Pictures of the real car:

    
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Screenshots:

History:

The Brabham BT20 is a Formula One car used by the Brabham Formula One team in 1966 and 1967, as well as a number of privateers from 1967 to 1969. The BT20 was the direct successor to the Brabham BT19 which was driven to the World Constructors' title in 1966.

The Brabham BT19 is a Formula One racing car designed by Ron Tauranac for the British Brabham team. The BT19 competed in the 1966 and 1967 Formula One World Championships and was used by Australian driver Jack Brabham to win his third World Championship in 1966. The BT19, which Brabham referred to as his "Old Nail", was the first car bearing its driver's name to win a World Championship race.

The car was initially conceived in 1965 for a 1.5-litre (92-cubic inch) Coventry Climax engine, but never raced in this form. For the 1966 Formula One season the Fédération Internationale de l'Automobile (FIA) doubled the limit on engine capacity to 3 litres (183 cu in). Australian company Repco developed a new V8 engine for Brabham's use in 1966, but a disagreement between Brabham and Tauranac over the latter's role in the racing team left no time to develop a new car to handle it. Instead, the existing BT19 chassis was modified for the job.

Concept

The BT19 was created by Australian designer Ron Tauranac for the Brabham Racing Organisation (BRO) to use in the 1965 season of the Formula One motor racing World Championship. The BT19, and its contemporary the Lotus 39, were built to use the new FWMW flat-16 engine from Coventry Climax. Only one example of the BT19 design was built, and it never raced in its original form. Climax abandoned the FWMW's development before the end of 1965, their existing FWMV V8 engines proving powerful enough to propel Jim Clark's Lotus 33 to seven wins and the drivers' championship.

For 1966, the engine capacity limit in Formula One was doubled from 1.5 litres (92 cu in) to 3 litres (183 cu in). It was not feasible to enlarge existing 1.5-litre engines to take full advantage of the higher limit and Climax chose not to develop a new 3-litre motor, leaving many teams without a viable engine for 1966.

The new 3-litre engines under development by other suppliers all had at least 12 cylinders. All other things being equal, more cylinders allow smaller and lighter moving parts, higher rotational speeds and thus greater peak power. However, more cylinders also mean more moving parts; these can result in greater overall engine weight and reduced reliability.

Jack Brabham, owner and lead driver of BRO, took a different approach to the problem of obtaining a suitable engine. He persuaded Australian company Repco to develop a new 3-litre eight-cylinder engine for him, largely based on available components; Brabham and Repco were aware that the engine would not compete in terms of outright power, but felt that a lightweight, reliable engine could achieve good championship results while other teams were still making their new designs reliable.

Brabham cars were designed and built by Motor Racing Developments Ltd. (MRD), which was jointly owned by Tauranac and Jack Brabham and built cars for customers in several racing series. The Formula One racing team, BRO, was a separate company wholly owned by Jack Brabham. It bought its cars from MRD but Tauranac had little connection with the race team between 1962 and 1965.

Chassis and suspension

Tauranac built the BT19 around a mild steel spaceframe chassis similar to those used in his previous Brabham designs. The use of a spaceframe was considered a conservative design decision; by 1966, most of Brabham's competitors were using the theoretically lighter and stiffer monocoque design, introduced to Formula One by Lotus during the 1962 season. Tauranac believed that contemporary monocoques were not usefully stiffer than a well-designed spaceframe and were harder to repair and maintain. The latter was a particular concern for Brabham, which was the largest manufacturer of customer single-seater racing cars in the world at the time. The company's reputation rested in part on BRO – effectively the official 'works' team – using the same technology as its customers, for whom ease of repair was a significant consideration. One mildly novel feature was the use of oval-section, rather than round, tubing around the cockpit, where the driver sits. In a spaceframe or monocoque racing car, the cockpit is effectively a hole in the structure, weakening it considerably. For a given cross sectional area, oval tubing is stiffer in one direction than round tubing. Tauranac happened to have a supply of oval tubing and used it to stiffen the cockpit area. The car weighed around 1250 pounds (567 kg), around 150 lb (68.0 kg) over the minimum weight limit for the formula, although it was still one of the lightest cars in the 1966 field. The race starting weight of a 1966 Brabham-Repco with driver and fuel was estimated to be around 1,415 lb (642 kg), about 280 lb (127 kg) less than the more powerful rival Cooper T81-Maseratis.

