Skellingthorpe helps hatch a monster!

In the autumn of 1939 Winston Churchill, as First Lord of the Admiralty, revived an idea from 1916 fora fleet of trench-cutting machines, under cover of darkness, to lead an infantry attack on the German defences, known as the Seigfried Line. The Departent of Naval Constructors, charged by Churchill to develop the idea quickly found themselves out of their depth and ultimately consulted the local firm of Ruston-Bucyrus for their earth moving expertise.

Under conditions of absolute secrecy a small of designers from Lincoln were seconded to the Admiralty in Bath to progress the initial concept. As the development progressed, a small design office was established in the Anchor Street works of Ruston-Hornsby where the draughtsmen worked under armed guard and the strictest security. The trench-cutting idea evolved as a large plough to clear the top two feet of top soil, revolving cutters below to dig the remaining sub soil to the required depth of five feet. Behind this were conveyors to transport the soil back and dispose of it in a bank on either side as the machine progressed, thus further concealing its progress. All of this excavating machinery was propelled by a powerful tracked engine unit which provided power for the cutters, conveyors and propulsion.

Before this concept could become reality, innumerable tests were require to establish things like ground resistance, cutting speed, rate of propulsion and the hose power required to turn the machinery as well as the caterpillar tracks. A test rig was designed and installed at Skellingthorpe west of Stones Place and behind the lakes, the area ultimately part of the Skellingthorpe Airfield and subsequently disappeared under houses of the Birchwood Estate. Many trials took place to provide the data required, all of which was collated for the benefit of the designers in their Lincoln Drawing Office. Winston Churchill made a secret visit to Skellingthorpe on 19th May 1940, to check for himself the progress of these tests and following the successful outcome, gave his approval for the continued development of the prototype and initial production machines.

A pilot machine was constructed in three sections and transported to Clumber Park. The three sections were bolted together and tracks fitted to commence digging and acceptance trials. The ultimate machine was a formidable monster, digging a trench 7'6" wide x 5' 0" deep and throwing banks of soil to a height of 5'0" on either side. "Nellie" (short for Department of Naval Land Equipment), weighed in at a colossal 130 tons, 77' 6" in length, 7' 5" wide (18' 6" at extremities of the plough and 10' 2" height to the top of the conning tower.) All powered by two Paxman-Ricardo 12 cylinder diesel engines, each developing 600 hp at 1500 rpm.

Military events turned against the use of Nellie by mid 1940, however development continued as a result of Churchill's insistence. The project stopped in Lincoln towards the end of 1941, however, the pilot machine, together with four working machines were handed over to the Royal Engineers who maintained these in working order until the final cancellation was agreed by Churchill on 1st May 1943.

This extract is taken from a book "'Nellie" the history of Churchill's Lincoln Built Trenching Machine' written by ex Ruston-Bucyrus Apprentice John T. Turner, first published in 1988.

Michael Boaden