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Rover 12
Rover 12
Rover 12
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The Rover 12 was a name given to several medium-sized family cars from the British Rover car company between 1905 and 1948.

1939-built Rover 12 Saloon (P2)

Rover 10-12 (1905-1907)

[edit]
Rover 10-12
open 4-seater without engine bonnet
Overview
ManufacturerRover
Production1905–1907
Model years1906–1907
Body and chassis
Body styleopen 4-seater
Layoutfront engine rear wheel drive
Powertrain
Engine1767 cc straight 4
Dimensions
Wheelbase84 in (2,134 mm)[1]
Rover 10-12
Layout
Configurationstraight four
Displacement1,767 cc (108 cu in)
Cylinder bore75 mm (3.0 in)
Piston stroke100 mm (3.9 in)
Output
Power output
  • not published
  • Tax horsepower 13.95

The Rover 10-12 was the fourth model Rover made, following their 8 hp, 6 hp and 16 hp. It was launched in November 1905 and displayed at that year's Olympia Motor Show. It had a four-cylinder, water-cooled, side-valve, monobloc engine of 1767 cc.

Rover 2-cylinder 12 (1909-1910)

[edit]
Rover 2-cylinder 12
Overview
ManufacturerRover
Production1909–1910
Powertrain
Engine1624 cc two-cylinder
Dimensions
Wheelbase88 in (2,235 mm) or 100 in (2,540 mm)[1]
Length140 in (3,556 mm)[1]

The new Rover 12 used a two-cylinder, water-cooled, side-valve engine of 1624 cc. The chassis and rear axle of this car would go on to be used in modified form in the 1912 cars.

Many of these cars saw use as taxis.

Rover sleeve-valve 12 (1910-1912)

[edit]
Rover sleeve-valve 12
4-seater standard flush-sided open tourer body 1911
Overview
ManufacturerRover
Production1911–1912
Body and chassis
Body style
  • open 2-seater
  • 4-seater tourer
  • chassis only
RelatedRover 12 2-cylinder and 4-cylinder
Powertrain
Engine1882 cc two-cylinder sleeve-valve
Transmissionmultiple dry clutch, universal joint to 3-speed gearbox, universal joint to enclosed propeller shaft and overhead worm final drive
Dimensions
Wheelbase
  • 100 in (2,540 mm)
  • 106 in (2,692 mm)[1]
  • Track: 50 in (1,270 mm)[2]
Length148 in (3,759 mm)[1]
Width61.5 in (1,562 mm)[1]
Kerb weight
  • chassis only 1,792 lb (813 kg)[1]
  • std 4-str car 2,352 lb (1,067 kg)[3]
Chronology
PredecessorRover 2-cylinder 12 horsepower
SuccessorRover Clegg 4-cylinder 12 horsepower
Knight-Rover sleeve-valve
Overview
ManufacturerDaimler Company Coventry
Layout
Displacement1,882 cc (115 cu in)[2]
Cylinder bore96 mm (3.8 in)[2]
Piston stroke130 mm (5.1 in)[2]
Cylinder block materialcast iron monobloc
ValvetrainKnight sleeve-valve driven by chains from skew drive from crankshaft
Combustion
Fuel systemDaimler twin-jet carburettor, gravity feed from scuttle
ManagementBosch dual-ignition
Fuel typepetrol from tank above driver's knees
Oil systemoil from sump pumped to troughs and splashed by big ends, sleeves by driver-operated mist spray
Cooling systemwater pumped to radiator and cooled by engine-powered fan
Output
Power output
  • not published
  • Tax horsepower 11.43[2]

A supplementary model of Rover 12 with a Knight-Rover two-cylinder, water-cooled, sleeve-valve engine of 1882 cc with a two-seater body was announced in October 1910 for the Olympia Motor Show though Rover's intention to produce it was published in mid-1910. Daimler engines were at that time cast in pairs of cylinders; this engine was half a four-cylinder 1909 22 hp Daimler.[4]

The Knight-Rover engine

[edit]

