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Huck®
BobTail® system
HOW TO FASTEN CHASSIS COMPONENTS
Introducing the Huck® Huck®
BobTail® BobTail® LockBolts® are used
worldwide by manufacturers looking to reduce the maintenance of bolted joints, avoid the hazards and the risks associated with welding, and speed up their assembly processes. Often the most vulnerable point on
a design is where there is an interface or joint between components. These fasteners can be used with any plated metals without damaging the plated/ fi nished surface – dissimilar metals with dissimilar coeff icients of thermal expansion also present no problems. BobTail®
Huck® fasteners are DiBt
approved, meaning they can be used in areas regulated by the building authorities as a replacement for non-preloaded structural bolting assemblies (EN 15048) or high- strength structural bolting assemblies for pre-loading (EN 14399). The values published can also be used in other applications such as rail or commercial vehicles.
A nuts and bolts comparison Lockbolts®
have a higher fatigue
strength than threaded fasteners and can be used in areas where access to the joint from both sides is guaranteed. Due to their high static load-bearing capacity under tensile loads and fatigue strength, they represent a great alternative to bolted or welded connections, especially when high demands are placed on safety over the entire products service life. Huck®
fasteners are
precision engineered to deliver quick installation speed, fatigue life and vibration resistance, and have been tested and proven on commercial, agricultural and defence vehicles around the world. BobTail®
fasteners also deliver
consistent clamp. Other mechanical fasteners such as nuts and bolts must be installed using torque, or rotational force which varies with friction. They also consist of two parts: a pin and a collar but uses an entirely diff erent installation method to nuts and bolts.
BobTail® installation process
As with nuts and bolts, BobTail® fasteners can be pre-
assembled by hand and have a pre-fi t-up function in the form of helical
grooves enabling the structure to be ‘lightly’
assembled. In chassis production, this helps with the ‘line-up’ of the cross bearers. Once the engineer is satisfi ed with
its alignment, the tool is then applied and can be permanently installed. The locking groove on the BobTail® pin is essential and diff ers from conventional bolts/set screws as it has a fl atter groove geometry. This results in a larger stress cross-section with the same nominal diameter and a lower notch sharpness. BobTail®
fasteners are a two-part
fastener comprised of a headed pin and a collar – the pin is made with pulling grooves at its tail end. The installation tool grips onto these grooves, pulls the work together, then the conical shaped cavity of the nose assembly is forced down the collar which is axially pressed fi rmly into the grooves of the pin by the processing tool. At this stage, the tool has progressively cold formed (swaged) the collar into the grooves of the harder pin. The squeezing action reduces the diameter of the collar, increasing its length. Stretching the pin and swaged collar generates the clamp force over the joint, then they combine to form the installed fastener providing a permanent and completely vibration resistant joint. Installation is quick; typically,
less than two seconds per fastener, and unlike traditional LockBolts® no pin-break is required, leaving no corrosion-prone area of bare metal to be collected. This direct metal-to- metal contact of the collar swaged into the grooves of the pin eliminates the loosening eff ects of transverse vibration. The setting process is complete
with the deformation of at least one of the six indicators (sizes 12mm/1/2” diameter and above) on the fl ange of the formed collar. In the case of collars without indicators (sizes 9.5mm/3/8” diameter and below), a ring gauge check can be performed to
The red coloured collar clearly indicates an uninstalled fastener.
Huck® BobTail® installed in a joining plate
examine the installation procedure. Once installed, the fastener
performs consistently for the lifetime of the joint without requiring checking or retorquing. Recognising the cost associated
with assembly time, installations are fast, smooth and shock free. The time saved is signifi cant considering the number of potential fastening points. The cost of the BobTail®
fastener
and installation tools could be more than those of a nut and bolt, but the high-fatigue strength of these fasteners means fewer are needed – joint integrity is not compromised, and overheads are quickly saved in other areas. Post-installation only requires a quick visual inspection, saving more time and expense. They have also been designed to be tamper-proof for an additional measure of security. Huck®
BobTail® fasteners are a
cost-eff ective fastening solution for applications where reducing labour and installation costs is essential. Quick, straight-forward installation and long-term reliability make them a preferred choice for optimising both time and budget resources. ●
For more information go to
www.starfasteners.co.uk
www.engineerlive.com 47 xx
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