Lightweight Jigger Testing

Introduction

For backcountry rescue, the aim is to use lighter weight gear balanced with functionality and performance. 

A couple of years ago, I made up a lighter weight jigger (4:1CD/5:1 pre-rigged pulley system) using a 6mm cord made with a Dyneema core with a polyester sheath.

Although we did some initial testing with a 5mm 4 on 2 Prusik and found it was suitable, we decided it was time to do more in-depth testing on all the components and the total jigger unit.

Testing Overview

What we set out to do

Test the various components used in the jigger.

Variations tested include:

  • 5mm Prusik loop tied with a double fisherman’s bend.
  • 5mm Prusik on 6mm cord: 3 on 3 Prusik hitch and 4 on 2 Prusik hitch.
  • 6mm cord tied with a scaffold hitch onto a pulley becket.
  • Lightweight jigger complete. 

Tested between:

  • 12mm pins
  • 12mm pin and 12mm carabiner
  • 12mm pin and pulley becket
  • 12mm carabiners and double pulleys

Methods and materials

Methods – Slow pull tests

  • As each test destroyed the cord, it was new for every test.
  • Carabiners that were undamaged, were reused for multiple tests.
  • All knots, bends and hitches had hand tension with all strands pulled tight.
  • Each testing series records the slow pull tests set up is the test report at the end.
  • The slow pull testing was in one location: Aspiring Safety, 1/6 Burdale Street, Riccarton, Christchurch, New Zealand. 
  • Vertical testbed 1.6m Electronic Universal Testing Machine, Model WDW-50: Maximum Test Force 50kN, sample rate 60 per second, Jinan Chuanbai Instrument Equipment Co Ltd
3on3 Prusik

Materials

Nautilus 5mm Dyneema/Polyester cord
  • Diameter: 5mm
  • Weight: 19g/m 
  • Breaking strength: 9.8kN
  • Materials: Dyneema core, Polyester sheath
  • Manufacturer: Nautilus Braids – nautilusbraids.co.nz
Nautilus 5mm Dyneema Polyester
Nautilus 6mm Dyneema/Polyester cord
  • Diameter: 6mm
  • Weight: 26 g/m
  • Breaking strength: 13.7kN
  • Materials: Dyneema core, Polyester sheath
  • Manufacturer: Nautilus Braids – nautilusbraids.co.nz
Nautilus 6mm Dyneema Polyester
SMC Micro PMP, Double Pulley
  • Diameter: up to 13mm
  • Weight: 136 g/m
  • Rating: 40kN
  • Material: Aluminium
  • Type: Ball Bearing
  • Sheave: 35mm
  • Manufacturer: SMC – https://smcgear.com
CT Snappy Steel Screw Lock
  • Weight: 237 g
  • Gate Opening: 22mm
  • Material: Steel, Zinc Plated
  • Rating: 40KN
  • Standards CE 0333, EN 12275:2013-H, EN 362:2004-M
  • Manufacturer: Climbing Technology
Snappy-Steel-SG
Aspiring 16mm tubular webbing
  • Width: 16mm
  • Weight: 34 g/m
  • Breaking strength: 12.5kN
  • Materials: Nylon
  • Standards: Certified to EN 565
  • Brand: Aspiring – https://aspiring.co.nz
WM1MG

Slow pull test results

Nautilus 5mm Cord Loop

  • Between: 12mm pins
  • # tests: 3
  • Item tested: Loop double fisherman’s
  • Avg. kN: 12.85 (66%)
  • Comment: Broke at the bend, core slipped through sheath one tail, sheath broke on one side of the bend.
5mm loop

Nautilus 5mm Prusik on 6mm Jigger Cord

  • Between: 12mm pins and 12mm carabiner
  • # tests: 3
  • Item tested: 3 on 3 Prusik
  • Avg. kN: 3.09
  • First slip kN: 2.89
  • Comment: Kept on slipping.
3on3 Prusik

Nautilus 5mm Prusik on 6mm Jigger Cord

  • Between: 12mm pins and 12mm carabiner
  • # tests: 3
  • Item tested: 4 on 2 Prusik
  • Avg. kN: 6.89
  • First slip kN: 5.42
  • Comment: Slipped initially then regripped. Stripped the sheath of the 6mm jigger cord.
4on2 Prusik

Nautilus 6mm Cord Scaffold hitch on pulley becket

  • Between: 12mm pins and pulley becket
  • # tests: 3
  • Item tested: Scaffold hitch with webbing edge protection
  • Avg. kN: 8.49
  • Comment: Broke sheath at the double overhand on becket (1) and at the figure-8 on a bight (2)
Scaffold Hitch Becket

Lightweight jigger complete

  • Between: 12mm pins and double pulleys
  • # tests: 3
  • Item tested: Lightweight Jigger complete
  • Avg. kN: 21.62
  • First slip kN: 16.97
  • Comment: Slipped initially then regripped. Stripped the sheath of the 6mm jigger cord.
Lightweight Jigger Complete

Analysis of slow pull testing

Nautilus 5mm Cord Loop

  • The loop tied with a double fisherman’s is suitable to use as it’s over 12kN. As a component in the system, it has greater strength than the 4 on 2 Prusik. 