The connecting rods for the two cylinders are side by side on the same crank pin, making firing points equidistant. The engine is mounted directly on the chassis frame. It can be seen from the illustration the rearmost bracket rolls over the flywheel, making the rear mountings much further apart from the front set than would be allowed by mounting the engine direct from the very short block. Magneto, distributor and water pump are driven by skew gear from the front of the crankshaft, as are the pinions and chains which drive the valve shafts operating the sleeve valves. The two-jet carburettor incorporates a silencer on its air intake. The first jet is used only at starting or at idle.[2]

A supplementary air supply controlled by a foot pedal operated at will by the driver provides an oil mist from inside the engine's crankcase to lubricate the tops of the valve sleeves. A three-plunger pump driven by the valve shaft forces oil from the sump to troughs under and in the path of the big ends. With each revolution the big ends dipping into the troughs throw oil to all parts of the engine. The dashboard has a telltale to warn if the pump is not working properly.[2]

Chassis

[edit]

The chassis was entirely new. The metal to metal multi-plate clutch requires no lubrication. Two plates are phosphor bronze, the others are steel. There is a double universal joint (a sliding block allows for withdrawal of the clutch) between the clutch and the gearbox. The gearbox is mounted on a separate underframe; all its shafts run on ball bearings. There are three forward speeds. The propeller shaft is fully enclosed and has a ball and fork joint at its forward end. Final drive is by overhead worm.

the concentric twin brake drums
 The brakes are unusual: both hand and pedal levers operate on the back wheels but upon different concentric drums, the outer drum being used by the foot brake. There are semi-elliptic springs front and rear, but at the rear of the plate springs are two coil springs on each side of the car which anchor the plate springs. Drive is transmitted to the frame by the front end of the semi-elliptic plate springs. There are no radius rods.[2]
rear suspension showing coil springs in plan and elevation

Road test by The Motor

[edit]

The test car was equipped with a four-seated torpedo body. The compact (106-inch) wheelbase left ample legroom for driver and passengers; there was space for luggage behind the front seat in front of the passengers. A spare gallon tin of oil and a tin of petrol was carried on one running board and a picnic hamper was strapped to staples on the running board on the other side, along with a large accumulator to run the electric lamps, all leaving ample room for ingress and egress through either door. "There was a slight tendency (for the rear wheels) to skid on very greasy roads." It was not necessary to add any water to the radiator during the ten days of the test. The Knight-Rover sleeve-valve engine was so silent the driver was often asked if it was running. "Would not hesitate to recommend it". "One of our passengers went off without saying a word and bought a similar car within 24 hours."[5]

Road test by The Automotor Journal

[edit]

"A nice smooth running little car". During acceleration there is a low periodic noise as of escaping steam which disappears once under way and the car runs silently. Smooth running requires a very particular adjustment of the ignition and throttle controls. Rover maintains its prejudice against foot-operated accelerators. The engine will pick up from standstill on top gear if the clutch is made to slip a little. There is a very powerful clutch stop which requires a gear change to be made in one rapid movement. If the change is missed it will be necessary to stop the car to engage any gear. If Rover fitted an accelerator pedal it would satisfy all opinions.[3]

Rover Clegg 12 (1912-1923) and 14 (1924)

[edit]
  • Rover Clegg
  • 12 and 14
1914 Rover Twelve designed by Clegg
Overview
ManufacturerRover
Production
  • 1911–1924
  • 13,000 approx made
DesignerOwen Clegg
Powertrain
Engine2297 cc side poppet valve straight 4[6]
Transmission3 or4 speed manual
Dimensions
Wheelbase
  • 110 in (2,794 mm)—1911
  • 116 in (2,946 mm)
  • Track 50 in (1,270 mm)[1]
Length
  • 163 in (4,140 mm)
  • 168 in (4,267 mm) [1]
Width65 in (1,651 mm)
Kerb weight
  • chassis only 1,568 lb (711 kg)
  • entire car - not published [1]
Rover 12
Overview
ManufacturerRover cars
Layout
Displacement2,297 cc (140 cu in).[6]
Cylinder bore75 mm (3.0 in)[6]
Piston stroke130 mm (5.1 in)[6]
Cylinder block materialcast-iron 4 en bloc[6]
Combustion
Fuel systemSU Carburettor[6]
Output
Power output
  • 22 bhp (16 kW; 22 PS)
  • 28 bhp (21 kW; 28 PS)[1]
  • Tax horsepower 13.95[6]

