Wednesday 16th March 2022

The wonderful world of Tribology

Tribology is a study that deals with the design, friction, wear, and lubrication of interacting surfaces in relative motion (as in bearings or gears). Using the reliable Control flex shaft coupling our customer has been using the compact shaft coupling design which consists of two anodised aluminium hubs and a unique middle element that transmits torque at constant velocity, with geat success.  

Ever wondered what’s really happening in a bearing contact? What happens when you run a solid lubricated bearing in air? How a grease lubricant behaves compared to an oil? The advanced bearing test rig at ESTL is helping us answer those questions. ESR Technology, with the support of the European Space Agency (ESA), operates the European Space Tribology Laboratory (ESTL), Europe's focus for expertise in space tribology.

Tribology is complicated. Various tribometers exist to remove some of this complexity so that lubricant behaviour can be studied in simplified contacts in some detail, but eventually the performance of new/existing lubricants needs to be evaluated in real components. This is where ESTL’s Advanced Bearing Test Rig (ABTR) can help.

Traditional bearing test rigs might only allow you to measure the bearing torque which is useful but lacks context. Is that high friction due to wear, a lack of lubricant or maybe even too much lubricant? The ABTR allows ESR to measure preload changes, electrical resistance changes and most importantly the axial shaft displacement which is a measure of the average lubricant film thickness in the bearing contacts. This can be done under vacuum and across different temperatures. Such information allows ESR to detect which lubrication regime the bearing is operating in, how much of the ball/raceway contact area is metal-to-metal when in boundary lubrication and even the very first onset of wear as the lubricant becomes less effective.

Recent work using the ABTR facilities has included the ongoing validation of a new self-lubricating polymer cage material, a promising replacement material for PGM-HT. This study, presented at the ESMATS 2021 conference,  and also available in Europe and Canada online through their Members Area in the ESR Technical Memo (ESA-ESTL-TM-0297 01-) showed a potential improvement in lifetime and performance based on the test results.

Figure: Typical axial shaft displacement measurement from ABTR for an oil lubricated bearing at different temperatures

For more information on the ABTR and how ESR Technology’s in-situ bearing measurements can benefit your space applications, please contact

For more Controlflex product information can be found here

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