Responding to demand for higher carrying capacities, Thornycroft introduced the 12 ton (12,192kg) QC rigid six wheeler in 1930. Although intended for on-road operation, the QC had a limited off-road capability at reduced load. The large and heavy QC was powered by the 104bhp NC6 petrol engine, a massive straight-six side-valve unit displacing over 11 litres. As usual with Thornycroft RSWs, power was taken from the gearbox via a propeller shaft to the differential of the leading back axle, from which a short shaft supplied power, also, to the differential of the rearmost back axle. Braking was on the rear axles only using a Westinghouse servo system. Three options of the vehicle were initially offered, the long wheelbase option had normal control and the shorter wheelbase model could be had with normal or forward control. Following the introduction of Thornycroft’s policy of naming its vehicles, while keeping alphanumeric designations, the QC was named Dreadnought QC/NC6 in 1931, indicating use of the NC6 engine.
The peaked cab of this 1933 Dreadnought RSW is reminiscent of steam locomotive practice.
The QC up to 1932 is more fully described in the pages headed Thornycroft lorries 1927 to 1932.
Engine improvements were introduced in 1933, when the ND6 petrol engine with overhead valves, rated at 133bhp, replaced the same-size side-valve NC6 petrol engine of 104bhp. Also, a diesel option was introduced using the large 11,339cc CIND6 six-cylinder engine. Three basic Dreadnought versions were offered in 1933, comprising the long–wheelbase normal control QC, normal wheelbase forward control QD and short-wheelbase forward control QE. Designations indicated engines used (e.g. Dreadnought QD/ND6, Dreadnought QC/CIND6, etc). The load capacity given for 1933 Dreadnoughts in Thornycroft’s specifications was 10 tons to 11 tons (10,160kg to 11,176kg), a reduction from the 12 tons (12,192kg) initially specified.
Dreadnoughts were not listed for 1934, and their demise was part of a pruning of Thornycroft’s RSW range, as shown below.
There were six RSWs listed in 1933
However, after pruning the RSW model range, only three RSWs were listed in 1934
Comparing the above lists of Thornycroft RSWs offered in 1933 and 1934, it can be seen that the Stag was introduced in 1934 to replace the Dreadnought and Jumbo of 1933. The Mastiff was evidently considered redundant in the face of the Amazon, which was therefore retained for 1934. The capacity gap between the Tartar and Amazon was plugged by the Wolfhound in 1933, but this gap seems not to have been considered important by 1934 so the Wolfhound was withdrawn.
The Dreadnought name lapsed until 1939, when a completely new Thornycroft Dreadnought RSW was listed for the UK market, with two front axles instead of, as in the previous models, two rear axles.
Dreadnought “QC/ND6” rigid six-wheeled freight chassis with six-cylinder engine
To carry a net load of 10/11 tons (10,160/11,176kg
This chassis is designed to carry a net load of 11 tons (11,176kg) provided a suitable body and cab are fitted. Combined with the latest developments in design and construction, ease of maintenance and accessibility have been given particular attention throughout.
Six-cylinder 133bhp, type ND6, watercooled petrol engine, 4¾ins (120.7mm) bore, 6½ins (165.1mm) stroke. Cubic capacity 11,339cc. Three point suspension with trunnions carried in rubber bushes, stresses in the crankcase due to frame distortion are thus almost entirely eliminated and a cushioning effect is ensured in the transmission of the torque reaction from the engine to the frame. The trunnions are bolted to vertical faces on the crankcase, which simplifies removal of the power unit from the chassis. Either engine or gearbox may be removed independently for overhaul leaving remainder of power unit in position on the vehicle.
Monobloc construction assisting rigidity of crankcase, fitted with special dry cast iron liners. The cylinder head is easily removable for decarbonising and grinding-in the valves.
Overhead valves operated by push rods and rockers from a single camshaft, housed in tunnel cast in the side of the cylinder block, and driven by a triple roller chain at the front of the crankshaft. Access to the rockers is obtained by removal of an aluminium cover secured by hand screws.
A deep-section casting of special alloy exceedingly well ribbed. To ensure extreme rigidity, long double-ended bolts pass right through the crankcase, securing the cylinder block at one end and providing support for the main bearing caps and keeper plates at the other. The bottom half is easily detachable for the inspection and taking-up of the main and big end bearings, etc.
A dynamically and statically balanced nickel-chrome steel crankshaft of ample dimensions, carried in seven white-metal lined bearings of 3½ins (88.9mm) diameter. A very efficient vibration damper is fitted to maintain smooth running over the whole speed range.
The oil is forced by pump through an efficient external oil filter to the main and connecting rod bearings, also to the camshaft bearings and rocker gear. The filter, which can be removed without draining the sump, incorporates a by-pass valve, so that in the event that the oil is too thick to penetrate the felt, the lubrication of the bearings is not restricted. The oil passes through a large gauze strainer before returning to the sump, which has a capacity of 7½ gallons (34.1 litres).
By high tension, automatic-advance magneto, combined with hand control operated from the steering column.
Float-feed automatic type with special starting jet in addition to pilot jet for slow running. Induction manifold heated by “hot spot” from exhaust. The throttle is controlled by accelerator pedal and adjustable lever on the steering column.
By centrifugal pump, driven direct from engine, and fan positively driven through a damper clutch.
A vertical desert type radiator, with detachable top and bottom water vessels, mounted on rubber buffers.
A single-plate dry clutch of large diameter and area, with specially-prepared fabric surfaces. The lightness of the driven member and the efficiency of the clutch stop make gear-changing simple and rapid.
