Cultivator No. 6
Encyclopedia
Cultivator No. 6 was the code name of a military trench-digging machine developed by the British Royal Navy
at the beginning of World War II
. The machine was originally known as White Rabbit Number Six; this code name was never officially recognised, but it was said to be derived from Churchill’s metaphorical ability to pull ideas out of hat. The codename was changed to the less suggestive Cultivator Number Six to conceal its identity. The name was later changed to N.L.E. Tractors. Winston Churchill
sometimes referred to the machine as his mole and the prototype machine was dubbed Nellie. It was lightly armoured and carried no weapons. It was designed to advance upon an enemy position largely below ground level in a trench that it was itself excavating. On reaching the enemy's front line, it would serve as a ramp for the troops, and possibly tanks, following in its trench.
Cultivator No. 6 was an enormous machine and was planned to be built in substantial numbers. The overall weight was 130 tons and the length was 77 in 6 in (23.62 m). The machine's development and production was enthusiastically backed by Winston Churchill
and work on it continued well past the point when there was no obvious use for it. In the end, only a small number of machines were constructed and none were used in combat. In his memoirs, Churchill, said about it: "I am responsible but impenitent".
, on 3 September 1939 the day Britain declared war on Germany, Winston Churchill
was appointed First Lord of the Admiralty and a member of the War Cabinet, just as he had been during the first part of World War I
. There followed a period during which the western allies watched Germany and Russia
devour Poland
, but with very little aggressive action being taken. The only significant fighting was at sea.
Britain despatched an expeditionary force to France where they took up positions on the northernmost portion of the French border with Belgium. A line of fortifications known as the Maginot Line
helped to defend France's border with Germany and much of the allies' effort went into extending these defences to the north. Trenches were dug, barbed wire
was stretched out and pillboxes were built, but hardly a shot was fired in anger. This period became known as the Phoney War. To the British and French public, this was a conflict between professional fighting forces and there was little appetite for an all-out ideological war. Perhaps Hitler would be satisfied with his conquests; if he would see sense, perhaps an honourable peace might be possible?
Churchill had no doubts as to Hitler's true character, he saw no hope of peace and he was appalled by the allies' lack of initiative. He had a number of ideas for taking the war to the enemy two of which required the invention of entirely new weapons. Churchill was a man of ideas and his position at the admiralty did not constrain him to strictly naval matters. When Churchill had served as the First Lord of the Admiralty in the First World War and he had been largely responsible for the establishment of the Royal Navy's Landships Committee which sponsored experiments with armoured tractors that eventually resulted in the invention of the tank. At that time, Churchill had also conceived the idea of an armoured vehicle that would dig its own trench as it advanced upon an enemy position, a trench sufficiently deep and wide to protect the machine itself and infantry and vehicles following in its wake. The idea did not catch on at the time. Now he resurrected that idea. The development of the trench digging machine was initially undertaken by the Department of Naval Constructors. Despite a lack of enthusiasm from the War Office
, it was planned to build a fleet of such machines.
Although Churchill lacked mechanical knowledge, he had a clear understanding of what he wanted. He saw this machine as one of very few aggressive initiatives by the allies during the Phoney War—the first few months of the war, characterised by a lack of real fighting. The machine he envisioned would be capable of breaking the stalemate of trench warfare that had developed during World War I and would thereby avoid the atrocious conditions and high casualty rate that resulted. The prospect of such fighting in World War II was made even worse by the construction of the Siegfried Line
(or West Wall): a continuous belt of barbed-wire entanglements, minefields, anti-tank obstacles, forts and trenches – the strength of which was greatly exaggerated by German propaganda. Churchill's trench cutters would cross no man's land
in the dark and protected by an artillery barrage
, the attacking force would advance in the relative safety of the cut trench and then burst upon the surprised defenders.
