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95-534: In the late thirties, there had been several projects to improve the Renault R35 light infantry tank. One of these was directed to the improvement of the horizontal rubber spring suspension system that, apart from being less reliable than originally hoped for, caused an uncomfortable ride, high track and tread wear and an unfavourable weight distribution. The type tended to get stuck in soft terrain. Several solutions were proposed, among them an overdrive , new wheel tyres,

190-562: A freewheel in the gear box, the fitting of grousers or studs on the existing tracks, or the adoption of a new track type. None of these were satisfactory. Apart from Lorraine, whose proposal based on the Lorraine 37L suspension was rejected as too heavy and complicated to refit, both the AMX factory and the Renault design bureau developed several solutions to this problem from 1937. AMX had its origin in

285-522: A Volvo version. The Volvo version kept the same package size as the J-type but with the updated 18 element freewheel and stronger splines through the planet carrier. The Gear Vendors U.S. version uses a larger 1.375 outer diameter output shaft for higher capacity and a longer rear case. Over a period of 40 years, Laycock Engineering manufactured over three and a half million overdrive Units, and over one million of these were fitted to Volvo motorcars. In 2008

380-602: A cart or wagon, and assaut ; attack or assault), soon shortened to char , had at the insistence of Colonel Estienne, already been adopted by the French and was in common use. Once orders for the vehicle had been secured it was the practice at Renault to refer to it as the "FT". The vehicle was originally intended to carry a machine-gun, and was therefore described as a char mitrailleur – mitrailleur (from mitraille ; grapeshot) had by this time come to mean "machine-gunner". Many sources, predominantly English language accounts, refer to

475-450: A curve describing the overall drag on the vehicle, it is simple to find the speed at which the total drag forces are the same as the maximum power of the engine. This defines the maximum speed the vehicle is able to reach. The rotational speed of the wheels for that given forward speed is simple to calculate, being the tire circumference multiplied by the RPM. As the tire RPM at maximum speed is not

570-413: A different gear ratio. If one is not supplied, the engine is forced to run at a higher RPM than optimal. As the engine requires more power to overcome internal friction at higher RPM, this means more fuel is used simply to keep the engine running at this speed. Every cycle of the engine leads to wear, so keeping the engine at higher RPM is also unfavorable for engine life. Additionally, the sound of an engine

665-796: A few. Another British company, the former aircraft builder Fairey , built a successful all-mechanical unit for the Land Rover , which is still in production in America today. The first production vehicle to feature the Laycock system was the 1948 Standard Vanguard Saloon. The first unit to be created was the A-type overdrive, which was fitted to many sports cars during the 1950s, and into the late 1960s. Several famous marques used A-type overdrives, including Jaguar, Aston Martin, Ferrari, Austin-Healey, Jensen, Bristol, AC, Armstrong Siddeley and Triumph's TR sports car range, from

760-460: A first Renault bought in 1919. These tanks formed a company deployed from 1921. After a first failure, they proved to be very effective and six more were delivered in 1925. The Spanish FT were the first tanks in history to take part in an amphibious assault , the Alhucemas landing . The French Army deployed two battalions of FT during the war, including one company of tanks with Kégresse tracks. After

855-407: A fixed-ratio transmission arrangement that was much simpler to build. Final drive ratios of 4:1 were common, meaning that the wheels would turn at one fourth the rate they would if directly connected to the engine. In an era when different models of car with different wheel sizes could be accommodated by simply changing the final drive ratio, it made sense for all transmissions to use direct drive as

950-506: A hexagonal one; it referred to the 18 horsepower engine; it indicated a version to which various modifications had been made. Renault records make no distinction between 1917 and 1918 output; the decision to arm FTs with a 37mm gun was made in April 1917, before any tanks had been manufactured; because of various production difficulties and design requirements, a range of turret types were produced by several manufacturers, but they were all fitted to

1045-409: A higher ratio first gear, which means more gears between the first and the last to keep the engine at its most efficient speed. This is part of the reason that modern automobiles tend to have larger numbers of gears in their transmissions. It is also why more than one overdrive gear is seldom seen in a vehicle except in special circumstances i.e. where high (numerical) differential gear is required to get

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1140-562: A large number of light tanks would be preferable to a smaller number of super-heavy tanks (the later Char 2C ). On 27 November 1916, Estienne sent to the French Commander in Chief a personal memorandum proposing the immediate adoption and mass manufacture of a light tank based on the specifications of the Renault prototype. After receiving two large government orders for the FT tank, one in April 1917 and