The new Rover 12 was first displayed at the November 1911 Olympia Motor Show as a 4-cylinder supplement to the 2-cylinder sleeve valve cars.[6] It was designed by Owen Clegg who had joined Rover from Wolseley. It had a four-cylinder, water-cooled, side-valve engine of 2297 cc with an SU carburettor made by Rover under licence. Around 5000 were made before World War I. The transmission was three-speed, separate from the engine, and drove the rear axle which had a worm drive. Semi elliptic leaf springs were fitted front and rear. Rear wheel brakes, operated by the hand lever were fitted, with a transmission brake operated by the foot pedal.

Post war, in 1919, the engine got a detachable cylinder head and electric starter.[7] A 6 in (152 mm) longer wheelbase chassis became an option in 1921. Advertisements in 1922 quote open two- and four-seat, saloon, limousine coupé and drophead coupé bodies being available at prices from £625 to £800.

In 1924 the model name was changed to the Rover 14 and a four-speed gearbox fitted although the three-speed remained an option on the open models. There was no change to the engine but the new name was claimed to more closely represent the treasury rating of 13.9 hp. A Weymann fabric bodied saloon was added to the range. The last of the cars was made in 1924 after around 13,000 had been made.[7]

1912 landaulette registered December 1912
1913 Rover 12hp Roadster
1914 Twelve in the Cotswolds
registered 31 December 1914

The Wilks' pilot scheme

[edit]

Rover Pilot

[edit]
Rover Pilot
Pilot with special sports body
Overview
Designerengine designer B H Thomas
Body and chassis
Body style
  • chassis only
  • pressed steel 6-light saloon
  • Weymann saloon
  • Weymann Sportsman's Coupé[8]
Powertrain
Engine
  • 1,410 cc (86 cu in) ohv st.6 12[8]
  • 1,577 cc (96 cu in) ohv st. 6 14[9]
Dimensions
Wheelbase
  • 104 in (2,641.6 mm)
  • 112 in (2,844.8 mm) Speed
  • track 50 in (1,270.0 mm)[8]
Kerb weight2,912 lb (1,321 kg)
  • Rover Pilot
  • and Speed Pilot
Layout
Displacement
  • 1,410 cc (86 cu in) 12[8]
  • 1,577 cc (96 cu in) 14[9]
Cylinder bore
  • 59 mm (2.3 in)[8]
  • 61 mm (2.4 in)[9]
Piston stroke
  • 86 mm (3.4 in)[8]
  • 90 mm (3.5 in)[9]
Output
Power output
  • not published 12
  • 35 bhp (26 kW; 35 PS) 14[9]
  • Tax horsepower 12.95[8]
  • Tax horsepower 13.84[9]

Spencer Wilks was given almost a free hand to make improvements from the time he began his work at Rover. Intending to cater for the market for then fashionable multi-cylindered engines, big cars might have 16-cylinders, Wilks asked Hillman engine designer B H Thomas to design a new small 6-cylinder engine to fit between Rover's Wild designed 10/25 4-cylinder and Poppe's 2 or 2½-litre 6-cylinder. Thomas's design was effectively a 10/25 engine with two more cylinders though dimensions differed to make it fit within the desired tax rating. It would form the basis for Rover's other engines for the 1930s. In its original version the new engine was described as "nice but quite gutless". It was at first squeezed onto the old scarcely altered Rover 8, 9/20, 10/25 chassis.[10]

Rover's new car was announced 21 August 1931 described in advertisements as: a 12-horsepower six-cylinder having a four-speed gearbox with a silent third gear, capable of 65 to 70 mph and 28 to 30 miles per gallon[11] A de luxe model included safety glass in all windows.[8]

Road test

[edit]

"The engine exerts its power with an air so modest as to be deceptive" declared Autocar in its report timed to match the release of the Pilot. Gear changing, said Autocar, is easy, it takes carelessness to make any noise. The intermediate gears are "unexpectedly quiet".[12]

