The innovation of hammer driven helical fixings originated from a GKN/Timber Research and Development Association (TRADA) programme undertaken in the 1970’s, headed by Chief Architect John Ollis. Together with his son Henry, Messrs Ollis and Ollis researched, tested, developed and patented a wide range of fixing and reinforcement technologies using extrusions, drawn tubes and wire sections.

As the originators and pioneers of the helical fixing concept the Ollises founded Helifix Ltd in 1984, to exploit their early-patented technologies under licence.

In the late 1990’s the Ollises formed the Thor Helical product development team to progress and nurture new concepts, with highly consistent characteristics, using precision engineering to tolerance levels that had not previously been achievable. This comprehensive second generation range of Thor Helical fixings, wall ties, reinforcement wires and anchors have been designed to suit a variety of construction and repair applications. New patents have been filed on many products, manufacturing methods and building applications, as one innovation has followed another.

PRODUCT CHARACTERISTICS - The Thor Helical wall tie and reinforcement products are fully manufactured in-house from 316 grade stainless steel wire, using a cold rolling process and ‘precise pitch’ twisting technology.

The wires are formed with large work hardened helical fins that extend radially around and along an unhardened core, acting in effect like a torsion spring and providing a unique elastic yield attribute. The production techniques used in manufacture of the helical wire enhances its ultimate tensile strength to more than double that of conventional stainless steel bars.

Balanced in profile, stiffness and pitch to optimise ease of driving and improve reliability, Thor Helical’s second generation helical products provide a highly engineered, yet simple and user-friendly, alternative to earlier product designs. Reliability and consistent performance are combined with rapid and cost effective installation rates.

WALL TIES – Thor Helical ties are in the form of a slackly pitched screw-like anchor, which is axially driven into masonry elements, usually via pre drilled pilot holes.

When subjected to a series of axially applied impact blows the angular face of the work-hardened helical fins react against the host material, initiating controlled self-rotation of the fixing as it cuts a precise and seamless spiral path into the host substrate.

The anchorage is achieved by virtue of the peaks and troughs of the helix becoming interlocked with the host material and acting upon the hosts cylindrical shear resistance at the notional circumscribed periphery of the helical fins.

The resulting accurate and tightly mating helical interlock delivers a mechanical connection that exerts no expansive stress and is not dependant on friction or adhesion.

Proven through independent testing programmes and 20 years of service use, hammer driven helical fixings can be used in a wide variety of construction materials including timber, aerated-concrete, brick, block and concrete.

REINFORCEMENT WIRES –Thor Helical bed joint reinforcement wires are grouted into slots prepared in existing walls for the purpose of crack repair, increasing flexural strength of masonry or creating load bearing reinforced masonry beams to combat the effects of lintel failure or localised ground movement. The highly deformed helical profile maximises bonding characteristics between the wire and grout, providing excellent compressive and axial strength along the full length of the grouted composite. Combining these strengths with the torsional yield characteristics of the wire, the composite unit is utilised to accumulate imposed loads and to disperse them along the full length of the reinforced zone to fully reinstate the structural integrity of distressed masonry and provide resilience against further cracking.

Where cracking has been caused by a failure in the support (i.e. failed arches, subsidence, etc.) retrospective masonry reinforcement can be used to enable the masonry to behave as a beam. Engineering input, either on a project specific basis or in the form of factored product specific load tables, must be used to establish the load carrying capacity of a beam given a known span between supports and a measured horizontal shear resistance of masonry within the reinforced zone.

By reinforcing two separate mortar beds, each with a pair of helical reinforcement wires embedded in high strength proprietary grout, a retrospective masonry girder beam is created. The reinforcement and the two surrounding masonry courses, which contribute to compressive strength, form chords that represent the upper and lower flanges of a beam, the un-reinforced masonry between the chords representing the web. The load bearing beam is able to accommodate normal cyclic movements yet provide resilience against more severe building failures and avoid catastrophic or sudden failure.


Back to Top