Churchill explained what he had in mind to Stanley Goodall who was then Director of Naval Construction
. In October 1939, the project was handed over to J H Hopkins. Hopkins, who had had a distinguished career in ship design was given the temporary rank of Assistant Director and he was tasked with bringing together a team of designers who would make Churchill's machine – his mole as he sometimes called it – a reality. A top secret department was set up under the Ministry of Supply
, this was known as the Department of Naval Land Equipment and was abbreviated to NLE giving rise to the name Nellie that was given to the prototype machine. At the start of the war, much of the Admiralty was moved away from London. It was for this reason that the trench digger project began in the Grand Pump Room Hotel in Bath. Here, Hopkins put the initial investigation into the hands of the brilliant, but inexperienced, Frank Spanner.
. The key feature of such machines was that the cutting was a continuous process that required a fairly constant power and from this comparison the trenching machine power requirement was estimated at about 1,000 hp half of which was for cutting and half for driving the machine forward.
Initial designs envisaged a large circular cutter the diameter of the trench to be dug and operating in the manner of modern tunnel boring machine
s. However, the design evolved to a more efficient arrangement with a huge plough
removing the top 2 in 6 in (0.762 m) of soil and a cutting cylinder rotating perpendicular to the line of the trench for digging out the lower 2 in 6 in (0.762 m). The trench profile was then squared off by a number of blades. The spoil was deposited on either side of the trench, wings on the plough blade pushing the spoil away from the edge of the trench to prevent it from falling back in. Hopkins presented this conception together with a static model to Churchill via Sir Stanley Goodall. Churchill approved the scheme and gave permission for development of a prototype to begin with an initial grant of £1,000,000.
The Navy turned to Ruston-Bucyrus Ltd
, an engineering
company specialising in excavating equipment. Ruston-Bucyrus had been established in 1930 and was jointly owned by Ruston and Hornsby based in Lincoln
, England and Bucyrus-Erie based in Bucyrus, Ohio
, the latter of which had operational control. On 6 December 1939, Churchill was told that Ruston-Bucyrus would be able to build 200 trench cutting machines by March 1941 and they proposed a wider version that would produce a trench in which tanks could drive. Churchill gave the go-ahead for the production of a prototype but deferred a decision as to the final quantities for the time being.
A scale model about four feet long was prepared by the firm of Bassett-Lowke
, they worked secretly in the cellars of a hotel in Bath – Bath being the temporary home of the Naval Construction department at the time. As soon as it was complete, Churchill ordered that it be taken to London. The model together with its accessories was packed into a mahogany box resembling a coffin; as it was carried to the station in Bath, many bystanders respectfully bowed their heads.
The working model was demonstrated to Churchill on 12 December 1939. For this a simulated soil had been developed from a mixture of sawdust and Plasticine
. The demonstration went so well that Churchill's smile of pleasure "almost dislodged his cigar" and he ordered that a further demonstration should be arranged for that evening, to which Churchill was accompanied by Prime Minister
Neville Chamberlain
, Chancellor of the Exchequer
Sir John Simon
and Chief of the Imperial General Staff Sir Edmund Ironside
. There is an apparent disagreement in the sources as to exactly what time this meeting took place. Newman (1956) gives 11 pm whereas Ironside (1962) specifies 7 pm. It is possible that Ironside was treated to a preview. Ironside later recalled:
Churchill used the model (or possibly another static model) to persuade the French to support the project to which they somewhat reluctantly agreed. An official order was placed with Ruston-Bucyrus on 22 January 1940. On 7 February 1940 the government gave approval for the construction of 200 narrow "infantry" and 40 wider "officer" machines, the latter creating a trench wide enough for tanks.
In the following weeks, the Germans noticed intense patrol activity in front of the Siegfried Line
as the French collected soil samples
so that technicians could determine the most suitable places for the Cultivator's to advance. However, the production of Cultivator almost immediately faced a problem as the Air Ministry
reserved for RAF use all the Rolls-Royce Merlin
engines being produced. Ruston-Bucyrus had intended to use the Merlin, but now had to change tack. They called in Sir Henry Ricardo who suggested using a pair of 600 hp lightweight diesel engine
s built by Davey, Paxman and Co. The change meant a great deal of redesign work, but the new arrangement had some advantages. Now one engine would be used for the cutter and one for moving the machine which simplified some aspects of the design and diesel fuel was safer than the petrol required by the Merlin engine.