1235-436: A larger wheel diameter. The systems with the six larger wheels or the ten smaller ones could also be used to upgrade existing vehicles. However, after tests from 19 May until 26 December 1938, an AMX design using six vertical coil springs covered with 8 mm armour plating with twelve road wheels per side, was selected on 16 February 1939. The type superficially resembled the suspension of the earlier Char D1 and Char D2 but

1330-513: A leading role in the offensives of 1918, when it received the popular name "Victory Tank". The British Army used 24 FTs for command and liaison duties, usually with the gun removed. Italy received 3 FTs in June 1918, but they did not see action and no other tanks were received until the end of the war. After the end of World War I, Renault FTs were exported to many countries (Belgium, Brazil, Czechoslovakia , Estonia, Finland, Iran, Japan, Lithuania,

1425-476: A long-time associate of Louis Renault, organized and supervised the new tank's mass production. The FT's tracks were kept automatically under tension to prevent derailments, while a rounded tailpiece facilitated the crossing of trenches. Because the engine had been designed to function normally under any slant, very steep slopes could be negotiated by the Renault FT without loss of power. Effective internal ventilation

1520-416: A nationalisation of parts of the Renault company, which resulted in a natural rivalry between the two design bureaux. Renault proposed a type with doubled wheels on the original bogies (which thus would result in ten road wheels per side) combined with a new track using shorter links, a second type with vertical coil springs and a third type lengthened with a sixth road wheel at the rear, which would also entail

1615-593: A possible manufacturer. Renault declined, saying that his company was operating at full capacity producing war materiel and that he had no experience of tracked vehicles. Estienne later discovered that the Schneider company was working on a tracked armoured vehicle, which became France's first operational tank, the Schneider CA . At a later, chance meeting with Renault on 16 July 1916, Estienne asked him to reconsider, which he did, favourably. Louis Renault himself conceived

1710-838: A revolt in Italian Libya in 1919. The French Army sent a company of FT tanks to Syria during the Great Druze Revolt . In Brazil, the FT tanks were used by the Old Republic to crush various revolts between 1924 and 1927 and by Vargas forces against the Constitutionalist Revolution . During the Rif War , after the Battle of Annual , the Spanish Army ordered 10 FT armed with Hotchkiss machine guns and 1 char TSF to supplement

1805-884: A section defended the Hue fortress . The last known use was in the 1980s during the Soviet–Afghan War , when some FTs were used as pillboxes or roadblocks. The FT was the ancestor of a long line of French tanks: the FT Kégresse, the NC1, the NC2, the Char D1 , and the Char D2 . The Italians produced the FIAT 3000 , a moderately close copy of the FT, as their standard tank. The Soviet Red Army captured 14 burnt-out Renaults from White Russian forces and rebuilt them at

1900-476: A successful circular turret which was mostly cast with some rolled parts. The Girod turret was also an "omnibus" design. Girod supplied it to all the companies producing the FT, and in the later stages of the war it became more commonplace than the Berliet turret. The turret sat on a circular ball-bearing race, and could easily be rotated by the gunner/commander or be locked in position with a handbrake. The Renault FT

1995-420: A total R 35/40 production that month of 91. It is uncertain how many R 40s were produced before production was halted in June 1940; certainly 130 and probably 145 hulls were manufactured, but likely these did not all have their turret fitted. It had been intended to keep production levels at 120 per month for the duration of the war and introduce the lighter welded FCM turret in the second half of 1940. In May 1940,

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2090-504: A variety of models, including 1968–1980 MGBs , the MGC , the Ford Zephyr , early Reliant Scimitars , TVRs, and Gilberns . The J-type overdrive was introduced in the late 1960s, and was adapted to fit Volvo, Triumph, Vauxhall/Opel, American Motors and Chrysler motorcars, and Ford Transit vans. The P-type overdrive marked the last updates and was manufactured in a Gear Vendors U.S. version and

2185-422: Is a range of gear ratios that can match engine power to air resistance, and the most fuel efficient is the one that results in the lowest engine speed. Therefore, a car needs one gearing to reach maximum speed but another to reach maximum fuel efficiency at a lower speed. With the early development of cars and the almost universal rear-wheel drive layout, the final drive (i.e. rear axle ) ratio for fast cars

2280-402: Is common. However, due to historical particularities, this was not always practical. In the conventional rear-wheel drive layout , the transmission system normally contained two sections, the "gearbox" or "transmission" mounted behind the engine, and the "final drive" mounted in the rear axle at the rear of the car. The reason for this separation of duties between the front and back of the car