The bodywork of the BT19 is glass-reinforced plastic, finished in Brabham's usual racing colours of green with gold trimming around the nose. Although the science of aerodynamics would not greatly affect Formula One racing until the 1968 season, Tauranac had been making use of the Motor Industry Research Association wind tunnel since 1963 to refine the shape of his cars. Brabham has attributed the car's "swept-down nose and the upswept rear lip of the engine cowl" to Tauranac's "attention to aerodynamic detail". During the 1967 season, the car appeared with small winglets on the nose, to further reduce lift acting at the front of the car.

Against the trend set by the Lotus 21 in 1961, the BT19's suspension, which controls the relative motion of the chassis and the wheels, is outboard all round. That is, the bulky springs and dampers are mounted in the space between the wheels and the bodywork, where they interfere with the airflow and increase unwanted aerodynamic drag. Tauranac persisted with this apparently conservative approach based on wind tunnel tests he had carried out in the early 1960s, which indicated that a more complicated inboard design, with the springs and dampers concealed under the bodywork, would provide only a 2% improvement in drag. He judged the extra time needed to set up an inboard design at the racetrack to outweigh this small improvement. At the front the suspension consists of unequal length, non-parallel double wishbones. The front uprights, the solid components upon which the wheels and brakes are mounted, were modified from the Alford & Alder units used on the British Triumph Herald saloon. The rear suspension is formed by a single top link, a reversed lower wishbone and two radius rods locating cast magnesium alloy uprights. Wheels were initially 13 inches (330 mm) in diameter, but soon upgraded to 15 in (380 mm) at the rear, and later still 15 in at the front as well. These increases enabled the use of larger, more powerful brakes. Steel disc brakes are used on all four wheels and were of 10.5 in (270 mm) diameter for the smaller wheels and 11 in (280 mm) for the larger ones.

The BT19 continued Tauranac's reputation for producing cars that handled well. Brabham has since commented that it "was beautifully balanced and I loved its readiness to drift through fast curves." Brabham referred to the car as his Old Nail; Ron Tauranac has explained this as being "because it was two years old, great to drive and had no vices."

Engine and transmission

The Brabham BT19's exhausts passed upwards between the upper radius rod and the chassis frame. The Brabham BT20 engine exhaust passes between the upper and lower radius rods.

Repco racing engines were designed and built by a small team at a Repco subsidiary, Repco-Brabham engines Pty Ltd, in Maidstone, Australia. Repco's 620 series engine is a normally aspirated unit with eight cylinders in a 'V' configuration. It uses American engine blocks obtained from Oldsmobile's aluminium alloy 215 engine. Oldsmobile's 215 engine, used in the F-85 Cutlass compact car between 1961 and 1963, was abandoned by General Motors after production problems. Repco fitted their own cast iron cylinder liners into the Oldsmobile blocks, which were also stiffened with two Repco magnesium alloy castings and feature Repco-designed cylinder heads with chain-driven single overhead camshafts. The internals of the unit consist of a bespoke Laystall crankshaft, Daimler connecting rods and specially cast pistons. The cylinder head design means that the engine's exhaust pipes exit on the outer side of the block, and therefore pass through the spaceframe before tucking inside the rear suspension, a layout which complicated Tauranac's design work considerably. The engine is water-cooled, with oil and water radiators mounted in the nose.

