Summary

The designers of the Z7
Letter from Mr. John Hereward Pitchford
Le Zebre and Ricardo in The Light Car
Successive owners

Rediscovered in the 21st century
General views, extracts from the plans
Summary of events
1924 Ricardo Z7, Le Zèbre Advertisement

Restoration work from 2019 to 2023
On the roads of France
Next Steps

A one-off 1100cc overhead valve sports torpedo.

Designed and built by Sir Harry Ricardo in 1924 to order from the "Le Zèbre" company. It is the only car of this type built and the last car entirely built by the Ricardo company. It is stamped with the number Z7 throughout, and period advertising mentions an 8/10 hp designation. The 1100 cc engine has a overhead valve, the front axle is a Perrot Piganeau type, the hubs are Rudge, and the carburetor is a bronze Solex. The car illustrates the work of Sir Harry Ricardo, not only the cylinder head, but also the internal circulation of the engine oil, and many other details. The engine has three main bearings, non-separated gearbox with a bore of 69 mm and a stroke of 73 mm. It was designed to compete with the best European productions of the time.

At the end of the 1910s, Le Zèbre found itself without a design office following André Citroën's hiring of some of his engineers to design the Citroën Type A, while Joseph Lamy, Le Zèbre's administrative partner, went on to create the Amilcar company with Emile Akar and the rest of the company's engineers! (See “L'épopée de la société Le Zèbre”, Phillip Schram). Le Zèbre therefore had to quickly find a solution to create its new model; the Type D was aging, so they turned to a talented young engineer, Sir Harry Ricardo.
A Le Zebre Z10 was designed by Sir Harry Ricardo and proved a success, with 500 units sold. Its two-liter side-mounted engine was robust and the car well-built, but the trend was for small sports cars, which was not the case with the Z10.Le Zebre management therefore commissioned the design office to create a sportier and smaller car, as the era seemed to desire. The project would be called the Z7. A large proportion of the car parts, mainly made of aluminum, would be cast or stamped with the inscription Z7 followed by the drawing cartridge number.

Note that a copy of the book of 106 large-format plans was provided to me by Ricardo Plc., which carefully preserves the original. At the time the prototype was produced in Shoreham-by-Sea, in Paris, the Le Zèbre company went bankrupt and the car remained the property of the factory until 1937, according to the texts left by Mr. John Pitchford, second CEO of Ricardo & Co and a young engineer in the late 1920s. It is also interesting to note that in his memoirs, J.H. Pitchford mentions Sir Harry Ricardo's interest and affection for this car, which he would use before the car disappeared in Provence in 1937 into the hands of his daughter, Kate Ricardo. The story goes that Sir Harry replaced his faithful Z7 with a Vauxhall Velox !

The designers of the Z7

Sir Harry Ralph Ricardo (1885-1974)

Harry Ralph Ricardo was born at a time when mechanical engineering was developing from a craft into a technology. The steam engine, the prime mover of the day, was only beginning to be threatened by the steam turbine, and the internal combustion engine was in its infancy. This engine was to become his lifelong interest. He brought to it not only the skill of an outstanding designer, which was soundly based on personal craftsmanship, but also a long lasting curiosity and originality in engineering research.
His contributions to the understanding of the ignition, combustion and detonation processes in spark- ignition and diesel engines were of the greatest importance; he gave the world the concept of the octane number as a means of rating the tendency of fuels to detonate.

His application of this knowledge and his ability in design is seen not only in his early engines, for example in the two-stroke cycle Dolphin and the four-stroke cycle engine for the tanks in 1917, but in his light high speed diesel engines, the prime mover of the modern truck, and the sleeve valve aero-engines which were the last and best of the large British piston engines for aircraft.

^{The Royal Society : https://royalsocietypublishing.org/doi/10.1098/rsbm.1976.0016}

One example among the many examples of collaboration by Sir Harry Ricardo (Bentley 4 Litre, Triumph Ricardo, Alfa Romeo Tipo 162 ...), the 1922 TT Vauxhall :
At all events, by 1921 the famous Luton Company was busy with a team of very advanced racing cars for the forthcoming TT, King doing the chassis, with Dr. (later Sir) Harry Ricardo, who was then at the height of his engine-research doctrines, and a friend of Percy Kidner, the Vauxhall Managing Director, designing the engine.