Of unit construction, providing four forward speeds and reverse, top gear being direct drive. The gear shafts, which are 2ins (50.8mm) diameter, run in large-size ball or roller bearings, and the gear wheels, with teeth 1.125ins (28.6mm) wide, are of special contour and ground to obtain silent running. A speedometer drive is incorporated with the gearbox.
The reduction ratios are as follows
Change Speed Control
Change-speed lever mounted direct on gearbox, light in operation, permitting easy engagement of gears.
The drive is transmitted from the gearbox by hollow propeller shafts with enclosed metallic universal couplings. An intermediate propeller tube immediately behind the gearbox is supported at the rear end by a ball bearing flexibly attached to one of the frame crossmembers.
Two cast steel casings with full-floating differential shafts of 2¼ins (57.2mm) diameter, driven by overhead worms.
The reduction ratios with standard and alternative tyre equipment are as follows, any of which can be provided, without extra charge, if specified when the chassis is ordered
36ins x 8ins (91.4cm x 20.3cm)
7¾ or 8.333
10.5ins-22ins (26.7cm-55.9cm) front
8.333 or 7¾
13.5ins-20ins (34.3cm-50.8cm) rear
40ins x 8ins (101.6cm x 20.3cm)
7¾ or 8.333
A 4ins x 3ins (101.6mm x 76.2mm) section axle body of 40 ton (40.64 tonnes) steel, forged in one piece. The 3ins (76.2mm) diameter swivel arms are of nickel steel with taper-roller thrust bearings on the pivot pins taking the weight and giving easy steering. The track rod is adjustable.
Internal expanding brakes are fitted to all six wheels. The foot brake assisted by three powerful vacuum-servo cylinders, operates shoes in 17ins (43.2cm) drums on all four wheels of the bogie and on the front wheels, two of the servo cylinders being connected directly to the latter. The hand brake actuates the shoes on the bogie wheels only.
All the brake gear is easily adjustable, but the facings consist of large fabric pads ensuring long life with a minimum of adjustment. The brakes are totally enclosed by dust covers.
Worm and wheel type with taper-roller bearings. The worm wheel is complete, thus permitting a fresh sector of the wheel to be brought into service should backlash develop through wear.
The vehicle has a turning circle of 80ft (24.4m) when fully laden. This will change when alternative tyres are fitted.
Lubrication of Chassis
By grease-gun and oil-gun, the nipples being grouped in accessible positions.
A pressed steel frame of channel section, reinforced in the centre, the dimensions of the channel being 9ins x 4½ins x 0.375ins (228.6mm x 114.3mm x 9.53mm). Body bearers are fitted across the top of the frame, in order that a lighter body may be fitted.
A 50-gallon (227.3 litres) steel tank with petrol gauge is fitted at the left hand of the chassis frame. A 2¾ gallon (12.5 litres) vacuum tank draws petrol from the main tank and delivers it by gravity to the carburettor.
Four inverted semi-elliptic springs independently pivoted at their centres to brackets rigidly attached to the chassis frame, in accordance with the Thornycroft system, giving even distribution of weight on all four wheels of the bogie under all conditions, irrespective of the relative movements of the axles, thus obtaining equal driving results from each wheel.
The springs form the only connection between the axles and frame, no torque tubes or radius rods being employed, the outstanding feature of this design being that the torque reaction is transmitted to the frame through the road springs, which ensure a cushioning effect, and thus relieve the frame of shocks.
The suspension is designed to permit a 6ins (15.2cm) difference in driving axle levels, buffers on the axles preventing excessive movement. The springs and pins are completely enclosed, thus protected from dust and mud.
Made of silico-manganese steel, ensuring very easy riding. The front springs, which are designed to be approximately flat under normal load, are secured to the axle by our patented type of relieving plate (Patent No. 199,522), which enables the holding-down bolts effectively to withstand the stresses due to flexing of the springs without suffering undue elongation.
In order to relieve the central bolt of shear stress, which would otherwise be caused by horizontal forces due to road shocks, etc., the holding-down bolts are inclined to one another, and special ears are provided on the top leaf to grip them.
Wheels and Tyres
36ins x 8ins (91.4cm x 20.3cm) straight-sided pneumatic tyres are fitted to disc wheels, single on the front axle and twin on the driving axles.
Alternatively, 10.5ins-22ins (26.7cm-55.9cm) in front, 13.50ins-20ins (34.3cm-50.8cm) rear low pressure tyres, or 40ins x 8ins (101.6cm x 20.3cm) straight-sided tyres may be fitted.
Exceeding 5 tons (5,080kg) weight unladen. £48.
Standard Chassis Weight
With 36ins x 8ins tyres (91.4cm-20.3cm) tyres, battery, standard lamps and dynamo, minimum oil in engine, gearbox and driving axles, but excluding petrol, water, tools, spare wheel and carrier: 6 tons 5cwt 3qrs (14,084lbs/6,389kg)
In Great Britain the laden bogie weight must not exceed 15 tons (15,240kg) and the gross vehicle weight 19 tons/19,304kg (maximum legal).
Standard Chassis Equipment
A 12 volt electric lighting set with dip and switch headlamps, two wing lamps, combined tail and “stop” light, 105 amp-hour battery, electric horn operated from centre of steering wheel, electric starter, engine speed governor, speedometer and mileage recorder, spare wheel with tyre and carrier, mechanical tyre pump, and a comprehensive kit of tools.
The following may be supplied at extra charge.
Information for these pages comes from contemporary Thornycroft technical and other data, as well as contemporary copies of The Commercial Motor.
Dreadnought 1933 outline diagram 120kb pdf
Dreadnought 1939 outline diagram 91Kb pdf