TOPICS
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BOLT
ON HOLDS
The first bolt on
holds for artificial climbing walls were designed or devised by
Leonard C. Anderson in the late 1960's.
Many forms of bolt on holds were developed in the early days. In
the early 1970's Gordon Bendall, before he founded Bendcrete,
experimented with glueing rocks to steel plates with epoxy resin so
they could be bolted or screwed to plywood panelled climbing walls.
It wasn't until 1985 that Francois Savigny invented the bolt on
hold we know it today, and founded Entreprise Climbing Walls.
Many materials have been used over the years to make bolt on holds
from rock, concrete, wood and resins. The most popular and practical
in the climbing wall industry was resin as it set very quickly and
allowed multiple holds to be cast from one mould. Resins used were
polyester, epoxy, polyurethane and acrylic but far the most popular
was polyester resin, it was cheap readily available, and it soon
became any industry standard.
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Bolt On
Holds
Wikipedia currently has no defintion for 'Bolt on holds' but
defines 'Climbing Holds,' an artificially made hand or foot hold
used on climbing walls to aid a clmbers progress. They are described
as a shaped grip that is usually attached to a climbing wall so
climbers can grab or step on it. On most walls, climbing holds are
arranged in paths, called routes, by specially trained route
setters. Climbing holds come in a large array of sizes and shapes to
provide different levels of challenge to a climber. Climbing holds
are either bolted to a wall via hex-head bolts and existing t-nuts
or they are screwed on with several small screws.
The
Anderson Climbing Holds
The first bolt on holds were designed
or devised by Leonard C. Anderson and first used in the
climbing wall at Royal Belfast Academical Institution in the late
1960’s.
The lack of flexibility that the
climbing walls offered at the time was a recognised problem.
Anderson’s solution was metal boxes with a nut at the back.
These were cemented or otherwise secured into a brick wall. Anderson
devised a matrix for their layout. They were fitted at 2’
vertical intervals and 2’ 6” horizontally. Into the
housing were fitted a hardwood (Beech) block that could be recessed,
fitted flush with the wall or shaped and fitted to project from the
wall.
The symmetrical appearance of the hold placements was aesthetically
pleasing and is still used to day though the hold density is much
greater. It also solved the age old problem of having projecting
holds into a multi use sports facility. Insert holds could be fitted
up to an 8’ height so as not to cause a hazard when the hall
was used for basketball or five a side. |
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West Common Sports Centre,
Scunthorpe (photo R Holmes, BMC) |
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Cast Resin
Holds
These have become the industry standard and is what we know today
as a bolt on hold.
Francois Savigny was an industrial
engineer and rock climber, founded Entre-Prises in 1985 with help
from Petzl Climbing Equipment. The first products to be sold were a
selection of modular bolt-on holds made from resinous concrete and
these were the first commercially marketed cast resin bolt-on
climbing holds. The importance of the bolt on climbing hold cannot
be underestimated. As for the first time climbs or routes could be
created and changed simply by screwing a resin hold on a wall using
a standard engineering bolt and fixing. It created a revolution in
the design of climbing walls from the heavy cast concrete structures
to the lightweight plywood or fibreglass structures we are familiar
with. It is interesting to note that in 1988 the BMC (British
Mountaineering Council) published the first of it’s Climbing
Wall Manuals, (Full tittle - Development, Design and Management of
Climbing Walls - A Technical Information Manual for Architects,
Leisure Mangers and Climbers) there is not one mention of cast bolt
on holds, but concentrated on setting rocks into brick walls or
precast concrete blocks with rocks set in them and large cast
reinforced concrete features. It was produced on the cusp of the new
age of climbing wall development. It was like Punk Rock wiping the
floor of the Progressive Rock, or to put it into context Grunge
taking over from Stadium Rock.
Early
Bolt On Hold Manufacturers
Metolius claim to have been making holds since 1986. Canyon
Holds, another French company were probably the next company to
start manufacturing cast resin holds. Rockworks were the
first British manufacturer of cast resin holds in 1988 and Nicros
in USA, have also been making holds since 1988. Today 100's of
manufacturers World wide produce climbing holds.