^{A 1922 TT Vauxhall Re-born : https://www.motorsportmagazine.com/archive/article/december-1982/58/a-1922-tt-vauxhall-re-born}

^{Non-exhaustive bibliography:
Harry Ralph Ricardo. 26 January 1885 - 18 May 1974 / William Hawthorne
Biographical Memoirs of Fellows of the Royal Society / Vol. 22 / Published By: Royal Society
Engines and Enterprise / The Life and Work of Sir Harry Ricardoby John Reynolds / Haynes Publishing
Grace's Guide To British Industrial History Harry Ralph Ricardo
Grace's Guide To British Industrial History Ricardo and Co
C.C.J. French, Ricardo at Shoreham (Sussex Industrial Society, 1995, paper 25)
H.R. Ricardo, Memories and Machines – The Pattern of My Life (Constable, 1968)
H.R. Ricardo and J.G.G Hempson, The High Speed InternalCombustion Engine, 5 th ed., (Blackie & Son Ltd, 2004)
Nahum, Foster-Pegg, Birch, The Rolls-Royce Crecy,( Rolls-Royce Heritage Trust, 1994)
Harry Ricardo - A Passion for Efficiency, The Man and Contribution (Morrison)}

^{The Board of Directors of Ricardo & Co., 1963. L to R: E.N. Soar, Viscount Combermere, Sir Ben Lockspeiser, Sir Harry Ricardo, J.H. Pitchford}

Oliver Thornycroft (1885 - 1956)

During the 1914-18 war he served as a Lieutenant, R.N.V.R., attached to R.N.A.S., and later joined the Mechanical Warfare Department (Tanks) as Director of the Experimental Station.
He then became Works Manager and Chief Engineer, Ricardo and Co., Shoreham in 1919, and continued in that post until 1939, when he became attached to the Admiralty department engaged in mine and anti-submarine weapon research.
In 1946 he was appointed Director, Aeronautical and Engineering Research, Admiralty, where he remained for four years, and subsequently carried on in business as a consulting engineer.

He was awarded the O.B.E. (1920), and appointed C.B. (1948). He was elected a Member of the Institution in 1934, and was also a Member of the Institution of Automobile Engineers and a Fellow of the Royal Aeronautical Society. Many articles were contributed by him to the technical Press.

^{Grace's Guide To British Industrial History Oliver Thornycroft}

^{Non-exhaustive bibliography:
1935/36 Institution of Automobile Engineers: Index
1939 Who's Who In Engineering: Name T
1953 Who's Who in the Motor Industry: Persons T
1957 Institution of Mechanical Engineers: Obituaries
Tank and Tracked Transport Experimental Establishment
Thornycroft Genealogy
Supercharging, Cecil Kimber and Supercharging
Grace's Guide To British Industrial History Oliver Thornycroft
At High Altitude - Cambridge University Press}

John Hereward Pitchford (1904 - 1995)

77th President of the Institution of Mechanical Engineers.
Pitchford was born in Penarth, Wales in 1904. He was educated at Brighton College and Christ’s College, Cambridge, where he read engineering. He worked at the research laboratories of Ricardo and Co., Engineers, Ltd. during the long vacations, and in 1926 he joined the firm full time. He worked in the research and development department and was particularly involved with combustion research, particularly the high-speed diesel engine. In 1939 he was appointed General Manager, and in 1962 he became Chairman of the company. He became President of the company in 1976 when he retired from the position of Chairman.

He served on the Scientific Advisory Council of the Ministry of Fuel and Power from 1953 until 1959. He was also President of the Fédération Internationale des Sociétés D’Ingénieurs des Techniques de l’Automobile (FISITA), which comprises the automobile engineering societies throughout the world.
Pitchford was President of the Institution of Mechanical Engineers in 1962 and was the first President to be a member of the Automobile Division.