2375-481: Is limited by the power required to drive it against air resistance, which increases with speed. At the maximum possible speed, the engine is running at its point of maximum power, or power peak , and the car is traveling at the speed where air resistance equals that maximum power. There is therefore one specific gear ratio at which the car can achieve its maximum speed: the one that matches that engine speed with that travel speed. At travel speeds below this maximum, there

2470-399: Is off, the automatic transmission shifting is limited to the lower gears. Overdrive should usually be selected when the average speed is above 70 km/h (40-45 mph). The automatic transmission automatically shifts from OD to direct drive when more load is present. When less load is present, it shifts back to OD. Under certain conditions, for example driving uphill, or towing a trailer,

2565-416: Is one additional consideration which meant that the top gear of most gearboxes was 1:1 or "direct drive". This is chosen for efficiency, as it does not require any gears to transmit power and so reduces the power lost by them. This was particularly important in the early days of cars, as their straight-cut gears were poorly finished, noisy and inefficient. The final drive then took this output and adjusted it in

2660-509: Is strongly related to the RPM, so running at lower RPM is generally quieter. If one runs the same RPM transmission exercise outlined above for maximum speed, but instead sets the "maximum speed" to that of highway cruising, the output is a higher gear ratio that provides ideal fuel mileage. In an era when cars were not able to travel very fast, the maximum power point might be near enough to the desired speed that additional gears were not needed. But as more powerful cars appeared, especially during

2755-409: Is the highest gear in the transmission. Overdrive allows the engine to operate at a lower RPM for a given road speed. This allows the vehicle to achieve better fuel efficiency, and often quieter operation on the highway. When it is switched on, an automatic transmission can shift into overdrive mode after a certain speed is reached (usually 70+ km/h [40-45 mph or more] depending on the load). When it

2850-448: Is thus overdriven, and a transmission capable of doing this became termed an "overdrive" transmission. The device for achieving an overdrive transmission was usually a small separate gearbox, attached to the rear of the main gearbox and controlled by its own shift lever. These were often optional on some models of the same car. As popular cars became faster relative to legal limits and fuel costs became more important, particularly after

2945-449: The 1973 oil crisis , the use of five-speed gearboxes became more common in mass-market cars. These had a direct (1:1) fourth gear with an overdrive fifth gear, replacing the need for the separate overdrive gearbox. With the popularity of front wheel drive cars, the separate gearbox and final drive have merged into a single transaxle . There is no longer a propeller shaft and so one meaning of "overdrive" can no longer be applied. However

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3040-545: The English company Laycock Engineering (later GKN Laycock), at its Little London Road site in Sheffield . The system devised by de Normanville was adopted and manufactured by Laycock after his chance meeting with a Laycock Products Engineer. De Normanville overdrives were found in vehicles manufactured by Standard-Triumph , who were first, followed by Ford , BMC and British Leyland , Jaguar , Rootes Group and Volvo to name only

3135-602: The Kingdom of Yugoslavia , although they were already obsolete. In May 1940, the French Army still had seven front-line battalions, each equipped with 63 FTs, one under-strength battalion as well as three independent companies, each with 10, for a total organic strength of 504. 105 more were in service in the colonies of Morocco and Algeria and 58 in French Levant , Madagascar and Indochina . Some FT tanks had also been buried within

3230-518: The Krasnoye Sormovo Factory in 1920. Nearly 15 exact copies, called "Russki Renoe", were produced in 1920–1922, but they were never used in battle because of many technical problems. In 1928–1931, the first completely Soviet-designed tank was the T-18 , a derivative of the Renault with sprung suspension. Approximately 41 FTs, two Russkiy Reno s, and three FT TSF survive in various museums around

3325-547: The Renault FTs of eight existing battalions and raise eight new battalions to bring their number to the planned final total of fifty light tank BCCs ( Bataillions de Chars de Combat ), forty of these equipped with Renault tanks. As the new vehicles looked quite differently from the original R 35, they were very generally, also in army documentation, called the "R 40"; however, this was never their official type designation; officially these were still Renault R35s and their production

3420-440: The transmission unit. It can either couple the input driveshaft directly to the output shaft (or propeller shaft ) (1:1), or increase the output speed so that it turns faster than the input shaft (1:1 +  n ). Thus the output shaft may be "overdriven" relative to the input shaft. In newer transmissions, the overdrive speed(s) are typically as a result of combinations of planetary/epicyclic gearsets which are integrated in

