The powertrain layout of a motorised vehicle such as a car is often defined by the location of the engine or motors and the drive wheels .
20-451: The Bristol RE was a rear-engined single-decker bus or single-decker coach chassis built by Bristol Commercial Vehicles from 1962 until 1982. It is often considered the most successful of the first generation of rear-engined single-decker buses. Initially, the RE was only supplied to subsidiaries of the nationalised Transport Holding Company (THC), by which Bristol Commercial Vehicles
40-451: A rear-engine design layout places the engine at the rear of the vehicle. The center of gravity of the engine itself is behind the rear axle. This is not to be confused with the center of gravity of the whole vehicle, as an imbalance of such proportions would make it impossible to keep the front wheels on the ground. Rear-engined vehicles almost always have a rear-wheel drive car layout , but some are four wheel drive . This layout has
60-441: A shaft to a differential in the centre of the car, which in the case of an M4 layout, distributes power to both front and rear axles. The rear-engine, four-wheel drive layout (abbreviated as R4) places the engine at the rear of the vehicle, and drives all four wheels. This layout is typically chosen to improve the traction or the handling of existing vehicle designs using the rear-engine, rear-wheel-drive layout (RR). For example,
80-590: Is between the rear axle and the rear bumper. Although common in electric cars, and in transit buses and coaches due to the elimination of the drive shaft with low-floor bus, this layout has become increasingly rare in fossil-fuelled passenger cars. The Porsche 911 is notable for its continuous use of the RR layout since 1963. Drivetrains where power can be sent to all four wheels are referred to as either four-wheel drive (4WD) or all-wheel drive (AWD). The front-engine, four-wheel drive layout (abbreviated as F4 layout) places
100-609: The 4,629 Bristol REs built, 3,242 were sold to subsidiaries of the NBC and its predecessor groups, THC and BET; 148 were sold to members of the Scottish Bus Group ; 405 to British municipalities and PTEs ; and 834 to other operators. The biggest customers were: Bristol Omnibus Company (439); Crosville Motor Services (288); Ulsterbus / Citybus (620); United Automobile Services (470); West Yorkshire Road Car Company (259). Rear-engine design In automobile design ,
120-570: The Porsche 911 added all-wheel drive to the existing line-up of rear-wheel drive models in 1989. In automotive design , dual-motor, four-wheel-drive layout is mainly used by battery electric vehicles by placing electric motors on both front and rear axles and drives all four roadwheels, creating a four-wheel drive layout. This layout is made possible by the small size of electric motors compared to internal combustion engines , allowing it to be placed in multiple locations. It also eliminates
140-469: The RE was bodied by Alexander (Belfast), with the X Type bodywork. Three of the ex-Citybus REs from Belfast were acquired by Pinewood Studios in October 2005, where they appeared in movies such as Children of Men and St Trinian's 2: The Legend of Fritton's Gold . These designations were suffixed by a code indicating the type of engine fitted: What was to be the first production chassis (212.001)
160-409: The engine at the front of the vehicle and drives all four roadwheels. This layout is typically chosen for better control on many surfaces, and is an important part of rally racing as well as off-road driving. Most four-wheel-drive layouts are front-engined and are derivatives of earlier front-engine, rear-wheel-drive designs. The mid-engine, four-wheel drive layout (abbreviated as M4 layout) places
180-405: The engine in the middle of the vehicle, between both axles and drives all four road wheels. Although the term "mid-engine" can mean the engine is placed anywhere in the vehicle such that the centre of gravity of the engine lies between the front and rear axles, it is usually used for sports cars and racing cars where the engine is behind the passenger compartment. The motive output is then sent down
200-436: The engine is located at the front of the vehicle and driven wheels are located at the rear. This was the traditional automobile layout for most of the 20th century, and remains the most common layout for rear-wheel drive vehicles. The mid-engine, rear-wheel drive layout (abbreviated as MR layout) is one where the rear wheels are driven by an engine placed just in front of them, behind the passenger compartment. In contrast to
