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The Terrapin was powered by two Ford V-8 petrol engines and was driven in the water by two propellers at the rear. There were two cargo holds and the driver sat in the centre of the vehicle.
The Terrapin was the British equivalent of the American DUKW, and although it was never built in the numbers that the DUKW achieved it made a useful addition to the amphibious load-carrying fleet used by the British army in 1944-5.
The Terrapin was designed by Thornycroft, but production was carried out by Morris Commercial. About 500 were built, and the bulk of them were used by the 79th Armoured Division, first going into action during the autumn of 1944 when they were used to supplement DUKWs during operations to open up the water approaches to Antwerp. The Terrapin was a straightforward amphibious design but it had some odd features, some of which were not to its advantage. One concerned its two Ford V-8 petrol engines, each one driving the four wheels set along each side; with the Terrapin in the water, the engines each drove one of the two propellers at the rear. The snag with this arrangement turned out to be that if one of the engines stalled for any reason the other engine kept driving, causing the vehicle to go into a rapid turn which could cause alarm and damage to all concerned. Thus Terrapin drivers had to be especially alert to this hazard. The two engines were mounted almost centrally to spread wheel loadings, but this had the effect of dividing the cargo compartments into two halves, Thus although the Terrapin could carry more than the DUKW it could not carry the really large loads such as guns or large vehicles.
The overall performance of the Terrapin was not all that good. It was rather slow on land and in the water, and it was in the water that this performance really mattered. When fully loaded the Terrapin had only a limited freeboard and it could be all too easily swamped in rough water, The top of the vehicle was completely open, but raised moulding boards around the holds could keep out the worst of the water. The driver was located roughly in the centre of the vehicle and his view to the front and rear was rather limited, meaning that other crew members had to give directions during tight landings or when travelling through restricted urban areas. The Terrapin was also a rather uncomfortable vehicle during bad weather conditions. Being seated in the open the driver and crew had to rough it, but an awning could be raised over the front compartment. This was meant to act as a spray shield in the water, but it could also double as weather protection; the trouble was that it restricted even further the driver’s forward view.
For all these drawbacks the Terrapin gave good service. Even before it was used operationally some of the drawbacks had been realized and Thornycroft was asked to produce a new design. This emerged as the Terrapin Mk 2, the original model thereupon becoming the Terrapin Mk 1. It had a large ‘one-piece’ hold, much better all-round performance and the driver positioned well forward under cover. The hull shape was improved to provide better seaworthiness and water manoeuvrability was much improved. But the Terrapin Mk 2 arrived on the scene too late: the war ended before it could be placed into production and the large numbers of DUKWs to hand meant there was no point in developing it further, and with the end of the war the Terrapin Mk Is were also withdrawn.
Specification
Terrapin Mk 1
Crew: 1+at least 2
Weights: unloaded 6909 kg (15,232 lb); loaded 12015 kg (26,488 lb)
Powerplant: two Ford V-8 petrol engines each developing 63.4 kW (85 bhp)
Dimensions: length 7.01 m (23 ft); width 2.67 m (8 ft 9 in); height 2.92 m (9 ft 7 in)
Performance: maximum land speed 24.14 km/h (15 mph); maximum water speed 8 km/h (5 mph)
Armament: none