The 620 engine was light for its time, weighing around 340 lb (154 kg), compared to 500 lb (227 kg) for the Maserati V12, but in 3 litre Formula One form only produced around 300 brake horsepower (220 kW) at under 8000 revolutions per minute (rpm), compared to 330–360 bhp (250–270 kW) produced by the Ferrari and Maserati V12s. However, it produced high levels of torque over a wide range of engine speeds from 3500 rpm up to peak torque of 233 pound feet (316 N·m) at 6500 rpm. Installed in the lightweight BT19 chassis, it was also relatively fuel efficient; on the car's debut Brabham reported that the BT19 achieved 7 miles per gallon (40 L/100 km), against figures of around 4 mpg (70 L/100 km) for its "more exotic rivals". This meant that it could start a Grand Prix with only 35 gallons (160 L) of fuel on board, compared to around 55 gallons (250 L) for the Cooper T81-Maseratis. The engine had one further advantage over bespoke racing engines: parts were cheap. For example, the engine blocks were available for GB£11 each and the connecting rods cost £7 each.

The BT19 was initially fitted with a Hewland HD (Heavy Duty) gearbox, originally designed for use with less powerful 2-litre engines. The greater power of the 3-litre Repco engine was more than the gearbox could reliably transmit when accelerating at full power from rest, with the result that Brabham normally made very gentle starts to avoid gearbox breakages. The HD was later replaced with the sturdier DG (Different Gearbox) design, also for the Brabham BT20, and was produced at the request of both Brabham and Dan Gurney's Anglo American Racers team. It later became a popular choice for other constructors.

The Brabham BT20 was driven in 7 out of the 9 races of Brabham's Constructors' Championship winning season in 1966, and the first three races en route to another championship in 1967.

The BT20 was very successful in these seasons, scoring 7 podiums and one win (at the 1967 Monaco Grand Prix) in its first 10 entries. Mid way though the 1967 deason, the Brabham BT20 chassis became of less use for the Brabham Racing Organisation, at which point they decided to start selling them. Starting from the British GP, Guy Ligier acquired one of them, racing it to sixth place at the Nürburgring Nordschleife, where the German GP was held. A Brabham BT20 was also passed on that year to Rhodesian John Love, who's South African Team Gunston was the first to introduce tobacco advertising in Formula 1, even before Team Lotus did, when he ran the car at the 1968 season opening round at Kyalami in South Africa. John Love continued to run the BT20 in 1967 in the South African F1 championship. Swiss Silvio Moser aquired Ligiers car in 1968 for Charles Vögele Racing in the World Championship, scoring a 5th place and two points in Holland. In 1969, Team Gunston passed it's BT20 on to Jack Holme, where Peter de Klerk and Clive Puzey continued to race it in the South African F1 championship. De Klerk recorded the Brabham BT20's last participation in a World Championship Grand Prix, when he raced the car at the season opener at Kyalami in South Africa. The car continued to be raced in the domestic series by Bruce van der Merwe untill the early seventies.
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Update description:

This is an update for the 1969 Brabham BT20 Repco. Drop these files in the car folder to install the update. This means putting them in the ...\Sierra\GPL\cars\cars69 directory .

Merge folder c10 together with the original c10 folder, resulting in a single c10 folder located in the ...\Sierra\GPL\cars\cars69 directory.

These files are compatible with Irridux' 1969 season update, and the original, unmodified 1969-Extra mod. If you wish to install the Irridux
1969 season update after this update, please reinstall this update after you've installed the Irridux 1969 season update for everything to work
correctly.

Disclaimer:

This is not a Papyrus/Sierra product. Use these files at your own risk (although they should not harm your computer in any way). Please do not sell these files for money. This is freeware.

Thanks to:

Paul Skingley
Jackseller
Charles 'CJM' Mark
GPLEA

Main features:

new car textures
new wheel textures
GPLEA wheel model
new steering wheel texture by Jackseller
new engine textures
new cockpit textures based on Jacksellers work

DOWNLOAD:

version 1.0 (June 10, 2014) ZIP file 5.49 MB

SRMZ forum release thread link:

here