More ground clearance required, a portal axle makes it possible!

A protal axle is a vehicle axle in which the center of the wheel and the center of the axle are not on the same plane. This creates an offset that, when viewed from the front, resembles a bridge or portal. A gear is fitted on both sides of the axle, in which spur gears or bevel gears are installed. The simplest form is a gear on the center of the axle, which drives a gear on the center of the wheel. A reduction or gear ratio can be generated by varying the gear wheel diameter. There are series versions with a pendulum or rigid axle.

Use and structure of the portal axis

There are two different variants for portal axes. The first is the axles of low-floor buses, and the offset is used to ensure a low aisle. An inverted portal is shown, the differential is also shifted sideways. This means that hall heights of around 40 centimeters can be realized, this increases comfort for passengers and they can get on and off faster. These axes are installed ex works. The second variant is the portal axles for off-road vehicles. Depending on the design of the axle and wheel diameter, several centimeters of ground clearance can be gained. In addition, the drive shaft can also be made weaker. The advantage of offset gears is exploited here, because they are usually geared down. This means that the drive shaft rotates faster than the wheel and thus the force that the shaft has to transmit is reduced. If a larger wheel is used in addition to the offset gear, the ground clearance can be increased further. Without offset gear, the ground clearance achieved could only be achieved via the wheel diameter.

Conversion only possible with a lot of effort

Anyone who can raise the necessary money will head for a conversion to a complete axle to take full advantage of the advantages described. Alternatively, special companies offer so-called bolt-on portals. Only the wheel holder is exchanged. The axles already installed remain unchanged. After the conversion has been completed, the changes must of course be entered, since it is a change in the vehicle geometry. The disadvantage of portal axes is that the increase in mechanical components also leads to an increase in susceptibility. However, there are many examples that demonstrate that operation with portal axes can also be guaranteed for decades. However, these are vehicles that are operated at a relatively low speed, such as the Unimog or the Steyr-Puch Pinzgauer. So there are not really disadvantages of a portal axis, if you ignore the price of up to EUR 20.000 and the fact that boarding is difficult. One of the most famous vehicles with a portal axle is certainly the G500 4 × 4² from Mercedes and the even bigger one G63 AMG 6 × 6.

We hope that you the info report on the topic / term portal axis (Further designations / keywords: KIT portal axes, Bolt On Portals) from the field of autotuning.