THE TRAILER’S ‘A’ FRAME (DRAWBAR) & SAFETY CHAINS
This is the front section of the trailer or caravan chassis to which the coupling body is attached.
The “A” frame or drawbar is required under the Australian Design Rules to be of sufficient strength for the specified trailer ATM, and must be able to be proven to do so by engineering calculation
Note: It is not advisable to add additional items to the drawbar. Increasing the downward load on the trailer drawbar will also increase the tow-ball weight on the towbar. Excessive overloading of the towbar ball weight will affect its performance and may void manufacturer’s warranty.
Safety chains are compulsory in all States and Territories of Australia. They must be strong enough to hold the trailer and prevent the drawbar from touching the ground, should the coupling fail or be accidentally disconnected from the ball.
Trailers less than 2,500kgs ATM must be fitted with at least one safety chain. Trailers over 2,500kgs ATM and up to 3,500kgs must have two safety chains fitted. Chains must comply with AS4177-4 and have a rating at least equal to the trailer ATM.
The chains attach the ‘A’ frame or drawbar of the trailer to the main towbar framework on the vehicle. The attachment must be fit for purpose of equivalent strength to the chains.
Safety chains must be stamped with the chain’s capacity, the manufacturer’s identification and the digits 4177.
The chains should be as short as possible, leaving only enough slack to permit tight turns. If two are required they should be crisscrossed under the trailer tongue to prevent the forward end of the drawbar from hitting the ground if the coupling becomes disconnected.
Safety Cables: Safety Cables of equivalent capacity to safety chains are also allowed on tow vehicles up to 3,500kgs ATM. It is vital that the chains are attached to the main towbar framework and not to a detachable ball mount or tongue.