The History of the SU Carburetter: Part 1 1904-1945

ORIGINS

The SU Carburetter was the brainchild of the late George Herbert Skinner. Born in Ealing in April 1872, the son of William Banks Skinner, a Director of the well known Lilly & Skinner Footwear distributors. Despite following his father in the footwear business, his real passion lay with the motorcar.

Herbert was educated at Castlebar School in Ealing, and although as far as known he had no technical training, by 1900 he had submitted three provisional patents covering his ideas.

In 1903 he is reported to have travelled to France to learn how to drive a car. The following year he and his younger brother, Thomas Carlyle Skinner,decided to put some ideas into practice and improve the carburation on a Star motorcar they owned at the time. The vehicle’s massive old carburetter was fitted with a glass top through which they could watch the flow of fuel from the jet.

It was clear that the suction (depression) on the jet varied in accordance with the demands made by the engine, and it seemed to them that a big improvement would be made if the jet could be located in an air channel of a size varied to suit different engine speeds, so ensuring a constant depression and air velocity.

A crude mechanism was evolved to bring this about, but it was then found that it lacked overall performance because, if a jet orifice was chosen that was suitable for full throttle running, then this would result in an over-rich mixture for slow running and vice versa. The answer to this problem was a tapered needle; this varied the size of the jet orifice according to engine demands.

A full patent was applied for by Herbert in February 1905 and granted in January 1906. Herbert’s application describes his occupation as “boot and shoe manufacturer”.

THE FIRST CARBS

If Herbert was the inventive genius, his brother Carl was the ‘practical engineer’. Carl was born in Ealing in June 1882 and educated at Leys School in Cambridge. Again it is not known where or even if he received any technical training. Carl joined the family business but by 1906 had teamed up with R.P. Wailes to manufacture and fit carburetters. There was a third brother by the name of John, of whose involvement little is known other than he appears to have been a director of the company by about 1913.

It is not clear when the first experimental carbs were produced, but they were almost certainly made at George Wailes & Co.’s works at 258 Euston Road, London. When George Wailes sold the works and premises in 1906, Carl became a partner with George’s son and they took temporary premises in the Euston buildings while new works at 386-388 Euston Road were being built.

For some years carburetters were fitted and tuned to individual cars. The new works had an 8ft by 16ft, 30 cwt (3,360 lbs) capacity lift which served all four floors as well as the roof and basement. Surprisingly, the top floor was used to fit and tune while the carburetters themselves were manufactured in the works below from working drawings prepared by the Chief Draughtsman, Mr J.O. Gardner, to Herbert’s sketches.

Herbert’s main responsibility appears to have been one of design and improvement, which he pursued with vigour and also protection by way of patents. A full patent covering the “constant depression” idea was granted in England in 1906. Further patents were taken out in Belgium, France, Germany, Italy and the U.S.A.

Herbert’s inventive genius was not confined to the SU; he took out patents in 1907 and 1908 on a hydraulic variable speed gear and a detachable strap for ladies’ court shoes and slippers, and later for a paraffin carburetter, an aero carburetter, and a supplementary fuel supply valve for cold starting.

There is some evidence to suggest that the carburetter was originally branded “The Union Carburetter” but this was soon superseded by “The SU Carburetter”, being the abbreviation of “Skinner’s Union” .

THE SU COMPANY LTD.

In 1910 the company moved to premises at 154 Prince of Wales Rd, Kentish Town, London. An old horse stable, the structure of which had been converted to allow production to take place, and a Limited Company was registered in the name of The SU Company Ltd on the 2nd of August 1910: Reg. No 11141.6.

The earliest financial information appears in the Company’s ledger dated April 30th 1911. It is not specific as to who the directors were at this time, but an entry in the accounts of 28th January 1913 shows director’s fees of £25 each to W.B. Skinner; G.H. Skinner and J.H. Skinner. By this time the accounts also show that Wolseley and Rover were regular customers of SU.

These early carburetters were fitted with leather bellows in place of the now familiar dashpot, and they appeared to have worked quite well. To maintain the leather bellows suppleness a regular application of glycerine was recommended.

The bellows themselves were made from glace kid by Herbert’s wife Mabel at their home. Sales to the company from Mrs Skinner for bellows-making are recorded in the accounts right through to 1928; presumably by this time for spares, not production.

THE FIRST WORLD WAR

With the outbreak of war in 1914, carburetter production virtually ceased, the factory being busily occupied on government contracts making machine-gun parts and tripods, bombs and aircraft carburetters. At this time there were about 250 employees.

Carburetter production resumed after the war; but progress was slow. There was a general recession within the motor industry due to inefficiency and high costs, and the company resorted to making wireless parts, windscreens, water stop cocks and other similar engineering work.

Some car manufacturers appreciated the qualities of the SU, and they were fitted to a number of quality cars such as Bentley, Napier and lnvicta. During this time the leather bellows were replaced by a brass piston (e.g in the 1927 sloper).

TAKEOVER

By the mid-twenties, after some initial problems, William Morris was fitting more and more SU’s to his cars and in his usual style acquired the by now struggling company in December 1926. The takeover relieved the Skinner family of the responsibility of keeping the SU company afloat which they had done for many years.

The company was immediately moved to the Midlands and installed in the works of another of Morris’s new acquistions, the Wolseley factory at Adderley Park, Birmingham. Carl came as part of the package, being made Managing Director.

This was a real turning point for SU, and with all the cars in the Morris empire to service, SU production increased rapidly. According to Wilf Webster who joined the company in 1929 as Assistant Draughtsman, money for expansion and development was no problem “We could have more or less whatever we wanted”, he said, and so new products now started to arrive thick and fast.

1929 saw the introduction of the HV type carburetter with bottom feed float chamber and also the Petrolift which was a successful forerunner of the electric pump. The Petrolift replaced the gravity feed petrol tanks or vacuum tanks which were the norm for this period.

In 1930 the HV was modified to take the top feed float chamber, followed by the OM and D type in 1931, the latter standing for “down-draught”, a design which required a spring in the suction chamber to return the piston to the idle position.

1931 was also the year that Herbert died, sadly never to see the heyday of his prodigy. In 1932 the first aero carburetter was developed and from this beginning a number were produced for both military and civil aircraft during the mid-to-late 1930’s, including the Rolls Royce Merlin engine.

The following year the L type petrol pump was introduced. This replaced the Petrolift and is still in production to this day in its original form.

SU CARBURETTERS LTD.

The 1930’s were a time of frenetic development; SU would and did make almost anything for anybody requiring a fuel system and the growth in output in both production and design was quite incredible.

In 1936 the name of the company changed to SU Carburetters Ltd. In 1937 the thermostatic automatic choke and the ubiquitous H Type were introduced, a series of carburetters with choke bores ranging from 1⅛” to 2″ in 1/8th increments which were to be the standard right through to the 1950s. In 1938 the hydraulic piston damper was introduced to provide acceleration enrichment.

Various new pump designs had appeared by now including the HP, LCS and double ended high capacity models. By 1939 nearly all Morris and MG vehicles as well as Riley, Wolseley, Alvis, Bentley, SS etc. were equipped with either an SU pump or an SU carburetter or both. SU was thriving.

In March 1939, according to a contemporary report, the SU factory covered 81,000 square feet and employed between 400 to 450 people making some 4,000 carburetters and 4,000 pumps a week plus quantities of aero-engine components. This year the Zinc die-cast piston was replaced by brass, since zinc distorted or grew with age resulting in loose piston rods, and the HV type carburetter was phased out.

Look out for Part 2 of this article to be posted shortly.

Click here to view a diagram and parts list for the H Type SU Carburetter.