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Citroen 7 CV

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MotorClássico, Lisbon, Portugal

in Wikipedia

Traction Avant monocoque

Front torsion bar suspension

The Traction Avant, French for "front wheel drive", was designed by André Lefèbvre and Flaminio Bertoni in late 1933 / early 1934. While not the first production front wheel drive car – Alvis built the 1928 FWD in the UK, Cord produced the L29 from 1929 to 1932 in the United States and DKW the F1 in 1931 in Germany – it was the world’s first front-wheel drive steel monocoque production car. Along with DKW’s 1930s models, the Traction successfully pioneered front-wheel drive on the European mass car market.

The Traction Avant’s structure was a welded monocoque (unitized body). Most other cars of the era were based on a separate frame (chassis) onto which the non-structural body ("coachwork") was built. Monocoque construction (also called Unit Body or "Unibody" in the US today) results in a lighter vehicle, and is now used for virtually all car construction, although body-on-frame construction remains suitable for larger vehicles such as trucks.
This method of construction was viewed with great suspicion in many quarters, with doubts about its strength. A type of crash test was conceived, taking the form of driving the car off a cliff, to illustrate its great inherent resilience.

The novel design made the car very low-slung relative to its contemporaries – the Traction Avant always possessed a unique look, which went from appearing rakish in 1934 to familiar and somewhat old fashioned by 1955.

The suspension was very advanced for the car’s era. The front wheels were independently sprung, using a torsion bar and wishbone suspension arrangement,[3] where most contemporaries used live axle and cart-type leaf spring designs. The rear suspension was a simple steel beam axle and a Panhard rod, trailing arms and torsion bars attached to a 3-inch (76 mm) steel tube, which in turn was bolted to the monocoque.

Since it was considerably lighter than conventional designs of the era, it was capable of 100 km/h (62 mph), and consumed fuel only at the rate of 10 litres per 100 kilometres (28 mpg-imp; 24 mpg-US).

Variants

Cabriolet

Traction Avant rear

1937 7C Coupe Traction Avant

A French "familiale" 11 F 1954, 6 windows, 9 seats

Citroën 11 Commerciale 5-door

Traction Avant rears. The boot was lengthened and its volume doubled in Autumn 1952.[4]
The original model, which was presented on 18 April 1934, was a small saloon with a 1,303 cc (79.5 cu in) engine. This model was called the 7A, which was succeeded in June 1934 by the 7B with a higher-power engine of 1,529 cc (93.3 cu in). The 7B in turn, was succeeded in October 1934 by the 7C with an even higher-output 1,628 cc (99.3 cu in) engine. Later models were the 11 (launched in November 1934), which had a 1,911 cc (116.6 cu in) four-cylinder engine, and the 15 (launched in 1938), with a 2,867 cc (175.0 cu in) six. The numbers refer to the French fiscal horsepower rating, or CV. The 11 was an 11 CV, but curiously the 15 was actually 16 CV. The 11 was built in two versions, the 11L ("légère", or "light"), which was the same size as the 7 CV, and the normal model 11, which had a longer wheelbase and wider track.

Citroën planned two variants that never entered production, since there was not enough funding available to develop them, except as running prototype vehicles. One was an automatic transmission-equipped model, based on the Sensaud de Lavaud automatic transmission, the other a 22 CV model with a 3.8 liter V8. The transmission (which was actually originally designed for the Citroen) was a "gearless" automatic, using the torque-converter alone to match engine revolutions to the drivetrain revolutions, much like the Dynaflow Transmission introduced later in the USA. The car was supposed to have a less spartan interior than the other Traction Avants and it was to feature Citroën’s own new V8 engine. About twenty prototypes were made, but when the project was canceled in 1935 due to Michelin’s takeover; they were probably all destroyed.[citation needed]

In addition to the 4-door body, the car was also produced as a 2-door coupé with a rumble seat, as a convertible and as an extended length Familial model with three rows of seats. There was even a hatchback-type Commerciale variant, in 1939, well ahead of its time, in which the tailgate was in two halves, the lower of which carried the spare wheel with the upper opening up to roof level. A one-piece top-hinged tailgate was introduced when the Commerciale resumed production in 1954 after being suspended during World War II.
Wartime disruption[edit]

