1. Introduction

Additional surface durability tests have been carried out on two pairs of MEGAGEARS® that were re-ground by Design Unit with  20µm lead crowning and 10µm parabolic tip relief on both left and right hand gears. The involute, lead and pitch traces and surface roughness measurements are shown in Annex 1.

The test conditions were as follows:

  • Pinion torque
 : 4000 / 4500Nm
  • Pinion speed
 : 3000rpm
  • Lubricant
 : 100 cSt Mineral Oil+ 4% Anglamol
  • Lubricant temperature
 : 70°C
  • Lubricant flow rate
 : 34l / min
  • Lubricant tank volume
 : 70l
  • Lubrication filtration
 : 20µm full flow

 

The gears were deemed to have failed when the area of macro-pitting was greater than or equal to 4% of one tooth flank or 1% of all  flanks. The gears were to be run for a total of 50×106 load cycles (280 hours) at each torque level unless the failure limit was exceeded at any stage.

2. Test Results

The results for tests run at torques of 4000 and 4500Nm are summarised in Table 2.1. Photographs of the failures that occurred on  the pinion and wheel flanks of MEGAGEAR® G-B13210-3 are shown in Figures 2.1 -2.3.

 

Table 2.1:            Summary of additional surface durability test results.

Test No. Gear Number Test Torque (Nm) Test Flank No. of Cycles (x106) Failure Mode
1 G-B13210-3

(Box A)

 4500 Wheel

(Right flank)

 5.77 Edge cracks across face on 2 teeth (secondary pitting damage on 1 tooth), edge cracks on 14 other teeth
G-B13211-3

(Box A)

 4500 Pinion

(Right flank)

 5.77 No surface failure, edge cracks on 12 teeth
G-B13210-4

(Box B)

 4500 Wheel

(Right flank)

 5.77 No surface failure, no edge cracks
G-B13211-4

(Box B)

 4500 Pinion

(Right flank)

 5.77 No surface failure, edge cracks on 4 teeth
2 G-B13210-3

(Box A)

 4000 Pinion

(Left flank)

 8.09 Edge crack across root on 1 tooth resulting in partial detachment of tooth cracked and pitted at 4500Nm, edge cracks on 8 other teeth
G-B13211-3

(Box A)

 4000 Wheel

(Left flank)

 8.09 No surface failure, edge cracks on 3 teeth
G-B13210-4

(Box B)

 4000 Pinion

(Left flank)

 8.09 No surface failure, edge cracks on 5 teeth
G-B13211-4

(Box B)

 4000 Wheel

(Left flank)

 8.09 No surface failure, edge cracks on 9 teeth

ANNEX 1

 


PROFILE, LEAD AND PITCH TRACES


SURFACE ROUGHNESS MEASUREMENTS

 

The Surface Durability of PEM MEGAGEARS with Crowning and Tip Relief (pdf)

December 2003