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STEERING CONVERSIONS FOR LEFT HAND DRIVE VEHICLES – Right hand drive conversions
INFORMATION FOR THOSE ASSOCIATED WITH THE DESIGN, MANUFACTURE, SALE, MODIFICATION, MAINTENANCE OR REPAIR OF MOTOR VEHICLES AND TRAILERS.
GPO BOX 594
CANBERRA ACT 2601
TELEPHONE 02 6274 7500
FACSIMILE 02 6274 7714
The details below are copied from the “Dept of Infrastructure” Australian Government website.
A common type of conversion utilises a replacement steering box sourced for a right hand drive vehicle. If this is impractical, the use of left hand drive steering boxes or racks, retained in their original left hand location and operated through gearboxes, may be used. Left hand drive steering boxes transferred to the right hand side and inserted in the chassis rail may only be used if the structural integrity of the chassis rail is shown to be maintained. This method of modification is generally inferior to other methods and as a result is not recommended.
With this method of right hand drive conversions, the steering box and all steering linkages remain unaltered. The upper section of the steering column is transferred to the right hand side and is connected to the lower section of the column. This is done by the means of two right angle gearboxes and an interconnecting cross shaft. This method of conversion, generally, is not recommended for vehicles required to comply with ADR 69/.. – Full Frontal Impact Occupant protection and/or ADR 73/.. – Offset Frontal Impact Occupant protection.
MA category for new models from 1 July 1995 and to all vehicles from 1 January 1998.
MB and MC category for new models from 1 January 1998. And to all vehicles from 1 January 2000. Also
NA1 category for new models built from 1 July 1998 and to all vehicles from 1 July 2000.
ADR 73/.. also applies to new models of MA category vehicles with a GVM of less than 2.5 tonnes. Built from 1 January 2000, and to all MA category vehicles with a GVM of less than 2.5 tonnes from 1 January 2004.
Only gearboxes specifically designed for motor vehicle steering applications may be used. These gearboxes are designed to withstand high torques at very low or zero rotational speed. They are also designed to eliminate backlash. To summarise, this is backlash which would typically produce free play in a steering application. Industrial or aeronautical gearboxes are not suitable also. This is because they are normally designed to transmit lower torque at medium to high rotational speeds. Input and output shafts of gearboxes must have a spline and cotter bolt recess.
All connections to the gearboxes must be by means of correctly mating splines with clamping cotter bolts.
Cross shafts must be articulated at both ends by means of universal joints or fail‑safe flexible couplings.
All components, i.e. gearboxes, couplings, cross shafts and steering column connections, must be designed to withstand a torque of 200Nm.
The cross shaft gearboxes must be securely mounted to substantial mounting brackets to correctly align with steering column and cross shafts.
With this method of right hand drive conversion, the steering box and all steering linkages remain unaltered. The upper section of the steering column is transferred to the right hand side and is connected to the lower section of the column by a chain drive unit.
This method of conversion is not recommended for vehicles required to comply with ADR 69/.. – Full Frontal Impact Occupant protection and/or ADR 73/.. – Offset Frontal Impact Occupant protection.
For these vehicles, an analysis must be conducted to show continuing compliance with these ADRs addressing at least the items identified under the section headed “STEERING – CROSS SHAFT”.
The chain drive and sprockets must be fully enclosed.
The drive chain shall be at least a duplex chain. Some method of adjustment to eliminate free play must be provided.
All components i.e. the chain, input and output shafts, bearings and steering column connections, must be designed to withstand a minimum torque of 200 Nm.
Input and output shafts of the unit are to be provided with a suitable means of connection to the respective shafts.
This is the preferred method of right hand drive conversion. A suitable right hand drive steering box is mounted on the right hand chassis rail and the idler is transferred to the left hand side. In effect, a mirror image of the original steering installation is created.
When selecting a substitute steering box, the following guidelines should be observed:
The steering box must be correctly located to replicate the original orientation of the steering box input shaft to the steering column and the pitman arm to the drag link.
The chassis rail may also require modification to provide a suitable mounting face. Any reinforcing of the chassis rail on the left hand mounting area must therefore be replicated on the right hand rail.
Suitable reinforcing tubes must be fitted through the chassis rail at each mounting point to prevent the retaining bolts crushing the box section.
Any modifications to the rail as a result must not reduce its strength or cause stress concentrations. Furthermore, allowance should be made in the design for the high torques from the steering box: during operation.