Department of Infrastructure
National Code of Practice
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.
STEERING BOX
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.
STEERING – CROSS SHAFT
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.
ADR 69/.., applies to vehicles of:
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.
For these vehicles, an analysis must be conducted to show continuing compliance with these ADRs. Above all, addressing at least the following items.
- Details of the mounting of the cross shaft or chain drive assembly. Further, an assessment of how the steering wheel may move (compared to the original configuration) in a crash test.
- Details of the location of the cross shaft or chain drive unit and brake crossover shaft. With relation to possible knee contact and femur load, giving due consideration to the possible forward movement of occupants during a collision.
- Details of the steering wheel/column mounting compared to the original configuration. Further, an assessment of the strength/movement of the mounting. This also needs to give consideration to the fact that the lower section of the steering column has been disconnected from the upper portion. Next, consideration should be given to possible implications for the support/location of the driver’s air bag.
- Details of any energy absorbing elements in the steering wheel column. Further, an an assessment of their performance compared to the original configuration.
- Details of construction and an assessment of the new passenger’s side dash in relation to its’ energy absorbing characteristics. This in comparison to the original dash, giving consideration to the extreme head movements often observed in crash testing. (eg head/knee strikes).
Right Angle Gearboxes
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.
Couplings
All connections to the gearboxes must be by means of correctly mating splines with clamping cotter bolts.
Cross Shafts
Cross shafts must be articulated at both ends by means of universal joints or fail‑safe flexible couplings.
Design Loadings
All components, i.e. gearboxes, couplings, cross shafts and steering column connections, must be designed to withstand a torque of 200Nm.
Gearbox Mounting
The cross shaft gearboxes must be securely mounted to substantial mounting brackets to correctly align with steering column and cross shafts.
STEERING ‑
FULLY ENCLOSED CHAIN DRIVE UNIT
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”.
Enclosure
The chain drive and sprockets must be fully enclosed.
Drive Chain
The drive chain shall be at least a duplex chain. Some method of adjustment to eliminate free play must be provided.
Design Loadings
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
Input and output shafts of the unit are to be provided with a suitable means of connection to the respective shafts.
STEERING ‑
RIGHT HAND DRIVE STEERING BOX
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.
This is the conversion we supply on our vehicles at American Car Company.
Right hand drive with right hand steering box = “Full Conversion”
Steering Box Selection
When selecting a substitute steering box, the following guidelines should be observed:
- The box should be sourced from a vehicle of approximate mass and specification to the vehicle being converted. As a result, Pitman arm length and arc of travel should be similar;
- Taper for attachment of the drag link ball joint also must match.
Steering Box Mounting
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.