When configured in digging order, the overall length of the machine was 77 in 6 in (23.62 m). The machine came in two parts that were hinged together. The head of the machine did the excavating and could be raised or lowered for ascent or descent.
The head of the machine was 30 in 6 in (9.3 m) long and 7 in 3 in (2.21 m) wide and 8 in 7 in (2.62 m) high and weighted about 30 tons. The head had a plough blade for cutting the top part of the trench to a depth of about 2 in 6 in (0.762 m), raising the excavated soil and pushing it to the sides of the trench. The lower part of the trench was cut to a depth of 2 in 6 in (0.762 m) by a cylindrical cutter superficially resembling the cutting blade of a cylinder lawnmower. Conveyors raised the excavated soil which was added to the plough's deposits at the side of the trench. The overall depth of the trench was 5 feet (1.5 m) and the spoil provided an additional cover of about 2 foot (0.6096 m).
The body of the machine came in two halves so that it could be divided for transportation, the front portion of the body was 23 in 4 in (7.11 m) long, 6 in 3 in (1.91 m) wide and 10 in 5 in (3.18 m) high and weighed about 45 tons; the rear portion was 28 in 4 in (8.64 m) long, 6 in 3 in (1.91 m) wide and 8 in 7 in (2.62 m) high and weighed about 55 tons.
The body was driven by two 2 foot (0.6096 m) wide tracks and on the surface steering was possible by means of dog clutch
es on the gear-box output shafts. When digging, only small changes in direction were possible by means of hydraulically operated steering doors, one on each side of the machine. There was an arrangement to draw an adjustable amount of spoil back into the trench and under the vehicle's tracks so as to counter any tendency to heel over.
. Clarke had prepared a paper "A Consideration of New Offensive Means" and followed this with "Notes on Design of Trench Forming Machines" for the Royal Engineers. His ideas filtered through the wartime bureaucracy and eventually reached the Cultivator project team. Clarke was interviewed by Churchill's scientific advisor, Professor Lindemann. In strict confidence, Lindemann told Clarke about work already in progress and he was sufficiently impressed to pass Clarke's suggestions up to Churchill himself. Clarke accepted a job as a temporary Civil Servant; he was hired as an Assistant Director of NLE with a salary of £1,000 per annum.
Clarke's idea was to use an armoured vehicle of some sort equipped with a hydraulic ram to insert explosive charges into the ground ahead. The resulting explosion would form a crater into which the machine would move before repeating the cycle. Clarke's machine would require thick armour to protect itself from its own explosions at the front and from the possibility of attack from the rear. None-the-less, the machine would be lighter and very much simpler than Cultivator. Also, Clarke's machine could simply blow its way through minefields and anti-tank obstacles that Cultivator could not deal with and when it came to a block house, Clarke's machine would push explosives under its floor and blow it up – whereas Cultivator was entirely unarmed. A significant disadvantage of Clarke’s machine was its modest speed, estimated by Clarke to be only 250 yards per hour.
On 30 June 1940, Clarke resigned from NLE. The design of the Clarke Machine had "got beyond him", but it seems equally likely that Clarke was now disenchanted with the whole idea and thought he could contribute to the war in other ways. Although Clarke's ideas were not immediately abandoned at NLE, it is clear that little progress with them was made.
blitzkrieg
attack on France
in 1940 it was clearly time to reconsider the usefulness of Cultivator No. 6. Churchill wrote to General Ismay
and CIGS Ironside:
The number of units was soon even more significantly reduced to just 33 machines and by July Churchill was finding other tasks to assign to Mr Hopkins. Even so, the project was not completely canceled – with Britain facing invasion and desperately short of conventional tanks it does seem remarkable that the project continued. Historian John Turner attributes this dogged persistence to Churchill's failure to get his mole accepted during the First World War. It was at this point that the original code name of Cultivator No. 6 was dropped in favour of N.L.E. Tractors.
