1797-8. This was the Navy's first steam engine. In 1800, a 22.37kW Boulton & Watt steam pumping engine was ordered and a three-storey engine house constructed. It began pumping on 11th April 1801.
A new building, the Block Mills, designed by the dockyard’s architect Samuel Bunce (d.1802), was erected to house the pulley block factory and the two steam engines. Constructed in red brick with hipped slate roofs, it consists of two parallel east-west ranges of three storeys with a central single-storey range between them. The south range (on the engine house sites) housed both engines, while the north range sits directly over the vaults. Inside, timber columns support large-section timber cross beams and timber flooring. In 1802, the factory was ready for the world’s first steam-powered production line.
The idea of streamlining the process of block manufacture was not new, though fully mechanising it using steam power was. Portsmouth's innovations drew on prior experience. From 1759, Walter Taylor (1734-1803) supplied the Navy with 100,000 blocks a year from his sawmill in Southampton. However, his machines (patented 1762) for the accurate sawing, boring and turning of blocks were manually operated. Intricate work was still done by carpenters. In 1791 and 1793, Bentham himself took out two patents for woodworking machinery. In Plymouth, William Dunsterville had constructed eight water-powered timber-framed block-making machines.
Meanwhile, engineer Marc Isambard Brunel (1769-1849, knighted 1841) too had been pondering the possibilities. On 9th March 1801, he obtained Patent No.2478 A New and Useful Machine for Cutting One or More Mortices Forming the Sides of and Cutting the Pin-Hole of the Shells of Blocks, and for Turning and Boring the Shivers, and Fitting and Fixing the Coak Therein. It was the first of his many initiatives to improve manufacturing techniques.
Brunel offered his invention to Samuel Taylor, son of Water Taylor, but was rebuffed. However, Bentham recognised its value. After demonstrating his models to the Admiralty, in August 1802 Brunel received approval for construction of full-size machines. Around this time, at Bentham’s request, the Admiralty purchased Dunsterville’s machines for £500. They were intended for temporary use, until the new machinery was operational, though it’s not clear whether they were ever installed in the factory.
Brunel was aided by Henry Maudslay (1771-1831), a skilled machinist and tool maker, and possibly also by Simon Goodrich (1773-1847), of the Navy board. Maudslay refined and improved Brunel's original ideas, exchanging most of the heavy timber framing for slender cast iron to hold the machinery rigidly in place. The metal frames improved production accuracy and later became standard for machine tool manufacturing. The as-constructed line also contained a greater number of specialised machines than envisaged in the patent, reducing the amount of hands-on carpentry required.
The manufacturing process at Portsmouth began by shaping a shell or case from a piece of elm, with an external groove for a rope or strap to hold the block in position on the ship. Between one and four rectangular mortises (slots) were cut through the case, and into each was inserted a circular 'shiver' (pulley) or sheave of lignum vitae (a dense hardwood). The pulleys were held fast inside the block by a central pin of iron or lignum vitae, fitted with bronze coaks (bushes) recessed into either side of the pulley(s) to reduce in-service friction.
Brunel and Maudslay’s machinery differed from those of Taylor and Dunsterville. The earlier machines relied on, sometimes substantial, intervention from their operators. The Portsmouth production line was far more automated, with the machines doing the skillful work. They could be operated by workers rather than artisans. However, the new machines didn't all work at the same rate and human hands still were required to ferry the part-finished blocks between different machines.
Nevertheless, the machinery was impressive. Each machine was largely handmade and designed specifically for its task. The only mechanical tools of the time were lathes for machining circular parts, and drilling machines for boring small holes. Milling, planing and shaping machines did not exist, so the precision finishes on flat surfaces were made by laborious hand chipping, filing, scraping and grinding. Each nut was made to fit its matching bolt.
As Carolyn Cooper writes, "It was the close personal interaction of Bentham, Brunel, and Maudslay that resulted in the perfection of the Portsmouth block making machinery and its system of production".
The demand for pulley blocks was such that the production line opened in stages as soon as the machines were finished. In 1803, medium blocks of 178-254mm were being made, followed in 1804 by small ones of 100-178mm and in 1805 by large blocks of 254-457mm. In March 1805, the Admiralty ended its contracts with the Taylors and other private block making companies. The same year, Brunel replaced some of the reciprocating saws with more efficient circular saws. Bentham later included a tilt hammer to rivet the coaks, previously done by hand.
