Welcome
Subscribe today for some amazing stories and content from our expedition team or find an outfitter for your next adventure.
Subscribe today for some amazing stories and content from our expedition team or find an outfitter for your next adventure.
Pulleys are a super helpful part of your rescue kit that makes unpinning a raft by setting up a progress capture system so much easier with less potential for damage to your rope. If you are trying to understand what is out on the market we have a helpful buyer’s guide at the bottom of the page otherwise you can find more info about pulleys below.
Carrying a pulley, or two, as part of your rescue kit can be a lot of added weight an expense which goes into your group or personal gear budget. Some boaters prefer an ultralight setup while others prefer the utility that a pulley brings. So, the big question is why would you want to carry a pulley?
Pulley Redirects - Pulley redirects are essentially using the pulley to change the angle of the direction of pull. there are 2 reasons why we would want to do this:
The object being pulled is in a precarious position such as the area where people need to pull from is wet. Setting up a pulley re direct 90 degrees to the flow of the river can help those pulling to get on dry land with more traction or to a spot with better footing.
You can re-direct those using a progress capture system to an area out of harm’s way of potentially flying metal and hardware should you have a failure in your progress capture system. This is useful to avoid turning a non-medical technical rope rescue scenario into a medical rescue scenario on top of your pinned boat issue.
Progress Capture Systems – A rescue knife is monster when it comes to cutting efficiency and retention while working. They are designed to be there when you need it and do a relatively small number of tasks extremely efficiently at the cost of all else. They will cut rope in a hurry, but don’t try to cut a melon with these.
Rope Damage - If you are intending to use a progress capture system, you can certainly get the job done with a couple of carabiners in place of a couple of pulleys. The reality with this is twofold though:
First, as we will discuss later, the carabiner creates a great deal of strain on both the rope and the carabiner itself as the progress capture multiplies the force under heavy loads.
Secondly carabiners have a high degree of utility for boaters and as such they get more abuse. This abuse leads to a higher likelihood of dings and damage to the meatal on the carabiner. Thus, using a carabiner can expose a rope under strain to be cut by small peels or dings in the metal causing failure to your progress capture system.
There are several products on the market like the Petzl Micro Traxion pulley or the SMC Advance Tech HX Progress Capture Pulley and our team had a lot of questions on how that held up vs a prusik for progress capture. How does the cam used in the system affect the rope that is used in it? This may seem like an obvious question, but does this system eliminate the need for prusiks completely? Progress capture systems are critical for river rescues and boat recoveries so systems that eliminate or help reduce setup time are critical for boaters so we were able to find a little bit of feedback on this.
SMC told us that the following “Advance Tech is really made for a pre-rigged 4 to 1 system, I would imagine most boaters use a standard Z drag similar to a crevasse rescue set up. It needs to be pre-rigged so that the cam that captures the rope’s progress is at the tail end of the system – this reduces the force on the cam by a factor of 4 preventing the potential for damage to the rope by the teeth.”
Mark Hirst brought up some fantastic considerations about these type of products.
The Teeth - Most boaters don't really research the rope properties of their throw rope when purchasing a throw bag. Most private boaters that I see carry a 8-10mm rope with a polypropylene sheath which is the property that makes a throw rope float. The teeth on the Micro Traxion are designed to bite into climbing ropes made from materials such as polyamide which is a lot more resistant to wear & tear than polypropylene and therefore a lot more resistant to the force created by the teeth. In a nutshell I have witnessed a mechanical progress capture device strip a polypropylene rope on the side of the river.
The Numbers - The pulley on a Micro Traxion is rated to 5kn (2.5kn) WLL on each side which is not much if you think about how the forces can quickly multiply when the kit is used as part of an MA system. Replacing a pulley like the Rock Exotica mini machined pulley which is rated to 30kn (15kn) on each side is actually much stronger than the pulley in the Micro Traxtion.
Use of a prusik as part of a progress capture system - In order to reduce the loss of progress from a traditional triple wrap prusik in your system you could simply make a 4 or even 5 wrap prusik which would shorten the distance between the prusik knot and your anchor or even play with using a French prusik knot to again reduce the loss of progress during a haul. When I was younger, I was always taught that the prusik was the fuse of your system. If your prusik is tied correctly and is starting to slip or fail you are probably overloading your system somewhere. By having a mechanical progress capture device, you are bypassing the fuse in your system which could have dire consequences.
Cost and other uses - The cost of a Micro Traxtion at 130 USD for a single use piece of equipment is high for a tool that you can only really use for one job. A prusik can be utilized with a carabiner and a paddle to help raise a line above the water. The same set up can also be used to sink a line under the water if needed. The cost of a prusik vs Micro Traxion is huge even if you use pre-sewn prusiks which are lighter and take up less space in your pfd.
A prusik minding pulley or PMP is a pulley whose side plates are extended to create a flange that protects the sheave of the pulley. A progress capture system such as a z-rig utilizing pulleys without these extended plates risks getting the prusik attached to the main line in the system sucked up into the pulley potentially binding up the system.
The extended plate is an important safety feature on the pulley because having the main element of the progress capture system bound up forces you to work around the bound-up pulley. With the heavy loads water pressure places on progress capture systems in whitewater this can quickly put you in an even worse position of dealing with a pulley under load while simultaneously dealing with a stuck boat. It can also lead to even more time in a rescue scenario. These pulleys are designed to bind up the prusik before it enters the pulley by forcing it to catch on the plates.
