Vibration-free fasteners ensure a clearer view
01 June 2012
With top models of BMW motorcycles capable of accelerating from standstill to 60mph in less than three seconds and achieving top speeds approaching 140mph, a clear view of the road behind is essential when riders undertake critical manoeuvres such as overtaking. A shaky rear view mirror is definitely unwelcome and a potential hazard.
BMW has avoided this problem by adopting a special anti-vibration fastening system for the rear view mirror assembly. Developed by fastening specialist Bollhoff, ‘SnapLoc’ provides a high-performance, ‘push-on/pull-off’ fastening system which, in addition to the safety gain, is also having a positive impact on manufacturing procedures because of its ease of application.
As well as minimising vibration of the mirror assembly, SnapLoc also allows quick and easy ‘snap-fit’ installation as well as disassembly for repair, replacement or servicing – and all without the need for special tools.
The customised fastening method developed for BMW comprises three SnapLoc ball pins which are fitted to the metal frame of the motorcycle. These connect with three mating couplings which are press fitted into the engineering plastic mirror housing and held in place by an undercut.
The ball pins, or studs, are injection over-moulded in glass filled nylon (PPA GF) engineering plastics around steel fasteners whose M6 threads are finished in a black Zn/Ni coating to enhance corrosion resistance.
The receiving couplings are precision injection moulded in black EPDM – X, a grade of material that provides resistance to UV exposure and as well as the positive snap-fit and essential long term vibration absorption properties that are critical to this application.
Bollhoff has developed three basic designs of SnapLoc for plate fastenings, for mounting domes and fixing with adhesive. Different ball diameters accommodate a range of stress conditions, while stud sizes and other physical dimensions can be varied to suit application requirements. Ball studs are injection over-moulded in engineering plastics around steel fasteners.
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