3515-432: The 1960s, this disparity between the maximum power point and desired speed grew considerably. This meant that cars were often operating far from their most efficient point. As the desire for better fuel economy grew, especially after the 1973 oil crisis , the need for a "cruising gear" became more pressing. The obvious solution to this problem would be to add more gears to the transmission. Indeed, in modern vehicles this

3610-634: The Chinese Fengtian Army of Zhang Zuolin in 1919. 14 more Renaults were bought in 1924 and 1925. These tanks saw action to protect the border from the Soviets in the 1920s and against the warlord Wu Peifu in 1926. After the Japanese invasion of Manchuria , nearly all were handed over to the Manchukuo Imperial Army . Renault tanks were also used in colonial conflicts, for instance crushing

3705-430: The FT as the "FT 17" or "FT-17." This term is not contemporary and appears to have arisen post World War One. In Estienne's biography, his granddaughter states, "It is also referred to as the FT 17: the number 17 was added after the war in history books, since it was always referred to at Renault as the FT." Lieutenant-Colonel Paul Malmassari (French tank officer and Doctor of History) states, "The Renault tank never carried

3800-548: The French tanks were also markedly slow (unlike the German tanks of the time). When the best French units were cut off by the German drive to the English Channel, around 390 FTs, previously used for training or stored in depots, joined the 184 to 192 FTs in service with internal security units. The Wehrmacht captured 1,704 FTs. They used about 100 for airfield defence and about 650 for patrolling occupied Europe. Some were used by

3895-619: The Germans in 1944 for street-fighting in Paris, but by this time they were hopelessly out of date. Vichy France used Renault FTs against Allied invasion forces during Operation Torch in Morocco and Algeria. The French tanks were no match for the newly arrived American M4 Sherman and M3 Stuart tanks. The last combat of the French Army FTs was during the Japanese invasion of French Indochina , when

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3990-572: The Netherlands, Poland, Romania, Spain, Switzerland, Turkey, and Yugoslavia). Renault FT tanks were used by most nations having armoured forces, generally as their prominent tank type. They were used in anti-Soviet conflicts such as the Russian Civil War and Polish-Soviet War . On 5 February 1920, Estonia purchased nine vehicles from France. French tanks deployed in Vladivostok were given to

4085-612: The R 35 had the largest production of any Allied (or indeed Western) tank but it was planned to having it surpassed by that of the much faster "H 39" , reflecting the emphasis on the formation of new armoured divisions, for which the slow R 40 was less than ideal; the "new" suspension was really rather old-fashioned and could not be combined with a high speed, as earlier experience with the Char D3 and Renault VO projects had shown. Nevertheless, apart from donations to allies and units already formed in June, another 800 vehicles were needed to replace

4180-579: The R 40 (30 and 29 respectively) and attached to the 2e DCR . This reflects the large matériel reserve of Renault tanks. Some R 40s perhaps replaced losses in the older battalions. One of the two tank battalions of the Polish 10th Armoured Cavalry Brigade being formed in France was also partly equipped with first 24 R 40s, which were then on 31 May given to 25 BCC, after which the Polish battalion received another 28 R 40s,

4275-568: The Renault FT the world's first modern tank. Over 3,000 Renault FT tanks were manufactured by France, most of them in 1918. After World War I , FT tanks were exported in large numbers. Copies and derivative designs were manufactured in the United States ( M1917 light tank ), in Italy ( Fiat 3000 ), and in the Soviet Union ( T-18 tank ). The Renault FT saw combat during the interwar conflicts around

4370-666: The TR2 through to the end of the 1972 model year of the TR6. In 1959, the Laycock Engineering Company introduced the D-type overdrive, which was fitted to a variety of motor cars including Volvo 120 and 1800s , Sunbeam Alpines and Rapiers , Triumph Spitfires , and also 1962–1967 MGBs (those with 3-synchro transmissions). From 1967 the LH-type overdrive was introduced, and this featured in

4465-411: The U.S. company Gear Vendors, Inc. of El Cajon, California purchased all the overdrive assets of GKN to continue production of the U.S. version and all spares for J and P types worldwide. The system features an oil pressure operated device attached to the back of the standard gearbox operating on the gearbox output shaft. Through a system of oil pressure, solenoids and pistons, the overdrive would drop