In September 1939 France declared war on Germany and in June 1940 the German army rapidly invaded and occupied Northern France.[1] The war years were characterised by a desperate shortage of raw materials for civilian industry and of petrol,[1] but these factors were not apparent instantly. The Paris Motor Show scheduled for October 1939 was cancelled at short notice, but Citroën’s own planned announcements had involved the forthcoming 2CV model rather than any significant changes to the Traction.[1] For the Traction, the last “normal” year in terms of production levels was 1939, and 8,120 of the 2910mm wheelbase 1628cc engined 7C models were produced.[1] This tumbled to 1,133 in 1940, which was the first year when the plant suffered serious air-raid damage – on this occasion caused by a German attack – on 3 June 1940. Production of the cars was suspended in June 1941, by when a further 154 had been produced in the six-month period just ended. The 7C would continue to appear in Citroën price-lists until March 1944, but production of this smaller engined “7CV” version of the Traction was not resumed after the war.[1] For the more powerful 1911cc engined 11 B-light models, the equivalent figures were 27,473 units produced in 1939, 4,415 in 1940 and 2,032 for 1941, though for this model production in 1941 ended only in November 1941 so the figure for that year represents 11 months of production.[1]

In 1945 production restarted only slowly: the 11 B-light reappeared very little changed from the 1941 cars except that headlight surrounds were now painted rather than finished in chrome. By the end of December 1945 the year’s production had reached 1,525.[1] Currency depreciation is evident from the car’s listed price which had been 26,800 francs in January 1940, and had risen to 110,670 francs in October 1945.[1] In 1945 the car was the only model available from Citroën, and as another sign of the times, customers not able to supply their own tires were charged an additional 9,455 francs for a set of five.[1] In May 1946, presumably reflecting an easing of the war-time tire shortage, the car could at last be purchased with tires at no extra cost, but by now the overall price of an 11 B-light had risen to 121,180 francs.[1]

The 11 B-normal model, differentiated from the 11 B-light by its 3090mm wheelbase, experienced a similar drop off in volumes between 1939 and 1941, with just 341 cars produced during the first seven months of 1941.[1] After the war, a single 11 B-normal was produced in 1946, in time to be presented at the October 1946 Paris Motor Show: production built up during 1947, but during the car’s ten-year post-war period the shorter 11 B-light would, in France, continue to outsell the 11 B-normal.

Initially the French army lacked enthusiasm for the Citroën Traction, believing that it offered insufficient ground-clearance for their needs.[1] Nevertheless, by September 1939 roughly 250 had found their way into military service. With losses of cars at the frontier mounting, Citroën supplied a further 570 to the army between February and May 1940, and subsequent deliveries probably took place before military defeat intervened.[1] During the war many of the cars were reregistered with "WH…" (Wehrmacht Heer/Army command) license plates, having been requisitioned by the German Army.[1] These gave reliable service both in France and further afield, notably in Libya and Stalingrad. Tractions were also favoured by the Resistance, and as occupation gave way to Liberation they turned up all over France with FFI inscribed proudly on their doors. Less gloriously, the cars were known as favourites among gangsters such as the then infamous Pierrot le Fou, and his Traction gang.

UK built cars[edit]

Left-hand drive versions were built in Paris, in Forest, Belgium, in Copenhagen, Denmark for the Scandinavian market, and right-hand drive cars in Slough, England. The Slough version of the 11L was called the Light Fifteen and the long wheelbase 11 was called the Big Fifteen. This confusing terminology referred to the British fiscal tax rating of the time, which was higher than the French, so the 11CV engine was 15HP in England. The 15CV model was called "Big Six" in reference to its 6-cylinder engine. They were equipped with the leather seats and wooden dashboards popular in the UK, had a 12-volt electrical system and were distinguished by a different radiator grille and different bumpers. Some models also had a sliding sunroof.
A 1,911 cc (116.6 cu in) Light Fifteen tested by the British magazine The Motor in 1951 had a top speed of 72.6 mph (116.8 km/h) and could accelerate from 0–60 mph (97 km/h) in 29.7 seconds. A fuel consumption of 25.2 miles per imperial gallon (11.2 L/100 km; 21.0 mpg-US) was recorded. The test car cost GB£812 including taxes.[5]