There were various problems with the development and the prototype machine, officially known as N.L.E Trenching Machine Mark I, but nicknamed Nellie was completed in May 1941.
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
at the beginning of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. The machine was originally known as White Rabbit Number Six; this code name was never officially recognised, but it was said to be derived from Churchill’s metaphorical ability to pull ideas out of hat. The codename was changed to the less suggestive Cultivator Number Six to conceal its identity. The name was later changed to N.L.E. Tractors. Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
sometimes referred to the machine as his mole and the prototype machine was dubbed Nellie. It was lightly armoured and carried no weapons. It was designed to advance upon an enemy position largely below ground level in a trench that it was itself excavating. On reaching the enemy's front line, it would serve as a ramp for the troops, and possibly tanks, following in its trench.
Cultivator No. 6 was an enormous machine and was planned to be built in substantial numbers. The overall weight was 130 tons and the length was 77 in 6 in (23.62 m). The machine's development and production was enthusiastically backed by Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
and work on it continued well past the point when there was no obvious use for it. In the end, only a small number of machines were constructed and none were used in combat. In his memoirs, Churchill, said about it: "I am responsible but impenitent".
Inception
After the outbreak of World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, on 3 September 1939 the day Britain declared war on Germany, Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
was appointed First Lord of the Admiralty and a member of the War Cabinet, just as he had been during the first part of World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
. There followed a period during which the western allies watched Germany and Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
devour Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
, but with very little aggressive action being taken. The only significant fighting was at sea.
Britain despatched an expeditionary force to France where they took up positions on the northernmost portion of the French border with Belgium. A line of fortifications known as the Maginot Line
Maginot Line
The Maginot Line , named after the French Minister of War André Maginot, was a line of concrete fortifications, tank obstacles, artillery casemates, machine gun posts, and other defences, which France constructed along its borders with Germany and Italy, in light of its experience in World War I,...
helped to defend France's border with Germany and much of the allies' effort went into extending these defences to the north. Trenches were dug, barbed wire
Barbed wire
Barbed wire, also known as barb wire , is a type of fencing wire constructed with sharp edges or points arranged at intervals along the strand. It is used to construct inexpensive fences and is used atop walls surrounding secured property...
was stretched out and pillboxes were built, but hardly a shot was fired in anger. This period became known as the Phoney War. To the British and French public, this was a conflict between professional fighting forces and there was little appetite for an all-out ideological war. Perhaps Hitler would be satisfied with his conquests; if he would see sense, perhaps an honourable peace might be possible?
Churchill had no doubts as to Hitler's true character, he saw no hope of peace and he was appalled by the allies' lack of initiative. He had a number of ideas for taking the war to the enemy two of which required the invention of entirely new weapons. Churchill was a man of ideas and his position at the admiralty did not constrain him to strictly naval matters. When Churchill had served as the First Lord of the Admiralty in the First World War and he had been largely responsible for the establishment of the Royal Navy's Landships Committee which sponsored experiments with armoured tractors that eventually resulted in the invention of the tank. At that time, Churchill had also conceived the idea of an armoured vehicle that would dig its own trench as it advanced upon an enemy position, a trench sufficiently deep and wide to protect the machine itself and infantry and vehicles following in its wake. The idea did not catch on at the time. Now he resurrected that idea. The development of the trench digging machine was initially undertaken by the Department of Naval Constructors. Despite a lack of enthusiasm from the War Office
War Office
The War Office was a department of the British Government, responsible for the administration of the British Army between the 17th century and 1964, when its functions were transferred to the Ministry of Defence...
, it was planned to build a fleet of such machines.
Although Churchill lacked mechanical knowledge, he had a clear understanding of what he wanted. He saw this machine as one of very few aggressive initiatives by the allies during the Phoney War—the first few months of the war, characterised by a lack of real fighting. The machine he envisioned would be capable of breaking the stalemate of trench warfare that had developed during World War I and would thereby avoid the atrocious conditions and high casualty rate that resulted. The prospect of such fighting in World War II was made even worse by the construction of the Siegfried Line
Siegfried Line
The original Siegfried line was a line of defensive forts and tank defences built by Germany as a section of the Hindenburg Line 1916–1917 in northern France during World War I...
