Plastic armour
Plastic armour (also known as plastic protection) was a type of
Development
In August 1939, the
Terrell was brought into the Admiralty to run an information-gathering section, concerned with the manner in which small ships were attacked by aircraft. Terrell collected reports and gathered a library of film showing attacks on ships. When visiting damaged ships, he found bridges and chartrooms riddled with bullet holes and sections of concrete in shattered pieces. He also saw dried blood. These grim scenes made a deep impression on Terrell.[5]
In August 1940, one of Terrell's staff, Lieutenant-Commander Lane, brought to his attention a report by a
I noticed that whenever machine-gun bullets struck the deck, there were no ricochets ... The surface of the deck is covered with a cork-filled mastic substance to aid waterproofing.[6]
Terrell found that the worn-out ship had been heavily caulked with Insulphate, a slightly elastic compound of
Just two days after receiving his first samples, Terrell tested them at a
Terrell recalled an old legal case that he had conducted for the
Terrell had new targets made to his specifications by Durastic Bitumious Products. The new targets, with a variety of sizes of granite chips and proportions of mastic and limestone, were delivered on 20 August. Testing was performed two days later and supplies of granite started to arrive at the Road Research Station for more trials. Terrell’s choice of the Road Research Station for a firing range was convenient, as they had all the necessary experience with dealing with stone and bitumen – though in his memoirs, Terrell insists that the original choice was simply good fortune.
Terrell coined the term "plastic armour" for his invention, partly because it was plastic in the sense of being malleable and ductile while hot, but also because he thought that the term might be confusing to German intelligence, who might assume that the product was made with the synthetic wood plastics then available.[9]
On 27 August, Terrell, Glanville and a Lee drafted a report detailing their efforts and giving a recipe for plastic armour; the entire development cycle had taken just 10 days.[10] The recipe required 55% granite, 38% limestone, and 7% bitumen; it was important that the stone was carefully graded and free from grit. The backing plate was vital; it would usually be 0.25-inch (6.4 mm) thick mild steel. Since this was from what vital parts of a ship's superstructure were made, it was possible to cast plastic armour in situ between existing plates and temporary wooden shuttering, usually to a thickness of 4 inches (100 mm). Where this was not possible, armoured plates could be factory made. Wooden backing could also be used when nonmagnetic protection was needed near the ship's compass.[11][12] The war had brought road building to a virtual halt, so plenty of suitably qualified workers and machines were available for the task of armouring Britain's ships.
Plastic armour was at first met with resistance from some senior officers. Terrell soon received enthusiastic support from the
There is no doubt that Plastic Armour is very greatly superior to any other non-magnetic material, excluding non-magnetic bullet-proof steel, so far tried ... it is most strongly recommended that the fitting of concrete protection should be discontinued and Plastic Armour fitted in its place.[13]
The report was forwarded to the DNC, but was rejected again.[14] Some within the navy objected to the use of the word armour to describe a mixture derived from road-building materials.[15] The DNC said that it would remove its objections provided the word "armour" was removed from the name of the product. The Trade Division insisted that the term "armour" was important for morale and that at this stage higher authorities decided that the DNC would be bypassed and production would start without their formal approval.[16]
The process and specification was patented secretly under an agreement that the British Crown had full use of the invention. Glanville insisted "in good faith" on his name appearing in the patent; Terrell acquiesced so the armour could be put into use without delay.
Plastic armour was available in large quantities and cost only £12+1⁄2 per ton – compared with heat-treated armoured plate at about £150 per ton and in short supply (though weight-for-weight somewhat more effective than plastic armour).[17] Plastic armour went into full production in October; facilities were soon in place in every major port involving every major road-building contractor in the country. Word spread abroad to Britain's allies. By the end of the war, plastic armour had been fitted to some 10,000 ships. Plastic armour was even used on the fighting ships of the Royal Navy, although in these cases the Department of Naval Construction insisted on referring to it as "plastic protection".[18]
Development and testing continued. Eventually, the bitumen of the original formulation was replaced by less expensive pitch and the Penlee granite was replaced by flint gravel. Elsewhere in the world, people used whatever stone was available.[19]
Terrell invented the Scorpion, a plastic armoured vehicle apparently similar to the
Terrell was appointed to the staff of the
After the war, Terrell and Glanville received a patent for plastic armour, after the invention was disputed by the manufacturers of Insulphate and applied to the Royal Commission on Awards to Inventors for their work on plastic armour.[24] The court hearing lasted for a full week, with the Crown protesting that plastic armour had been developed in the normal course of the men's work. If this had been the case, it would have reduced the size of the award. The court found in favour of Terrell as sole inventor, granting an award of £9,500 in recognition of the usefulness of the invention and the initiative with which it was developed. Terrell, in turn, passed some of the award on to Glanville.[25][26] The award was a considerable sum: £9,500 in 1946 is equivalent to £360,000 in 2019.[27])
American production
In August 1943, American experiments on the general problem of protection against
Tank protection
The original plan for tank protection with plastic armour was to produce HCR2-filled steel panels, small in size to reduce the area damaged by a single projectile, which could be fastened to an
References
- ^ Terrell, 1958, pp. 59–61.
- ^ Unattributed. Mr Edward Terrell - Obituary. The Times 22 November 1979 p. 16G.
- ^ Terrell, Edward. US Patents 2215942, 1724980, for example.
- ^ Terrell, 1958, p. 21
- ^ Terrell, 1958, p. 33
- ^ a b Pawle, 1956, p. 53
- ^ a b Terrell, 1958, p45-56.
- ^ National Archive. T 166/21 Awards to inventors - Terrell and others. Second day p. 19
- ^ Terrell, 1958, p. 57
- ^ Terrell, 1958, p. 59
- ^ Terrell, 1958, p78.
- ^ Pawle, 1956, p52.
- ^ Pawle, 1956, p. 56
- ^ Lorber, 2003, p. 126
- ^ Terrell, 1958, p. 91
- ^ Lorber, 2003, p. 127
- ^ Terrell, 1958, p. 100
- ^ Terrell, 1958, p. 95
- ^ National Archive. T 166/21 Awards to inventors - Terrell and others. Second day. p. 38
- ^ Terrell, 1958, pp. 129–135.
- ^ "Plastic Protective Plating (image of vehicle)". IWM Collection s. Retrieved 17 March 2019.
- ^ Terrell, 1958, p.166
- ^ National Archive. ADM 1/13712. RN Officers – Double step in acting rank – Terrell.
- ^ Terrell, Edward; Glanville, William Henry. Improvements in Armour. British Patent 578951.
- ^ Terrell (1958) Admiralty Brief pp. 232–233
- ^ National Archive. T 166/21 Awards to inventors - Terrell and others.
- Gross Domestic Product deflator figures follow the MeasuringWorth "consistent series" supplied in Thomas, Ryland; Williamson, Samuel H. (2018). "What Was the U.K. GDP Then?". MeasuringWorth. Retrieved 2 February 2020.
Further reading
- White, Merit P.: Effects of Impact and Explosion, 1946
- Pawle, Gerald (1956). The Secret War 1939-45. London: Harrap.
- Terrell, Edward (1958). Admiralty brief: the story of inventions that contributed to victory in the Battle of the Atlantic. Harrap.
- Lorber, Azriel Paper (2003). Misguided Weapons. Brassey's US. ISBN 978-1-57488-528-6.
- "The National Archives". Repository of UK government records. Retrieved 19 February 2007.
External links
- "The Story of Plastic Armour". Caird Publications. Retrieved 27 December 2012.