AUSTRALIAN HEAVY VEHICLE WHEEL ALIGNMENT ASSOCIATION
code of practice
This Code of Practice is to cover axle correction to the steer axles of all light, medium and heavy transport vehicles. The standards contained herein provide the minimum standards for repair procedures and axle correction by industry. Users of this Code should refer to appropriate State Transport regulations for the details of specific local requirements.
This Code of Practice was drafted at the request of the membership of the Australian Heavy Vehicle Wheel Aligners Association following their National meeting 1995. The Code is a result of extensive consultation amongst the membership and industry and it represents the motor industry’s commitment to improving the safety of operation of all vehicles involved with axle correction.
Vehicle Categories Covered By This Code:
All transport vehicles fitted with l-beam front axle assemblies, including buses, prime movers and twin steer vehicles.
Vehicle Categories NOT Covered By This Code:
Four wheel drive vehicles or any other vehicle equipped with a tubular section axle assembly. Any rear or drive axle assembly.
1) All persons involved with axle correction should be trained and qualified to meet all State requirements.
2) The requirements of the employer.
3) Should be familiar with the contents of this document.
4) Should be familiar with industry standard practices for axle correction and wheel alignment, and ensure all ‘l’ beam steer axle camber adjustment is carried out in accordance with AS/NZS 4737:2002.
Repairers will, at all times, keep adequate records of all procedures undertaken.
These records shall include details of -
Initial readings (L and R) for:
- Toe in
Final readings (L and R) after adjustment for:
- Toe in
Owners name and contact number or address
Any information on special operating conditions relevant to the repair.
Recognised Safety Procedures Should Be Observed At All Times
Before any work is undertaken, the vehicle shall be cleaned (if needed) to a degree where a thorough visual examination of the axle assembly and related suspension components can be undertaken.
All axle components will be checked for wear, road damage, cracking or any other defect liable to affect structural integrity.
All springs, spring hangers, shackle bushes, shock absorbers, shock absorber mountings, steering linkages and suspension pivot linkages are to be examined to ascertain their service ability prior to any adjustment taking place.
Particular attention is to be paid to the condition of king pins and stub axle bushings.
Initial wheel alignment readings are to be taken of all measurements and recorded prior to any correction taking place.
Following conventional alignment adjustments and/or axle correction, the final readings are to be recorded on the job record.
All vehicles should be road tested to establish the effect of any corrections undertaken, and their effect on vehicle driveability by a correctly licensed driver.
Axel Correction Procedure:
Before commencing the following procedures it is imperative that all prescribed cautions and safety requirements should be strictly observed
1) All axle corrections undertaken will be performed in a professional manner using recognised equipment suitable for the task.
2) No correction of an axle is to be undertaken to compensate for driveability problems before measurements have been taken of the alignment and other relevant factors.
3) All corrections should preferably take place outboard of spring pad or similar where possible. If the axle cannot be corrected as is prescribed to the satisfaction of the operator, the axle should be removed from the vehicle and corrected by alternate means.
4) An axle configured to disallow correction as per paragraph (3) must be limited to a maximum spring pad angularity from parallel of 1° and a height indifference of 10mm. Should it be impossible to achieve the desired correction outboard of the spring pads, then the amount of correction inboard will be limited to the absolute minimum, bearing in mind the parallel requirements and tolerances of spring pads and similarly height indifference (from side to side).
5) All corrections will be undertaken as cold procedures and at no stage is heat to be applied to any forged axle or associated component, however all procedures should take place at an ambient temperature of over 10°.
6) During the correction process no shock loadings are to be placed on the axle - all force used is to be a progressive nature, eg. hydraulic mechanical press.
7) Procedures involving twisting of the axle assembly to correct caster variations are to be kept to the minimum.
8) Procedures involving correction of camber settings are to be kept to the minimum required and at no stage are to exceed 1.5° on any one wheel. Acceptable levels for camber variation side to side should not exceed 2°, in normal circumstances.
9) Pressure must not be applied to the thrust bearing nor any side loading to the steering knuckle or king pin location. Should excess force be applied to the king pin/thrust bearing resulting in deformation, the assembly should be stripped for further examination.
10) Any axle exhibiting signs of being corrected to a factor greater than previously mentioned or showing suspect sign such as stress cracking, fatigue or heating should be subject to close inspection and crack testing in situ where possible. Otherwise removal and/or disassembly is required to allow thorough examination.
11) Following the undertaking of any axle correction, the entire assembly must be given a close visual and physical examination before the unit is operated on any road.
12) In any situation where the operator feels that any axle may be suspect due to prior corrections of any nature should follow procedures as per paragraph (10)
It is recommended that where equipment or expertise does not exist inhouse, all work of this nature should be sent out to specialised engineering establishments.
Should the work be performed inhouse, staff MUST be trained and competent in the procedures used to test the assembly.
Acceptable testing procedures include, but are not limited to, magnaflux, magnetic particle, dye testing for cracks and black light inspections.
All personnel involved in inspection and testing of axles will exhibit an understanding of the nature of stresses in metal occurring as a result of sharp edges, drilled holes and other similar foci.
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