As Brunel informed Goodrich, by 10th October 1807, the Block Mills could supply all the pulley blocks the Navy required. The completed line had a total of 43, or perhaps 45, steam-driven machines, capable of making three sizes of blocks simultaneously. Some of them could cut between two and 10 blocks at once. The Sadler engine was replaced by a 22.37kW steam engine made by Fenton, Murray & Wood.
In 1830, the Fenton, Murray & Wood steam engine was replaced by a Maudslay, Son & Field beam engine. In 1837, the Boulton & Watt steam engine was replaced with another from the same manufacturer.
Instead of a flat fee, Brunel's salary for the work was equivalent to the amount of money saved by his machinery in one full year of operation. This was calculated as £17,093 for 1808, and paid in instalments in 1808-10. Maudslay received £12,000. The mills produced 130,000 pulley blocks in 1808 valued at £50,000, with capacity peaking at 140,000 blocks per year. It was claimed that six men could now do the work previously done by 60 men, and the enterprise paid for itself within three or four years.
Unaccountably, the mass production techniques pioneered at Portsmouth were not applied to other British production lines until the 1850s.
In the late 19th century, the hipped slate roof of the south range was renewed. It is possible that the north range may once have had a flat roof to accommodate a water cistern for firefighting. However, some time around World War I (1914-18), the roof was reconstructed in slate with brick gables, all supported by a Belfast truss.
Block making declined in the 20th century as the use of sail power declined. Manufacturing ceased at the Portsmouth Block Mills in 1965 (or 1983). The building fell into disrepair and by 1998 was classed as 'At Risk'.
In August 1999, the building was Grade I listed for its "international significance as the earliest application of steam-powered machine tools for mass production". It is also a Scheduled Ancient Monument (No.395). It is not open to the public.
Some of the production line survives in situ, including remnants of the former overhead power transmission equipment. The frame of the 1801 Boulton & Watt beam engine is in the west end of the south range, while the first floor of the north range contains the lignum vitae saw, the treenail machine and the cornering machine. More of the machinery is on display in dockyard’s museum. Some can also be seen in London’s Science Museum, including drawings by Brunel and the original 1804 machine that made coaking recesses in the pulleys.
Inspections in 2003 and April 2005 confirmed that the building and its machinery were suffering the effects of extensive water ingress, rising damp from the reservoir beneath and timber decay. Scheduled Monument Clearance was agreed in March 2006, and in April an assessment made of the work required to restore the building to wind and watertight condition by repairing or replacing as-found, rather than restoration. Work commenced in January 2007.
Wherever possible, the original fabric was preserved and repaired rather than replaced. Works included replacement of the north range roof structure, re-slating of the roofs, brickwork and joinery repair, some lime mortar repointing, roof drainage improvements, parapet rebuilding, timber beam and flooring repair using reclaimed or new timber, and the installation of fire control measures. The project was completed in August 2008, at a cost of £2.5m.
The Block Mills are no longer on the 'At Risk’ register.
Machinery manufacture: Henry Maudslay
Steam engine (1797-8): James Sadler
Steam engine (1801, 1837): Boulton & Watt
Steam engine (1807): Fenton, Murray & Wood of Leeds
Steam engine (1830): Maudslay, Son & Field
Architect (Block Mills): Samuel Bunce
Engineer (Block Mills, 2006-8): WYG Management Services
Contractor (Block Mills, 2006-8): Cathedral Works
Leadwork (Block Mills, 2006-8): Richardson Roofing
Woodwork (Block Mills, 2006-8): Green Oak Carpentry
Research: ECPK
"The Restoration of Portsmouth Dockyard Block Mills (Built 1803), 2006-8" by Ann Coats, Dockyards, The Naval Dockyards Society, Vol.14, No.1, pp.14-18, July 2009
"The Portsmouth System of Manufacture" by Carolyn C. Cooper, Technology and Culture, Vol.25, No.2, pp.182-225, April 1984
reference sources   CEH SouthBDCE1Science

Pulley Block Factory (Portsmouth Block Mills) and machinery