I've reading/watching a load of stuff about self-lining and the Petzl shunt seems to the one bit of gear that really divides opinion - some seem to see it as the pefect solution, others as a death trap. Whatever system I end up using I'm going to back up the main ascended with a toothed device of some kind.
Everything I've read (which is admittedly, not much on this one) seems to suggest that the Safe Tec Duck R would be a good (read safer?) alternative to using a shunt. Does anyone have experience using the Duck?
The Duck solves a few of the issues with the Shunt - low strength, low sliding force, need to be on two sides of one rope - but doesn't tackle the big one. Which is how easily it can be accidentally overridden and fail to stop a fall.
The Duck (apparently) has been known to fail.
Thanks for the advice. I guess the Roll n Lock and the mini traxion are 'different' device types in that the Roll n lock doesn't have teeth as such - coupled with the fact that I've already got one so will reduce cost might try that setup out close to the ground.
There is an interesting HSE report looking at the safety of ascenders, including the shunt. It was written in 2001 (by Lyon Equipment) so doesn't include the Duck. Google CRR 364/2001 if this is your sort of thing.
The report suggests that the factors of safety of the shunt are low, with the frame bending at quite low (static) loads. As Adam above says the Duck is an improved design in this respect.
Having said this I still use the shunt, a fall during self top roping should only be a sag onto the rope, which generates very low forces. If the shunt slips, which has never happened to me, and slides until it hits my safety knot, I think the impact forces should still be tolerable, although these forces will be lower with a dynamic rope. The dynamic tests in the report used a fall factor of 2 so very severe and certainly not what would be experienced during top rope soloing. So as long as you don't grab the rope or shunt itself during a fall I think it is a reasonably safe device.
What about the Petzl ASAP? Surely being designed for fall arrest should make it the device to use?
At £160 ish - I'd imagine that's why most don't use them
As it would be 'following' you up a foot below your attachment point, you'd always be falling onto it rather than 'sitting' onto it unless you manually moved it above you. And the chance of the absorbing lanyard ripping... £40 per fall?
The ST ENForcer is another option, it attempts to reduce grab potential, but in reality it's still simple to override.
I had a look at that one and came to the same conclusion, its essentially a Duck R with a stainless cam but twice the weight.
Gonna have a go with a few options while on a safety top-rope to see what I think works.