THE DUPLEX DRIVE TANKS OF D-DAY

Unfortunately our speaker from the Aylsham Roman Project due to speak to us could not make it.  It was to our advantage that Stuart Burgess who works for Norfolk Museum Services stepped in at the last minute.  Stuart is a Landscape Archaeologist and has carried out a detailed study of Fritton Lake’s WW2 heritage.  Fritton Lake, owned by the Somerleyton Estate was requisitioned in 1943 for the elementary phase of training and development of the Duplex Drive  amphibious swimming tanks fondly referred to as Donald Duck tanks.   In 1942 disaster unfolded on the beaches of Dieppe whilst unloading tanks, both infantry and craft became easy targets.

The 79^th Armoured Division was established and were charged with the development of the Swimming Tank.  Valentine tanks were used in the prototype, Duplex drive refers to the fitted propellers allowing propulsion through the water which supplemented the usual track.  Providing enough buoyancy with the tanks weighing 30 tonnes was a difficult engineering problem but there was not enough time to develop new vehicles.  The DD tanks were considered to be vital in providing close fire support to infantry on D-Day.

The problem was solved by a floatation screen made of waterproof canvas fitted to the tank’s hull just above the running gear.  A series of tubular frames were mounted horizontally giving the shape to the screen which was held taut by metal struts and vertical tubes filled with compressed air. When collapsed it enabled the tank to enter into combat role.  It became clear that although permission was given by the Ministry of Supply for the manufacture of 450 Valentine DD’s, it became clear that the Sherman was more suitable for use with the screen, one reason was that the Sherman could move in water with its gun forward ready to fire as soon as land was reached also the Valentine was older and generally of inferior design.

247 Valentine DD and 693 Sherman DD were built in the United Kingdom during 1943-4.

On the calm waters of Fritton Lake crews learnt to waterproof and maintain their tanks, including learning how to use Amphibious Tank Escape Apparatus.  Security was key and being surrounded by woodland Fritton Lake was and still is one of the most important historical places of WW2.  Following their Freshwater training the crews moved to saltwater training this took place at Stokes Bay Gosport.  Having loaded onto landing craft the tanks would be launched into the Solent, 1200 yards off the Isle of Wight at Osborne. By March 1944, 1200 men had participated in the training.

The intention on D-Day was for the DD tanks to arrive on the beaches minutes before the infantry to provide armoured support.  Despite poor weather over half were launched into the Channel.  A third were lost at sea due to the bilge pumps not being able to cope with water coming over the screens, those that did swim to shore provided significant support to the Infantry.

In this year as we celebrate the end of WW2, we were, and are reminded of the brave and courageous young men and women who gave themselves for the freedom that we enjoy today.

 DD Sherman Tank with its

 Flotation screen lowered.