It’s been a while since our last update, and we have a lot to share, so we’re going to split this up over a few weeks, and try to be more regular with our updates going into next season.
This update will focus on rope. We’ll cover how we test and assess ropes for the PL1 and share our recommendations. In our next update we’ll go into detail about the development of our Loop System accessory kit
We’ve tried to test a practical range of options and constructions, but it’s not an exhaustive list, and we have more rope samples on the way to continue testing. Similarly, many potentially viable ropes we have tested in the shop still need to be tested on the slopes. This is a continuous project for us, but we get lots of questions on this subject and I want to share some recommendations based on what we know so far.
Theses are just a few samples of the rope we've tested with the PL1 and the custom tensioner wheels designed to accommodate different ropes.
Process
The first test to check the viability of a rope is a static load test. To do this we use a mock PL1 with a locked gearbox. We install the rope in the device, and pull on it from the other end with a hoist. We use a scale to read the tension.
This is much more useful to us than the rope’s specified breaking strength, which doesn’t account for how the PL1 actually grips the rope.
If a rope looks promising after a static test, we will run a dynamic bench test, where we put some load on the rope with our high tech rope tensioner and then run it through the PL1. This gives us a better indication of how the rope holds up to actual use, before we take it onto the snow.
It does the job, but there's room for improvement with our current rope tensioner rig.
The final test is in the field. It’s harder for us to control all the variables in the field, but ultimately this is the most valuable test for us. This is where we find out how ropes will last over time and how they’re affected by different conditions.
Failure Modes
For ropes that feature an outer sheath, we typically see failures occur before the specified breaking strength. While the core of the rope can greatly increase the tensile strength, the strength of the sheathing is typically the limiting factor for any rope used with the PL1. Even if the core remains intact, once the sheathing fails the PL1 will no longer be able to ascend below that point.
We also see premature failure when ropes are very slick. Many high performance ropes run into this issue with the PL1. A dyneema rope may have a breaking strength exceeding 2000 lbf, but it won’t exceed 100lbf if it starts to slip in the pulleys. Many of these ropes also feature urethane coatings, which allow them to perform well initially, but slip and fail after a few runs when they are wet or the coating has worn.
Summarized Results and Recommendations
Compatible ropes typically have a nominal diameter between 3mm and 5mm or ⅛” to 3/16”. Note that rope construction will dramatically affect how that nominal diameter compares to the actual thickness when that rope is pinched in the pulley.
For most PL1 users our recommendation remains to use 550 paracord from any reputable source.
550 Paracord
- Very Stretchy
This can lead to issues when trying to stop or slow down mid run, or simply from rope piling up as you build tension. - Very Affordable
Available from numerous sources, anywhere in the world - Light and Very compact
0.5 lb/100’ and highly compressible - Average Grip and Strength
We see sheathing failures start at roughly 300 lbf tension.
It’s worth noting that while 750 paracord has an increased breaking strength over 550, the strength of the sheathing is seemingly identical, and we’ve observed no improvement in our testing.
If you are looking to reduce issues from stretch and can accept more bulk and higher prices there are several high performing options we can recommend. The following ropes all exceeded the 400 lbf load rating of our test setup without failure, and have been tested on the snow.
New England Ropes Finish Line 5/32”
- Available to consumers in 600’ reels
- 0.8 lb/100’
Mammut Nylon Static Cord 4mm
- Available in stores at many locations
- Difficult for consumers to source large reels
- Expensive if purchased by the meter or foot
Teufelberger Polyester Accessory Cord 4mm
- Available to consumer in 300’ reels
- 0.8 lb/100’
Teufelberger Nylon Accessory Cord 4mm
- Available to consumer in 300’ reels
- 0.7 lb/100’
- Some stretch
- Lower breaking strength than the Polyester version, and we noted more abrasion from use
Custom tensioner wheels allow us to test heavier gauge ropes.
Heavier Ropes
We’re working on expanding the ropes that are compatible with the PL1 by simply using new tension wheels.
At this point we aren’t actively working on a product that would be rated for overhead lifting or hauling, but gripping heavier ropes can still add functionality and value for our customers.
We tested a custom tension wheel with a heavy 6mm rope from Amazon and a higher end 5.4 mm V-TX rope from Sterling. Both ropes easily exceeded the limit of our scale on the static test, but we still need to test how they perform in real world conditions.
Next Steps
As I mentioned at the top, we are continuing to bring in new rope options and test them out. If you have a particular rope you are interested in using with the PL1 I’d love to hear from you so that we can test a sample here.
Our current setup has some limitations and we’re planning some upgrades. This summer we’ll install a more accurate load cell that can read higher loads, and a new rig that will help us better simulate real world use and capture more data.
A sneak peek at the prototype remote and receiver for the Loop System, which we're excited to discuss in our next update.
We’re still hard at work on the loop system, and in the next update we’ll cover the progress we’ve made, design decisions, and the project timeline.
Let it snow,
Zoa Engineering Team