4560-530: The absence of infantry support, the vehicles later withdrew. From then on, gradually increasing numbers of FTs were deployed, together with smaller numbers of the older Schneider CA1 and Saint-Chamond tanks. As the war had become a war of movement during mid-1918, during the Hundred Days Offensive , the lighter FTs were often transported on heavy trucks and special trailers rather than by rail on flat cars. Estienne had initially proposed to overwhelm

4655-401: The adapted cast APX-R1 turret, giving the type a good antitank capacity, and a tail to facilitate climbing. The number of rounds carried decreased from 102 to 90. A fundamental advance in tactical effectiveness compared to the R 35 was that the R 40s were equipped with a radio set, which had not been standard for any French light tank until then. In May, about sixty R40s were manufactured out of

4750-529: The automotive aftermarket you can also retrofit overdrive to existing early transmissions. Overdrive was widely used in European automobiles with manual transmission in the 60s and 70s to improve mileage and sport driving as a bolt-on option but it became increasingly more common for later transmissions to have this gear built in. If a vehicle is equipped with a bolt-on overdrive (e.g.: GKN or Gear Vendors) as opposed to having an overdrive built in one will typically have

4845-450: The axle), and tire size. The rotation speed problem comes into effect when the differential gearing is a high ratio and an overdrive is used to compensate. This may create unpleasant vibrations at high speeds and possible destruction of the driveshaft due to the centripetal forces or uneven balance. The driveshaft is usually a hollow metal tube that requires balancing to reduce vibration and contains no internal bracing. The higher speeds on

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4940-451: The basic FT body without any distinguishing reference; all FTs had the same model 18 hp engine. The Renault manual of April 1918 is entitled RENAULT CHAR D'ASSAUT 18 HP , and the illustrations are of the machine-gun version. The official designation was not changed until the 1930s when the FT was fitted with a 1931 Reibel machine gun and renamed the FT modifié 31 . By this time, the French Army

5035-426: The benefit to fuel economy. Overdrive is included in both automatic and manual transmissions as an extra gear (or two in some cases). When using overdrive gearing, the car's engine speed drops, reducing wear and normally saving fuel. Since 1981 U.S. corporate average fuel economy (CAFE) legislation, virtually all domestic vehicles have included overdrive to save fuel. One should refer to the car's owner's manual for

5130-408: The car is over-geared , and cannot reach its potential top speed, i.e. the car could travel faster if it were in a lower gear, with the engine turning at higher RPM. The power produced by an engine increases with the engine's RPM to a maximum, then falls away. The point of maximum power is somewhat lower than the absolute maximum engine speed to which it is limited, the " redline ". A car's speed

5225-451: The days before automatic transmissions were common, especially in the 1950s, many rear-wheel drive American cars were available with an overdrive option. With substantial improvements developed in Muncie, Indiana , by William B. Barnes for production by its Warner Gear Division, BorgWarner provided the box that was factory-installed between the transmission and a foreshortened driveshaft. Since

5320-399: The driveshaft and related parts can cause heat and wear problems if an overdrive and high differential gearing (or even very small tires) are combined, and create unnecessary friction. This is especially important because the differential gears are bathed in heavy oil and seldom provided with any cooling besides air blowing over the housing. The impetus is to minimize overdrive use and provide

5415-876: The end of the war, the French tanks remained in North Africa to finish the "pacification" of Morocco in the Atlas Mountains . When the Spanish Civil War broke, half of the Renault crews remained loyal to the Spanish Republic while the others joined the rebels . France later sent 32 FTs to the Republicans; the number of FTs sold to the Republicans by Poland is unclear; estimates vary between 16 and 94. Renault FT tanks were also fielded in limited numbers during World War II , in Poland, Finland, France, Greece, Romania and

5510-576: The enemy defences using a "swarm" of light tanks, a tactic that was eventually successfully implemented. Beginning in late 1917, the Entente allies were attempting to outproduce the Central Powers in all respects, including artillery, tanks, and chemical weapons. Consequently, a goal was set of manufacturing 12,260 FT tanks (7,820 in France and 4,440 in the United States) before the end of 1919. It played

5605-455: The existing vehicles with the cheaper Renault vertical coil suspension was considered, as it could be done by field workshops and thus pose less of a burden to French industry. The change, however, was delayed and went only into effect in May 1940 from the 1541st vehicle onwards. It coincided with a number of other improvements, such as a longer and thus much more powerful SA38 Long 35 37 mm gun in

