A portal axle (or portal gear lift) is an off-road vehicle suspension and drive technology where the axle tube or the half-shaft is offset from – usually above – the center of the wheel hub and where driving power is transferred to each wheel via a simple gearbox, built onto each hub.[1] It gives two advantages: ground clearance is increased, particularly beneath the low-slung differential housing of the main axles — and secondly, any hub reduction gearing allows the axle half shafts to drive the same power but at reduced torque (by using higher shaft speed). This reduces load on the axle crown wheel and differential.
Comparison between normal and portal axlesPinzgauer portal axle
The portal gear configuration is also sometimes called a drop gear or drop gearset configuration[2][3] (which, despite its similarity to the term dropped axle, produces the opposite effect).
Compared to a normal layout, portal axles enable the vehicle to gain higher ground clearance, as both the axle tube and differential 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 results in lowering the center of gravity for a given ground clearance. Where a vehicle also requires a reduced top speed, in at least one gear, the gear ratio can also have this effect. The military Kübelwagen of WWII used a ratio of 1.4:1 to provide a 2.5 mph walking speed in first gear,[4] as well as a useful lift of 50 mm.
As they require 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.[5]
1930 Farmall tractor with rear portal axle1961 Porsche F 108 tractor with rear portal axle
They are also used in railways and low floor buses[6][7] although, in the case of the latter, the device is engineered in the opposite way to those fitted to off-road vehicles - the axle is below the center of the wheel. Thus, the inverted portal axle allows the floor of the bus to be lowered, 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 onto the final flange of the axle tube. This approach allows existing vehicles to be converted to use portal gear lifts without modifying the axles (Volvo C303 or Unimog 404).
A related development is the use of an epicyclic hub gearbox. This is mounted in-line with the half shaft, so that there is no change in ride height. They are often used for large and heavy vehicles, where the wheel diameter already gives adequate ground clearance. The reduction gearbox allows the half shafts to turn faster than the wheels, thus requiring less torque for the same power. This permits a smaller and lighter half shaft and internal drivetrain.
Hub gearboxes were an iconic feature of the Alvis FV600 chassis vehicles, such as the Stalwart and Saracen. The FV600 used a version of the DAFH-drive, with a single differential between sides and all wheels on each side linked by an internal driveshaft and bevel gearboxes to the half shafts. This has no differential axle between wheel stations on each side and so 'wind-up' was a regular problem for these vehicles when driven on roads. If individual wheels were out of phase with their neighbours, possibly caused by cornering or slightly varying tyre diameter, this could place a considerable force on the gearbox, leading to breakages. For this reason, it was regular practice when driving on tarmac to bump the vehicle over a kerb or other object at times, to allow this wind-up to be released. On slippery surfaces like sand or mud there is enough slippage between the tires and ground to dissipate the tension.
They are now found on many large quarrying dump trucks and heavy plant vehicles.
Wikimedia Commons has media related to Portal axles.
^"New Spicer portal axles for compact utility tractors - introduced by Off-Highway Systems Group of Dana Corp". Diesel Progress North American Edition.
^(PDF). www.internationaldelivers.com. Archived from the original (PDF) on 9 July 2006. Retrieved 22 May 2022.{{cite web}}: CS1 maint: archived copy as title (link)
^. Archived from the original on 2007-10-08. Retrieved 2007-12-04.
