Joseph Crossfield and Sons Ltd of Warrington bought their first vehicle during WW1 in 1915, a Type Q. Shortly afterwards, the firm bought three Type Js, and as a result of the excellent service Crossfield received from its Thornycroft lorries, the firm bought another 21 Thornycrofts after the war, among which were four Type Qs. The 5 ton (5,080kg) Q was an early contemporary of the 4 ton (4,064kg) Type J, and both these vehicles shared the same 40hp engine, a large 6,256cc M/4, a T-head straight 'four'. Furthermore, this engine was also used in Crossfield's 3 ton (3,048kg) Type X lorries and the firm considered the commonality of engines and other parts between all three vehicles to be a useful asset, minimising spares holdings and storage space.
Type Q box van from Thornycroft's 1924 brochure
Like other Thornycroft lorries, the Q was a conventional, straightforward four-wheel design, with a front engine oriented fore and aft, a four speed gearbox, rear wheels driven by a propeller shaft, and a worm drive for the differential located in the rear axle. Unlike in certain later vehicles, the Q's engine and gearbox were separate items.
The Type Q was updated for 1924 with a larger and more powerful engine nominally rated at 50hp, but, in fact, offering 58bhp at 1,600rpm. This latter data was not included in Thornycroft's brochure, possibly to encourage moderate driving in the interests of engine life! Designated BB/4, this engine was a massive 6,970cc straight 'four' with an unusual valve layout comprising overhead inlet and side exhaust valves (ioe), presumably aimed at producing a more efficient cylinder head design than the L and T-heads also used by Thornycroft. Despite the trend towards power units in which engine and gearbox were built as one unit, these two items were separate in BB/4-based powertrains.
Thornycroft introduced an uprated 6 ton (6,096kg) version of the Q in 1924 to take over from the 6 ton (6,096kg) Type W. The uprated Q 6-tonner (6,096kg) had a wheelbase extended to 16ft (4.88m) from the 5-tonner's (5,080kg) 14ft 6ins (4.42m), but, apart from a 2cwt (102kg) increase in chassis weight and greater length, there was little, if any, difference between the 5 ton (5,080kg) and 6 ton (6,096kg) Qs. Both versions were powered by the BB/4 engine, as was a six-wheel articulated development of the Q rated at 10.75 tons (10,922kg).
Ashby's Staines Brewery operated this 40hp Type Q. HMAS
In late 1923, Thornycroft entered a fully loaded lwb 6 ton (6,096kg) Q in a road test under RAC observation. As sales brochures did not list the 6 ton (6,096kg) version of the Q until 1924, then this might have been a pre-production lorry. It was certainly a non-standard vehicle, as the 6,970cc BB/4 engine was replaced for the road test by a smaller, but similar, 4,531cc AB/4 ioe engine, no doubt to minimise petrol consumption. The lorry had a total running weight of 10.95 tons (11.13 tonnes) returned a petrol consumption of 11.28mpg (25litres/100km) over 1,008miles (1,622km) giving a load carrying performance of 123.34 ton-miles/gallon (44.52 tonne-km/litre). Corresponding oil and cooling water consumptions were 1,697mpg (0.166 litres/100km) and 1.75 gallons (7.96 litres), respectively, both of them high by current norms, but acceptable in 1924.
The Q's ton-mile/gallon figure from the above road test was considered a very good result, and better than the previous 1923 best from a Swiss Saurer 5/5.5 ton (5,080/5,588kg) lorry which returned 104.66 ton-miles/gallon (37.78 tonne-km/litre); the Saurer also used more oil, but less cooling water than the Thornycroft. It would have been more realistic to base the results on the payload rather than, as was done, the total vehicle weight. Also, good though the Thornycroft's test results may have been, the non-standard AB/4 engine powering the Q during the test was small for a 6-tonner, and whether or not this relatively underpowered vehicle made a satisfactory load carrier on all but the flattest of surfaces is open to question.
A more realistic test vehicle would have been a Q in standard trim with its rightful large BB/4 engine, and while petrol consumption might have gone up, so, too, would the 11.9mph (19.1kph) average speed achieved over the course (allowing for running time only). The trial route for both Thornycroft and Saurer lorries included London (Swiss Cottage), Barnet, Welwyn, Hitchin, Bugleweed, Tempsford, Eaton Socon and back. The Thornycroft trial occupied 10 days in all, the lorry did not coast when going down hill and there were no involuntary stops.