5700-614: The first model of turret. Meanwhile, the Berliet Company had produced a new design, a polygonal turret of riveted plate, which was simpler to produce than the early cast steel turret. It was given the name "omnibus", since it could easily be adapted to mount either the Hotchkiss machine gun or the Puteaux 37mm with its telescopic sight. This turret was fitted to production models in large numbers. In 1918 Forges et aciéries Paul Girod produced

5795-474: The fundamental meaning, that of an overall ratio higher than the ratio for maximum speed, still applies: higher gears, with greater ratios than 1:1, are described as "overdrive gears". The power needed to propel a car at any given set of conditions and speed is straightforward to calculate, based primarily on the total weight and the vehicle's speed. These produce two primary forces slowing the car: rolling resistance and air drag . The former varies roughly with

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5890-596: The ground and encased in concrete to supplement the Maginot Line . The fact that several units used the Renault FT gave rise to the popular myth that the French had no modern equipment at all; actually, they had as many modern tanks as the Germans; however, the majority had one-man turrets and were less efficient than German tanks such as the Panzer III and IV. The French suffered from strategic and tactical weaknesses rather than from equipment deficiencies, although many of

5985-451: The highest gear. As noted earlier, however, this would cause the engine to operate at too high an RPM for efficient cruising. Although adding the cruising gear to the main gearbox was possible, it was generally simpler to add a separate two-gear overdrive system to the existing gearbox. This not only meant that it could be tuned for different vehicles, but had the additional advantage that it could be offered as an easily installed option. With

6080-416: The last thirteen on 19 June. There are no known surviving R 40 vehicles. Overdrive (mechanics) Overdrive is the operation of an automobile cruising at sustained speed with reduced engine speed (rpm), leading to better fuel consumption, lower noise, and lower wear. The term is ambiguous. The most fundamental meaning is that of an overall gear ratio between engine and wheels, such that

6175-410: The latter, in accordance with French grammar, renamed char mitrailleuse (machine-gun tank). It is frequently claimed that some of these tanks were designated FT 18. Reasons given for the claim include: it distinguished tanks produced in 1918 from those of 1917; it was applied to FTs armed with cannon as opposed to those with machine-guns; it distinguished FTs with a cast, rounded turret from those with

6270-418: The letters FT stand for the French terms faible tonnage (low tonnage), faible taille (small size), franchisseur de tranchées (trench crosser), or force terrestre (land force), none of these names are correct. Neither was it named the FT 17 or FT-17. The name is derived from the two-letter production code that all new Renault projects were given for internal use: the one available was 'FT'. The prototype

6365-708: The name FT 17 during the First World War, although the initials F.T. seem to appear in August 1917." Some confusion might also have been caused by the fact that the American version of the vehicle, produced in the US under licence from Renault, was designated the M1917. When it was decided to equip the FTs with either cannon or machine-guns, the cannon version was designated char canon (cannon tank), and

6460-445: The new tank's overall design and set its basic specifications. He imposed a 7-ton limit to the FT's projected weight. Renault was unconvinced that a sufficient power-to-weight ratio could be achieved with the production engines available at the time to give sufficient mobility to the heavy tank types requested by the military. Renault's industrial designer Rodolphe Ernst-Metzmaier generated the FT's execution plans. Charles-Edmond Serre,

6555-543: The option to use the overdrive in more gears than just the top gear. In this case gear changing is still possible in all gears, even with overdrive disconnected. Overdrive simply adds effective ranges to the gears, thus overdrive third and fourth become in effect "third-and-a-half" and a fifth gear. In practice this gives the driver more ratios which are closer together providing greater flexibility particularly in performance cars. An overdrive consists of an electrically or hydraulically operated epicyclic gear train bolted behind

6650-432: The order was increased to 7,820 in 1918, production was distributed in roughly the same proportion. Louis Renault agreed to waive royalties for all French manufacturers of the FT. When the US entered the war in April 1917, its army was short of heavy materiel and had no tanks at all. Because of the wartime demands on French industry, it was decided that the quickest way to supply the American forces with sufficient armour

6745-482: The other in June 1917, Renault was able to proceed. His design remained in competition with the super-heavy Char 2C until the end of the war. The prototype was refined during the second half of 1917, but the Renault FT remained plagued by radiator fan belt problems throughout the war. Only 84 were produced in 1917, but 2,697 were delivered to the French army before the Armistice. Although it has sometimes been stated that

