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SABR Case Study


  • Provide the 4WD transverse transmission for a World Rally Car team


  • Basic clean sheet concepting performed to determine initial transmission configuration
  • Initial bearing sizing determined from standard bearing catalogue
  • Gears were designed in order to meet the pre-defined duty cycle requirements using the integrated GEAR software

Intermediate Design

  • Shaft stress and bearing life assessed
  • Bearing with lower than ideal life re-specified and results reviewed
  • Model updated to represent assembly sequence and manufacturing information

Detailed Design

  • Shaft oil holes and detailed fillet radii modelled resulting in automatic calculation of shaft stress concentration factors
  • In parallel with the prototype test program, a study was performed to reduce one area of high stress as defined by SABR
  • SABR optimised shafts were phased in to replace the original design during the vehicle test program
  • As predicted by the SABR analysis, the original shaft failed during rig testing, with the optimised design meeting all the durability requirements
  • Further study performed to reduce mass without compromising stress


  • Class leading gearbox reliability leading to a number of significant podium places and trophies



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