Portal gear
Encyclopedia
Portal axles are an offroad technology where the axle
tube is above the center of the wheel
hub.
casing are tucked up higher under the vehicle.
Due to the gear reduction at the wheel which lessens the torque
on all the other drivetrain
components, the size of the differential casing can be reduced to gain even more ground clearance. Additionally, all drivetrain elements, in particular the transfer gearbox and driveshafts can be built lighter. This can be of use in lowering the center of gravity
for a given ground clearance.
As it requires a heavier and more complex hub assembly, however, these systems can result in an increased unsprung weight
and require robust axle control elements to give predictable handling. In addition, at higher speeds the hub assembly can overheat.
They are also used in railroads and low floor buses
. Although in the case of buses, the device is engineered in the opposite way to those fitted to off-road vehicles - the axle is below the center of the wheel. This, the inverted portal axle, allows the floor of the bus to be lowered, thus easing access to the bus and increasing the available cabin height.
Bolt-on Portals (or drop boxes) are a housing with a set of gears which bolts on to the final flange of the axle tube. This approach allows existing vehicles to be converted to portals without modifying portal axles (Volvo C303
or Unimog 404).
Off-road vehicle
s fitted with portal axles include:
Axle
An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...
tube is above the center of the wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...
hub.
Description
Compared to normal layout, portal axles enables the vehicle to gain a higher ground clearance, as both the axle tube and differentialDifferential (mechanics)
A differential is a device, usually, but not necessarily, employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles—and in the other way, it...
casing are tucked up higher under the vehicle.
Due to the gear reduction at the wheel which lessens the torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
on all the other drivetrain
Powertrain
In a motor vehicle, the term powertrain or powerplant refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive...
components, the size of the differential casing can be reduced to gain even more ground clearance. Additionally, all drivetrain elements, in particular the transfer gearbox and driveshafts can be built lighter. This can be of use in lowering the center of gravity
Center of gravity
In physics, a center of gravity of a material body is a point that may be used for a summary description of gravitational interactions. In a uniform gravitational field, the center of mass serves as the center of gravity...
for a given ground clearance.
As it requires a heavier and more complex hub assembly, however, these systems can result in an increased unsprung weight
Unsprung weight
In a ground vehicle with a suspension, the unsprung weight is the mass of the suspension, wheels or tracks , and other components directly connected to them, rather than supported by the suspension...
and require robust axle control elements to give predictable handling. In addition, at higher speeds the hub assembly can overheat.
They are also used in railroads and low floor buses
Low-floor bus
A low-floor bus is a bus that has no steps between one or more entrances and part or all of the passenger cabin. Being low floor improves the accessibility of the bus for the public, particularly the elderly or infirm, or those with push chairs, and increasingly, those in wheelchairs.In the modern...
. Although in the case of buses, the device is engineered in the opposite way to those fitted to off-road vehicles - the axle is below the center of the wheel. This, the inverted portal axle, allows the floor of the bus to be lowered, thus easing access to the bus and increasing the available cabin height.
Bolt-on Portals (or drop boxes) are a housing with a set of gears which bolts on to the final flange of the axle tube. This approach allows existing vehicles to be converted to portals without modifying portal axles (Volvo C303
Volvo C303
Volvo Cross Country C303 is the base model of a range of military vehicles produced by Volvo.The car was developed in the late 60s based on the successful L-3314 series and went into production in 1974. This version was produced both as a 4x4 and a 6x6. An 8x8 was planned but dropped. Engines were...
or Unimog 404).
Examples
Off-road vehicle
An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks...
s fitted with portal axles include:
- UAZ-469UAZ-469The UAZ-469 is an all-terrain vehicle manufactured by UAZ. It was used by the Red Army and other Warsaw Pact forces, as well as paramilitary units in Eastern Bloc countries. In the Soviet Union, it also saw widespread service in all state organizations that needed a robust off-road vehicle.The...
- Mercedes-Benz UnimogUnimogUnimog is a range of multi-purpose auto four wheel drive medium trucks produced by Mercedes-Benz, a division of Daimler AG. The name Unimog is pronounced in German and is an acronym for the German "UNIversal-MOtor-Gerät", Gerät being the German word for machine or device...
- Steyr Puch Haflinger
- Steyr-Daimler-Puch PinzgauerPinzgauer High Mobility All-Terrain VehicleThe Pinzgauer is a family of high-mobility all-terrain 4WD and 6WD military utility vehicles. They were manufactured in Guildford, Surrey, United Kingdom, by BAE Systems Land & Armaments. The vehicle was originally developed in the late 1960s by Steyr-Daimler-Puch of Graz, Austria, and was named...
- Volkswagen KübelwagenVolkswagen KübelwagenThe Volkswagen Kübelwagen was a military vehicle designed by Ferdinand Porsche and built by Volkswagen during World War II for use by the German military...
- Volkswagen BusVolkswagen Bus-Light commercial vehicles:One of five generations of Volkswagen vans:*Volkswagen Type 2 , generation T1 *Volkswagen Type 2 , generation T2 *Volkswagen Type 2 , generation T3...
- Volvo C303Volvo C303Volvo Cross Country C303 is the base model of a range of military vehicles produced by Volvo.The car was developed in the late 60s based on the successful L-3314 series and went into production in 1974. This version was produced both as a 4x4 and a 6x6. An 8x8 was planned but dropped. Engines were...
- Land Rover Defender 130CC-R(hino)Land Rover Defender 130CC-R(hino)The Land Rover Defender 130CC-R is a joint venture project to develop a new highly mobile off-road vehicles.-The long range expedition and press support vehicle:...
- AM GeneralAM GeneralAM General is an American heavy vehicle manufacturer based in South Bend, Indiana. It is best known for the civilian Hummer and the military Humvee, that is assembled in Mishawaka, Indiana...
HMMWV - International FTTS
- AM GeneralAM GeneralAM General is an American heavy vehicle manufacturer based in South Bend, Indiana. It is best known for the civilian Hummer and the military Humvee, that is assembled in Mishawaka, Indiana...
Hummer H1Hummer H1The Hummer H1 is a civilian off-road vehicle based on the M998 Humvee, which was created by AM General. The vehicle was produced from 1992 through 2006, and was the first of what became the Hummer line... - Toyota Mega CruiserToyota Mega CruiserThe Toyota Mega Cruiser is a large, heavy-duty sport utility vehicle introduced by Toyota in 1995. The largest SUV ever built by Toyota, it resembled the Hummer H1, and like the Hummer, was designed primarily for military use with the Mega Cruiser seeing duty as infantry transports equipped with...
(Civilian model and JGSDFJapan Ground Self-Defense ForceThe , or JGSDF, is the army of Japan. The largest of the three services of the Japan Self-Defense Forces, the Ground Self-Defense Force operates under the command of the chief of the ground staff, based in the city of Ichigaya, Tokyo. The present chief of ground staff is General Yoshifumi Hibako...
's High Mobility Vehicle) - Tatra T 810Tatra T 810Tatra T 810 is a medium truck made by Czech company Tatra. Unlike other Tatra trucks, it doesn't use the traditional Tatra conception of backbone chassis and swinging half-axles, but the customary truck architecture with conventional frame.-History:...
medium truck