Blocks and the Portmouth Block Mills
From the end of the 18th century the Royal Navy needed about 100.000 blocks of different sizes. They were used in a variety of ways, including lifting sales and handling guns. A ship with 74 guns could use a thousand different sizes. These were made by hand, but varied in quality depending on the craftsman's skill.
Blocks from the Mary Rose, photo taken 1980 by National Geographic
This was to change in 1802 when Marc Isambard Brunel presented a steam-powered engine to the Admiralty and Sir Samuel Bentham, who had been appointed Inspector General of the Naval Works in 1795, was immediately impressed. For this enabled him to fulfil his task of modernising the Portsmouth Dockyard much better. The engine was connected to the steam engine that emptied the dry dock and in January 1803 began production of medium-sized blocks in the Block Mill. However, as no single machine could produce everything, a production line was set up so that mass production could take place.
A block consists of three main parts: the shell, the sheave and the pin for holding the latter in the shell. Manufacturing each of these parts involved a series of distinct processes and machines before the final hand-assembly. The metal pins and the bell-metal coaks that were inserted as bearings for the pins in the sheaves were manufactured elsewhere, but the pins were finished and polished on site. The various machines used in the manufacturing process are: The elm shells passed through the following machines, starting as rectangular blocks of wood and finally being completed by hand: Converting Saw > Boring Machine > Mortising Machine> Corner Saw> Shaping Engine > Scoring Engine> Spokeshave and finishing.
The iron pin [wooden pins were used for blocks intended for use in powder magazines] was cylindrical forged to a short length at one end, so that it remained square to bite the shell and prevent rotation. In block milling, the pins went through two processes: Pin lathe [to smooth the metal] > Pin polishing machine [final polishing].
The sheaves passed through the following machines: Converting Saw> Rounding or Crown Saw> Coaking Engine> insertion of coak at this point> Drilling Machine > insertion of rivets! Riveting Hammer> Broaching Engine > Face Turning Lathe.
Brunel's Morticing Machine right and Brunel's Shaping Engine (left) , from Brewster's Edinburgh Encyclopaedia (1811)
This led to the fact that in May the road for the small blocks and from 1805 the road for the big blocks was built. In total 45 machines were installed. The machines were modified and different techniques were tried out until in September 1807 it was considered that the plant was capable of supplying the entire block required by the Navy. By 1808, the 45 machines were producing 130,000 blocks per year, and ten unskilled men were able to achieve the output of 100 skilled workers using the craftsman model.
The Central Range of the Block Mills c.1900
The capital costs of the project were recovered within three years. Brunel received a sum equal to the annual savings; in 1810 he calculated this at £ 21174 12s 10d.
The block mills today
When the public heard about the Portsmouth block mill it became a tourist attraction and a fence had to be erected to keep people out. Despite public attention, its mass production principles were not widely used in British manufacturing until the 1850s. Given that the productivity gains were so dramatic, it is difficult to understand why the lessons learned from the Portsmouth block mills were not applied elsewhere. Production finally ceased in 1965
