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SRT Climb Systems

Updated: Aug 18, 2023

The ultimate guide to Stationary Rope Technique (SRT) climb systems



I have personally spent lots of time with these devices, and found that any of these (when set up correctly) can be used to effectively perform safe and efficient tree work. There are certain factors/features however which I have found to make a significant difference in usability. The following are my primary considerations and the pros and cons of each device individually.

Arborist climbing devices for SRT or SRS single, stationary rope systems
Common SRT systems

If you don't want to read this whole article you can get the gist of it from this video: (If you want to go deeper keep reading!! there is lots more in this article than on that video)


The features that matter


Certifications:
  • Some of the devices released in the US in the last few years have little to no “official certification” this may not matter to you personally so long as they have been tried, tested, and proven to be safe when used correctly0. However, employer might not allow equipment without some official stamp of approval.

Tolerance of contamination on ropes:
  • This is critical because a clean rope may not always be available. All these systems work well on a clean fresh rope, but work in the trees exposes lines to dirt, pitch and other contaminants. For example, the Akimbo is one of my all around favorite devices, and I used it almost exclusively when I have new ropes, but as soon as those ropes have ANY sap on them the akimbo goes back in the toolbox to be replaced by a system that won't jam with a little pitch.

Ease of installation midline:
  • Many climbing techniques require repositioning the climb system in the tree and if that can be done efficiently without dropping pieces then that saves time and effort. Conversely, if the whole rope must be threaded through the device (ZigZag) or removing creates loose gear (OG rope runner) time will be wasted. However, the fixed nature of the ZigZag on the rope may inspire confidence in those who are more concerned about their device failing, so this compromise may be acceptable to some.

Length and ergonomics:
  • It is often best to be close to the climbing anchor, and if the climb system is too long or worse, both long and rigid then it can force a climber out of ideal position because of that limitation.

Smoothness of releasing:
  • Because many movements within the canopy require precise balance, and the climb line is a primary point of contact which helps maintain balance smooth and consistent release of friction is necessary to move efficiently in the tree. A device that has jerky, inconsistent, or two-handed release will be irritating and inefficient.

Rope Walking Compatibility:
  • The rope walking technique is the most efficient way to make a long ascent without a powered ascender, so anytime frequent rope ascents are necessary within the canopy avoid using a device or system (like most rope access descenders) which cannot easily be integrated to a rope walking system.

 

Hitch Cord, Rope Wrench, Tether and Pulley SRT Climb System


The performance of this type of system depends on which combination of hitch cord, climb line, wrench and tether are used. Each combination has its own compromises, and some are better than others. The adjustable wrenches like the ISC Apex and the Notch Flow have some extra adjustability which can be nice (I’ve never wanted more adjustability myself but I am only 170 lbs plus gear) and there are a variety of tethers some soft and some rigid. Overall, these pros and cons are consistent through most configurations.


Pros

SRT Climb System
Rope Wrench, Hitch, Pulley, Tether

  • Less new gear needed

  • Use familiar hitch cord combinations

  • Uses familiar techniques to MRS closed systems

  • Easy switch between SRT and MRS

  • Can replace hitch cord if sappy or burnt

  • Easy to adjust for different climb lines

  • Easy to inspect

  • Cheap to replace hitch cord

  • Easy to bend and resists cross-loading (with soft tethers)

  • Midline attachable

Cons

  • Hard to know when to retire cord

  • Inconsistent performance because of lots of variables

  • Long make for tricky positioning

  • Slow to install or uninstall

  • Easy to mis-configure

  • Can be more expensive over time replacing hitch-cord

  • Long sit-back


Rope Runer

SRT Climb System
RopeRunner Pro


Pros

  • Consistant Friction

  • Adjustable to accept different climb lines

  • Fairly tolerant of contaminated rope

  • Tested to relevant CE and EN standards

  • Simple to install

  • Midline attachable

  • Easy to switch between SRS or MRS

  • Compatible with rope from 11mm-13mm

  • Easy one handed use

  • Easy to inspect.