Nautilus 5mm Prusik on 6mm Jigger Cord

  • The 3 on 3 is not suitable to use as a load capture on the third line as it keeps on slipping at 3kN.
  • The 4 on 2 is suitable to use as a load capture on the third line as it breaks at nearly 7kN. In theory, the 4 on 2 Prusik would hold 1/3 of the load when rigged on the 3rd line. Therefore the estimated strength of the system would be 7N x3 = 21kN

Nautilus 6mm Cord Scaffold hitch on pulley becket

The scaffold hitch with webbing edge protection is suitable as it’s over 8kN. As a component in the system, holding 1/3 of the load, it has greater strength than the 4 on 2 Prusik.

Lightweight jigger complete

The lightweight jigger complete with the Prusik loop tied with a double fisherman’s, the 4 on 2 Prusik rigged on the 3rd line and a scaffold hitch tied on the pulley becket is over 20kN and is suitable. 

Weight and volume of the jigger

Weight comparisons

Estimated

What the manufacturers record as the weights for the equipment.

Item Lightweight Jigger Grams Standard Jigger Grams
Carabiners x 2 DMM PerfectO - Locksafe 66 gm 132 Edelrid HMS Strike Triple Locking  74 gm 148
Cord x 10m Naulitus 6mm 26 g/m 260 Edelrid Powerloc 8mm 41 g/m 410
Small double pulleys x 2 Rock Exotica Double Six 1” Pulley 93gms* 186 Rock Exotica 1.1” Mini Double 141gm  282
Prusik x 1m Naulitus 5mm 19 g/m 19 PMI 6mm Accessory Cord 26 g/m 26
TOTALS 597 866

Difference: 866 – 597 = 269gm

The estimated saving is 31% in weight from standard to the lightweight jigger.

* Note: Rock Exotica no longer makes the double six 1” pulley

Actual

Actual weight with the testing photos side by side

  • Lightweight Jigger = 0.56kg (560gms)
  • Standard Jigger = 0.90kg (900 gms)

Difference: 900 – 560 = 340gm. 

The actual saving is 38% in weight from the standard to the lightweight jigger.

jigger std weight

Volume comparisons

To get comparative volume comparisons we put the respective jiggers in two different sized PVC bags as shown in the photos that follow.

Lightweight Jigger

Standard Jigger

Height: 15cm

Diameter: 9cm

Volume: = Area of the base (Pi.r2) x height

= (3.14 x 4.52) x 15

= 64 x 15

= 954 cm3

Height: 16cm

Diameter: 12cm

Volume: Area of the base (Pi.r2) x height

= (3.14 x 62) x 16

= 113 x 16

= 1809 cm3

Difference: 1809 – 954 = 855 cm3 

Saving is 47% in volume from the standard to the lightweight jigger.

volume jigger side
volume jigger base

Conclusions

For backcountry rescue, the aim is to use lighter weight gear balanced with functionality and performance.  

  1. The testing shows that the lightweight jigger is suitable for backcountry rescue as its overall strength is 20kN+. 
  2. The cord allowed the rigging to be smaller and lighter due to:
    • the greater strength of the Dyneema core (compared with nylon) while;
    • the performance benefits of the polyester sheath (higher melting point) needed for the Prusik load capture. 
  3. The lightweight jigger saves one-third of the weight (300 grams) compared to a standard jigger in a side-by-side weight comparison.
  4. The lightweight jigger saves half the volume (850 cm3) compared to a standard jigger in a side-by-side volume comparison.

Note: This article is about technical rescue rigging. It relates to specific rigging techniques that require lots of practice to master and judgment to use in the right place. This article does not constitute training of any sort.

This post is only a summary of the results. Check out the testing report below for more in-depth information and analysis.

Frequently Asked Questions

Question 1
  • Have you done any testing with the standard jigger? 
Answer 1
Question 2
  • How do you rig a jigger, so it works efficiently? 
Answer 2

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