Lucy:
Carryfast:
A proper rear steer means that all the trailer axles counter steer to reduce cut in.No, it doesn’t. It’s called a “rear steer” because it’s just the rear axle steering.
Trailers where all the axles turn are described as “positive steer”.(Source for last bit - Rikki from here. He pulls 6-axle versions.)
The trailer described by the OP is fitted with a passive steer system. It self tracks, is not linked to the fifth wheel, and has no outside power involved in its operation. As he says, there is a locking device which can only be engaged when the wheels are in the straight ahead position, to permit the trailer to be driven successfully in reverse.
A trailer with positively steered axles may have one or more of its axles steered by either mechanical or hydraulic means, usually controlled from a turntable which is built into the trailer at the rubbing plate. On these systems, when articulation takes place between the vehicle and the trailer, there is displacement, either mechanical or hydraulic, which is transmitted to the rear turntable, causing it to steer the trailer from the rear. Tridec is probably the manufacturer of the most commonly used system. Muldoon, from Ireland, also produce a similar system, but theirs tend to be operated by a hydraulic displacement system.
The other system, which is more sophisticated and expensive, is Command Steering. This is usually only found on specialist low loader trailers, and those used for very long loads.
With a command system, the driver, or an assistant, can, by using an electro hydraulic system, change the steering angle of the trailer wheels, regardless of the relative angle of the tractor and trailer, and this can even be done when the outfit is stationary.