Cons

  • Loose components that can be dropped

  • Somewhat slow and tedious to remove mid-line

  • Easy to side-load

  • Somewhat long making for challenging positioning

  • Known Mild failure potential under a fairly common condition (dirty or damaged spring on the bird )

  • Hard on fingers to release under load

  • Not the most consistent in release, and difficult to adjust

  • Tends to flatten ropes with repeated descent and then creep



Zigzag with Chicane


Pros
SRT Climb System
Petzl ZigZag and Chicane

  • Incredibly consistent performance

  • Easy to find and common

  • Approved by relevant CE and EN standards

  • Very tolerant of rope contamination

  • Easy to learn/train when transitioning from hitch-cord

  • Built-in Pulley allows for easy 3:1 rescue lift or V-Rig

  • Simple, obvious installation (difficult to misconfigure)

  • Built in swivel

  • Very smooth operation

  • Compatible with rope 11.5mm - 13mm

  • Can be use for a two person descent with additional friction

Cons


  • Requires specific carabiner to use

  • Easy and dangerous to cross-load

  • Difficult to inspect

  • Not mid-line attachable

  • Not repairable

  • Wears out quickly on dirty ropes

  • Long and clumsy in SRT

  • Difficult to pull slack through device



Akimbo


Pros
SRT Climb System
Rock Exotica Akimbo

  • Easy to adjust

  • Very compact

  • Easy to inspect

  • Easy and fast to Install midline

  • Easy to switch between SRS and MRS

  • Easy one handed use

  • No loose parts


Cons

  • Jams severely with sap/pitch on the rope

  • Drags on ascent

  • No built in Swivel

  • Limited rope selection

  • Not certified to conform to current standards for Industrial use Ascenders, or Descenders

  • Expensive


Rock Exotica Unicender


Pros
SRT Climb System
Rock Exotica Unicender

  • No Setback

  • Tends easily

  • Consistent performance

  • Easy to install or remove midline

  • Easily switch between MRS and SRS

  • Tolerates a rope with contamination

  • Short and difficult to cross-load

  • Functions well with a wide variety of rope diameters.

  • No loose parts


Cons

  • Cannot be used one handed

  • Difficult to modulate friction

  • Not smooth while learning

  • When in SRS a panic can easily result in an uncontrolled descent.

  • Tending slack is awkward

  • Expensive

  • Lacking EN, ANSI or CE certification

Taz Lov2/3


Pros
SRT Climb System
Taz Lov2/3

  • Easy and fast to install or remove midline

  • Minimal sit-back

  • Drags when tending

  • Consistent performance

  • Compact and difficult to cross load

  • No loose parts

  • Can be used with a 200kg Load with added friction in rescue scenario

Cons
  • Limited to 10-11mm ropes

  • Requires two handed use

  • Is difficult to operate smoothly

  • Unusual to find in the US

HitchHiker XF


Pros
SRT Climb System
HitchHikerXF

  • Use familiar hitch cord combinations

  • Easy switch between SRT and MRS

  • Easy to replace hitch cord if sappy or burnt

  • Easy to adjust for different climb lines

  • Easy to inspect

  • Cheap to replace hitch cord

  • Easy to bend and resists cross-loading (with soft tethers)

  • Midline attachable

Cons
  • Hard to know when to retire cord

  • Inconsistent performance because of variables inherit to using friction hitches

  • Slow to install or uninstall

  • Easy to mis-configure or tie wrong

  • Can be more expensive over time replacing hitch-cord

  • Long sit-back

  • Slack tending can be rough.

  • Lacking CE, EN, or ANSI certifications.

Rope Access Descenders

(Petzl ID, EDELRID Megawatt et. al.)

Pros
SRT Climb System
EDELRID Megawatt

  • Smooth controlled descent

  • Most have anti-panic features

  • Minimum sit-back

  • Long history of safe use in rope access

  • Easy to install midline

  • Clear documentation for testing and certifications

  • No loose pieces

  • Most can be used to perform a rescue with 200kg load on one device with added friction.

Cons


SRT Climb System
Petzl ID

  • Most have narrow rope diameter compatibility

  • CANNOT be used in a rope walking system

  • Must use a RAD system or similar to ascend

  • Can be difficult to pull slack through device

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