A 2,866 cc (174.9 cu in) six-cylinder model was tested by the same magazine in 1954 and for this car the top speed found was 81.1 mph (130.5 km/h), acceleration from 0–60 mph (97 km/h) 21.2 seconds and fuel consumption 18.6 miles per imperial gallon (15.2 L/100 km; 15.5 mpg-US). The test car cost GB£1,349 including taxes.[6]
Engineering[edit]

Citroën 11 CV Légère

The Traction Avant used a longitudinal, front-wheel drive layout, with the engine set well within the wheelbase, resulting in a very favourable weight distribution, aiding the car’s advanced handling characteristics. The gearbox was placed at the front of the vehicle with the engine behind it and the differential between them, a layout shared with the later Renault 4 and 16 and first generation Renault 5 but the opposite way round to many longitudinal front-wheel drive cars, such as the Saab 96 and Renault 12 and 18 and most Audi models. The gear change was set in the dashboard, with the lever protruding through a vertical, H-shaped gate.[7] Because this vertical orientation could have resulted in the car dropping out of gear when the lever was in the upper positions (i.e., second or reverse gears), the gear shift mechanism was locked when the mechanical clutch was engaged and released when the clutch pedal was depressed. The result of this layout, along with pendant pedals, umbrella-type handbrake control and front bench seats, was a very spacious interior, with a flat and unobstructed floor. The low-slung arrangement also eliminated the need for running boards to step into or out of the vehicle. These features made them ideal for use as limousines and taxi cabs, and they were quite popular among drivers and passengers alike. Until 1953, black was the only color available.

Impact on Motorsport[edit]

Another technical significance of Tranction Avant was the cast aluminium alloy transaxle, which was pioneered by Hans Ledwinka in the early 1930s for Tatra V570 used in front of the engine located in the rear, but was quite radical at the time.

As well as being a considerable part of the weight savings, the manufacturing facility for this transaxle contributed to the below mentioned financial crisis. But when John Cooper looked for a light transaxle case for Formula One rear engine revolution, Traction Avant unit was about the only candidate, as Volkswagen magnesium alloy transaxle was much smaller and lacking the space needed to house heftier gears needed for Formula One. The Traction Avant transaxle was used on Cooper T43 which won a F1 championship race as the first mid-mounted engine car to do so in 1958, and on its successors Cooper T45, T51 and T53. Cooper T51 won the GP World Championship in 1959.

Unlike the Volkswagen alloy case used by Hewland, the Traction Avant case could not be used up side down, as the input shaft height was much higher in relation to the output shaft axis so that the oil level needed to lubricate the gears would exceed the then-unreliable input shaft oil seal height if used upside down. So the engine needed to sit high above the ground with the oil sump space below, which was not needed by dry-sump racing engines. But the French transaxle was used by several racing car constructors in the late 1950s to 60’s with various levels of success.

In the case of Jack Brabham, who personally visited the ERSA foundry in Paris to discuss a possibility to strengthen the case ,[8] the transaxle became known as "ERSA Knight" with an additional spur-gear set mounted in the bellhousing spacer (engine to transaxle adapter) suggested by Ron Tauranac, named for Jack Knight who designed the modification and made the straight-cut gears. The height offset created by the spur gear set enabled the engine to sit lower, and became the reason why Cooper T53 was called the ‘Lowline’, which not only made Brabham the World Champion in 1960 but also became the precursor to the establishment of Brabham as a Formula One constructor.

Impact on Citroën[edit]

1954 six-cylinder 15CV with hydropneumatic suspension fitted to the rear wheels – in ‘high’ position

Traction Avant as modern wedding car

The development costs of the Traction Avant, combined with the redevelopment of its factory, were very high and Citroën declared bankruptcy in late 1934. The largest creditor was Michelin, who then owned Citroën from 1934 until 1976. Under Michelin, Citroën was run as a research laboratory, a test bed for their radial tires and new automotive technologies.
In 1954 Citroën’s experiments with hydropneumatic technology produced its first result, the "15H" – a variant of the 6-cylinder model 15 with a self-leveling, height-adjustable rear suspension, a field trial for the revolutionary DS released the following year.