How
are Bolt on Holds Made
The bolt on hold has changed little in the intervening years since
it was invented in 1985. There are certainly more of them, more
colours and the range of sizes is now vast. First the shape is
carved often from a closed cell polyurethane foam. The texture of
holds is defined by the grade of foam used, and it is similar to
Oasis foam (florists foam), but being closed cell it doesn't absorb
water. Once carved the holes for the fixings are made into the foam
former. A silicone rubber mould is made around the foam former by
setting the hold in a box with removable sides. The rubber is poured
over and left to set. With the sides removed the silicone rubber can
also be removed. The flexibility of the silicone allows the foam
former to be removed. The silicone is excellent at picking out all
the faint features of the foam. With the silicone rubber turned
upside down it becomes a simple mould. The polyester resin mixture
is poured into it an allowed to set. Once set the flexibility of the
silicone allows even quite complex shapes to be pulled from it.
During the setting process the polyester resin produces a exothermic
reaction. This heating of the silicone will eventually cause it to
harden and become less flexible.
In the late 1980’s there was no standard fixing design each
manufacturer used what they thought practical Entreprise used a M10
bolt fixing whilst Canyon used a M12 fixing and also produced glue
on holds. A least one manufacturer used M8 bolts. All holds were
produced with an inset flat area to take either a cap head or button
head bolt. The flat area was often reinforced by casting into the
hold a flat washer. By the early 1990’s the industry had
settled on an M10 fixing bolt. Many manufacturers changed to a
countersunk fixing as they identified the in-situ washer as a
weakness as many holds broke along this. The countersunk fitting
allowed the bolt a greater surface area contact, and therefore
required less torque in tightening to stop the hold form turning or
spinning.
Polyester
Resin Holds
Most companies that manufacture bolt or screw on holds, climbing
holds, still use a polyester resin mixture the type used by many
fibreglass companies.
In the Entreprise (UK) brochure, 2011/2012,
about 90% of their range is in Polyester resin. Entreprise USA (March
2011) advertises approximately 350 PU holds of their 1000+ hold
range. HRT (Walltopia) appear to have close to a 50/50 split with
Polyester holds to polyurethane holds. Nicros use corn/soya oil
in their holds they do not say what percentage, and presumably it
is a polyurethane resin. Bendcrete claim it is the cost of remoulding
its holds as the main reason they have not marketed polyurethane
holds.
The resin mixtures are good at taking
the form in the silicon moulds and therefore can create detailed
textures and with variety of silica based fillers can be very
durable and less prone to polishing than with resin alone. The
longevity of the holds depends as much on the fillers as the type of
resin and pigments used and the environmental conditions it is
subjected. As well as, how the hold is treated. Many holds on
climbing walls have been known to be still in use after 20 years or
more. Heavily used holds in a climbing centre may have lost the
texture after only a year and therefore replaced even though the
structural integrity of the hold is not compromised. Outside they
are also subjected to heat and cold. UV degradation of many general
purpose resin may mean the holds only last a few years before they
become brittle. The colour also fades very quickly outside when
inferior pigments are used, so as the holds age they become more and
more brittle until they eventually crack.
Because polyester resin holds are not
flexible, they will often crack suddenly if they are being tightened
down on a wall that is not completely flat, ask anyone that has
route set on curved resin walls. A final problem is the weight of
resin climbing holds. As hold sizes have grown and grown, in many
cases the resin aggregate composite has become an impractical
material to use. Even when the hold is hollow-backed, resin
aggregate is still quite a heavy material to be carried up the wall
in a bucket. We say Polyester as a generic term to refer to both
isothalic, orthothalic polyester and the slightly different
vinylester. The reason polyester holds are so popular is because it
is cheap, usually less than half the price of Polyurethane resins.
So despite all the health and safety hazards encountered in
production it remained the industry standard for 25 years.
Primary Health Concerns in Manufacture
Eyes - Can cause severe irritation,
redness, tearing, blurred vision.
Skin - Prolonged or repeated contact
can cause moderate irritation, defatting, dermatitis.
