It’s not that difficult
Small trailers (up to 4500kg ATM) are governed under a VSB1
Unlike vehicle registration standards which can vary on year of production, these standards are legislated for ALL trailers
Easy enough to search the standards but I’ll copy in the relevant details at bottom
Take home points re safety chains
Minimum of one safety chain up to 2.5T ATM that meets the Australian Standard AS 4177.4-1994. It must comply but doesn’t “have” to be stamped as such - but you’ll have to prove it complies.
2.5T to 3.5T two safety chains each meeting standard or designation of 3500kg
Shackles also have to meet thes requirements but in the VSB there is no reference to them being rated or standardised BUT how do you know their strength without a rating. Note that there needs to be no deformation or bending up to this load limit.
1.5x9.8xATM
So let’s say an ATM of 1995kg (just under breakaway brake requirements) shackles and chain must NOT deform with a load of 29,400N
This does not take into account WLL or safety factors but since lifting gear uses a 6x WLL factor
A simple 0.5T “rated” WLL shackle should have a deformation limit of 29,400N. Now that shackle will have a 13mm pin and a 0.75T WLL shackle only runs a 13.5mm pin. I’d run a 0.75T WLL for a little headspace.
So although the legislation does not state you need to use a painted yellow rated shackle, it is incumbent on you as the operator to prove that the shackle you use is capable of withstanding 29,400N (for an up to 2T ATM trailer)
The easiest way to make that proof is using a rated shackle!
Now the chains, that’s easy! A Simple tiny 6mm grade 80 chain has a WLL of 1.1T. 6mm chain won’t eat a 13mm pin! Pretty much any chain that can fit a 13mm shackle pin will be wayyyy over rated for an up to 2T trailer.
Vehicle Standards Bulletin 1
Note Manufacturers should consider the merits of including a parking brake function when designing the braking system. ADR 38/03 clause 8 and 14 provides guidance for parking brake systems.
16. DRAWBARS, SAFETY CHAINS, SAFETY CHAIN ATTACHMENTS AND COUPLINGS
16.1Drawbars
Drawbars must be securely attached to a substantial portion of the trailer.
Drawbars must withstand the following forces applied at the centre of the intended coupling without detachment or any distortion or failure, which will affect the safe drawing of the towed trailer:
Longitudinal tension and compression (N) 1.5 x 9.81 x ATM (kg)
Transverse thrust (N) 0.5 x 9.81 x ATM (kg)
Vertical tension and compression for rigid drawbar trailer (N) 0.5 x 9.81 x ATM (kg) (For further information, refer to ADR 62/01 clause 14)
16.2Drawbar Safety Chains
All pig trailers with rigid drawbars (with or without breakaway brakes – but excluding converter dollies) and, any other trailer without breakaway brakes, must be fitted with safety chains that are marked in accordance with the relevant Australian Standard and (or cables as applicable) complying with the following:
trailers that do not exceed 2.5 tonnes ATM must have at least one safety chain complying with Australian Standard AS 4177.4-1994 or Australian Standard AS 4177.4-2004 ‘Caravan and light trailer towing components – Part 4: Safety chains up to 3500kg capacity’, or be a safety cable with a certified load capacity of the same;
trailers over 2.5 tonnes and not exceed 3.5 tonnes ATM must have two safety chains of designation of 3500 kg complying with Australian Standard AS 4177.4-1994 or Australian Standard AS 4177.4–2004; trailers over 3.5 tonnes ATM must have two safety chains made from steel of a minimum 800 MPa breaking stress that conforms to the mechanical properties of Grade T chain as specified in Australian Standard AS 2321-1979 ‘Short Link Chain for Lifting Purposes (non calibrated) or Australian Standard AS 2321–2006 Short Link Chain for Lifting Purposes. Each chain must be sized such that the minimum breaking load exceeds the ATM.
(For further information, refer to ADR 62/01 clause 14)
16.3 Drawbar Safety Chain Attachment Points
Safety chain attachment points are the means by which the safety chains are attached to the drawbar. These points must be located as near as practicable to the tow coupling. Where two points of attachment are required, they must be mounted one on either side of the centreline of the drawbar.
Each safety chain attachment point must be capable of withstanding the following minimum forces without incurring either any residual deformation that would interfere or degrade the function of the assembly, or any breaks, cracks or separation of components:
VSB 1 – Revision 5 Page 27 of 40 June 2009
Caution
welding.
Safety chains, which have the mechanical T grade property, are not suitable for
Vehicle Standards Bulletin 1
Longitudinal tension and compression (N) 1.5 x 9.81 x ATM (in kg) Vertical tension and compression (N) 0.5 x 9.81 x ATM (in kg).
(For further information, refer to ADR 62/01 clause 14)
Caution Load levelling bars should only be used with towbars designed for load levelling. Very high forces can be generated when the vehicle and trailer combination travels through dips in the roadway. These high forces may exceed the design limits of the towbar and or its mountings.
Caution Drawbar safety chain attachment points should not come into contact with the road surface when the trailer is disconnected.
