To get the maximum length and weight on the roads here around u need one or two stearable axles on your trailers.
Stearing can then be made with three designs:
- Friction stearing, where the wheels stear by the force when u turn. Theese got a lock that u engage when reversing.(theese are most common)
- Stearing by a spesial system around your kingpin.(kingpin has a second pin at the back, so truck and kingpin is not turning) It has a rollerbearing on top of the kingpinplate that turns when u turn the trailer. Then there is a hydraulic sylinder connected between the kingpinplate and the frame. This gives u a hydraulic system that produse force to the stearing sylinders on the axles.
- Electronic kingpin that gives a signal to a electronic brain that desides how much the axles should stear.
Most of the last two also got a lever in the cab making it possible to stear the wheels manualy.
Some producers also got a system where u need to charge the hydraulic acumulators that power the stearing once a week.(Goldhofer)
Added a pic of a 10 axle Goldhofer with extension, 106t payload.(212 000lbs)
Goldhofer even got axles with 45degree stearing angle...