In a seemingly retrograde step, Thornycroft powered its new vehicles for 1926 by engines with less advanced L-heads than the BB/4's ioe valves. Perhaps production and maintenance issues put paid to Basingstoke's interesting ioe engines.
Specification of Thornycroft 4½/5ton (4,572/5,080kg) Chassis Type "Q" March 1924
For a nett load of 100cwt (5,000kg) in an open Lorry Body, or 90cwt (4,500kg) in a Van Body.
Chassis Weight, in running order, 76cwt (3,861kg) (Laden).
Gross Load, including cab and body, 120cwt (6,096kg).
Total Laden Weight 196cwt (9,957kg).
Front, 52cwt (2,642kg).
Rear, 144cwt (7,315kg).
This model is eminently suitable for motor coach and omnibus bodies.
50hp (type BB/4). Four-cylinder, monobloc with detachable top. Inlet valves over the exhausts. Bore 4¾ins (121mm) x Stroke 6ins (152mm).
Damp-proof high-tension magneto.
Of improved float feed type. A pilot jet is fitted for starting and slow running.
The carburettor throttle is controlled by a lever on the steering column and also by a foot accelerator. The magneto is controlled by a second lever on the steering column.
Placed on the dashboard where it is accessible for easy filling, and allows of a constant gravity feed to the carburettor under all conditions. The capacity is 20 gallons (91 litres), and a very large filler is fitted which does away with the need for a funnel.
Of the cone type. A pressed steel cone lined with ferodo engages the cast-iron flywheel. This is of large diameter, ensuring smooth running, absence of slip, and maximum life of clutch lining. The clutch springs are easily accessible for adjustment. A large and efficient clutch stop is fitted to facilitate gear changes. Between the clutch and the gearbox, a leather disc-type universal coupling is fitted.
A one-piece casting with large inspection cover. Ball bearings on primary and secondary shafts with ball thrust behind brake drum. The drive on top is direct with three indirect gears and a reverse. At 1,000rpm of engine the road speeds are as follows: Reverse, 1.8mph (2.9kph); first 2.2mph (3.5kph); second 4mph (6.4kph); third, 6.8mph (10.9kph); fourth, 11.6mph (18.7kph).
Operated through a gate type quadrant.
Live axle fitted with overhead type worm gear. The central portion of the axle is composed of a cast-steel casing of ample strength into which is fitted the differential worm gear, carried in a self-contained housing which, without taking the load off the road wheels, can be removed bodily at any time. Standard ratio 10.66 to 1.
Two brakes are fitted: a foot brake, of the contracting type, operating on a drum at the rear end of the gearbox; and a hand brake of the expanding type, which is applied on the rear wheels direct. The drums are of very large diameter. Both brakes can be adjusted for wear by hand without the use of tools.
A sheet metal mud-shield under the fore part of the chassis protects the mechanism from dust and mud.
The axle body is of H-section steel, drop forged in one piece. The swivel arms are of the central pivot type which render steering very easy in spite of the weight of the vehicle.
Channel section pressed steel. Strong, but light. The engine and gearbox under-frame is suspended on the three-point system, so that twisting of the frame members due to uneven road surfaces has no harmful effect whatever.
This is fitted with ball bearings and ball thrusts, which help to render the steering very easy.
The minimum width of road for reversing direction without using reverse gear 57ft (17.4m).
Nominally 34½ins (876mm) diameter over tyres on front, 41½ins (1,054mm) over tyres on back. Of cast steel with solid rubber tyres. The wheels are carried on phosphor-bronze floating bushes of large size.
Solid rubber singles on front wheels, 140 x 720mm; twins on back wheels, 160 x 850mm fitting sizes.
Minimum clearance underneath chassis, fully laden, about 10ins (254mm).
14ft 6ins (4.42m).
Front wheels 5ft 11½ins (l.82m.). Centre-to-centre of twin tyres on back wheels 5ft 10ins (1.78m).
Chassis diagram 121kb pdf
Dimensions information 84kb pdf