Frame revisions

In February 1932 "following a reorganisation of the company's management"[note 1] Rover announced strengthening of the Pilot and Family Ten chassis by using heavier gauge material and re-designed cross members to improve torsional rigidity. These improvements were, they said, the outcome of lengthy testing on New Zealand's and Australia's roughest roads carried out to make the cars suitable for overseas use. The Pilot scuttle was made wider to give more foot room. The crankcase had been enlarged to provide a larger oil capacity, compression ratio lifted and petrol was now supplied from a new rear tank by Autovac. All Pilot brakes now had a vacuum servo. Springing had also been improved. Safety glass was now standard throughout the Pilot range. There were detail improvements in the de luxe car now trimmed in hide.[13]

Speed Pilot and Pilot 14

[edit]

It was announced in July 1932[9] that the engine's size had been expanded to 1577 cc and 14 fiscal horsepower. Fitted with three carburettors and with a claimed output of 35 horsepower it was sold as Rover's Pilot 14 and in long wheelbase tuned form Speed Pilot.[9]

Special plant was installed at Rover's works to spray the inside of all body panels with asbestos to ensure quietness fire-proofing etc. and insulation from extremes of heat and cold.[9]

Also in July 1932 the Pilot received the wholly new chassis of the Ten Special, its flexible engine mountings,[10] Startix and the new gearbox and freewheel. The new brakes were Lockheed hydraulic with large diameter drums, they were self-compensating and self-lubricating.[9] The Speed Pilot's special engine had a high efficiency head and a higher compression ratio and a special camshaft. The wheelbase was 8 inches longer.[14]

Radiator cap mascots

Viking head mascots fitted to Pilots and Speed Pilots had the wings on the helmets swept back almost to the horizontal.[15]

Underslung frame

But the chassis frame which previously rose over the back axle was now straightened and set to run beneath the back axle. While this limited suspension movement it allowed lower bodywork with a more sporting appearance.[10]

Road test of Pilot 14

[edit]

Under test by The Times its correspondent wrote that the 1577 cc car's great charm lay in its quietness at all times, furthermore the engine was silky and the intermediate gears produced no hum. Pick-up was good in view of the size of the engine and the weight of the car. The suspension permitted wheel bounce. The clutch pedal was too close to the steering column.[16] Twelve months later a subsequent road test reported that fresh modifications allowed the engine a more spontaneous response. Wheel bounce remained a problem.[17]

Success

[edit]

The success of Spencer Wilks' Pilot set the style for Rovers until 1949. The New Deal cars came out twelve months later in late summer 1933.[10]

Rover 12 P1 (1934–1936)

[edit]
  • Rover 12
  • P1 & P2
1935 6-light saloon
Overview
ManufacturerRover
Production1934–1948
22401 made [18]
Body and chassis
Body style
  • chassis only
  • 6-light saloon
  • sports saloon
  • 2-door coupé
  • open 4-seater
Powertrain
Engine1496 cc ohv straight 4
Transmission4-speed manual
Dimensions
Wheelbase105 in (2,667 mm)(1934)
112 in (2,845 mm)(1935 on)[1]
Length169.5 in (4,305 mm) to 172 in (4,369 mm)[1]
Width62 in (1,575 mm)[1]
Chronology
PredecessorRover Pilot
Badge

The new 12 launched at the end of August 1933[19][20] was part of the new range introduced by the Wilks brothers. It had a new 1496 cc, four-cylinder engine producing 53 bhp. The chassis was also new but based on the one seen on the 1933 Speed Pilot and was "underslung" going under the rear axle. The four-speed transmission featured a freewheel mechanism. The suspension was conventional with rigid axles and half elliptic leaf springs all round. The early cars had a 112 in (2,845 mm) wheelbase but this was stretched by 3 in (76 mm) for 1935 with the extra space giving the rear passengers more leg room. A top speed of 70 mph and economy of 24 mpg was claimed in contemporary advertisements.

The bodies were traditionally built with steel panels fitted to a wooden frame. A six light Saloon (£278), four light Sports Saloon with small external boot (£298) and four-seat tourer (£288) bodies were available. 5775 of this version were made.[18] This car became known to enthusiasts as the P1.