(or West Wall): a continuous belt of barbed-wire entanglements, minefields, anti-tank obstacles, forts and trenches – the strength of which was greatly exaggerated by German propaganda. Churchill's trench cutters would cross no man's land
No man's land
No man's land is a term for land that is unoccupied or is under dispute between parties that leave it unoccupied due to fear or uncertainty. The term was originally used to define a contested territory or a dumping ground for refuse between fiefdoms...
in the dark and protected by an artillery barrage
Barrage (artillery)
A barrage is a line or barrier of exploding artillery shells, created by the co-ordinated aiming of a large number of guns firing continuously. Its purpose is to deny or hamper enemy passage through the line of the barrage, to attack a linear position such as a line of trenches or to neutralize...
, the attacking force would advance in the relative safety of the cut trench and then burst upon the surprised defenders.
Churchill explained what he had in mind to Stanley Goodall who was then Director of Naval Construction
Director of Naval Construction
The Director of Naval Construction was a senior British civil servant post in the Admiralty, that part of the British Civil Service that oversaw the Royal Navy. The post existed from 1860 to 1966....
. In October 1939, the project was handed over to J H Hopkins. Hopkins, who had had a distinguished career in ship design was given the temporary rank of Assistant Director and he was tasked with bringing together a team of designers who would make Churchill's machine – his mole as he sometimes called it – a reality. A top secret department was set up under the Ministry of Supply
Ministry of Supply
The Ministry of Supply was a department of the UK Government formed in 1939 to co-ordinate the supply of equipment to all three British armed forces, headed by the Minister of Supply. There was, however, a separate ministry responsible for aircraft production and the Admiralty retained...
, this was known as the Department of Naval Land Equipment and was abbreviated to NLE giving rise to the name Nellie that was given to the prototype machine. At the start of the war, much of the Admiralty was moved away from London. It was for this reason that the trench digger project began in the Grand Pump Room Hotel in Bath. Here, Hopkins put the initial investigation into the hands of the brilliant, but inexperienced, Frank Spanner.
Development
The machine had a simple task to perform. Essentially, the requirement was to cut a trench with a section of about six feet (2 m) square and for this some sort of cutter was required. Correctly estimating the power required to perform this feat was essential to the success of the project, but the nearest comparable machine the designers could take figures from were the giant bucket and chain excavators used in Germany for open cast mining of ligniteLignite
Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...
. The key feature of such machines was that the cutting was a continuous process that required a fairly constant power and from this comparison the trenching machine power requirement was estimated at about 1,000 hp half of which was for cutting and half for driving the machine forward.
Initial designs envisaged a large circular cutter the diameter of the trench to be dug and operating in the manner of modern tunnel boring machine
Tunnel boring machine
A tunnel boring machine also known as a "mole", is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through anything from hard rock to sand. Tunnel diameters can range from a metre to almost 16 metres to date...
s. However, the design evolved to a more efficient arrangement with a huge plough
Plough
The plough or plow is a tool used in farming for initial cultivation of soil in preparation for sowing seed or planting. It has been a basic instrument for most of recorded history, and represents one of the major advances in agriculture...
removing the top 2 in 6 in (0.762 m) of soil and a cutting cylinder rotating perpendicular to the line of the trench for digging out the lower 2 in 6 in (0.762 m). The trench profile was then squared off by a number of blades. The spoil was deposited on either side of the trench, wings on the plough blade pushing the spoil away from the edge of the trench to prevent it from falling back in. Hopkins presented this conception together with a static model to Churchill via Sir Stanley Goodall. Churchill approved the scheme and gave permission for development of a prototype to begin with an initial grant of £1,000,000.
