Portsmouth Block Mills
The Portsmouth Block Mills are part of the Naval Base Portsmouth in Portsmouth , Hampshire , England, and was during the Napoleonic wars to supply the British Royal Navy with blocks built. They are considered the cradle of the Industrial Revolution in England and the origin of mass production using machine tools . The Admiralty also used the first stationary steam engines here .
Since 2003, English Heritage has been making detailed inspections of the buildings and keeping records of the machines used.
Portsmouth Shipyard Development
In 1800 a Boulton & Watt balancing steam engine was ordered as a reserve and housed in the three-story machine house. This steam engine was replaced by another model from James Watt and Co in 1837 .
Demand for blocks
The Royal Navy had a high demand for blocks for naval shipping. However, the handcrafted blocks, which were hand-made by suppliers, suffered from inconsistent quality, delivery problems and high manufacturing costs. Around 1000 blocks of various sizes were used for a typical ship. The Royal Navy used over 100,000 blocks annually. Bentham devised several machines for block production, but did not develop them any further and how they work is unclear today. Marc Isambard Brunel presented the Admiralty in 1802 with a system for block production with machine tools, the patent of which he owned. Bentham valued the superiority of Brunel's system and in August 1802 he was authorized by the Admiralty to develop it.
Three sets of manufacturing machines were built, each for a range of block sizes. Each was arranged in the flow of the manufacturing process to enable line production. The courtyard between the two existing Wood Mill buildings was walled and roofed in order to receive a new workshop for the block production.
The first set, for medium-sized blocks, was installed in January 1803. This was followed by the second set for small blocks in May 1803 and the third for large blocks in March 1805. There were numerous changes to the machine arrangement and various modifications of the factory until September 1807. Ultimately, the needs of the Navy could be met with around 130,000 blocks produced in the Year 1808.
Production process of blocks with machine tools
In the Block Mills, 45 machine tools were operated by two 30 hp (22.4 kW) steam engines. They were divided into 22 different types of machines, including circular saws, lathes and mortising machines . With just 10 machine operators, the work performance of 110 trained craftsmen could be achieved.
A block consists of four individual parts: the housing, the roller (s), the axle to fix the latter in the housing and a plain bearing made of metal or a bushing to minimize wear between the roller and axle. The size and number of rollers can vary.
Manufacture of the housing
- First, rough pieces are sawn from a tree trunk, which are then cut into a cuboid shape with a circular saw.
- A hole is drilled for the axis and one or more holes perpendicular to it to accommodate the mortise chisels (depending on the number of tenons). The clamping device that holds the block to be processed presses reference points into the wood, which guarantee exact positioning and dimensional accuracy during subsequent clamping.
- The blocks are chiselled by an automated machine. The chisels perform vertical lifting movements, while the vice in which the component is clamped is moved gradually with each stroke. When the required tapping depth is reached, the machine stops working automatically and the block to be processed can be exchanged.
- The corners of the housing are cut off with a circular saw with angled guides.
- The four side surfaces are rounded. This is done using a machine in which several blocks are clamped onto a rotating wheel. A milling cutter is moved in a circular path over the surfaces of the housings as the wheel rotates. The radius is determined by a worker. After each machining step, the components are rotated 90 degrees in order to machine the next surface.
- Finally, each block is slotted with a milling cutter to give the safety line a guide.
Manufacture of the rollers
- From lignum vitae strains individual slices are cut. The circular saw used allowed the trunks to rotate freely in order to maintain an even cut thickness. The exact positioning for each new cut was achieved by using a threaded spindle .
- With the help of a hole saw , the misshapen wooden discs are provided with a central hole in one step and brought into their circular shape.
- A profile for receiving the pin is milled into the roll on both sides.
- The pin is inserted into the roller and a locking ring is riveted to fix it in its position.
- The spigot is on the size of the axis cleared .
- The roller is faced on both sides on a special lathe and the rope groove is milled.
Manufacture of the axles
- The axle blanks were forged slightly oversize and were square on one end.
- The cylindrical part was turned to the final size on a special lathe.
- They were rolled smooth with hardened dies.
- According to one source, they were additionally tinned to prevent rust from forming.
Manufacture of the metal studs
- These were cast from bell metal and were molded from the mold with oil grooves in the inner bore. One end of the pin had a flange and a loose ring was pushed onto the other so that together they made a receptacle for the rivet connection.
Assembly process
- The housings were smoothed by hand with a scraper and then manually combined with the axle and roller. The finished blocks were stored in the block mills and distributed as required.