1936 6-light saloon
1936 6-light saloon
1934 sports saloon
1935 sports tourer

Rover 12 P2 (1937–1948)

[edit]

An updated version appeared in 1937 with mainly styling changes but the chassis was stiffened and Girling rod brakes replaced the hydraulic ones that had been fitted to earlier cars. Bodies were a 6-light saloon and a 4-light sports saloon.[21] There were no more tourers pre war but 200 were made in 1947 and 1948[22] with the first four bodies by Rover and the remaining 196 by AP Coachbuilders of Coventry. The 1938 models had fixed bonnet sides and for 1939 synchromesh was added to the top two ratios on the gearbox. Disc wheels became an option to wire wheels in 1939 and standard on post war models.

11,786 were made pre war and 4840 after.[23]

This final Rover 12 model was part of the Rover P2 range, along with Rover 10, Rover 14, Rover 16 and Rover 20 variants.[24]

The final cars were made in 1948 and there was no real replacements as subsequent models featured larger engines.

  • 1937 sports saloon
    1937 sports saloon
  • 1947 six-light saloon
    1947 six-light saloon
  • 1947 six-light saloon
    1947 six-light saloon
  • 1947 sports tourer
    1947 sports tourer
  • 1947 sports tourer instrument panel
    1947 sports tourer instrument panel
  • 1947 sports tourer
    1947 sports tourer

Notes

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Rover 12

View on Grokipedia
from Grokipedia
The Rover 12 was a designation applied to several medium-sized family cars produced by the British car company from to 1948, representing multiple iterations that evolved from early side-valve designs to more refined overhead-valve engines. Introduced in as Rover's third automobile model, the initial Rover 12 featured a 1767 cc side-valve engine and was part of the company's early expansion into the automotive market, with production continuing through various updates until 1924. In 1911, an updated version incorporated a 1882 cc sleeve-valve engine, followed by the 1912 model with a larger 2297 cc engine that powered approximately 13,000 units until the line was rebranded as the Rover 14 in 1924. The name was revived in 1934 under the leadership of the Wilks brothers, who introduced a new Rover 12 with a 1496 cc overhead-valve inline-four engine producing 53 brake horsepower, capable of a top speed of 70 mph and fuel economy of around 24 miles per gallon. These later models, known as the P1 series from 1934 to 1937 and the P2 series from 1937 to 1948, were offered in body styles including saloons, coupés, and open four-seaters, with dimensions typically measuring 169 to 172 inches in length, 62 inches in width, and a 112-inch . Equipped with a four-speed (or three-speed in earlier variants), the 12 emphasized quality semi-handbuilt construction and comfortable seating for up to five passengers, with a total production of about 22,401 units during this period. The model played a significant role in establishing 's reputation for reliable, mid-range vehicles in the pre- and post-war British automotive landscape.

Early 12 hp Models (1905–1912)

Rover 10-12 (1905–1907)

The Rover 10-12, launched in November 1905, represented the third automobile model produced by the , following the 8 hp and 6 hp designs, as the firm transitioned from its established motorcycle production to expanding its automotive lineup. This entry-level model was powered by a four-cylinder, water-cooled, side-valve displacing 1767 cc, delivering 10-12 horsepower and marking an early step in Rover's diversification into family-oriented vehicles. Production commenced in 1906, with approximately 100 units built in total, underscoring the company's nascent but growing presence in the British motor industry. Designed as an affordable option for families, the Rover 10-12 featured an open four-seater body style suitable for , emphasizing practicality over luxury in an era when automobiles were still novelties for the . Its conventional ladder-frame provided a stable foundation, incorporating shaft drive to the rear wheels via a three-speed transmission separate from the and a worm-drive rear , which were standard choices for reliability and ease of . With a of 84 inches, the offered modest performance, achieving a top speed of around 30-35 mph, making it accessible for urban and light touring applications. This model symbolized Rover's strategic shift from and manufacturing—where the company had gained prominence since the 1880s—to automobiles, helping to establish its reputation as a of dependable, budget-conscious cars. Designed by Edmund W. Lewis, it contributed to Rover's adaptation of motorcycle-derived expertise in lightweight to car production. It served primarily as a versatile family conveyance, bridging the gap between basic runabouts and larger models in Rover's portfolio. Later developments drew from this design, evolving into simplified two-cylinder variants suited for commercial service.

