High-speed electric motor demands bespoke solution 29 August 2018

Engineers from TFC were faced with a problem when asked by one of its leading automotive electric motor OEM’s to supply a 33mm external retaining ring capable of withstanding rotational speeds in excess of 17,000rpm.

Conventional external retaining rings (circlips) are limited by centrifugal forces, when the forces involved are sufficient to lift the ring out of the groove and, in this case, the standard Spirolox® rings could only be considered suitable for rotational speeds of around 8,000rpm.

TFC Ltd therefore supplied a special custom designed self-locking ring that allowed the ring to function properly at higher rpms. The self-locking feature utilises a small tab on the inside turn of the ring that locks into a corresponding slot on the outside turn. In addition to withstanding higher rotational speeds, the ring is also capable of sustaining vibration, functioning under rapid acceleration and absorbing a degree of impact loading.

All Smalley Spirolox® rings are manufactured using a unique edge-winding process, which is as flexible as it is precise. It accommodates design changes without the need for additional tooling or die modifications. This process facilitates the development of prototypes allowing the production of low quantity custom orders quickly and economically. Even after the initial prototypes are produced, the same process allows the design to be altered with simple machine adjustments or even a change of raw material size.

Deputy Editor

Claire Aldridge Deputy Editor t: +44 (0) 1727 814 450


Having joined the magazine in 2012, Claire developed her knowledge of the industry through the numerous company visits, exhibitions and conferences she attended both in the UK and abroad.

Responsible for social media and the online platforms, Claire prides herself on keeping readers well informed and up to date with the latest industry news.