The axle load (also called axle driving mass , wheelset driving mass or wheelset load ) of a vehicle is the proportion of the total mass ( net weight + mass of the load ) that is allotted to an axle or a wheel set of this vehicle.
The axle load is given in tons (t).
With uniform distribution of the load and of the net weight of a vehicle, all axes are balanced load: .
In addition to the effective axle load, the dynamic axle load caused by the driving speed is also decisive for wear .
High axle loads have a disproportionate effect on wear and tear on the road surface and the associated consequential damage ( potholes ). A study by the American Association of State Highway and Transportation Officials (AASHO) shows that the extent of damage increases with the fourth power of the axle load; A doubling of the axle load damages the road surface 16 times as much as the initial load, a quadrupling already causes 256 times the damage. That is why in most countries the maximum axle load permitted in regular traffic is stipulated by law.
The axle or wheelset load is calculated with half the number of wheels for wheels that are arranged in pairs opposite one another and with axes of rotation at the same spatial height - meaning is the position in relation to the longitudinal direction of the vehicle - but do not have a physically connecting axle or shaft . Double tires are counted as single wheels.
Truck and articulated trucks , which use today's widespread limit of the maximum permissible total weight of 40 t, are usually built with five axles (wheel sets), each of which is loaded with 8 t. The wheels of the steering first axle are individual wheels, sometimes with a slightly larger diameter. The following axes often have twin tires.
Heavy trucks typically run with a tire pressure of 8 bar . If a single-tire axle is loaded with 8 t, idealized 1000 cm 2 of contact area are created, simplified a rectangle of 20 × 25 cm in size per tire.
Self-propelled vehicles are used for special transports (heavy, long, wide and / or high). These are essentially rigid and coupling platforms with a grid-like arrangement, individually steerable and hydraulically defined loaded (isostatic suspension) pairs of wheels. Two wheels sit on a mechanical axle, very close to the central, mostly steerable suspension of this axle on the vehicle. At the level of an imaginary, geometric axis of the vehicle, there are typically four such pairs of wheels, i.e. eight tires; but a multiple of that if self-propelled vehicles are coupled to one another at the side.
Most of the main railway lines in Germany are approved for wheelset or axle loads of 22.5 t . The highest wheel set or axle load used by a railway company is known to be 40 t at Fortescue Railways in Australia. Maximum axle loads of around 10 t are common for trams. For some years now, portal axles have been installed in low-floor trams whose pairs of wheels are not connected by a (short, direct) mechanical axle.
The axle load can result in route-class-dependent speed restrictions in order to limit the wear and tear on the superstructure .
Most excess axle loads can be treated as exceptional consignments , as long as the design of the wagon allows. However, great differences between the axle loads of a wagon should be treated with particular care, as they greatly increase the likelihood of derailment .
- Anselm Ott, Patrick Jochem: The Costs of Transport Infrastructure - A Comparison ( Memento from June 25, 2007 in the Internet Archive ) fuks.org, web.archive.org, Transfer, No. 34, after October 22, 2006, archived 25. June 2007, accessed on May 1, 2019, pp. 10–15, here: p. 12.
- Note Compare independent suspension
- Note Assumption: flexible tires
- RIV Annex II , Loading Guidelines Volume 1, Chapter 3.1
- John Kirk: Fortescue opens the world's heaviest haul railway railwaygazette.com, July 14, 2008, in English, accessed February 9, 2012.
- vehicles. In: karlsruher-modell.de. TransportTechnologie-Consult Karlsruhe GmbH (TTK), accessed on January 17, 2017 .
- The ratio of 2: 1 for two-axle wagons and 3: 1 for bogie wagons must not be exceeded during regular operation ( RIV Annex II , Loading Guidelines Volume 1, Chapter 3.3)