Many (most?) of us top-rope self belay with a shunt on a regular basis and are pretty casual about it. Most people I know use the Petzl method (as per instructions with the shunt) - ie locker from belay loop directly into metal eye of the shunt plus some sort of elastic system over the shoulders to hold the locker up (this both reduces the fall distance and orientates the locker/shunt eye correctly). I always use double ropes through the shunt, never use a back up, take many falls on it and have never had a problem. However a few weeks ago, Gavin Peckham using the above configuration experienced a total failure: the shunt locked open as he sat back at the top of a climb. If he hadn't hit a ledge on the way down he would probably have died. Bruce Sobey was there and, being an engineer, investigated and came up with the brief accident report below. You can get further details from him at bsobey at telkomsa dot net.

Hi All

Recently Gavin Peckham injured his achilles tendon in a fall at Wit Umfolozi after the shunt slipped. After a full investigatin we are positive that the cause was that he had connected a karabiner directly to the shunt (as per Petzl's instructions) instead of using a short sling threaded through the eye. If the karabiner moves up, it may jam in the eye, and a fall can side load the shunt, causing it to lock open. I have a full report with photos showing how this happens, which I will send to anyone who requests it.


The upshot is:

1. NEVER connect directly into a shunt with a karabiner! Use a short sling or prussic cord threaded through the eye of the shunt to connect to.
2. Make sure your connection is not long enough to hook on the top of the shunt. If you only have long slings, tie a knot in the end of one to make a short piece to thread through the shunt.
3. When passing an overhang it is a good idea to tie a knot in the rope below you in case the shunt slips.
4. Some people also clip two quick draws around the ropes in case the shunt breaks. One is clipped around both ropes, and one between the ropes. Although with a soft connection there is a lot less force on the eye, it seldom harms to take extra safety precautions, especially when climbing alone.

Safe climbing,

Bruce Sobey

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LCD SCUM

Hello Bruce,

Thank you for this information!

Thanx

Edit: missed the part where Bruce said he have the pictures available on request, corrected my post accordingly...

Bummer to hear about the injury, thankfully not too serious!! I have spent hours on a shunt exploring new lines and have had some very scary falls onto the device. Here is what I have gathered from those experiences:

One can connect direct with a biner, I use one of those 'stop turning over' belay biners with the plastic clip across the biner. The important thing is that the shunt goes on the narrow end of the biner, that way there is less chance the biner can ride up over the arm of the shunt as the narrow end of the biner is simply to small (crossloading is still a possibility however!). Never just clip in without some sort of retainer that will prevent side loading, even a peice of tape will do the job. Avoid slings long enough to loop over the top the arm. Its important to realise that shunts were never designed for topropoing (although we all (ab)use them for this). The arm and eye are cast aluminium pieces, all cast parts (particularly in a material like aluminium) are prone to cracking and dramatic failure in the case of severe shock loads! -not good news!

There is yet to be a decent auto-feed, auto-lock toproping self-belay device developed. The Croll doesnt cut it in my books, or rather it does cut your rope sheath with all the nasty teeth inside it. Moral: avoid toproping with the shunt if possible. If you have to use it back it up! Try attaching a loosely fitted prussik (6mm cord) to the ropes above the shunt which will slide up the rope with the shunt as you ascend. The quickdraw arrangement Bruce describes doesnt sound like it would hold any kind of fall. Prussiks are hugely underrated and should be used way more by climbers. Check the shunt frequently, pulling it as far up the rope as possible and making sure its positioned correctly. Shunts will not lock properly if you fall off whilst toproping on very overhanging rock (in fact they slide raising the possibilty of melting the rope when they do eventually clamp down!), place lots of gear to hold your ropes in to the rock face and to keep the feed coming directly from above the shunt.
Take care ppl!