^{Institution of Mechanical Engineers : https://archives.imeche.org/archive/institution-history/president-gallery/593814-1962-john-hereward-pitchford}

^{Non-exhaustive bibliography:
Nature, May 12, 1962 voL. 194
Harry Ricardo – A Passion for Efficiency by David Morrison
Ricardo at Shoreham — Windmill Hill Mill Sussex Industrial Archaeology Society}

Letter from John Hereward Pitchford
^{June 14, 1974}

There was a third Le Zebre which, in many ways, was by far the most interesting of the three. This was a project which came a good deal later than the 2 liter car, and was similarly designed entirely at Shoreham. This third car had a 1100 cc 4 cylinder overhead valve push rod engine of a very neat and tidy design much in advance of its time in this class of vehicle.

It had been used on and off by Q.T. over a period, but latterly seemed to become redundant whereupon i made an offer of £50 for it with the firm saw fit accept. This vehicle was, of course, a prototype and in fact the only one build, with all the chances and risks that this incurred.

At just about the time i took this car over, the Riley 9 came on the market with a considerable flourish and Ernest Bass, who was the engaged on lubrication oil test in various motor car at Shoreham lost no time in persuading his lords and masters to buy him a Riley 9 for test purposes. The rather satisfactory thing was that i could always see him off on acceleration and maximum speed between Lancing Manor and the Works without any bother at all! The engines were, of course, of identical size.

I had been told at the time i bought this car that it had a somewhat ‘tender’ differential assembly, but i was too much attracted by the vehicle otherwise to take much notice of this. However, the advice proved all two well founded and one well remembered day, after listening to John Mc Cormack at the Dome, and half way up North Street between two buse, then of the Tillings Stevens petrol, electric variety - with, as you will remember, were not at their best on hills - there was a shattering bang from back of the car and some pretty horrible consequential noises, and i came to rest, and so did the bus behind me, with had to have passenger assistance to start moving again and get around me.

When the axle was dismantled, the weakness referred to at the time i bought it had shown itself only too well. However, RJC, who seemed to feel himself in some measure personally responsible for this weakness in the design of the axle see about designing a completely new crown wheel and differential unit which was made jointly by Ricardos and Oppermans at what must have been a fantastic cost (i only know that i paid some very nominal sum).

However, in order to change certain dimensions in the differential assembly and so avoid a continuance of the weakness, it proved necessary to use a straight toothed crown and pinion in place of the original helical design. The result of this, as may be imagined, was that the rear axle sang a loud clear tune at all times, and at a rather later date when i had sold this car, having got tired of the tune, to Kate Ricardo, who was then a student at Brighton Tech. she could be heard from far away on her journey to work in the mornings and on her return in the evenings.

What became of this car finally i have no idea, and i regret this very much, because at that time it was an outstanding performer of extremely good mechanical design throughout, except for the rear axle, and with superlative four wheel brakes - not so common even then. I can only say that i am pretty sure that Kate had this car until about 1937.

^{John Hereward Pitchford - June 14, 1974}

Le Zebre and Ricardo

^{From John Loveridge, ex- Ricardo Historic Assets Manager}

The Light Car and Edwardian Section
^{No: 167 / November 2020, pages 20 à 22}

l1

Rediscovered in the 21st century

I found the car in Provence in the estate of a 1920s sports car enthusiast of around a hundred cars. The sale mentions a false identity of the car since it is sold as a Sigma Type R, an identification plate of this type being fixed to the dashboard. Quickly, it had to be admitted, it was not a Sigma, but what car could it be then?

After numerous contacts, a long and diligent search, the numbers of the numerous castings of the engine, the chassis and the various elements allowed me to define its probable origin. Obtaining a copy of the plans of the Ricardo Le Zèbre held by the company Ricardo Plc then removed all doubts about the origin and identity of the car. It was a high-performance car for its time and unique.

I would like to thank the author of the reference book "L'épopée de la société Le Zèbre", Phillip Schram, who put me in touch with the company Ricardo Plc.

Once restored, it would remain the last car entirely designed and built by Sir Harry Ricardo. Since then, from McLaren and Bugatti transmissions to Rolls-Royce engines, 205 Turbo 16 viscous couplings, etc., Ricardo & Co has never designed a complete car again.

While the chassis and bodywork are in good condition except for the paint, the engine requires restoration work. The upholstery also needs to be redone, and the soft top is missing. Otherwise, the car is complete and in relatively good condition. A conservative restoration is required.

