Tamiya 1/20 Brabham Alfa Romeo BT46

KIT #: 20050
DECALS: Two options
REVIEWER: Mark Hiott
NOTES: Clear cowl, with driver figure


The Brabham BT46 was a Formula One racing car, designed by Gordon Murray for the Brabham team, for the 1978 Formula One season. The car featured several radical design elements, the most obvious of which was the use of flat panel heat exchangers on the bodywork of the car to replace conventional water and oil radiators. The concept did not work in practice and was removed before the car’s race debut, never to be seen again. The cars, powered by a flat-12 Alfa Romeo engine, raced competitively with modified nose-mounted radiators for most of the year.

Alfa-Romeo’s sportscar-derived flat-12 engine had a capacity of 2995 cc. The engine featured a cast magnesium engine block with aluminium crankcase and magnesium or aluminium cylinder heads. There were four gear driven valves per cylinder. In Formula One form it delivered about 520 bhp at 12,000 rpm, about 50 bhp more than the Cosworth DFV engines used by most teams, as well as a peak 324 lb/ft of torque.  However, the power came at the expense of greater size, increased fuel and oil consumption and about 40kg more weight. The car used a revised and lighter version of the 6-speed gearbox designed for the BT45B. Brabham designed the gearbox casing, which was cast by Alfa Romeo and used Hewland gears.

The BT46s debuted at the third race of the 1978 season, the South African Grand Prix on 4 March 1978, with the revised nose mounted radiators. The cars were immediately competitive, although reliability was suspect. After the winning debut and subsequent withdrawal of the BT46B “fan car” at the Swedish Grand Prix the Brabham team completed the season with the standard BT46s. Niki Lauda winning the Italian Grand Prix in the standard car, albeit after Mario Andretti and Gilles Villeneuve were penalised a minute for jumping the second race start after Ronnie Peterson’s fatal accident at the first start. The BT46 appeared for the last time in the Formula One World Championship at the first round of the 1979 season in the hands of Nelson Piquet. Niki Lauda also used the car to qualify for that race, as the new BT48 was proving troublesome, although he did race the new car. Piquet retired on the first lap after a multi-car collision that wrecked the BT46.

The "B" variant of the car, also known as the "fan car", was introduced at the 1978 Swedish Grand Prix as a counter to the dominant ground effect Lotus 79. The BT46B generated an immense level of downforce by means of a fan, claimed to be for increased cooling, but which also extracted air from beneath the car. The car only raced once in this configuration in the Formula One World Championship... when Niki Lauda won the 1978 Swedish Grand Prix at Anderstorp. The concept was declared illegal by the FIA before the car could race again. The BT46B therefore is the only F1 car with a 100% winning record.

(Another variation on the theme was produced later in the season. Like the BT46B, the BT46C removed the radiators from the front wing assembly leaving a clean aerodynamic wing and moving the center of gravity further back again. The standard radiators were replaced by units mounted behind the front wheels out of the airstream in a region of positive pressure. The BT46C only ran in practice for the 1978 Austrian Grand Prix. The drivers complained of reduced revs and straight line speed. It was not used in the race and never appeared again.)


If you've ever built a Tamiya F1 kit, what's in the box should look familiar to you. The only difference is that this is a "clear cowl" version that allows one to show off all the neat stuff inside. Molded in several colors, with a nice set of chrome wheels, a solid plastic cowl is not included. The molding is crisp and the kit shows a good amount of detail. A clear blue-tinted windscreen is also a nice touch. Wires are included for the engine and hoses for the oil coolers.

The instructions are an 8 page, 17 step booklet and, in typical Tamiya fashion, show photos of the assembly process in the margins. A parts layout is also included. there are color callout, but no paint numbers are given.

The decals are the star of the kit. Well printed, they include both solid and translucent decals for the clear cowl. Versions are given for cars driven by either Watson or Lauda.


 Tamiya kits really have the best fit of any car kits. I didn't have any trouble at any point during construction. Construction begins with the engine. You will have to install the ignition wires during the process. The block was assembled and then painted as a whole. Once done, all the various bits were attached. Don't forget the decal for the oil filter. The transaxle is then assembled and attached to the back of the engine. When attaching the exhaust, attach part #A18 and A19 (the rear pipes) first, then parts #A8 and A9 (front pipes).

Moving on to the chassis, I installed the front lower suspension and the lower body panel before painting the body. It makes taking care of any seams easier. The remainder of the chassis was assembled as per the instructions. The engine is then attached to the rear of the chassis.

The tires and rear wing were assembled, but left off until after decaling. The tires use, the now standard, poly caps to hold them in place. The front ones are inserted in the brake rotors and the rears are in the wheels themselves.


The instructions contain color callouts for all the assembly steps. I followed most of them with few variations. The engine was painted MM Steel with a MM Gunmetal transaxle. The suspension was painted MM Flat Black. The chassis was painted MM Bright Red with MM chrome where called for. The Goodyear logos on the tires were painted with MM acrylic flat white. (this being an older kit, the rub-on logos were not included)

Decals are included for either Watson or Lauda, I chose to do Lauda's car. The only real differences are the car number and the drivers helmet. The decals went down with no trouble, although I was worried about the translucent decals. Now that I look at the car I noticed that I installed the front number too low, it should be up on the windscreen.

The last bits installed were the mirrors, rear wing and tires.


Another great Formula 1 kit from Tamiya. It is a bit complicated for a first time builder, but if you have a couple Tamiya kits under your belt, this is a great addition to your F1 collection.


Internet for the history.

Mark Hiott

March 2012

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