Inhalation - Excessive inhalation of
vapors can cause nasal irritation, dizziness, weakness, fatigue,
nausea, headache, possible unconsciousness, and even asphyxiation.
Swallowing - Can cause
gastrointestinal irritation, nausea, vomiting, diarrhea. Aspiration
of material into the lungs can cause chemical pneumonitis
Chronic: Repeated overexposure may cause central nervous system
damage, kidney damage, liver abnormalities, lung damage, cardiac
abnormalities, reproductive organ damage, skin sensitization and
dermatitis.
However because polyester resins
contain about 50% Styrene it is classed as type II carcinogen,
because of studies on mice showed a significant increase of lung
cancers. The Styrene Information and Research Center (SIRC) reported
no link between styrene exposure and an increased incidence of
cancer has been found collectively in eight studies of workers in
the reinforced plastics and composites industries prior to 1992.
Primary Safety Concerns
Highly flammable and contact with
strong alkalies, strong mineral acids, and oxidizing agents. Methyl
ethyl ketone peroxide (MEKP) is used as the catalyst to harden the
polyester resin. MEKP is an organic peroxide and extremely dangerous
solvent. It is a very volatile liquid that quickly fills the air
with toxic fumes that can cause permanent damage to the central
nervous system. A similar organic peroxide was used as a torpedo and
rocket propellant. A simple fact that it provides it’s own
oxygen to burn and in doing so releases more oxygen to feed more
fuel. In contact with copper it will expand hundreds of times at a
rate of 5.2km/s. In a confined space this is effectively and
explosion. For further reading see the Russian submarine
The
Kursk or the
2006
transatlantic aircraft plot
Polyurethane
Resin Holds
Currently most commercial hold manufacturers are moving to holds
made from polyurethane or polyurethane mixtures. Polyester resin
holds though still dominate the market. Polyurethane is not new to
climbing as those of us who lived through it will bear witness to.
When cast bolt on holds were first invented many climbers were
wearing it, but they new it as lycra, elastane or spandex. In
manufacturers literature they often refer to them as PU holds. They
are sometimes wrongly refered to as urethane holds. Urethane is
Ethyl Carbamate and polyurethanes neither contain nor are produced
from ethyl carbamate. Polyurethanes, especially those made using
aromatic isocyanates, contain chromophores which interact with light
causing deterioration, therfore may not be suitable for long term
outdoor use.
Polyurethane is a better product for
holds because it is lighter, more flexible, and less prone to
chipping and breakage than resin or natural materials. More
importantly there are less of the health and safety effects
associated with polyester resins. Like other resins, polyurethane
mixtures can vary, and different mixtures have varying strengths.
The manufacturing principle is the same as polyester resin. Measure
the liquid isocyanate and resin blend at a specified ratio, mix them
together with any fillers until a homogeneous blend is obtained,
dispense the reacting liquid into a mold, wait until it cures, then
demold the finished hold.
Primary Health Concerns
R36 Irritating to eyes. R37 Irritating to respiratory system. R65
Harmful may cause lung damage if swallowed
Primary Safety Concerns
Flammable
Future
Development - Corn (Maize) and Soya based Resins
In February 2009 – Nicros owner and President Nate Postma
announced that, Nicros, is proud to be the first climbing handhold
manufacturer to introduce the use of an environmentally-conscious,
Corn/Soy-Based resin into its Super-Mix recipe. This resin, made
from renewable resources, is now used in the production of all
Nicros and PM Climbing Systems training tools and handholds. Postma
said, “This new resin is an important step forward in
supporting the effort to reduce petroleum consumption.”
These are known as natural oil
polyols, also known as NOPs or biopolyols, are derived from
vegetable oils by several different techniques, and the primary use
for these materials is in the production of polyurethanes. Since
2004 the biggest investor in these has been Ford who have used
polyurethane foam derived from soya oil in it's car seats since
2008. We have yet to see any
significant change in the marketing of bolt on holds in favour of
polyols, but it is certain that major manufacturers of polyurethane
will be introducing it into their resins.
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Acknowledgements and References:
Me
Wikipedia -
Polyurethane
BMC
General Acknowledgements:
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