Page 54 - Rappelling

The ⁄8-inch-diameter
3
Powers Power Bolt
expansion bolt with a
stainless steel hanger
has become the
minimum standard for
climbing and rappelling
bolt anchors.

The performance and strength of the bolt relies, to website (www.powers.com); you’ll get an excel-
a great extent, on two things: the tolerance (diam- lent tutorial on the various types of bolts and how
eter) of the hole and the strength of the rock itself. strong they are in differing rock types.
In good rock the ⁄8-inch Power Bolt is rated at over Even if you’re not an expert in mechanical
3
7,000 pounds shear strength, with a pullout strength engineering or in identifying bolt design and
of roughly 5,000 pounds. type, you should know what to watch for when
Since these bolts are really designed for the inspecting a bolt anchor. An obvious red flag is
construction business, the Powers Fastener com- rust. SMC “death hangers,” Leeper hangers, home-
pany lists strength ratings based on the density of made aluminum hangers, and any bolt or hanger
the concrete they are placed in. Concrete is given with obvious signs of corrosion should never be
a psi (pounds per square inch) rating. For example, trusted. Look closely and identify the diameter
“2,000 psi concrete” means that if you took a of the bolt. A ⁄8-inch-diameter bolt has become
3
square inch of concrete, it would take a weight of the minimum standard, along with a stainless steel
2,000 pounds to crush it. Hard, fine-grained granite hanger. A bolt with threads and a nut holding the
is denser than 10,000 psi concrete, and soft sand- hanger in place is generally not as strong as the
stone is more like 1,000 psi concrete. hex head types.
Once a bolt has been installed, it’s impossible to The rock should not show cracks emanating
see what’s going on beneath the surface (e.g., the from the bolt placement—a more common prob-
length of the bolt), and all you’ll see is the head of lem with contraction bolts than expansion bolts.
the bolt, again making identification of the type of In a good placement, the hanger should be
bolt more difficult. flush against the rock and should not budge or
If you’d like to educate yourself, peruse be deformed in any way. A “spinner” is a bolt that
“mechanical anchors” on the Powers company protrudes enough so that the hanger can be easily

Rappel Anchors 43

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