Directly after the introduction of the Citroën ID, a simplified and more competitively priced version of the still revolutionary DS, production of the Traction Avant ended in July 1957. Over 23 years, 759,111 had been built, including 26,400 assembled in Slough in England, 31,750 assembled in Forest near Brussels and 1,823 assembled at Cologne in Germany. The total reflects the production stoppage during World War II.

The Traction Avant today[edit]

Big Fifteen sedan

In 2006, the oldest surviving 7A has production number ("coque nr") AZ 00-18, and is displayed in partly dismantled shape (engine and front wheels detached) in the Citroën Museum in Paris. The oldest running 7A is probably number AZ-00-23, which was, until 1 September 2006, in possession of a Dutch owner and is now with a Slovenian owner.
Traction Avants are fairly robust vehicles even by modern standards; however, they are prone to leaking water inside the cabin and care needs to be taken when buying one. Every few years, Traction Avant enthusiasts ship their vehicles to an exotic location for a rally. In 2002, for example, a group of over 30 Traction Avants drove from Los Angeles to New York without incident. [1]

Boston and Providence – Bussey Bridge Train Disaster March 14, 1887

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Jamaica Plain Historical Society
www.jphs.org/transportation/bussey-bridge-train-disaster….

March 14, 1887 dawned gray and cold in Dedham, Massachusetts. It was a snappy Monday morning with the temperature at about 34 degrees. Shortly after 6:00 a.m., Boston & Providence Railroad engineer Walter White and his fireman Alfred Billings steamed their engine, the D.B. Torrey, the short distance from the Dedham engine house to the impressive stone edifice that was the Dedham depot of the Providence Railroad.

Engineer White, a 31-year veteran on the Dedham to Boston run, cautiously backed into the train of nine open-platform, red-varnished coaches that made up the 7:00 A.m. train to Boston. The yardman dropped the pin into the coupling and White and the Torrey were tied to the head end. This was the only day in the week when he would trail nine cars, for on Mondays the passenger load required one extra car.

The run was familiar to White. He’d covered the same route for three decades, and today, as usual, he would follow the 6:10 to Boston. His passengers would be businessmen, workingmen, and store girls – about 100 by the time they left Roslindale, the community halfway between Dedham and Boston’s Park Square Depot.

The D.B. Torrey was a trim little 440 American Type locomotive, the mainstay of American railroads of the 1880’s. She was built by the Rhode Island Locomotive Works in 1880 and weighed 35½ tons. She had just been fitted with a new stack, slightly smaller than her original, and this caused her to steam with a little more difficulty than usual. But this was the only thing out of the ordinary that morning, and it meant simply that Billings would labor more with the coal scoop and White wouldn’t have the power normally available.

Promptly at 7:00 a.m., the train of partially-filled wooden coaches chugged out of Dedham Square over the bridge across High Street and into the outskirts of town. It steamed through snow-covered meadows and crossed the iron bridge spanning Mother Brook. Billings watched the boiler pressure gauge needle dance between 90 and 105 pounds, down a bit from the normal pressure that powered the Torrey.

Back in the coaches, Conductor Myron Tilden and his assistants William Alden and Webster Drake busied themselves taking tickets, while brakeman John Tripp, Winfield Smith, and Elisha Annis remained alert for the engine whistle that would send them to the end platforms to wind the brakewheels. Their effort, added to the air brake on the Torrey, would be more than sufficient to stop the train under normal circumstances. The day of the automatic air brake was just dawning, and while mainline trains were equipped with such systems, branch trains had yet to be modernized.

At each of the closely spaced stations – Spring Street, West Roxbury, Highland, and Central – the train picked up more of its human cargo. Five stops after leaving Dedham the train stood in Roslindale station. By then, nearly 200 passengers occupied the eight coaches and one combination baggage and smoking car coupled to the end of the train.

White’s watch showed him seven minutes late. The timetable called for a 15 minute run from Dedham to Forest Hills, about a mile and a half from Roslindale. The extra car, the cool morning which made wheel bearings stiff, and the poor steaming of the Torrey had combined to lose time from White’s schedule. Regardless, he was better than halfway into Boston on a routine Monday morning in March.

