After an absence of about two years, the Sturdy name was resurrected in 1935 when two examples of the new model were displayed at the Commercial Motor Show at Olympia, London, in November for the 1936 model year. The Sturdy was rated for a 4 ton to 5 ton load (4,064kg to 5,080kg) and was powered by Thornycroft’s new four-cylinder TC4 side-valve petrol engine. This unit displaced 3,865cc, had a Ricardo cylinder head and was rated at 60bhp@2,400rpm, a speed at which, incidentally, the engine had not reached its power peak - the latter probably occurred at around 2,600rpm resulting in an estimated 61bhp.
This may be a wartime photo of a forward-control Sturdy.
The Sturdy entered production in 1936, and was offered as a forward control lorry with two wheelbase options. During 1936, the Sturdy range was extended to include normal and forward control models, each with two wheelbase options and alternative capacities of 4 tons (4,064kg) or 5 tons (5,080kg). These eight versions were all powered by the TC4 petrol engine; normal control models were designated as YE/TC4 and forward control models as ZE/TC4.
Thornycroft offered a special lightweight cab and body for the 5 ton (5,080kg) versions in order to keep unladen weight within the 2½ ton (2,540kg) legal maximum for the 30mph (48.3kph) speed limit and £30 tax class. In keeping with modern trends, Thornycroft used coil ignition for the TC4 as standard, although an operator who still preferred a magneto could have one at extra cost. Starting the engine manually by swinging the starting handle was expected of drivers on the standard model, and a starter motor was offered only as an extra.
A test of a Sturdy 5 tonner (5,080kg) in 1936 by The Commercial Motor journal recorded an average fuel consumption of 11.6mpg (24.3 litres/100km), and a creditable maximum speed on the level of 40mph (64.4kph) at 2,768rpm. However, the test team managed to get the test vehicle up to nearly 50mph (80.5kph) on a descending section! At this speed the engine was spinning at nearly 3,460rpm - an impressive and frenetic rotational speed! The 0 to 30mph (64.4kph) acceleration time of 30 seconds makes an interesting comparison with the corresponding figure of 21.5 seconds for the 1939 Nippy 3 tonner (3,048kg) with the same engine. The test team found the noise in the cab on the high side, and suggested that sound-proof lagging fitted under the bonnet would be an improvement.
In 1937, the Sturdy range comprised the eight versions already mentioned as well as two ZE/TC4 forward control tipper versions, with 3.5cu yds and 4cu yds capacity, respectively (2.68cu m and 3.49cu m). The normal control YE/TC4 tractive unit was added to the range in 1937, for hauling a 6 ton to 8 ton (6,096kg to 8,128kg) semi-trailer.
In late 1938, three 5 ton (5,080kg) Sturdy variants were announced for listing in 1939 with Thornycroft’s new six-cylinder MD6 diesel engine, a small 3,905cc unit of 75bhp. However, WW2 broke out on 3 September 1939, and diesel versions of the Sturdy had to wait until the end of hostilities in 1945 before they could be introduced. During the conflict Thornycroft, along with its war production, maintained vital lorry production for civil operators, mainly of petrol-driven Sturdy and Nippy types. Both these vehicles continued in production when the war ended in 1945, with petrol and diesel options (see below).
Thornycroft small diesel engine: Thornycroft’s small six-cylinder MD6 diesel engine, mentioned above, was designed for the Sturdy and had a Ricardo-type cylinder head. The new diesel was ready for production some time during 1939, but the outbreak of WW2 that year prevented its series manufacture. However the engine was further developed during the six years of war, as and when Thornycroft’s heavy workload allowed, including bench testing and road trials covering 100,000 miles (160,900km). Manufacture started in 1945, the year WW2 ended. By this time Thornycroft’s small diesel was designated TR6, and was rated at 67bhp@2,200rpm. The engine powered diesel versions of the Sturdy and Nippy.
“Sturdy” Class 5-Ton (5,080kg) chassis, petrol-engined forward-control type “ZE/TC4” short-wheelbase
In-line cylinders. A single casting of iron is used for the cylinder block and crankcase, with side valves housed in the cylinder block. Renewable exhaust valve seatings, dry cylinder liners and Thornycroft-made aluminium-alloy pistons are fitted. The cast-iron cylinder head is of the Ricardo-type.
The camshaft operates the valves through inverted-mushroom type tappets, and is driven by a triple-roller chain.
Crankpin and main-journal diameters are 2¼ins (5.72cm).
Forced feed system from a pump.
By carburettor. The inlet manifold has an exhaust-heated hot spot.
By centrifugal water pump (incorporates a carbon gland).
Single dry plate clutch of 12ins (30.5cm) diameter.
Unit with engine and clutch, and providing four forward speeds and a reverse speed. Shafts are 9ins (22.9cm) long between bearing centres. The gear lever is mounted on a forward extension to the gearbox casing.
The overall gear ratios are as follows (including final drive)
Road speed at 2,400rpm (mph/kph)
Propeller Shaft. Two-piece open tubular propeller shaft, with three Layrub universal joints.
One piece type.
Incorporates fully floating half-shafts, overhead worm final drive and differential.
Leaf type. Front springs are 3ft 4ins (1.02m) long, rear springs are 4ft 2ins (1.27m) long. All springs are 2.5ins (6.35cm) wide.
Drum brakes on all four wheels, pedal operated through a Dewandre vacuum-servo system. The diameter of all drums is 16ins (40.6cm). Front shoes are 2½ins (6.35cm) wide, rear shoes are 4½ins (11.4cm) wide. Frictional area of front brakes is 130sq ins (838.7sq cm), and frictional area for rear brakes is 238sq ins (1,535.5sq cm).
Operates on all four wheels by non-servo mechanical means.
The turning circle is 48ft (14.6m) on both locks; 3¼ turns of steering wheel from lock to lock.
Pressed steel. Maximum depth of side members is 8ins (20.3cm).
A 20-gallon (90.1 litres) fuel tank is carried on the nearside of the chassis frame. A vacuum device, draws the fuel from the main tank and delivers it by gravity to the carburettor.
Wheels and Tyres
Tyres are 34ins x 7ins (86.4cm x 17.8cm) on pressed steel wheels, single front, twins at rear. The standard position for carrying the spare wheel and tyre is at the rear underneath the frame.
An electric lighting set, dynamo, spare wheel, tyre and carrier, etc. An electric starter is available at extra cost.
Final drive (rear axle) ratio is 7.25.
Information for these pages comes from contemporary Thornycroft technical and other data, as well as contemporary copies of The Commercial Motor.
Sturdy outline diagram 51kb pdf