CASE STUDY 1

Wheel studs that operate in a severe operating environment

A customer came to Geographe for a problem with their 40T BPW trailer axles frequently breaking the wheel studs, with the wheels consequently becoming detached from the trailer.

Geographe analyzed all the components and possible contributing factors to the problem with numerous test and observations undertaken to devise a solution for the customer.

After the completion of the investigation, Geographe’s findings were that there was increased stress in certain areas minimising the studs effectiveness, the internal edge breaks on all holes in the new hubs were also inadequate. Because the chamfers are so small the corresponding radius on the studs interferes and compounds the already highly stressed area.

Geographe’s recommendations included:

• the internal radii of the studs to be increased from 0.8mm to a minimum of 1.5mm decreasing the stress in the area by 24%. This is the highest stress area of the studs and so will improve the stress distribution and therefore contribute to improved life.
• the edge on the hubs to be increased to a full chamfer of 2.0 mm
  
• the 32mm diameter shoulder on the studs to be increased to achieve an interference fit.

Geographe also measured certain torque levels for maximum usage and new procedures were recommended for the assembly of the studs onto the wheel hub and drums to ensure the studs were more effective and had increased longevity to decrease the trailers downtime.