Slowly, White notched the Torrey’s throttle out. The engine barked through a shallow earth cut just east of the station and began the slight downgrade toward Forest Hills. Out of the cut and onto a high embankment the train rattled above the frozen ice and snow covered meadows below.

About a quarter mile ahead, the single-track Dedham Branch crossed South Street on a spindly iron truss bridge known as the Bussey Bridge. It took its name from the old Bussey family farm that later was to become a part of the would-famous Arnold Arboretum. In earlier days, as a wooden bridge, it was sheathed in tin to prevent it from catching fire. The iron structure, which replaced it, was still known as the Tin Bridge.

The Bussey Bridge, toward which 200 souls in nine fragile coaches were heading, was by any standards, a peculiar structure. It crossed the street at an incredibly oblique angle, its spindly iron trusswork bridging a gap of some 120 feet between high granite abutments. So sharp was the angle of the span that the floor beam which ran from the center of the truss on one side rested on the end of the truss which supported the other side of the bridge. Its design was such that certain structural members carried a disproportionate share of the load of every locomotive and car passing over the structure. And this was a violation of the laws of physics and mechanics that would not be tolerated forever.

That March morning, Engineer White approached the old Tin Bridge at a cautious speed. It was a habit, arising from restrictions placed on the bridge prior to its rebuilding in 1876.

There was no indication whatever of any danger as the D. B. Torrey and her nine red coaches rolled toward the bridge. To the engine crew the bridge appeared as solid and safe as ever. White could see meadows stretching away on either side of the embankment, their pale, frozen grass surface punctuated occasionally by stands of bare maples and elms.

The familiar rumble White had heard as his engines crossed innumerable bridges during his career filled his ears as he passed over Bussey Bridge that morning. As the Torrey reached the Boston end of the span, however, White felt a sudden jarring of the engine’s front end, and as the drivers reached the far abutment there was a strong shock unlike anything he had ever felt passing over the bridge.

Immediately he looked back and saw the first car off the track, careening drunkenly behind him. His blood ran cold as he watched the second, third, and fourth cars dancing insanely, trailed by an ugly cloud of smoke and dust where five more cars loaded with passengers should be crossing the bridge,

Instinctively he knew that his train, save the first three or four cars, had gone through the bridge. In the seconds it took for the awesome spectacle to unfold, White’s hands pulled the reversing lever – the fastest way to bring the Torrey to a halt. By now the force of the writhing cars and their human cargo had snapped the coupling at the tender and the Torrey was free.

As the engine came to a halt, White’s reflexes told him there was nothing he and his fireman could do. He knew there was a Dedham-bound train with Engineer Tim Prince in the cab waiting for him at Forest Hills. It was loaded with laborers headed for Dedham to work on a bridge project. He knew too, that these husky workers might well mean the difference between life and death to those trapped in the coaches which lay in a heap beneath where the Bussey Bridge once stood.

Before the engine stopped, White threw the reversing lever ahead, yanked the throttle out, and the Torrey lunged forward again. White grabbed the whistle cord, and the polished brass steam whistle atop the Torrey’s dome screamed in anguish as she roared toward Forest Hills.

Woodcutters in the woods beside the tracks and residents along the line were stopped by the piercing wails of the whistle. They watched as the Torrey raced down the track, her engineer and fireman frantically waving and pointing back in the direction she had come from. That some kind of calamity had occurred was obvious.

In what seemed like seconds, the Torrey was at Forest Hills. White and Billings yelled to station agent William Worley that a train had gone through the bridge and to send Jim Prince’s three-car train with its laborers to the scene.

Immediately Prince had his engine barking at full throttle up the branch toward the ill-fated commuter train. White leaped from his cab and ran into the small frame depot where he ordered Worley to telephone for doctors and ambulances.

Five minutes later he was again aboard the Torrey, headed back to the scene to give what help he could to the dead and injured.

What met them when they returned was a ghastly panorama. Three cars teetered on the frozen roadbed, their wheels torn from beneath them, underbodies and platforms smashed to kindling. Behind the third car the roof of the fourth lay on roadbed, torn from the rest of the car body, which was some 50 feet below. The fifth through the ninth cars were either at the bottom of the embankment or in the chasm where the bridge had stood.

