Coupling Selection Criteria and Descriptions

The coupling is the vital link that joins the trailer to the towing vehicle.

As a dedicated quality supplier, AL-KO, ensures that each and every trailer coupling in our extensive range conform to the relevant Australian performance standards. This guarantees that every AL-KO coupling you use is safe and capable of performing to a high standard.

To select a suitable coupling, consider the following:

• What types of brakes are being used?
• What is the maximum total loaded weight of the trailer planned to be?
• Can I use a 50mm ball or do I need a ring type attachment?
• Is there a need for a specifc application? Eg. anti-sway, off road, commercial?

Trailer couplings comprise some specifc groups based on their planned usage.

FIXED COUPLINGS:

This style of coupling, usually suited to a 50mm Australian Standard tow ball, is suitable to be used where either there are no brakes fitted to the trailer or the braking system does not require activation from a sliding or overrun coupling.

AL-KO couplings are simple to attach to the towball and provide safe secure attachment of the trailer to the tow vehicle.

Typical applications for domestic trailers are up to 750 kg loaded mass, where no brakes are required. For independent brake systems such as electric or power operated like the Sens-a-Brake system for marine trailers over 2000 kg, a fixed coupling is the appropriate selection. Fixed couplings for 50mm towballs are suitable for up to 3500 kg total laden trailer mass as long as the appropriate braking system is fitted to the trailer.

OVERRIDE OR OVERRUN BRAKE COUPLINGS:

On trailers between 750 kg and 2000 kg total laden mass, braking systems that use an override principal are acceptable, as long as they provide adequate braking for the trailer and tow vehicle combination.

The principal of this type of coupling is a sliding shaft attached to the tow ball housing of the coupling, and as the tow vehicle slows down the force of deceleration is passed through the coupling shaft and pushed either on a mechanical linkage (for mechanical brakes) or acts on a linkage connected to a hydraulic cylinder providing hydraulic pressure to a braking system (hydraulic brakes) .

This type of coupling is efficient if the ball load is not excessive and when load levelling devices are not used, as these devices impede the smooth operation of the coupling, hindering the brake performance.

SWAY CONTROL COUPLINGS:

AL-KO has a specifc coupling designed to reduce trailer sway. This 50mm ball type fixed coupling is designed to be used on trailer up to 2500 kg total loaded mass and with a maximum tow ball weight of 250 kg.

This unique product incorporates a clamping system that grips the sides of a specially designed 50mm towball and resists movement of the trailer. This action slows down any tendency for the trailer to sway or veer from a straight condition. This is particularly beneficial when large trailers such as caravans are buffeted by side winds or by a passing truck and trailer combination.

RING TYPE COUPLINGS:

When used in a commercial or defence department application, often a 75mm ring type towing eye is requested.

This style of coupling is similar in function to ball type couplings (fixed
and override) but instead of the connection to the tow vehicle being a standard 50mm ball, the connection is a 75mm inside diameter ring and this attaches to a pintle hook fitted to the tow vehicle. These types of couplings are primarily used in applications where the tow vehicle is a heavy commercial truck. As the Australian Standard AS4177 states the 50mm towball to have a maximum capacity of 3500 kg loaded trailer mass, ring couplings are used when higher loads are involved.

OFF-ROAD COUPLINGS:

When a coupling is used for rough off-road use the Australian Standard degree of articulation (or angles of available movement) may be insuffcient. When off-road 4WD vehicles tow trailers in rugged outback conditions it is advisable that a coupling specifcally designed to have greater angular movement is used.

AL-KO has a range of suitable "off-road" couplings in both fxed and override functions to provide the appropriate articulation for this use.

As this is a specifc application we suggest you contact your nearest

AL-KO customer service officer for specific advice.