The basic design for these has been about for a while, but I was recently shown a way to incoorporate a screamer into the design.
Let me know what you think.
Video description below:
A homemade alternative to a Black Diamond Spinner or Grivel Double Spring Leash.
To prevent you dropping your ice tools when climbing 'leashless', and is strong, possibly strong enough to hold a short fall.
This system has Four key advantages.
1. Its high strength so you can belay off your axes.
2. It keeps the umbilicals out the way of your ropes, reducing tangles.
3. Costs £5 if you only have to buy the webbing and shock cord.
4. It may be more likely to hold a fall than commercial systems.
I would never recommend anyone fall off while winter climbing, however, I'd expect that a short slump onto the system with your tools in a solid ice placement or icy crack may be held.
It won't snap very easily if you fall on it. The weakest point is the webbing at 16kN, presumably reduced to around 12kN by the knots.
It is custom made to your size. On a BD spinner leash for example, you may fall 20-60cm before the leash comes tight - therefore shock loading the placements and then leaving you dangling well below your tools. With this system you should set it up so there is only a couple of cm spare. This should mean its more of a slump than a fall.
The addition of a screamer as the harness link, possibly a low-force activation version such as a Yates Ice-Scream or Scream-Aid could reduce the forces on your tool placements. Whether this is of benefit is open to debate as they are not designed for this and you will fall further as the device deploys. A via ferrata energy absorber could possibly be used instead.
Other modifications you may choose.
-Using a maillon or screwgate on the tool end.
-Avoiding the larksfoot on the harness with another maillon.
-Adding a spinner from a hardware store!
-Attach to the tool by looping it through, as in the last link below - this is strong and the lightest way currently devised.
Although the stretchy cords look rubbish, they actually hold the umbilicals nicely up and out of the way of your ropes, harness and gear. This makes it less likely to get in a tangle. I'm planning on modifying mine to hold some petzl flutes (or homemade version!) to keep my screws handy.
Disadvantages.
1. If you don't have the kit lying around this may be a more expensive solution than a commercial one.
2. It could end up heavier than a commercial system.
3. Some people may find it too complicated.
4. You'll get some odd looks.
Any feedback is welcome.
Further reading.
http://coldthistle.blogspot.co.uk/2011/01/ice-tool-umbilicals-repost.html
http://www.alpinedave.com/leashless_rig.htm
http://www.blackdiamondequipment.com/en-us/journal/climb//qc-lab-how-strong...
http://coldthistle.blogspot.co.uk/2012/04/it-can-be-simple-solution-socks-a... 