6840-425: The overdrive function, if enabled, could be shifted by simply easing up on the accelerator without depressing the clutch pedal , the action was much like a semi-automatic. Also, an electrically operated solenoid would deactivate the unit via a switch under the accelerator pedal providing the equivalent of the kickdown of the automatic. A knob connected to a bowden cable , similar to some emergency brake applications,

6935-433: The proper speed to run at overdrive. All engines have a range of peak efficiency and it is possible for the use of overdrive to keep the engine out of this range for all or part of the time of its use if used at inappropriate speeds, thus cutting into any fuel savings from the lower engine speed. Overall drivetrain reduction comes down to three basic factors: transmission gearing (including overdrive), differential gearing (in

7030-399: The revs on whatever gears it was used on by 22% (.778). For instance, the overdrive system applied to a Triumph TR5 operates on 2nd, 3rd and top gear. When engaged, the overdrive would drop the revs from 3000 by 666 RPM, or from 3500 the drop would be 777 RPM to 2723 net. The advantages this reduced rpm had on fuel consumption was most often quite near 22% decrease during highway driving. In

7125-429: The same as the engine RPM at that power, a transmission is used with a gear ratio to convert one to the other. At even slightly lower speeds than maximum, the total drag on the vehicle is considerably less, and the engine needs to deliver this greatly reduced amount of power. In this case the RPM of the engine has changed significantly while the RPM of the wheels has changed very little. Clearly this condition calls for

7220-406: The speed of the vehicle, while the latter varies with the square of the speed. Calculating these from first principles is generally difficult due to a variety of real-world factors, so this is often measured directly in wind tunnels and similar systems. The power produced by an engine increases with the engine's RPM to a maximum, then falls away. This is known as the point of maximum power . Given

7315-459: The steering qualities. However, the AMX system also had its drawbacks. It added a weight of 1.1 tonne to the tank, while the weight penalty was just seven hundred kilogrammes with the Renault six-wheel suspension and only 110 kilogrammes for the ten wheel system. Also, the longer track links caused a heavy clattering during road travel, reminiscent of the noise made by the Renault FT . Fuel consumption

7410-516: The transmission may "hunt" between OD and the next highest gear, shifting back and forth. In this case, switching it off can help the transmission to "decide". It may also be advantageous to switch it off if engine braking is desired, for example when driving downhill. The vehicle's owner's manual will often contain information and suitable procedures regarding such situations, for each given vehicle. Virtually all vehicles (cars and trucks) have overdrive today whether manual transmission or automatic. In

7505-635: The transmission. For example, the ZF 8HP transmission has 8 forward gears, two of which are overdrive (< 1:1) gear ratios. In older vehicles, it is sometimes actuated by a knob or button, often incorporated into the gearshift knob, and does not require operation of the clutch . Newer vehicles have electronic overdrive in which the computer automatically adjusts to the conditions of power need and load. The vast majority of overdrives in European cars were invented and developed by Edgar de Normanville , and manufactured by

7600-459: The use of front-wheel drive layouts, the gearbox and final drive are combined into a single transaxle. There is no longer a drive shaft between them and so the notion of "direct drive" is inapplicable. Although "overdrive" is still referred to, this is now mostly a marketing term to refer to any extra-high ratio for efficient cruising, whether it is achieved through the gearbox ratios, or by an unusually high final drive. Generally speaking, overdrive

7695-461: The vehicle moving as in trucks or performance cars though double overdrive transmissions are common in other vehicles, often with a small number on the axle gear reduction, but usually only engage at speeds exceeding 100 kilometres per hour (62 mph). FT-17 The Renault FT (frequently referred to in post-World War I literature as the FT-17 , FT17 , or similar) is a French light tank that

7790-534: The war was over. The first turret designed for the FT was a circular, cast steel version almost identical to that of the prototype. It was designed to carry a Hotchkiss 8mm machine gun . In April 1917 Estienne decided for tactical reasons that some vehicles should be capable of carrying a small cannon. The 37mm Puteaux gun was chosen, and attempts were made to produce a cast steel turret capable of accommodating it, but they were unsuccessful. The first 150 FTs were for training only, and made of non-hardened steel plus

7885-589: The world but was considered obsolete at the outbreak of World War II . The FT was designed and produced by the Société des Automobiles Renault (Renault Automobile Company). It is thought possible that Louis Renault began working on the idea as early as 21 December 1915, after a visit from Colonel J. B. E. Estienne . Estienne had drawn up plans for a tracked armoured vehicle based on the Holt caterpillar tractor , and with permission from General Joffre , approached Renault as