220-822: The following features: This layout was once popular in small, inexpensive cars and light commercial vehicles. Today most car makers have abandoned the layout although it does continue in some expensive cars, like the Porsche 911 . It is also used in some racing car applications, low-floor buses , some Type-D school buses , and microcars such as the Smart Fortwo . Some electric cars feature both rear and front motors, to drive all four wheels. Car layout Layouts can roughly be divided into three categories: front-wheel drive (FWD), rear-wheel drive (RWD) and four-wheel drive (4WD). Many different combinations of engine location and driven wheels are found in practice, and
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#1732793354747240-572: The front motor must reduce torque and power in order to prevent the front wheels from spinning as weight transfers to the rear of the vehicle. The excess power is transferred to the rear motor where it can be used immediately. The opposite applies when braking, when the front motor can accept more regenerative braking torque and power. However dual motors usually have less range. In addition, electric vehicles may be equipped with more than two electric motors to achieve greater power output and superior handling. The first mass-produced triple-motor layout
260-633: The introduction of the Leyland National . From 1976, the RE remained in production only for the Northern Irish state-owned bus companies Ulsterbus and Citybus , and for export to Christchurch Transport Board, New Zealand. In Great Britain , the RE was most commonly fitted with bodywork by ECW , but several other manufacturers also built bodywork on the chassis. Some coaches were fitted with Duple Commander, Plaxton Panorama Elite or Alexander M Type bodywork. In Northern Ireland,
280-400: The location of each is dependent on the application for which the vehicle will be used. The front-engine, front-wheel-drive layout (abbreviated as FF layout) places both the internal combustion engine and driven wheels at the front of the vehicle. This is the most common layout for cars since the late 20th century. Some early front-wheel drive cars from the 1930s had the engine located in
300-409: The middle of the car. A rear-engine, front-wheel-drive layout is one in which the engine is between or behind the rear wheels, and drives the front wheels via a driveshaft, the complete reverse of a conventional front-engine, rear-wheel-drive vehicle layout. This layout has only been used on prototype and concept cars. The front-engine, rear-wheel drive layout (abbreviated as FR layout) is one where
320-406: The need of a drive shaft that are commonly used by conventional four-wheel drive vehicles to create space for batteries that are commonly mounted on the floor of electric vehicles. The layout is also beneficial to distribute available electrical horsepower to maximize torque and power in response to road grip conditions and weight transfer in the vehicle. For example, during hard acceleration,
340-449: The rear-engined RR layout, the center of mass of the engine is in front of the rear axle. This layout is typically chosen for its low moment of inertia and relatively favorable weight distribution. The rear-engine, rear-wheel drive layout (abbreviated as RR layout) places both the engine and drive wheels at the rear of the vehicle. In contrast to the MR layout, the center of mass of the engine
360-552: Was changed to a pre-production model (number REX.003), with a coach body built by ECW but devoid of any seats and fittings. It was used by Bristol Commercial Vehicles at its Brislington Experimental Shop for a few years. It was fitted and ran with a horizontal version of the contemporary Bristol BVW engine, and also fitted with a turbo-charger. Later the Gardner engine was refitted, the body completed and sold to West Yorkshire as their fleet number CRG1 OWT241E. The most popular model
380-611: Was the RELL, with 2,839 constructed; there were 976 of the RELH model and 698 RESL. The two least successful models were the REMH, with 105 sold to just three customers, and the RESH with 11 built for four customers. A sixth model, designated REML, was advertised from 1968 but none was built. This would have had the 20-foot (6.1 m) wheelbase of the REMH but a low frame suitable for a bus body. Of
400-658: Was wholly owned. From 1965, when Leyland purchased a 25% shareholding in Bristol and the company's products became available to non state-owned bus operator customers, the RE also gained popularity with companies in other sectors, including the British Electric Traction (BET) Group and many municipal operators. From 1972, sales to the National Bus Company (NBC), which had taken over the operations of both THC and BET) began to dry up, due to
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