Longitudinal engine

Longitudinal motor, six cylinders online in a Rover SD1

In automotive engineering and motorcycle technology, a longitudinal engine or longitudinal engine is an internal combustion engine in which the crankshaft is oriented to along the major axis of the vehicle, that is, from front to back.

Longitudinal mounting of the crankshaft in automobiles

• The rear longitudinal motor with the engine placed behind the gearbox. Traditional vehicle arrangements Everything back. Its reason for being was in the production economy, allowing large and cheap vehicles to produce: The gearbox is situated in prolongation of the stork, forming a transaxis in which the engine goes behind the cross shaft of the rear wheels, allowing an optimal inhabitability. The transmission is fixed to the chassis so the suspension must necessarily be independent, using oscillating axes or semi-tired arms. This arrangement presents the inconvenience of placing the weight of the engine behind the rear wheels, as far as stability is concerned, the engine is as short as possible as the Volkswagen Type 1 or Porsche 911 engines.

• Central-longitudinal rear engine with engine placed before the gearbox. Also known as the "central rear" engine, used for the first time in series at the Rumpler Tropfenwagen and in some pre-war mercedes like the Mercedes 150, is now only used in sports vehicles such as the Porsche Boxster or the Toyota MR2 to limit the rear inhabitability.

• Front longitudinal motor with gear box behind the front axle and rear propulsion. More common layout in the 20th century, can be used both with rear independent suspensions and for example most of the Mercedes-Benz range, as well as with rear dependants as in practice all the classic rear propulsion models, in which case we speak of "Hotchkiss transmission".

• Central-longitudinal motor front, with the gearbox located in front of the front axle and front traction. Disposition used by the Citroën pioneer in the Avant and DS, by Renault in its transition to the front traction in the (R-16, R-4 and R-5 and derivatives), as well as by many industrial vehicles. This arrangement favors weight-sharing and technically allows you to directly attach the "all-back" vehicle transmission as the Renault 8 (the rear longitudinal motor behind the gearbox) to the front of the "all-front" vehicles like the Renault 4, in which by economy even maintained the original control of the gearbox, driven by a long bar that crossed the engine compartment.

• A longitudinal motor with the gearbox behind the front axle and front traction. Typical layout used by many pioneer brands of the front traction. Technically it is a simpler system than the central-logitudinal motor because it allows a simpler drive of the gearbox and that the motor the transverse, because it allows the use of semiejes of equal length. In return it implies that the weight of the engine is "matched" in front of the front axle -as on the other hand it is usual the rear-wheel drive and forward motor- although downloading the rear axle of the mass of the transmission as in those, which means a disfavorable weight distribution. Used by Renault in the R-12,R-20, R-25 and its derivatives, by some Japanese brands and currently the Audi from the Audi A4

• Longitudinal motor with gearbox in the fork and front traction. In-sump system of Triumph Motor Company/Saab. Developed for the Triumph 1300, it was the response of Leyland to the system developed by the rival group BMC for the Mini, using a similar layout but with the motor located longitudinalemte, had the inconvenience of the large height of the set, which conditioned the shape of the body,.

• Central motor-longitudinal front and total traction. Disposition used in versions with connectable front traction of the 4X4 versions of some vehicles with longitunal motor and rear traction like the "X" versions of the BMW brand, used as a basis for their first hybrid prototypes or many SUVs such as the Jeep Wrangler. In these vehicles there is a transfer box following the gearbox that usually also makes the gearbox functions. From this box part a transmission axis makes each of the axes.

Longitudinal mounting of the crankshaft on motorcycles

Moto Guzzi Jackal with a 90° longitudinal V2 engine.

The lengthwise crankshaft V2 engine as seen in Moto Guzzis and some Hondas is less common in motorcycles. This configuration is better oriented for cardan shaft transmission, eliminating in this case the need for a 90º mesh at one of the ends of the cardan shaft. A bike with a cardan shaft throughout, fits perfectly in typical frames, leaving a very good space for a cardan shaft, apart from the fact that the cylinders can have a very good airflow for cooling. The assembly of the engine with crankshaft along also implies a reaction to torque in cases of acceleration and deceleration pronounced to the engine. To counteract it, you can have a flywheel or an alternator with a rotation opposite to the rotation resulting from the crankshaft and motor train.

Controversy

Unlike in cars where the crankshaft is located directly under the cylinders and therefore oriented in the same direction as them, in motorcycle engines the orientation of the crankshaft is often perpendicular to that of the cylinders (as in motorcycles). V2 engines), so the term transverse or longitudinal usually refers to the orientation of the crankshaft with respect to the transmission. However, not all sources use that convention, notably Moto Guzzi, which uses it inverted, because They call it a transverse engine to the longitudinal crankshaft, since it needs to change the axis of rotation by 90 degrees to drive the drive wheel with transmission chain. (Although a cardan shaft motor would need that longitudinal axis unchanged at 90° to transmit motion to the drive wheel.) . That is why it is better to specify that transverse or longitudinal refers to the axis of the crankshaft., or to the axis of the cylinders: cylinders mounted transversely .