Summary of events

From 1924 to 1937

Le Zèbre commissioned a study and a prototype from Ricardo & Co, which studied and built it, but having gone bankrupt of “Le Zèbre”, the Z7 remained the property of the Ricardo factory before being sold to J.H. Pitchford and then to Kate Ricardo, Sir Harry's daughter. While the car was owned by the factory, it was used by Sir Harry Ricardo, according to the memoirs of J.H. Pitchford, future president of Ricardo & Co and a young engineer in the 1920s.

From 1937 to 2019

No confirmation except for the memories of the daughter of the third owner. The seller's father would have been the third owner, in any case the seller indicates that her father had bought it in the 70s from the heir of a metal merchant from Provence, who was supposed to have had it since the war.

Restoration work from 2019 to 2023

Some of the many works undertaken:

Engine 69 mm x 73 mm

Disassembly
When disassembling it appeared that the block was frozen and cracked in several places. The rest was usable but relatively worn, it was decided to restore the whole thing.

Welding
The complete block required complete repair of the cracks by laser welding at a Dassault Aviation subcontractor.

Rectifications, machining, spelters

Bearing adjustment, Machining of new connecting rod half-shells, Connecting rod caps, rings and bolts, New valve guides, Seat grinding, Crankshaft grinding, Half-shell adjustment, Connecting rod boring, rounding, adjustment, Cylinder head surfacing, Block reboring and honing, Valve and head gasket replacement …

Reassembly
All dismantling - reassembly, analyses and diagnostics operations were carried out by Matthieu Catusse of the MC AR preparations establishments, between 2020 and 2023

Testing
Testing took place during the winter of 2022 and spring of 2023. It has been in regular use since then.

Four speeds gearbox

Secondary Shaft
The first gear on the intermediate shaft was damaged. Since the four gears were machined from the same billet as the shaft, everything had to be reground.

Bearings
All bearings are replaced with new ones upon reassembly.
The gearbox works perfectly well.

Transmission
New, specially sized flectors were remanufactured and fitted. The tunnel has been balanced.

Fuel system

Carburetor
The Solex MOV 30 carburetor was clogged with gasoline molasses. The carburetor has the bowl bolt that acts as a disassembly tool.

Fuel tank
The tank is apparently not original and was drilled on the top. Welding, painting, reassembly, it is usable again even if it is no longer original.

Fuel pipes
Also completely clogged with caramelized gasoline molasses, the circuit is made up of copper tubes and a three-way valve.

Cooling circuit

Radiator
The radiator grille was blocked, and salvage was impossible. The core had to be replaced.

Cylinder Head Intake Manifold
Eroded by time and stagnant glycol, the cast aluminum intake manifold was leaking profusely.

Saddlery
The two seats and the benches were redone in leather and horsehair by a professional in Anjou.

Chassis

Trapezoidal chassis width 1m25, wheelbase 2m62. The chassis was in good condition and did not require any intervention.

Suspensions
The Repusseau shock absorbers were incomplete; they needed to be rebuilt using Hartford parts.

Tires
Replacing all four tires was essential on this car, which hadn't been driven for a long time.

Electricity

Wiring Harness
The wiring harness appears to have been redone. A modern fuse box has been added, but should be replaced to restore the original appearance.

Headlights
The original headlights have disappeared, replaced by Marshalls, then by poor-quality headlights that have since been replaced by BRCs.

Ignition
The magneto and breaker were probably rebuilt in the 1970s or 1980s. No work was required as it was functioning properly.

Miscellaneous

Transmission
New, specially sized flectors were remanufactured and fitted. The tunnel has been balanced.

Brakes
The bowls have been surfaced to be perfectly round.
The brake pads have been replaced.

Saddlery
The two seats and the benches were redone in leather and horsehair by a professional in Anjou.

·

On the roads of France

Next steps

1 : Châtillon-sur-Indre (36) - 05/2024
2 : Mazières-en-Gâtine (79) - 07/2024
3 : Thouars (79) - 09/2024
4 : Bressuire (79) - 05 / 2025
5 : Lésignac-Durand (16) - 01/2026
6 : La Roche-Posay (86) - 04/2026
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