What Every Engineer, Architect, Contractor, And Building Owner Need To Know Before Using Helical Ties On A Project
- 07 July, 2017
- By Admin: admin
- Comments: 00
Due to the litigiousness in the building industry it is vital to know you are choosing the best most up to date product. Up to now vital details have been left out, exposing the specifier, contractor, and even the building owner to potential legal problems down the road. Below are facts not claims, to show the differences in helical ties.
The Manufacturing Process
All helical ties being used in the United States are formed from roll-profiled wire that is subsequently spun between centers to form a twist, much like a rubber band twisted on a balsa-wood toy plane, whereby the wire is secured at one end and spun from the other. This has several drawbacks:
- The pitch of the spun wire is tighter at the secured end than it is at the spinning end, the wire between progressively varies between the two. The end of the tie that goes into the masonry taps a female thread into the masonry. Due to the variations of pitch the trailing sections of the helix tend to widen the female thread, destroying the tight threaded connection and reducing axial performance. This will also make the tie more difficult and slower to install.
- The unrestrained spinning process can break over stressed over brittle wire, while wire that is almost at failure point may not break and will proceed to market.
Thor Helical ties are produced using a patented die method of twisting the wire which ensures pitch accuracy is maintained and does not vary along the length of the fastener. This will ensure that when the leading end of the fastener taps a female thread into masonry, the trailing sections of the helix will follow without widening the female thread and will result in a tight threaded connection that will maximize axial performance.
The core to fin ratio of helical ties in the market place have a disproportionate central mass to fin ratios, from one size to the next. The core gets smaller in relation to the fins on larger diameter helical ties. The reduced material content will provide for less torsional capacity. This will also make the product bendy and susceptible to buckling when used as a hammer-in fastener in hard materials.
Thor Helical ties are designed with an optimum cross sectional profile to maximize torsional strength through perfect core fin ratios. The core of a 9mm Thor tie is larger than the competitors 8mm or 10mm products which will provide more torsional capacity and ease of installation.
The tensile strength of wire used in making helical products being sold varies widely in tensile properties from 62tpsi-93tpsi. This wide variation is due to one or more of the following.
- 304 and 316 grade stainless steels cover quite a wide band, including those with high carbon and low carbon variants. Accordingly feed wire that is within the general 304 and 316 specification varies widely in tensile strength.
- During the series of roll-shaping passes the wire is work hardened and its tensile strength is doubled. The 8mm and 10mm sections reach maximum stress/hardness/brittles prior to finished shape being formed. Part-rolled wire needs to go, at least once, to a third party for annealing prior to final rolling. Part-shaped re-annealed wire comes back within a wide band of tensile strength.
Thor Helical products reduce the variation of the feed wire by selecting a specific grade of steel within the 304 and 316 bands. We also eliminate third party inert-annealing by selecting a more malleable grade of steel within the 304 and 316 bands that work-hardens to full strength before becoming over stressed.
Product Limitations- Thin & Weak Materials
The helical fasteners currently available are not suitable for tying very thin or very weak materials to a masonry back-up.
Thor Helical has developed helical fasteners with heads or spreader clips that can secure thin or very weak materials to a masonry backup. Potential uses include:
- Fixing thin-walled layers (drywall, plywood, stucco, etc)
- Fixing insulation materials (foam, mineral wool, eps, etc)
Product Usability- Reliable, Cost-Effective & Safety
Current helical wall tie products generally come in two diameters 8mm (for small wall cavities) and 10mm (for larger wall cavities) but if the substrate is very hard these ties are not recommended. They make a Asymmetrical tie that come in two diameters 8mm and 10mm to go into harder substrates. This can create problems at job sites if the installer is not trained properly on what tie to use in different situations. This also forces the contractor to carry many more ties to do a particular job. Currently wall ties are installed and recessed into the masonry with a telescopic adaptor setting tool that goes into a SDS hammer drill. This tool has a number of drawbacks:
- Safety-This telescopic tool is long, cumbersome and requires the user to operate an SDS drill with just one hand on the drill. This can increase operator fatigue and possible accidents due to the fact of having outstretched hands.
- Cost-This type of setting tool is complicated in its structure and extremely expensive to manufacture.
- Reliability- The driving pin within this tool requires differential heat treatment and can often fail, as can the spring-loading mechanism within the adaptor. Worse yet if it does break while in use, multiple parts may fall to the ground.
Thor Helical makes the decision of which tie to use very easy, we produce one 9mm diameter tie that can go into any substrate and any wall cavity space, no special ties are needed. Our insertion tool permits the user to keep both hands on his drill during installation and allows him to work at closer quarters to the masonry. Our setting tool is of one piece design, very reliable, and low cost.