Two-Cylinder 12 (1909–1910)

The Two-Cylinder 12 represented a simplified and cost-effective evolution in 's early lineup, introduced amid economic challenges facing the British motor industry following the global financial , which triggered a and depressed demand for luxury vehicles. Primarily designed for urban taxi service rather than private ownership, the model emphasized affordability and durability to appeal to commercial operators during this period of industry contraction. Its short production run from 1909 to 1910 reflected these pressures, as Rover sought to streamline while targeting a less affected by private buyer hesitancy. Some sources suggest production began in 1908 and totaled up to 400 units. At the heart of the Two-Cylinder 12 was a water-cooled, side-valve, inline two-cylinder displacing cc, with a bore and stroke of 97 mm by 110 mm, rated at 12 horsepower. This powerplant featured magneto ignition with a fixed spark timing and a simple choke mechanism via a plate, paired with a three-speed gearbox for straightforward operation. Compared to the more complex four-cylinder engines of prior Rover models, the twin-cylinder design offered reduced maintenance demands, making it suitable for high-mileage duty where frequent servicing was essential. The was engineered for robustness, with a standard of 88 inches (7 feet 4 inches) and a track width of 50 inches (4 feet 2 inches), allowing for extended body configurations up to 100 inches in to accommodate larger compartments. Reinforcements in the frame supported heavier loads typical of commercial use, while the rear prioritized load-bearing capacity over speed. Controls were arranged for practical operation, including driver-side placement of the , gear lever, and spare wheel, necessitating passenger-side entry; braking combined a foot , , and compression system. Despite initial intentions for fleets, the model's turning circle of approximately 22-23 feet was deemed insufficient by authorities like , limiting its adoption. Production totaled approximately 100 units, with around 50 built each year, underscoring the model's brief lifespan and Rover's pivot toward more versatile designs post-recession. Only one example is known to survive today, restored in the late after acquisition in the 1960s. The and components influenced subsequent experiments, serving as a precursor to the sleeve-valve 12's smoother operation.

Sleeve-Valve 12 (1910–1912)

The Sleeve-Valve 12 represented a brief but innovative departure for , introducing a licensed sleeve-valve in a compact aimed at luxury-oriented buyers seeking smoother operation than conventional poppet-valve designs. Produced from 1910 to 1912, this two-cylinder model featured a water-cooled of 1882 cc displacement, rated at 12 hp, and was built in limited numbers as an experimental luxury offering before Rover shifted to more conventional configurations. The -Rover engine employed a double- mechanism, where an inner sleeve with a short and an outer sleeve with a longer slid independently within each to control and exhaust ports, eliminating the need for valves, springs, and overhead camshafts. This design allowed for larger port openings to improve airflow and while significantly reducing mechanical noise and vibration compared to contemporary poppet-valve engines, earning it the nickname "Silent " for its exceptionally quiet running. The retained a conventional pressed-steel frame with improved semi-elliptic leaf-spring suspension, offering wheelbases ranging from 100 to 106 inches for flexibility in body styles such as open tourers or enclosed landaulette bodies. Power was delivered through a three-speed gearbox separate from the , the rear wheels via a worm-gear final drive, with a reported top speed of around 40-45 mph under optimal conditions. Contemporary evaluations highlighted the model's refined performance, with road tests noting its silent operation and economical fuel use during touring, though the complexity and higher manufacturing costs limited its commercial viability. By 1912, Rover transitioned away from the two-cylinder sleeve-valve setup toward simpler four-cylinder poppet-valve engines to broaden market appeal and reduce production challenges. This paved the way for the Clegg-designed models.