7980-587: Was 40% higher. The variant was named the Char léger modèle 1935 R modifié 1939 . At first, it was literally envisaged as a modification, also to be retrofitted to existing vehicles, but the emergency caused by the outbreak of war in September led to a change in policy: the new suspension would only be implemented on the R 35 production run, from the 1501st vehicle onwards, to take place in February 1940. In late 1939, retrofitting

8075-521: Was also provided to lock out the unit mechanically. Using overdrive with the main 3-speed transmission in 2nd gear was similar in ratio to 3rd gear, and with the main transmission in third, the overall ratio was fractional (i.e., "true overdrive"). This was important in reducing wear, tear, noise, and difficulty in control. Such add-on overdrive boxes were available from the 1930s to the 1970s for cars and light trucks. Today, most petrol and diesel cars and trucks come with an overdrive transmission because of

8170-408: Was among the most revolutionary and influential tank designs in history. The FT was the first production tank to have its armament within a fully rotating turret. The Renault FT's configuration (crew compartment at the front, engine compartment at the back, and main armament in a revolving turret) became and remains the standard tank layout. Consequently, some armoured warfare historians have called

8265-417: Was at first referred to as the automitrailleuse à chenilles Renault FT modèle 1917 . Automitrailleuse à chenilles means " armoured car [lit: motorized machine gun] with tracks." By this stage of the war, automitrailleuse was the standard word for an armoured car, but by the time the FT was designed there were two other types of French tank in existence, and the term char d'assaut (from the French char –

8360-430: Was chosen to give the ratio for maximum speed. The gearbox was designed so that, for efficiency, the fastest ratio would be a "direct-drive" or "straight-through" 1:1 ratio, avoiding frictional losses in the gears. Achieving an overdriven ratio for cruising thus required a gearbox ratio even higher than this, i.e. the gearbox output shaft rotating faster than the engine. The propeller shaft linking gearbox and rear axle

8455-464: Was equipped with several other Renault models and it had become necessary to distinguish between the various types. About half of all FTs were manufactured in Renault's factory at Boulogne-Billancourt near Paris, with the remainder subcontracted to other companies. Of the original order for 3,530, Renault accounted for 1,850 (52%), Berliet 800 (23%), SOMUA (a subsidiary of Schneider & Cie ) 600 (17%), and Delaunay-Belleville 280 (8%). When

8550-526: Was in fact inspired by the Char B1 suspension. It also used the same track as the Char B1, reducing the number of track links compared with the R 35 from 125 to 56. The AMX suspension resulted in a superior speed on varied terrain and could climb steeper slopes. The Renault system with ten wheels to the contrary slowed the tank and led to a higher fuel consumption. This was not compensated by a discernible improvement of

8645-453: Was provided by the engine's radiator fan, which drew its air through the front crew compartment of the tank and forced it out through the rear engine's compartment. Renault encountered some early difficulties in getting his proposal fully supported by Estienne. After the first British use of heavy tanks on 15 September 1916 during the Battle of the Somme , the French military still pondered whether

8740-499: Was subsumed under the R 35 run in the statistics; their serial numbers are continuous with the older R 35 run. Two new tank battalions, originally intended and trained to be equipped with Hotchkiss tanks to form the half-brigade of the new 4e DCR (fourth armoured division of the Infantry), the 40e Bataillion de Chars de Combat and the 48e BCC , were during the campaign of 1940 from 19 May as an emergency measure partly equipped with

8835-412: Was to allow the drive shaft to run at lower torque, by using higher RPM. As power is the product of RPM and torque , running the shaft at higher RPM allowed more power to be transferred at lower torque. Doing so reduced the torque the driveshaft had to carry, and thus the strength and weight required. Although the designer was theoretically free to choose any ratio for the gearbox and final drive, there

8930-522: Was to manufacture the FT in the US. A requirement of 4,400 of a modified version, the M1917 , was decided on, with delivery expected to begin in April 1918. By June 1918, US manufacturers had failed to produce any, and delivery dates were put back until September. France therefore agreed to lend 144 FTs, enough to equip two battalions. No M1917s reached the American Expeditionary Forces (AEF) until

9025-676: Was widely used by French forces in 1918 and by the American Expeditionary Forces (AEF) on the Western Front in the closing stages of World War I . Its battlefield debut occurred on 31 May 1918, east of the Forest of Retz , east of Chaudun , between Ploisy and Chazelles, during the Third Battle of the Aisne . This engagement, with 30 tanks, successfully broke up a German advance, but in

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