Published in The Professional Mountaineer – Summer 2017
Words and Photos by Trevor Massiah
In the previous issue I looked at the lessons learned over the years from bolt placements and the advantages of titanium bolts over stainless steel glue-in bolts. Glue-in anchors that flex or deform can crack the resin, thus creating a crevice. Corrosion loves a crevice and this is therefore likely to shorten the working life of a plated steel or stainless steel anchor.
Here is some guidance for placing titanium bolts, gained from placing thousands over the years. At the time of writing the certified 8mm Eterna bolt (from Titan Climbing) appears to me to provide the best and most permanent solution, but the same placement principles apply to other ring bolts.
1. Before drilling, check that the intended bolt position is in good rock by listening for a solid ringing sound when it’s hit with a hammer. Choose a position that is a good distance away from cracks and edges. It is also worth considering how the gate on the bottom and top of the quick draw will sit against the rock.
2. To place the Eterna bolt, use a 14mm drill bit to drill a 10mm deep hole where you want the top shaft of the bolt to be. Then drill a series of holes as close as possible to each other, directly below. Each hole should be drilled a few mm less deep than the previous hole. A total of three pilot holes should be sufficient with a 14mm bit to spread along a 45mm line. Return to the original pilot hole and angle the drill bit onto the bottom lip of the hole then drill down at an angle, drilling out the gap between each hole until you are left with one vertical trench. The angle of the trench should suit the curve on the eye of the bolt.
|Trenching/recessing the vertical back bar of the eye of the bolt can greatly increase both strength and performance. Martin Roberts of Titan carried out tests on trenched and non-trenched bolts. The results showed that the yield strength (load at which the bolt permanently deforms) increased by around 50% for bolts that were trenched i.e. from around 10~11kN to 15~16kN. The bolts deformed elastically (flexed under load and sprung back to their original shape when the load was relieved) at a low load around 4kN when not recessed but when recessed this load increased greatly to around 12~13kN. The typical service load is below those figures, so this greatly reduces the potential problem of fatigue.|
3. Once the trench is finished, drill your hole for the shaft of the bolt at the top (where your original pilot hole was). The hole should be drilled at a 90 degree angle to the rock face. In normal circumstances this hole can be over-drilled by about 5 to 10mm.
|On steep rock, over drilling can be problematic as the bolt can slide out of the hole. The Eterna bolt has a special design feature that allows for easier installation on steep rock:
Tape the drill bit at 9.5cm and stop drilling when the tape is flush with the edge of the trench, flush with the rock. When placing the bolt gently tap it with a suitable hammer for the last 15mm for a tight interference fit. The last 15mm of the bolt is slightly over 15mm in diameter but will squeeze down then try to spring back once tapped into the 14mm hole, improving the grip.
Do not use a normal steel hammer as it will leave iron deposits on the titanium bolt and the iron will rust, which may cause corrosion issues with the titanium anchor itself. Either use a proper stainless steel climbing hammer, or a rubber or wooden mallet.
4. Check that the bolt fits easily into the hole: the vertical shoulder of the bolt should fit neatly into the trench. If any extra length is necessary, this can be achieved by drilling down on the bottom lip of the trench. The reason for the slot is to semi-recess the eye of the bolt to help ensure the strongest possible bolt installation for the given position. It also greatly reduces the effects of fatigue during normal use due to the increased stiffness. I always carry three bolts with me and check each one to allow for any slight variation in size.
5. It is vitally important that the hole and trench are clean, and free of any rock dust before proceeding any further. I use a Hilti wire hole brush (a Metolius brush or a shaved down hard tooth brush with the bristles cut short can also work well) and a manual Hilti blow pump for alternate brushing and blowing. Alternate between brushing and blowing until dust is no longer visible.
6. Use the epoxy resin as per the manufacturer’s instructions. I recommend the tried and tested Hilti HIT RE-500. Pure epoxy resin is often as hard if not harder than the rock it is being placed in, so the more glue you use the better. It will also provide a greater chance of a good seal from the rock and increased adhesion to the bolt.
|It is important to express and discard three full trigger pumps as a precaution before gluing your first bolt. I usually express the three full-trigger pulls into a plastic bag on the ground and then make three test beads somewhere on the ground or on the rock. This allows you to check how the glue has cured when you return the next day. If the beads are soft there was a problem with the mix. (If starting a new tube high up, one pull of the trigger for each bead.) The guns have an automated puncture system and one of the tubes is usually punctured slightly before the other leading to an uneven mix at the start.
There is a balance between speed of curing vs. “going-off” within the nozzle, and times vary depending on temperature. In hot climates, you should have a good 20mins prior to the resin going off in the nozzle.
7. Insert the nozzle fully into the hole. Almost fill the hole with resin by pulling on the trigger gently while slowly withdrawing. Try to avoid creating any air pockets by only withdrawing the nozzle while resin is being expressed. Insert the bolt, slowly rotating it as you do so. If you feel any resistance it will be an air pocket, this is best solved by withdrawing the bolt 1-2cm and inserting again, you may hear a small popping sound when the airlock is broken.
8. Continue inserting the bolt until it sits neatly in the trench. Having an ice-lolly-type stick is useful for dealing with any glue that oozes from the hole (a good excuse for a Magnum!). This can be used to backfill the trench and tidy up at the end. You can also use them to scrape excess glue from the nozzle.
9. It is important that the bolt is not recessed so far that larger snapgates do not fit. I test this while drilling with a solid gate on the bolt before gluing. The inside of the bolt eye should be flush with the rock surface.
10. You should leave at least 24 hours before loading even in a hot climate, although the glue should be cured within 12hrs, this is also where the test beads you made before gluing are helpful. Hit them with a hammer; if they’re completely dry, hard and brittle, then the bolts will be good.
Trevor Massiah is a Mountaineering Instructor based in Spain and is the owner operator of Rock and Sun which runs climbing and bouldering courses and holidays in many parts of the world. He has been working in the outdoors for 33 years and has climbed extensively around the world. His favourite crags are Pembroke, Taipan wall and the Needles California. He has put up many routes – both trad and sport – in the UK, Thailand, Australia, China and India, and is currently involved in rebolting existing routes and developing new routes in Thailand and the Costa Blanca.