The Chris Tan Death Slide

The mission was to construct a shock-absorber ( screamer) out of components found on an average rack. Furthermore, the rig had to be "reusable". This has an advantage over mission-specific, shop bought shock-absorbers, which are "use once". Although some manufacturers offer a "return for a re-stitch" service, this is not really viable mid-route or if you are based in the middle of nowhere.

Fig. 1

Overview of the Rig

The rig consists of:

A long nylon sling, tied off at the protection end with a figure of 8. ( top of Fig. 1)
A prussik loop, a French prussik attached to a karabiner and the rope ( bottom of Fig 1.). The prussik is set high, i.e. close to the figure of 8.

The idea is for the prussik knot, karabiner and rope ( Slider section) to slide down the sling when loaded. This will dissipate energy from the fall. An over hand knot can be tied at the bottom of the rig, to shorten the distance of the slide. ( See Fig. 2)

Note: Click on the pictures for an enlargement ( 1-2mb)

Fig. 2

Fig. 3

The Slider Section

The Slider section consists of a French Prussik, connected to the rope with a karabiner. ( See Fig. 3)

Note: The karabiner is also clipped into the sling to ensure that the prussik loop is not the only means by which the CT Death Slide is connected to the rope. ( See Fig. 4, rope removed for clarity)

Fig. 4

Fig. 5

The Protection Section

This is simply a figure of 8 tied into the sling to form a short loop. This is clipped into a quickdraw or karabiner which is connected to the "suspect" protection.

Additional Notes

1. Prussik rigs vary greatly in performance. Their ability to grip or slide depend on:

Diameter and length of the prussik loop
Thickness of the sling
Condition of the sling; wet, muddy, iced up, etc
Other factors not listed above.

2. You should test this rig in a safe environment using components on your rack, before employing it in the field.

Your dodgy protection must hold at least your body weight. That will be the minimum load applied to the protection when the rig comes to rest.
A good bounce test in a safe environment can generate up to twice your body weight..
Bounce test with a variety of prussik loops ( different lengths and diameters), to find a rigging that either:
- slides easily, i.e. less shock on your protection.
- or one that requires more force to shift.
Select a rigging according to the state of your protection.

3. Some thoughts on loading:

The rig should not start to slide with a load of bodyweight or less. It would be pointless as the rig will not be absorbing sufficient energy to safeguard the suspect protection. Furthermore, it would increase the length of the fall.
The rig must hold bodyweight ( See above).
I think the optimum set up would be a loading of 1.5 to 2 times bodyweight before sliding. This will start to dissipate the energy from the fall without overloading the suspect protection.
Anything higher than 2.5 times bodyweight will probably overload the protection.

Testing

4. I have not performed any exhaustive testing of the rig. A couple of drop tests with a heavy rucsac. If you have a highly developed lemming instinct, please get in touch. Alternatively, if you have access to any stress testing equipment, I would be interested in seeing just how the rig performs.

As with any Chris Tan Death Product™, usual disclaimers apply. Use at your own risk! < Usual laugh follows>

Note: Usual copyright & disclaimers apply. If you would like to use the information or any of the pictures contained in these pages, contact Chris Tan by first removing the Walnut.

Update and Health Warning

5. 20 May 2006: I have now done some testing of the rig. The test was done at an indoor wall. I used the rig as a quickdraw, climbed 1 bolt ( 3-4 feet) above it and jumped off. I noted how much slide the rig gave. I was aiming for the Slider section to move about half way down the sling before stopping.

6. The tests high-lighted some problems.

It is extremely difficult to get the prussik just right. More often than not, it is too slick or too grabby, even using the same cord and just retying the prussik knot.
Temperature and humidity also affect the behaviour of the prussik.
It would not be practical to rig this in a live situation and expect the prussik to slide when subjected to the appropriate amount of force.
If you are planning on living a celibate life style, falling on a grabby prussik is a good start. My nads did hurt!