Product Safety Advisory 07/01/19
Wire Sling Strength Variations
If you have
purchased Moses TOMAHAWK aid climbing pitons made in 2019, the wire slings
may not have been swaged properly in order to achieve their highest strength
(close to or equal to the tensile strength of the wire itself). More and
more of us rely on TOMAHAWKS for both progress and protection so both
placement security and sling strength are important.
- OUR TENSILE TESTING
From time to time we tensile test various products. For decades we have
tested carabiners, cams, nuts, quick draws and all sorts of stuff - singly
or as may be rigged on a climb. Not to get too techy, but our rig includes
a hydraulic pull back ram cylinder and a Dillon 10,000 lb Dynometer. We
affectionately call it "The Destroyer".
- ULTRATAPE SLINGS FITTED TO TOMAHAWKS
Recently we tested the strength of our Ultratape Sling when fitted to
a Moses Tomahawk Piton. It’s been a popular option for both upper
and lower holes for a variety of reasons. Hand placed Tomahawks can be
so darn good that many of us consider them better lead protection than
the smaller half of our micro nut rack. We had a pretty good hunch of
the outcome ahead of time because we regularly add this Sling (with 4
bartacks) to various aid hooks - with minimum breaking strengths way North
of 3,000 lbf. The set up was to apply slow-pull force to a Moses Tomahawk
Piton via our Ultratape Sling (upper hole) and Moses’ burly 1/8"
wire sling at the bottom. These were connected to a 7/16" diameter
steel carabiner at one end and a 7/16" diameter hardened steel bolt
at the other. Web or wire - the goal is always to produce a splice that
is stronger then the looped material that bears on the carabiner or bolt.
We expected the Tomahawk wire sling (same size as a #10 Stopper TM) would
fetch a similar value of the #10's rating - 10kN (2250 lbf)... and if
the Ultratape was cut or the weakest link, we wanted to know about it!
FINDINGS - ULTRATAPE VS WIRE SLING
What concerned us were two very different results:
1) Some Tomahawk's wire slings failed at very low strengths - some less
than 500 lbf and closer to the strength of a 1 or 2 Stopper TM (not the
#10) and possibly exceeding the force of an aggressive “bounce test”.
The rest similarly failed (ie wire pulled out of swage) in the 900 lbf
testing of the same Tomahawks (no wire sling) proved the Ultratape Sling
was quite durable and strong - again over 3,000 lbf in the upper eye with
minimal visible damage. This suggested we take a closer look.
A bit about swaged cables – so you know what you are clipping: Aluminum
swages are commonly known to net 50% of rated cable strength in straight-line
pull tests. Copper swages are capable of making a straight splice as strong
as the cable itself and 1/8” galvanized cable tensile strength is
advertised at 2,000 lbf. Swaged loop slings theoretically are twice as
strong as straight line splices and typically we see loops fail at their
support points (carabiner or bolt) - not the swage - so a good Copper
swaged sling (as Moses uses on Tomahawks) should fetch over 2,000 lbf.
dug around and found a 2017 Tomahawk and tested it with a similar sub-optimum
result (under 1,000 lbf), again with the wire pulling out of the swage.
2016 or maybe 2017 Tomahawk checked in as should be expected with the
wire sling breaking at 2010 lbf - which was encouraging. See photo below.
We then tested a 2017 #3 Moses. Alumahead (1/8" cable w/ Aluminum
swage) over the more "friendly" carabiner and bolt which
netted 2700+ lbs and remained unbroken! Although inconclusive, these limited
test results suggest revisiting both the swaging process and quality control
points for Tomahawk Slings. Do to these variations and inconsistencies,
we have alerted Moses Enterprises, shared our test samples and results
and recommendations for a remedy - which we hope will be forthcoming very
INTERIM OFFER TO KEEP YOU CLIMBING
In advance of a published manufacturer's solution, we want to offer our
Friends and Customers a couple of options. At minimum, Mountain Tools
will accept unused Tomahawks for exchange. Once assured and proven that
new production wire slings meet common industry strengths, we will replace
your Tomahawks. This will take time. Keep in mind, Tomahawks are primarily
an aid climbing progression piece and are not currently strength rated.
That said, all gear placements should be suspect, evaluated carefully
and tested before relying on them.
A quicker fix
is for us to add an Ultratape Sling at the bottom hole of your Tomahawks
(new or used). Ultratape's proven toughness and Minimum Breaking Strength
should boost you confidence – certainly on aid and while making
carefully calculated free moves. **If you have received your Tomahawks
in April, May or June 2019 and decide to choose this remedy – for
the slight cost of return postage - we will add a sling free-of-charge.**
See our Resling Page for additional info.
your continued patronage and trust in us.
Your Partners in Climb,
Larry and Jane
800 5.10-2-5.14 / +831 620-0911
* You can read
about UIAA Standards, EU Norms and CE Certifications online - as they
pertain to PPE (Personal Protective Equipment), pitons and other climbing
** For Resling
Service send your recently purchased Tomahawks with a copy of your invoice
via post to:
Mountain Tools / Tomahawks
Carmel, CA 93922
For more information