In the climbing world if you don’t have a PMP there is a way you can create an improvised Prusik minding pulley system with a machine nut and washer. Setting this system up in the river world is never recommended for a couple of reasons. First you should never improvise a PMP system under load. There will rarely if ever be a real-world scenario where using a pulley on the river will not be under load. Second the threads on the nut and the washer will bite down hard on your rope causing damage to the rope and potentially snapping a line under load. Third, a standard washer likely cannot hold up to the strain of the weight on the rope and could fold into the pulley or snap in pieces. In either of the above cases, it is very possible to send metal shards or pieces of hardware flying at the people involved in the rescue operation. Basically, just don’t do it, buy a PMP if you are concerned about this issue.
The sealed bearing will provide greater protection from the grit, etc. you were referring to. Our bearing on the Swiftwater is sealed and oiled which will help protect against corrosion as well. Sealed bearing units typically cost a bit more as well. Needle (or roller) bearings have more theoretical contact area so they can withstand a higher load but they will also have more friction so efficiency of mechanical advantage systems will be reduced. They also tend to be a bit more expensive. Ball bearings have a smaller theoretical surface area so they work better with lighter loads and have less friction but they are also less expensive. The working loads that rope rescue pulleys are subjected to are within the limits of both roller and ball bearings so the strength of roller vs. ball bearings is moot unless you know you are going to have high impact forces on a pulley systems which is not something that would normally happen. As a river guide, Chris from SMC said the main issue both designs face is when they are stored wet over medium to long periods of time. It’s important to dry the rescue kit when not in use. Apparently, this is not always a common practice.
In the typical boating unpin kit that is sold through distributors like NRS there are two pulleys, several prusiks, and a 11-13mm static line. This kit is pretty standard for outfitters since in the United States these sorts of kits are often regulated by government agencies, but what is the reality of what most boaters will encounter on the river? For the average rescue scenario it is most likely to be performed by a throw bag or two (this is in fact an IRF standard) of 9-11mm diameter so it brigs up an important question What size pulley should we be using? The strength reduction of a rope passing over a pulley is primarily dependent on the following:
Rope diameter
Pulley diameter
Contact angle (typically 180deg)
Rope material (nylon, polyester, etc.)
Rope construction
For most rescue applications, our friends at SMC Gear have this advice to offer:
A larger pulley will be more efficient – the size makes a bigger difference than bushing vs bearing. Larger ropes are much more ergonomic in the hand which would be important unless you have a way to grab it (say with an ascender or prusik). We generally recommend a pulley diameter that is at least 4x the rope diameter. This is expressed as the D/d ratio: D = pulley diameter, d = rope diameter. So, for a 1/2in rope, using D/d ratio of 4, the minimum recommended pulley diameter = 2in. Even with a D/d ratio of 4, you can expect as much as a 20% reduction in strength for many ropes. The strength reduction of a typical ½” nylon or polyester rope over a carabiner can be as high as 50%.
In terms of strength and when to retire – the bearing unit will get pitted way before the pulley’s integrity is compromised – this is noticeable by inspecting the rotation of the sheave and feeling/listening for slight clicks. Other things to look for is any sort of deformation at the clip in point on the side plates. Cyclic static loads within the working load limit will not reduce the efficiency of a pulley. Contamination and loads that are high enough for the bearing to “Brinell” the race (essentially, the ball bearing deforms the track that it rides in) will reduce the efficiency of the pulley.
MSRP $ 54.99
The SR Rescue Pulley is compatible with ropes up to 13 mm and works great where a simple redirect is needed. All Sterling pulleys are constructed from high-strength aluminum side plates and feature a sealed ball bearing sheave that helps keep out dirt and grit.
Type: Single, Prusik-Minding
Weight: 190 g (6.7 oz)
Maximum Break Strength: 16 kN (3,597 lbs)
Axle: Sealed Ball Bearing
Dimensions: W 5.9 - in; L 7.5 - in
Max Rope Diameter: 13 mm
MSRP $ 50.00
Made using high quality aluminum, this lightweight pulley weighs 6 oz. and features a 2’’ sheave. Anodized side plates feature a series of holes that help to minimize the hydroplaning effect that might occur with a typical pulley. These side plates are also configured to work as a Prusik Minding Pulley and are precisely tensioned for easy one-handed operation and secure placement at any point along the rope. High quality sealed ball bearings help to provide the optimal efficiency that is so crucial in rope rescue systems. They help to reduce the performance-robbing resistance that is inherent in most multiple component systems and are not prone to failure under misaligned loads or with twisted gear that may occur with needle bearings. The wide and flat base maximizes the effectiveness of a Prusik hitch while a unique side plate formation allows the use of larger ropes in a compact pulley. The top hole accepts 2 large rescue carabiners or multiple small carabiners and allows the carabiners to be rotated freely and completely even while closed. Features Red and Black side plates.
Type: Single, Prusik-Minding
Weight: 170 g (6 oz)
Maximum Break Strength: 34 kN (7,644 lbs)
Axle: Sealed Ball Bearing
Dimensions: W - 4 in; L - 3 in
Sheave Diameter: 2” Aluminum
Max Rope Diameter: 13 mm (1/2 in)
MSRP $ 12.95
BlueWater Ropes Micro Pulley. Lightweight and compact for a multitude of uses. Features an anodized aluminum frame, bright aluminum sheave and a steel axle. These pulleys are not intended for high speed applications such as zip lines. Available in black only.
Type: Single
Maximum Break Strength: 22 kN
Axle: Ball Bearing
Dimensions: W - 1.4 in; L - 3.2 in
Sheave Diameter: 1.25” Aluminum
Max Rope Diameter: 13 mm (1/2 in)