Important production-specific innovations
The specially designed machine tools made use of many features and functionalities that were used for the first time and are state of the art today.
- The drilling process left indented reference points on the wooden blocks in order to align them precisely in later processing steps. The following clamping devices were designed for this.
- Various machines had cone clutches.
- Brunel used interchangeable turning tools in tool holders, which are similar to those in today's universal lathes.
- For some work steps, mandrels were used to center the rollers over the axle bore.
- In some cases, two-jaw chucks were used to hold the workpiece. These are pioneers of today's three-jaw chucks.
- The mortising machines could be set to stop automatically after the machining was completed.
- The rollers and axles of the blocks were interchangeable as they corresponded to defined tolerances and were not adapted to each block.
- Due to the variable block size, the workflow can be viewed as batch production . Nevertheless, in principle there is an assembly line production . This manufacturing method was not to gain a foothold in Great Britain for many decades. Ultimately, thanks to the success of Henry Ford, it was taken over.
- The entire system was developed to be operated by unskilled workers and did not have to be staffed by trained craftsmen. Each worker was trained on at least two machines and could be deployed in the company as required.
Manufacture of the block machines
Brunel's patent describes machines with wooden frames. These white many of the principles of the variants actually built later, but the basic design differs massively. The evaluation machines manufactured for the Admiralty are now on display in the National Maritime Museum . When the contract between Brunel and the Admiralty was signed, he immediately hired Henry Maudslay to manufacture the machines. The influences of Bentham, Maudslay, Simon Goodrich and Brunel themselves can be seen in the final constructions. Due to Bentham's absence in Russia, Goodrich himself started production in the Mills block. Brunel's pay was taken from the Navy's savings under the new system.
The production machines were almost entirely handmade. The only exceptions were turned parts and bores that were machined. At that time there was no milling, machine planning or shaping. All surfaces were machined, filed and scraped by hand. There are indications that flat surfaces were ground in order to achieve the high precision. Each nut has been adjusted and numbered for its corresponding bolt to allow for correct assembly. This was typical of the time when standard parts were not yet available. Cast and wrought iron, brass and gunmetal were used for production. This made it possible to significantly improve the rigidity of the machines and their manufacturing accuracy compared to the original design. These and similar materials are still used today to manufacture machine tools.
Another story
The Block Mills have always been owned by the Navy and are therefore not open to the public. The production of blocks with the original machines has ebbed over the years, production ended in the 1960s. Parts of the machines, the transmission and the shells of the machine houses are still there today. The National Museum of Science and Industry , London, has a selection of machines donated by the Admiralty between 1933 and 1951. Others are on display at the Dockyard Apprentice Museum in Portsmouth. Various websites claim that the Smithsonian Institution in Washington, DC also has machines from Portsmouth in its collection. However, according to the institution, this is a myth.
The block mills have been idle for many years, although many parts of the transmission have been preserved, albeit in poor condition. The building itself is also in poor condition and is a high priority with English Heritage and the Department of Defense. A project has been active since 2006 to ensure the preservation of the buildings and their contents.
References
- ^ Coad, Jonathan, The Portsmouth Block Mills: Bentham, Brunel and the start of the Royal Navy's Industrial Revolution, 2005,
- ^ Ian McNeil: An Encyclopedia of the History of Technology . Routledge, London 1990, ISBN 0-415-14792-1 .
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- The English Heritage reports and other documentation may be consulted as they become available in the National Monuments Record at Swindon, Wiltshire. [1]
- Gilbert, KR The Portsmouth Block-making Machinery , London, 1965
- Cooper, CC The Production Line at Portsmouth Block Mill , in Industrial Archeology Review VI, 1982, 28-44
- Cooper, CC The Portsmouth System of Manufacture , Technology and Culture , 25, 1984, 182-225
- Coad, Jonathan, The Royal Dockyards 1690-1850 , Aldershot, 1989
- Coad, Jonathan, The Portsmouth Block Mills: Bentham, Brunel and the start of the Royal Navy's Industrial Revolution , 2005, ISBN 1-873592-87-6 .
- Wilkin, Susan, The application of emerging new technologies by Portsmouth Dockyard, 1790-1815 , The Open University PhD Thesis, 1999.
- Cantrell, J. and Cookson, G. eds. Henry Maudslay and the Pioneers of the Machine Age , Stroud, 2002
Web links
- National Museum of Science and Industry, London - Making of the Modern World
- Photographs of block making machines in The National Museum of Science & Industry
Coordinates: 50 ° 48 ′ 12.6 " N , 1 ° 6 ′ 33.5" W.