Clegg Models (1912–1924)

Clegg 12 (1912–1923)

The Clegg 12, launched in 1912, represented a significant advancement for the , engineered by Owen Clegg to prioritize reliability, , and durability in a medium-sized . Clegg, who joined Rover from in 1910, designed the model as the sole offering in the lineup by that year, replacing earlier variants with a focus on robust construction suitable for broader market appeal. The car's monobloc cast-iron engine block and interchangeable components facilitated efficient manufacturing, transforming Rover's production processes during a period of industry transition. Although Clegg left Rover in 1912 to join Darracq, his design principles continued to underpin the model through its production run. At its core was a 4-cylinder side-valve displacing 2297 cc, rated at 12 horsepower (with a taxable rating of 13.9 hp), equipped with an licensed by and featuring pumped lubrication for the first time in the company's history. The 's single-piece cast-iron construction provided enhanced strength and improved cooling, contributing to the model's reputation for longevity. Built on a 110-inch with semi-elliptic leaf springs and a worm-drive rear , the Clegg 12 supported various body styles, including 4-5 seat tourers and saloons, with a curb weight of approximately 1 ton. was modest yet practical, achieving a top speed of around 45 mph and fuel economy of 18-22 , making it suitable for everyday use. Production reached nearly 13,000 units over its 1912–1923 run, with about 5,000 completed before halted civilian output in 1915. During the war, Rover pivoted to military contracts for motorcycles, lorries, and cars, leveraging the Clegg 12's design principles of interchangeability and robustness to support adaptations that ensured the company's . Resuming in 1919 with refinements such as a detachable , electric starter, and an optional 6-inch longer from 1921, the model saw its production peak in the early . This emphasis on durability over luxury innovation helped Rover recover post-war, filling market gaps left by pre-1914 models and paving the way for the enlarged Clegg 14 in 1924.

Clegg 14 (1924)

The Clegg 14 was introduced in 1924 as an evolution of the established four-cylinder Clegg 12 design, renamed the Rover 14 to better reflect its 13.9 hp taxable rating while preserving the 2297 cc displacement of the straight-four powerplant. Evolving from the design by Owen Clegg, this version marked the final year of production for the model, with limited output contributing to the overall run of approximately 13,000 units from 1912 to 1924. Chassis refinements for the 1924 model included a slightly extended of 116 inches (2946 mm) to enhance stability, alongside upgraded rear-wheel brakes operated via a for better . Primarily offered in saloon bodywork, it catered to family-oriented buyers seeking a reliable medium-sized suitable for everyday use. This upgrade addressed growing customer demand for additional power in response to intensifying competition from other British manufacturers during the mid-1920s. However, the Clegg 14 was soon phased out following a 1923 refresh aimed at clearing inventory, paving the way for 's shift toward more upscale offerings and eventual major redesigns.

Pilot Scheme (1931–1933)

Rover Pilot

In 1931, brothers Spencer and Maurice Wilks initiated the Pilot scheme at to modernize engineering through prototype and early production development. The original Rover Pilot featured advanced six-cylinder overhead-valve engines designed by B.H. Thomas, with displacements of 1410 cc (12 fiscal horsepower) initially, later expanded to 1577 cc (14 fiscal horsepower) in 1932. The Rover Pilot prototype and early models had a 104-inch for balanced proportions and a top speed of approximately 60 mph, emphasizing smooth performance and structural integrity. These specifications positioned the Pilot as a for refined dynamics, including early explorations of suspension systems suited to contemporary road conditions. Production figures are approximate, as pre-war records were destroyed during . Early road tests underscored the Pilot's potential; the Autocar review in 1931 praised its quiet acceleration and responsive handling, while in 1932 acknowledged its overall refinement yet highlighted challenges in achieving full production readiness. Approximately 4,396 units of the 12 hp and 14 hp Pilot models were built from 1932 to 1933 to validate the chassis design ahead of the broader P-series rollout. This experimental phase laid the groundwork for subsequent iterations, such as the Speed Pilot variants.