April 05, 2024
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A portal axle or portal gear lift is an off road vehicle suspension and drive technology where the axle tube or the half shaft is offset from usually above the center of the wheel hub and where driving power is transferred to each wheel via a simple gearbox built onto each hub 1 It gives two advantages ground clearance is increased particularly beneath the low slung differential housing of the main axles and secondly any hub reduction gearing allows the axle half shafts to drive the same power but at reduced torque by using higher shaft speed This reduces load on the axle crown wheel and differential Comparison between normal and portal axlesPinzgauer portal axleThe portal gear configuration is also sometimes called a drop gear or drop gearset configuration 2 3 which despite its similarity to the term dropped axle produces the opposite effect Contents 1 Description 2 Examples 3 In line gearboxes 4 Manufacturing 5 See also 6 ReferencesDescription edit nbsp Simple portal gearbox from a WW2 Volkswagen Type 82 KubelwagenCompared to a normal layout portal axles enable the vehicle to gain higher ground clearance as both the axle tube and differential 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 results in lowering the center of gravity for a given ground clearance Where a vehicle also requires a reduced top speed in at least one gear the gear ratio can also have this effect The military Kubelwagen of WWII used a ratio of 1 4 1 to provide a 2 5 mph walking speed in first gear 4 as well as a useful lift of 50 mm As they require 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 5 nbsp 1930 Farmall tractor with rear portal axle nbsp 1961 Porsche F 108 tractor with rear portal axleThey are also used in railways and low floor buses 6 7 although in the case of the latter the device is engineered in the opposite way to those fitted to off road vehicles the axle is below the center of the wheel Thus the inverted portal axle allows the floor of the bus to be lowered easing access to the bus and increasing the available cabin height nbsp A Land Rover Defender fitted with bolt on portal axlesBolt on portals or drop boxes are a housing with a set of gears which bolts onto the final flange of the axle tube This approach allows existing vehicles to be converted to use portal gear lifts without modifying the axles Volvo C303 or Unimog 404 Examples editVehicles fitted with portal axles include AM General HMMWV 8 and Hummer H1 International FTTS 9 Land Rover Defender 130CC R hino 10 Mercedes Benz G500 4 4 and G63 AMG 6x6 6x6 truck 11 Mercedes Benz Unimog 12 Porsche 597 citation needed Porsche 911 in Porsche 997 GT3 R Hybrid 2010 13 Praga V3S 1952 1989 3 ton all terrain truck 6x6 Steyr Puch Haflinger Steyr Daimler Puch Pinzgauer 14 Tatra T 805 small truck Tatra T 810 medium truck Toyota Mega Cruiser Civilian model and JGSDF s High Mobility Vehicle Volkswagen Type 2 first generation Transporter Kombi Microbus dubious discuss Volkswagen Type 82 Kubelwagen 4 Volkswagen Type 166 Schwimmwagen Volkswagen Type 181 Volvo C303 Volvo C202 LuAZ ZAZ 969 UAZ 469 Only some military versions UAZ BarsIn line gearboxes edit nbsp Alvis StalwartA related development is the use of an epicyclic hub gearbox This is mounted in line with the half shaft so that there is no change in ride height They are often used for large and heavy vehicles where the wheel diameter already gives adequate ground clearance The reduction gearbox allows the half shafts to turn faster than the wheels thus requiring less torque for the same power This permits a smaller and lighter half shaft and internal drivetrain Hub gearboxes were an iconic feature of the Alvis FV600 chassis vehicles such as the Stalwart and Saracen The FV600 used a version of the DAF H drive with a single differential between sides and all wheels on each side linked by an internal driveshaft and bevel gearboxes to the half shafts This has no differential axle between wheel stations on each side and so wind up was a regular problem for these vehicles when driven on roads If individual wheels were out of phase with their neighbours possibly caused by cornering or slightly varying tyre diameter this could place a considerable force on the gearbox leading to breakages For this reason it was regular practice when driving on tarmac to bump the vehicle over a kerb or other object at times to allow this wind up to be released On slippery surfaces like sand or mud there is enough slippage between the tires and ground to dissipate the tension They are now found on many large quarrying dump trucks and heavy plant vehicles Manufacturing editToday portal gear lifts are manufactured for use in utility task vehicles UTV See also editDropped axleReferences edit nbsp Wikimedia Commons has media related to Portal axles New Spicer portal axles for compact utility tractors introduced by Off Highway Systems Group of Dana Corp Diesel Progress North American Edition U S patent 20 130 240 282 U S patent 6 095 005 a b Ludvigsen Karl 2014 Professor Porsche s Wars Pen amp Sword Military pp 134 135 ISBN 978 1 52672 679 7 Exaxt 4WD Archived 2008 12 19 at the Wayback Machine Railway Technology Portal axle with SAB V60 rubber sprung wheels and sound absorbers ArvinMeritor Reveals New Second Generation Inverted Portal Axle Archived 2007 11 01 at the Wayback Machine 4WD Glossary amp FAQ Archived 2007 12 11 at the Wayback Machine Archived copy PDF www internationaldelivers com Archived from the original PDF on 9 July 2006 Retrieved 22 May 2022 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link An Expedition Truck on Portals Mercedes releases 6x6 G63 AMG specs and pics w Video Archived from the original on 2013 04 10 Retrieved 2013 03 15 The Unimog Principle Archived from the original on 2008 07 18 Retrieved 2007 12 04 Michael Trzesniowski Rennwagentechnik Grundlagen Konstruktion Komponenten Systeme Vieweg Teubner Verlag Wiesbaden 2012 page 782 783 ISBN 978 3 8348 2209 3 portal compare htm Archived from the original on 2007 10 08 Retrieved 2007 12 04 Retrieved from https en wikipedia org w index php title Portal axle amp oldid 1214780166, wikipedia, wiki, book, books, library,