The rear car, which had been the smoker, was smashed, turned upside down. The next car was thrown on its side and stove in; the next car dropped square on its wheels and stood upright. The succeeding two cars were telescoped and lapped onto each other and a part of the sixth car was wedged between the telescope and the embankment. All the cars were smashed and broken, twisted and entwined with the iron beams and girders of the bridge. Broken rails, twisted and jagged bars of iron, and splintered wood combined with badly mangled dead and injured in a scene of horror.

Within minutes, spurred on by White’s alarm, help was arriving from everywhere. Residents and shopkeepers, workers and doctors from Roslindale arrived in time to extinguish one small fire and help in removing the injured. Hundreds worked feverishly to remove the wounded. A special train carrying doctors, hastily assembled by railroad officials from the professional buildings around Park Square Depot in Boston, arrived to render medical aid.

When all the passengers had been removed the dead and near-dead numbered 23. Most of the dead had been killed instantly. Some of the injured survived a few hours, one several days. Over 100 were injured, more than half of them seriously.

What caused this terrible disaster? The Boston Globe that evening speculated that a weakened span failed under the weight of the train.

The Massachusetts Board of Railroad Commissioners convened the day after the wreck and sat until April 4, gathering facts upon which to determine the cause. What it heard from survivors, railroad officials, the builder of the Bussey Bridge, and outside engineering experts was a story of an incredible collection of circumstances culminating in the tragic collapse.

The primary cause was determined to be a pair of iron hangers which formed an integral part of the supporting network of iron rods making up one of the two trusses upon which the rails rested. Improperly designed and manufactured, they weakened gradually with the passage of time and failed catastrophically that morning. The weight of the Torrey snapped the hangers, and the bridge immediately began to disintegrate as the train crossed the span.

The parade of witnesses described how the Boston & Providence in 1876 entered into a contract with one Edward Hewins, representing the Metropolitan Bridge Company, to rebuild the bridge. Testimony further revealed that he alone was the Metropolitan Bridge Company. When pressed on this point by the commissioners, Hewins testified it had been his intention to organize a bridge company at the time but never got around to doing it. The two trusses which made up the ill-fated bridge were actually fabricated by two separate iron works. The Commissioners found that the railroad had never investigated the Metropolitan Bridge Company and that no one involved in making the contract really knew enough about iron bridge building to pass intelligently on the structure’s design and specifications. In fact, it was generally admitted during the hearings that the company didn’t even employ an expert to review the design of the bridge once it had been built.

One railroad employee who had inspected the bridge regularly was a machinist who was not trained to look at key structural parts for signs of failure.

Six years earlier the Commission had recommended a series of structural tests for the bridge, which were never conducted. Crossties were spaced too far apart for safety. The bridge was not equipped with guardrails to catch the wheels of a derailed train and guide them safely across. And, tragically, the Westinghouse automatic air brake was not in operation on the train even though it was becoming more common on the nation’s railroads. Had it been in use, it might have prevented the fatal plunge of coaches into the chasm following the separation of the train from the engine.

Fire, the real horror of most train wrecks of the era, didn’t occur because the B & P followed a policy of bolting its coal-burning, car-heating stoves to the floor and bolting the doors shut, thereby, eliminating the possibility of hot coals igniting the wooden wreckage.

The wreck was a calamity for the Boston & Providence, which for almost twenty years previously had not had a train accident resulting in injury or loss of life to a passenger.

Today the Boston & Providence is long gone, along with its Dedham Branch to West Roxbury. Where once stood the Dedham depot, a municipal parking lot serves Dedham shoppers. Trains still cross South Street in Roslindale on the Penn Central’s Needham Branch. But the Bussey Bridge they use is a solid, substantial granite arch, which has safely carried passenger and freight trains since before the turn of the century. It stands as a stone monument to the hapless passengers on the 7:00 A.M. train and the quick-thinking engineer whose fast action that Monday morning in March saved so many lives.

Written by Edward J. Sweeney. Originally published in Yankee Magazine, March 1975. Image courtesy of Library of Congress Prints and Photographs Division, Digital ID: cph 3g03155