Speed Pilot and Pilot 14

In 1933, Rover evolved its Pilot scheme with the introduction of the performance-focused Speed Pilot and the standard Pilot 14, incorporating refinements based on feedback from earlier prototypes to enhance handling, power, and reliability. The Speed Pilot featured a tuned version of the 1,577 cc overhead-valve inline-six-cylinder , delivering approximately 35 through modifications including triple carburetors, paired with a 112-inch (9 feet 4 inches) . The Pilot 14 utilized a similar 1,577 cc configuration rated at 14 fiscal horsepower in its standard form, providing a balance of everyday usability and refinement for family-oriented applications. Both models benefited from significant chassis advancements, including Lockheed hydraulic drum brakes for superior stopping power, an ENV synchromesh four-speed manual gearbox with freewheeling capability for smoother shifts, and Luvax-Bijur automatic chassis lubrication to reduce maintenance needs. Production of the Speed Pilot and Speed 14 (including Pilot 14 variants) totaled approximately 584 units from 1933 to 1936. Road tests of the period underscored the models' capabilities; a 1933 Autocar evaluation of the Speed Pilot four-seat tourer reported a 0-50 mph time of 12.8 seconds, a top speed of 77 mph, and notable stability at high speeds, praising its refined ride and . These tests helped validate the designs' robustness, positioning Rover for wartime production readiness by demonstrating efficient, durable suitable for scaled . Overall, the Pilot scheme from 1931 to 1933 resulted in approximately 4,980 units across its variants (combining 12/14 hp Pilot and Speed models), serving as a critical bridge to the subsequent P-series models through innovations in aerodynamics, such as the underslung chassis for lower center of gravity, and fuel efficiency optimized for the era's economic constraints. This laid the foundation for the P1's four-cylinder adaptation, emphasizing modular design principles. Production figures are approximate due to lost records.

P-Series Models (1934–1948)

Rover 12 P1 (1934–1936)

The 12 P1, introduced in 1934, marked the production launch of Rover's first mass-market 12 hp model derived from the experimental pilot scheme, targeting pre-war family buyers seeking modern engineering in an affordable package. It utilized a newly designed 1,496 cc four-cylinder overhead-valve engine producing 53 at 4,200 rpm, paired with a four-speed featuring freewheeling on the top three ratios for smoother driving. The underslung , carried over from the pilot prototypes, measured 105 inches in wheelbase in 1934 and 112 inches from 1935 onwards and incorporated independent front suspension with torsion bars, enhancing ride quality and handling compared to contemporaries. Body styles for the P1 included a four-door saloon with rear-hinged doors, a two-door sports saloon, coupé, and open four-seater tourer, all built with panels on an wood frame for durability and elegance. The saloon achieved a top speed of 70 mph and fuel economy of around 25 , making it suitable for long-distance family travel while maintaining a refined character. It positioned Rover as an accessible luxury brand, competing directly with mass-produced models from Morris and Austin by offering superior build quality and performance without excessive cost. Following validation through the limited-run pilot models, production ramped up at Rover's factory, with 5,775 units assembled by 1936, including variants for export markets such as and . Contemporary reviews praised the P1's exceptional ride comfort, attributed to its advanced suspension and low-slung design, which provided a stable and quiet motoring experience ideal for Britain's improving road network. This positive reception helped solidify Rover's reputation for quality engineering in the mid-1930s segment.

Rover 12 P2 (1937–1948)

The Rover 12 P2, introduced in 1937 as an evolution of the preceding P1 model, featured a revised 1496 cc overhead-valve four-cylinder engine delivering 53 bhp. The chassis was stiffened with a 112-inch wheelbase for enhanced stability and ride comfort, while Girling rod-operated brakes replaced the earlier hydraulic system. Building on the P1's foundational chassis design, the P2 emphasized refinement and modernity in Rover's compact 12 hp lineup. Styling updates included faired-in headlights integrated into flowing front wings for a sleeker profile, alongside an improved saloon interior with better upholstery and trim materials. Mid-production refinements in 1938 added fixed sides to the bonnet for easier access, while 1939 models incorporated synchromesh on the top two gearbox ratios and piston-type hydraulic dampers for smoother performance. Pre-war production from 1937 to 1940 totaled 11,786 units, encompassing saloon, tourer, and drophead coupé variants. Wartime demands halted civilian production in 1940, with Rover redirecting efforts to military contracts. Post-war resumption in 1945 faced significant delays from material shortages and retooling challenges, limiting output to 4,841 units through 1948. The model achieved a top speed of 70 mph and fuel efficiency of 24 mpg under contemporary testing conditions, reflecting its balanced engineering amid rationing constraints. Production ceased in 1948 as Rover phased out the 12 hp line in favor of larger P3-series models, marking the P2's role in bridging pre- and post-war designs. Overall, 16,627 P2 units were built across its lifespan.

References

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