Anchor system protects rock climbers

Serco Ryan and Fischer Fixings have joined forces to supply a unique undercut anchor system for protecting rock climbers at some of Yorkshire's toughest limestone cliffs.

Serco Ryan and Fischer Fixings have joined forces to supply a unique undercut anchor system for protecting rock climbers at some of Yorkshire's toughest limestone cliffs.

The FZEA internal threaded undercut anchors and set screws have been specified and donated to the Yorkshire Bolt Fund for replacing the dangerously corroded and poorly fitted bolts, currently being used by climbers around the county.

Requiring a shallower cone recess and less battery power to fit than previous designs, the FZEA anchor system removes holding stresses in the rock as well as providing foolproof safety features to ensure bolts are correctly placed.

Due to the geometric fracturing of the rock, Yorkshire limestone cliffs offer high, smooth, thinly protected and often severely overhanging climbs, naturally lending themselves to bolting in order for climbers to safely put up new routes.

The popularity of these areas and climbing in general has led to increased traffic even on the hardest of climbs, but recently some of the bolts placed in the 1980s have begun to fail, even while climbers are just using them to rest on between difficult sequences of moves.

To keep these places safe and open, Yorkshire climbers have teamed up to provide the manpower and generate the money needed to re-bolt many of the classic climbs.

David Musgrove, the well known climber and treasurer of the Yorkshire Bolt Fund, approached Serco Ryan as one of the UK's largest fastener suppliers with a view to finding out why these old bolts were failing and sourcing suitable replacements.

"The process of replacing bolts is involved and labour intensive", explained Musgrove.

"Helpers have to abseil down the cliffs (reaching 150ft at their highest point) with portable drills to remove the old bolts, drill new holes, place and tighten the new bolts, all at the end of a rope".

Problems were compounded by the fact that cheaper resin-based systems used up a lot of battery power, requiring more trips back home for mains recharging.

After inspecting some of the failed high tensile steel bolts, it was discovered that a reaction between the zinc plating on the bolts and the stainless steel hangers had caused advanced corrosion to the anchor bolt.

As a result, Serco Ryan enlisted one of its partners - Fischer Fixings to help find a stainless solution that required less drill power, and donate them to the project fund.

Initial research into the bead-like granular make-up of the limestone showed that it provided a surface too smooth to gain the maximum grip from the 10 x 100mm stainless and resin capsule through bolts currently used by the climbers.

The research also highlighted another important problem that the strong alkali nature of the rock softened some of the cheaper polyester-based resins over time, making a new solution even more important than previously thought.

David Frankland, Fischer Fixings' Technical Field Engineer, met with Musgrove at the impressive cliff at Kilnsey crag to trial a product unique to the Fischer range that would be safer and quicker to use than previous methods.

"We were initially approached with a view to supplying standard stainless through bolts", explained Mr Frankland.

"But our experience in fixing secondary steel work on concrete structures and tunnels, in seismically active areas, has enabled us to develop what we believed to be a better product for the job - the new high tensile FZEA internal threaded undercut anchor".

This fixing requires a specialist drill bit that uses a slightly wider tip to produce an inverted conical hole, enabling steelwork to be held in place even if the concrete cracks, making it ideal for testing in the varying quality limestone at the Kilnsey crag.

The undercut anchor system also avoids expansion stresses to the bolt and the rock, helping avoid the problems of fatigue and increasing the overall weight bearing of the fixing from a shallower, narrower and quick to drill hole.

Once the hole is drilled, the body of the FZEA fastener is inserted and a setting tool used to expand it to fill the chamber hollowed out of the limestone.

The correct sized set screw is then inserted and the hangers fastened in place to which the climbers clip the rope.

"Benefits to the climbers include a waisted bit to ensure holes are drilled to the correct depth", continued Frankland.

"The body of the fixing is also designed with 1mm of sacrificial metal on the outside edge, which becomes impressed with four dots from the setting tool when the bolts are safely secured.

A quick visual check and a twist on the inserted bolt head after the hanger is attached is all that is required to test the fixing, avoiding the need for resins to dry before use or even the more vigorous testing required by other anchor designs.

There is no halfway holding with the FZEA anchors, either they immediately hold or they don't, and can be instantly tested using a torque wrench on the bolt head.

Musgrove explains that a 12mm wide and 40mm hole is required by the Fischer system, which is nearly half that required by traditional through bolt systems, reducing the amount of power used by the drill.

"I supervised Frankland as he installed the first bolt at Kilnsey and was impressed by the speed of instalment and the fact that the reduced amount of stress on the fastener allows us to safely replace the bolts at a later date as new holes can be drilled much closer to the old fasteners".

Frankland commented: "Initial tests of the new anchors show they will withstand at least 2000kg of static force, and they have been used on a number of routes so far".

Fischer Fixings donated £500 worth of anchors to the fund and sourced the required M10 20mm set screws free of charge from Serco Ryan.

"As well as re-bolting some of the classic climbs at Kilnsey, we have also being sharing the potentially life saving knowledge gained in the project with climbing clubs in nearby Derbyshire, which also sports many high calibre limestone climbing venues", said Musgrove.

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