Cultivator No. 6 - Alternative Design

Alternative Design

In April 1940, came a huge 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 mine. 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.