Portal axis
A portal axle is a type of driven axles, each with a countershaft gear on the vehicle wheels . In each of the wheel carriers there is a single-stage spur gear ("offset gear ") that acts from the shafts on the wheels . The axle bridge with the drive shafts is therefore offset parallel to the wheel axles, which is used in all-terrain vehicles to increase the ground clearance between the driven wheels by placing a higher axle bridge. In the case of low-floor vehicles in local public transport, the axle bridge is lowered. The lower floor in the passenger compartment makes it easier to get in and out.
Ground clearance
In order to achieve a large ground clearance, differential gears and associated drive shafts are moved upwards. The gain in ground clearance is between 50 and 400 mm depending on the axle construction and the diameter of the vehicle wheels. Such portal axles are available as portal pendulum axles like the VW Kübelwagen , Tatra 805 , Steyr-Puch Haflinger and Pinzgauer ; or as a rigid axle on the Unimog from Daimler-Benz, the Praga V3S , the Volvo C303 , the Lancia / Fiat / Iveco-ACL75 / ACM80 , the Iveco 75-13 AW or Magirus-Deutz 130M7FAL or the Renault TRM 2000 , as well as the Sisu SA-110 and Tatra 810 . At the US HMMWV , the wheel carriers with reducing gears are parts of double wishbone wheel suspensions .
Since the axle drives usually reduce the torque on the wheel and thereby increase the torque on the wheel, the transmission components between the motor and the axle drives can be made smaller and therefore lighter due to the higher speed (lower torque), similar to the axles with planets.
Low floor
In the case of low-floor buses , on the other hand, inverted, i.e. lower-lying portal axles are used on the driven rear axles in order to enable a low floor level inside. In addition, the differential is offset a little to the side, i.e. next to the central aisle. The rather low ground clearance is accepted in favor of a consistently low passenger floor (no steps or ramps in the axle areas).
The low- floor tram of the R series of the Frankfurt am Main tram even completely dispenses with a common mechanical drive train for right and left wheels. The individual electric motors, standing vertically next to one wheel on each side of the vehicle, drive the wheels via angular gears.
Reduction
The first generation of the VW Transporter , which was produced from 1950 to 1967 , also had a portal axle with reduction gears, but not to increase the ground clearance, but to be able to install a standard Beetle gearbox and still have a larger reduction .
Portal chassis
Machines with portal trolleys are portal cranes and compost converters .
disadvantage
- Higher unsprung mass
- Higher focus
Individual evidence
- ^ Leske, Schäffler: Transmission. 1994, Section 6.3.2.
- ↑ Systematic innovation and ef fi ciency. ZF axle systems for city buses and coaches. (PDF) ZF Friedrichshafen AG. P. 14. Retrieved January 26, 2014.
literature
- Alfred Leske, Roland Schäffler: The safe way to the master craftsman examination in the automotive trade, transmission. Verlag Vogel Business Media , Würzburg 1994, ISBN 3-8023-1435-2 .
