The following article was submitted to us by David Lister (Listy). It’s a fascinating look at one of the innovations of World War 2 – the Nellie tunnelling machine.
In October 1911 Winston Churchill was appointed the head of the Admiralty, and in February 1915 he set up and headed the Naval Landships Committee. Influenced by various ideas including the idea of armoured cars and HG well's short story "The Land Ironclads", the committee came up with new and inventive ideas to break the stalemate of the First World War. The end result was of course the Tank.
One of the ideas that Churchill had during World War One was a machine designed to tunnel and burrow under no man’s land and surprise the enemy. Now, while that sounds fanciful, remember there was an entire aspect of the war fought underground (and a remarkable story it is too, I would strongly suggest you go look it up). Equally the idea of tunnelling as a weapon had gone back thousands of years, but was normally used during sieges. However, Churchill wasn’t to stay in his post for long, and by May had been removed.
In September 1939, Churchill was re-appointed the head of the Admiralty. Now, you have to remember the conditions of the time, the so-called Phoney War. The French had no political stomach for a fight after the heavy casualties of World War One. So they had the Maginot Line. The Germans were dug in on the Siegfried Line, which the Allies overestimated in its abilities. So you had two solid walls of fortifications with a killing ground in between.
Equally the British were digging in with barbed wire and trenches. So to people at the time it looked like everything was on course for a repeat of World War One. It was considered that attacking the vaunted Siegfried Line was an impossible task as the casualties would be worse than the last war.
It’s at this point that Winston Churchill revisited his idea of the tunnelling machine to create trenches across no man’s land which infantry could use to protect them from enemy fire. Churchill saw it as one of the few offensive ideas of the time, and what’s more, now he was in a position to do something about it!
With this in mind, during October 1939, Churchill set up the Naval Land Equipment committee, chaired by JH Hopkins, an experienced and well-regarded ship designer. Curiously the Committee came under the Ministry of Supply not the Admiralty. Due to many functions of state being moved out of London due to fears of Luftwaffe attack, the Committee took up residence at the Grand Pump House Hotel in Bath.
Churchill referred to the machine as his "Mole", while the Committee called it ‘Cultivator No6’ or later ‘NLE tractor’. The initials NLE led to the nickname for the prototype of “Nellie”. One of the engineering firms involved called it a "No-man’s Land Excavator". However, these all referred to the same vehicle. It had originally been planned to create two types. One was to dig a trench for infantry, while the other, larger machine would dig a trench wide enough for tanks. These were termed "Infantry" and the wider machine "Officer".
The machine itself was designed to use a single naval Merlin Engine providing 1000 horsepower, with 50% being used to power the cutting and the rest for locomotion. However, this was soon found to be impractical because the RAF had taken all Merlin production for its fighters and the Merlin could only produce 800 horsepower under continuous use. Instead it was decided to use two 600 h.p. diesel engines from Paxman Engineering. This had the advantage of providing more power, simplifying the design of Nellie and being safer as they used diesel rather than petrol.
Nellie herself was 77 feet (34.4 metres) long, weighing in at 130 tons. She was built in two sections, the head and body. The head had the cutting gear and could be angled up or down to stay buried or return to surface. Minor course corrections while tunnelling could be achieved by deploying hydraulic flaps or doors on the side you wanted to turn towards; these would act much like an airbrake does and slew the contraption slightly to one side.
For digging there was a huge plough on the front that split and moved the top 2.5 feet (76 cm) of earth, and a huge rotating cutting cylinder that removed the bottom 2.5 feet. The spoil from this was carried along a conveyor belt and deposited on the banks of the trench to a height of another 3 feet (1 metre).
The machine was lightly armoured even though the intention was that she would never take any incoming fire due to being in the trench. The plan for Nellie’s use was to have it dig across no man’s land at night under the cover of an artillery barrage, and when they reach the enemy lines the troops would rush the German positions.
The head and body could be detached for transport. To make life easier for shipping the body could be split into two.
When surfaced Nellie could travel at 3mph (4.8 kph), while digging at 0.67 mph (1kph). During an hour of digging the machine would move over 8000 tons of soil.
There were two alternate designs to the one above. The first was a rotary cutting head, much like a modern tunnelling machine. The second design had incredibly thick front armour, and a hydraulic ram that would push explosive charges into the ground in front of it. These would detonate and the machine would drive into the crater, and then repeat the process. This design came from an engineering officer totally independent of the NLE committee. The hydraulic design had the advantage of being able to knock out German bunkers by placing an explosive charge under it, but it was a lot slower than the NLE design. In the end the Nellie won out.
After the design had been selected a 4 foot (1.3m) scale working model was built. This was then packed into a box and carried to Bath train station. On its way, many people bowed their heads thinking it was a coffin. For the demonstration, a land surface was created using Plasticine and sawdust to represent the dirt. The model performed beautifully and Churchill was ecstatic, to the point that one bystander thought he was grinning so much he was about to drop his cigar! Later on, there was another demonstration with Churchill, the Prime Minister Neville Chamberlain, the Chancellor of the Exchequer and the Chief of the General Staff.
The model was also shown to the French who supported the plan.
On 7th of February 1940, an order was placed for 200 Infantry and 40 Officer machines. At full production it was envisioned NLE tractors could be built at a rate of 20 per Week.
However, on the continent the Germans realised something was afoot when they noticed increased French patrols in front of the Siegfried Line. These patrols were gathering soil samples, to allow the experts to select the best assault site.
When the Germans attacked France, the need for the machine vanished. Almost immediately Churchill slashed the funding for the NLE committee by 50%, and a few days later even further. Surprisingly, production was dropped to 33 machines but not cancelled. Churchill did say that the resources freed from this project should be devoted to tank production.
In May 1941 Ruton-Bucyrus of Lincoln built the first machine, which was sent for trials at Cumber Park in Nottingham. These trials lasted from June 1940 to January 1942.
In the end, 5 NLE tractors were completed. Four were scrapped at the end of the war. Four Officer Machines were also half built, but these were scrapped in May 1943.
The last Cultivator No6, was the pilot model. Nellie, as she was called during the trials. She was scrapped in the early 1950's.