The Navy turned to Ruston-Bucyrus Ltd
Ruston-Bucyrus
Ruston-Bucyrus Ltd was an engineering company established in 1930 and jointly owned by Ruston and Hornsby based in Lincoln, England and Bucyrus-Erie based in Bucyrus, Ohio, the latter of which had operational control and into which the excavator manufacturing operation of Ruston and Hornsby was...
, an engineering
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
company specialising in excavating equipment. Ruston-Bucyrus had been established in 1930 and was jointly owned by Ruston and Hornsby based in Lincoln
Lincoln, Lincolnshire
Lincoln is a cathedral city and county town of Lincolnshire, England.The non-metropolitan district of Lincoln has a population of 85,595; the 2001 census gave the entire area of Lincoln a population of 120,779....
, England and Bucyrus-Erie based in Bucyrus, Ohio
Bucyrus, Ohio
As of the census of 2000, there were 13,224 people, 5,559 households, and 3,552 families residing in the city. The population density was 1,812.0 people per square mile . There were 5,955 housing units at an average density of 816.0 per square mile...
, the latter of which had operational control. On 6 December 1939, Churchill was told that Ruston-Bucyrus would be able to build 200 trench cutting machines by March 1941 and they proposed a wider version that would produce a trench in which tanks could drive. Churchill gave the go-ahead for the production of a prototype but deferred a decision as to the final quantities for the time being.
A scale model about four feet long was prepared by the firm of Bassett-Lowke
Bassett-Lowke
Bassett-Lowke was a toy company in Northampton, England, founded by Wenman Joseph Bassett-Lowke in 1898 or 1899, that specialized in model railways, boats and ships, and construction sets...
, they worked secretly in the cellars of a hotel in Bath – Bath being the temporary home of the Naval Construction department at the time. As soon as it was complete, Churchill ordered that it be taken to London. The model together with its accessories was packed into a mahogany box resembling a coffin; as it was carried to the station in Bath, many bystanders respectfully bowed their heads.
The working model was demonstrated to Churchill on 12 December 1939. For this a simulated soil had been developed from a mixture of sawdust and Plasticine
Plasticine
Plasticine, a brand of modelling clay, is a putty-like modelling material made from calcium salts, petroleum jelly and aliphatic acids. The name is a registered trademark of Flair Leisure Products plc...
. The demonstration went so well that Churchill's smile of pleasure "almost dislodged his cigar" and he ordered that a further demonstration should be arranged for that evening, to which Churchill was accompanied by Prime Minister
Prime minister
A prime minister is the most senior minister of cabinet in the executive branch of government in a parliamentary system. In many systems, the prime minister selects and may dismiss other members of the cabinet, and allocates posts to members within the government. In most systems, the prime...
Neville Chamberlain
Neville Chamberlain
Arthur Neville Chamberlain FRS was a British Conservative politician who served as Prime Minister of the United Kingdom from May 1937 to May 1940. Chamberlain is best known for his appeasement foreign policy, and in particular for his signing of the Munich Agreement in 1938, conceding the...
, Chancellor of the Exchequer
Chancellor of the Exchequer
The Chancellor of the Exchequer is the title held by the British Cabinet minister who is responsible for all economic and financial matters. Often simply called the Chancellor, the office-holder controls HM Treasury and plays a role akin to the posts of Minister of Finance or Secretary of the...
Sir John Simon
John Simon, 1st Viscount Simon
John Allsebrook Simon, 1st Viscount Simon GCSI GCVO OBE PC was a British politician who held senior Cabinet posts from the beginning of the First World War to the end of the Second. He is one of only three people to have served as Home Secretary, Foreign Secretary and Chancellor of the Exchequer,...
and Chief of the Imperial General Staff Sir Edmund Ironside
Edmund Ironside, 1st Baron Ironside
Field Marshal William Edmund Ironside, 1st Baron Ironside GCB, CMG, CBE, DSO, was a British Army officer who served as Chief of the Imperial General Staff during the first year of the Second World War....
