Monday, Oct 14, 2013 at 12:45
In the current regulatory system Articulation is pretty
well, no longer a factor in either regestration or licencing.....just about everything is assessed bassed on mass alone.
As far as the definition....it comes from heavy transport and the term "Fifth wheel trailer" that refeers to the
turntable used in heavy transport is not commonly used in Australia.
Overseas it is common to "adjust" the fifth wheel, moving the
turntable back and
forth to manipulate the load on the prime mover....that too is not common in Australia, most prime movers have turntables in fixed positions....they do all sorts of weird stuff overseas
This use of the term "Fifth wheeler" comes from America and realy only seems to be used in relationship to caravans in this country.
If you where in the horse or livestock community, you are more likely to refeer to an articulated trailer as a goosekneck trailer
The fact remains there are 3 basic types of trailers permitted on Australian roads.
The pig trailer...a rigid drawbar trailer with a single axle group like most box trailers and the majority of caravans.....considered a poor choice in heavy transport because of its inherant instability...they are a pig of a thing.
The dog trailer....a self steering trailer that has an axle group front and rear and carries itt whole weight on its own wheels.....called such because it follows around like a
well trained dog.
and
Articulated trailers.....this is the group that contains semi trailers, fifth wheel trailers, gooskneck trailers or what ever else you want to call it.
If ya doubt me
check out VSB 14.
Even more confusing a lot of the time the articulated trailer has no
turntable and is hitched using a ball....thus there is no fifth wheel.....but people still persist in calling them "Fifth wheelers"
Where the hitch point is in relation to the rear axle, is a design matter and determines how the load from the trailer hitch is shared on the tow vehicles front and rear axles.
BUT almost without exception the hitch is close to the centre of the rear axle......sometimes maybe forward of it sometimes to the rear of it.......but it is not placing the drawbar load way out beyond the rear of the vehicle on a lever that tends to place more load than borne on the ball on the rear
suspension and lift the front
suspension.
One significant advantage of an articulated combination (or what ever else you want to call it), is that it is possible to place a lot more of the trailer weight on the tow vehicle than would be permitted rear hitched.
SO on a light vehicle (say a light truck) with a passenger car licence limit of 4.5 tonnes GVM, it may
well be possible to tow a trailer that actually weighs 5.5 tonnes ATM. a full tonne borne on the tow vehicle.
Ball weights written for rear hitched towing do not apply and it is reasonable to put 30% or more of the trailer mass on the tow vehicle.
The other big advantage of articulated towing is, when properly designed the addition of hitch down force does not tend to take weight off the front wheels of the tow vehicle....in fact it may place more down force on the front wheels making steering and front wheel traction more reliable.
Articulated towing is by far the most stable and most civilised towing arrangement available that is why it predominates in heavy transport.
We are even finding Coca Cola now running single axle semi-trailers towed by medium rigid primemovers in preference to rigid trucks.
because that are more manoverable......and they can be driven on a medium rigid licence.
cheers
FollowupID:
799870