. There is an apparent disagreement in the sources as to exactly what time this meeting took place. Newman (1956) gives 11 pm whereas Ironside (1962) specifies 7 pm. It is possible that Ironside was treated to a preview. Ironside later recalled:
Churchill used the model (or possibly another static model) to persuade the French to support the project to which they somewhat reluctantly agreed. An official order was placed with Ruston-Bucyrus on 22 January 1940. On 7 February 1940 the government gave approval for the construction of 200 narrow "infantry" and 40 wider "officer" machines, the latter creating a trench wide enough for tanks.
In the following weeks, the Germans noticed intense patrol activity in front of the Siegfried Line
Siegfried Line
The original Siegfried line was a line of defensive forts and tank defences built by Germany as a section of the Hindenburg Line 1916–1917 in northern France during World War I...
as the French collected soil samples
Soil test
In agriculture, a soil test is the analysis of a soil sample to determine nutrient and contaminant content, composition and other characteristics such as acidity or pH level. Tests are usually performed to measure the expected growth potential of a soil...
so that technicians could determine the most suitable places for the Cultivator's to advance. However, the production of Cultivator almost immediately faced a problem as the Air Ministry
Air Ministry
The Air Ministry was a department of the British Government with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964...
reserved for RAF use all the Rolls-Royce Merlin
Rolls-Royce Merlin
The Rolls-Royce Merlin is a British liquid-cooled, V-12, piston aero engine, of 27-litre capacity. Rolls-Royce Limited designed and built the engine which was initially known as the PV-12: the PV-12 became known as the Merlin following the company convention of naming its piston aero engines after...
engines being produced. Ruston-Bucyrus had intended to use the Merlin, but now had to change tack. They called in Sir Henry Ricardo who suggested using a pair of 600 hp lightweight diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
s built by Davey, Paxman and Co. The change meant a great deal of redesign work, but the new arrangement had some advantages. Now one engine would be used for the cutter and one for moving the machine which simplified some aspects of the design and diesel fuel was safer than the petrol required by the Merlin engine.
Design
Cultivator was designed to cut a trench 7 in 6 in (2.29 m) wide and 5 feet (1.5 m) deep and it would dispose of the spoil on banks either side of the cut trench. It could dig at 0.42 or or travel at 3.04 miles per hour (4.9 km/h) on the surface.When configured in digging order, the overall length of the machine was 77 in 6 in (23.62 m). The machine came in two parts that were hinged together. The head of the machine did the excavating and could be raised or lowered for ascent or descent.
The head of the machine was 30 in 6 in (9.3 m) long and 7 in 3 in (2.21 m) wide and 8 in 7 in (2.62 m) high and weighted about 30 tons. The head had a plough blade for cutting the top part of the trench to a depth of about 2 in 6 in (0.762 m), raising the excavated soil and pushing it to the sides of the trench. The lower part of the trench was cut to a depth of 2 in 6 in (0.762 m) by a cylindrical cutter superficially resembling the cutting blade of a cylinder lawnmower. Conveyors raised the excavated soil which was added to the plough's deposits at the side of the trench. The overall depth of the trench was 5 feet (1.5 m) and the spoil provided an additional cover of about 2 foot (0.6096 m).
The body of the machine came in two halves so that it could be divided for transportation, the front portion of the body was 23 in 4 in (7.11 m) long, 6 in 3 in (1.91 m) wide and 10 in 5 in (3.18 m) high and weighed about 45 tons; the rear portion was 28 in 4 in (8.64 m) long, 6 in 3 in (1.91 m) wide and 8 in 7 in (2.62 m) high and weighed about 55 tons.
The body was driven by two 2 foot (0.6096 m) wide tracks and on the surface steering was possible by means of dog clutch
Dog clutch
A dog clutch is a type of clutch that couples two rotating shafts or other rotating components not by friction but by interference. The two parts of the clutch are designed such that one will push the other, causing both to rotate at the same speed and will never slip.Dog clutches are used where...
es on the gear-box output shafts. When digging, only small changes in direction were possible by means of hydraulically operated steering doors, one on each side of the machine. There was an arrangement to draw an adjustable amount of spoil back into the trench and under the vehicle's tracks so as to counter any tendency to heel over.
Alternative design
In April 1940, came a most unexpected surprise. Someone else had invented a high speed trenching machine envisaged to be used in a similar way but working by quite different means. The inventor was Cecil Vandepeer Clarke who had recently worked on the limpet mineLimpet mine
A limpet mine is a type of naval mine attached to a target by magnets; they are so named because of their superficial similarity to the limpet, a type of mollusk....
. Clarke had prepared a paper "A Consideration of New Offensive Means" and followed this with "Notes on Design of Trench Forming Machines" for the Royal Engineers. His ideas filtered through the wartime bureaucracy and eventually reached the Cultivator project team. Clarke was interviewed by Churchill's scientific advisor, Professor Lindemann. In strict confidence, Lindemann told Clarke about work already in progress and he was sufficiently impressed to pass Clarke's suggestions up to Churchill himself. Clarke accepted a job as a temporary Civil Servant; he was hired as an Assistant Director of NLE with a salary of £1,000 per annum.
Clarke's idea was to use an armoured vehicle of some sort equipped with a hydraulic ram to insert explosive charges into the ground ahead. The resulting explosion would form a crater into which the machine would move before repeating the cycle. Clarke's machine would require thick armour to protect itself from its own explosions at the front and from the possibility of attack from the rear. None-the-less, the machine would be lighter and very much simpler than Cultivator. Also, Clarke's machine could simply blow its way through minefields and anti-tank obstacles that Cultivator could not deal with and when it came to a block house, Clarke's machine would push explosives under its floor and blow it up – whereas Cultivator was entirely unarmed. A significant disadvantage of Clarke’s machine was its modest speed, estimated by Clarke to be only 250 yards per hour.
On 30 June 1940, Clarke resigned from NLE. The design of the Clarke Machine had "got beyond him", but it seems equally likely that Clarke was now disenchanted with the whole idea and thought he could contribute to the war in other ways. Although Clarke's ideas were not immediately abandoned at NLE, it is clear that little progress with them was made.
Persistence
With the devastating GermanGerman Army
The German Army is the land component of the armed forces of the Federal Republic of Germany. Following the disbanding of the Wehrmacht after World War II, it was re-established in 1955 as the Bundesheer, part of the newly formed West German Bundeswehr along with the Navy and the Air Force...
blitzkrieg
Blitzkrieg
For other uses of the word, see: Blitzkrieg Blitzkrieg is an anglicized word describing all-motorised force concentration of tanks, infantry, artillery, combat engineers and air power, concentrating overwhelming force at high speed to break through enemy lines, and, once the lines are broken,...
attack on France
Battle of France
In the Second World War, the Battle of France was the German invasion of France and the Low Countries, beginning on 10 May 1940, which ended the Phoney War. The battle consisted of two main operations. In the first, Fall Gelb , German armoured units pushed through the Ardennes, to cut off and...
in 1940 it was clearly time to reconsider the usefulness of Cultivator No. 6. Churchill wrote to General Ismay
Hastings Ismay, 1st Baron Ismay
General Hastings Lionel "Pug" Ismay, 1st Baron Ismay, KG, GCB, CH, DSO, PC was a British Indian Army officer and diplomat, remembered primarily for his role as Winston Churchill's chief military assistant during the Second World War and his service as the first Secretary General of NATO from 1952...
and CIGS Ironside:
The number of units was soon even more significantly reduced to just 33 machines and by July Churchill was finding other tasks to assign to Mr Hopkins. Even so, the project was not completely canceled – with Britain facing invasion and desperately short of conventional tanks it does seem remarkable that the project continued. Historian John Turner attributes this dogged persistence to Churchill's failure to get his mole accepted during the First World War. It was at this point that the original code name of Cultivator No. 6 was dropped in favour of N.L.E. Tractors.
There were various problems with the development and the prototype machine, officially known as N.L.E Trenching Machine Mark I, but nicknamed Nellie was completed in May 1941.