Introduction

There has been a lot of talk lately about how different brakes are slipping with different sizes of rope and under different loads. So, I thought I would test the 6 different brakes that I own (besides the MPD) with a variety of different sized ropes to see just when each brake would start to slip.

Methods

I found a place in my local park that had 2 trees spaced at about 15 feet apart and set up two anchors. I attached the end of the rope with a figure-8 knot to one anchor, then attach the other end to the brake that I was testing. I then attached the hook from my small chain hoist to the brake and had that connected to my dyno. I then proceeded to tension the rope up to about 1200 lbs, or whenever the brake started to slip.

The 6 brakes that I tested were:

1. CT Sparrow
2. Petzl I'D
3. Petzl RIG
4. Edelrid Eddy
5. Petzl GriGri 1
6. Petzl GriGri 2

I tested 3 different rope sizes with each of these 6 brakes: 11mm, 10mm, and 9mm. Each of these ropes had similar characteristics and the same sheath construction, so the only variables were stretch and size.

Results

Here is a nice table that shows the results from the test. Keep in mind that when I say no slippage, this was only up to about 1,150 - 1,250 lbf. Also, the numbers below indicate when the brake started to slip.

Discussion

These results are very surprising to me. I am quite surprised at how badly the CT Sparrow did with smaller diameter ropes. However, it was designed for 10.5mm - 11mm ropes, so that shouldn't be that big of an issue. What also surprised me was how well the GriGri 2 performed. I was under the impression that this device was of poor quality. But, it was designed for a large range of rope sizes, so I guess it makes sense.

All the devices performed excellently with the use of 11mm rope. This goes to show that this size of rope is best for pulley systems. You won't ever experience slipping and your system will be super strong at the same time. I typically only use 11mm rope for most of my pulley systems.

Some things to note:

• All the ropes I used had the same sheath construction. So, if a rope has a different type of sheath, it may perform differently that the results above.
• The temperature outside was around 60-degrees Fahrenheit, which has an effect on the results. If it is hotter outside, or the humidity is higher, you may experience more slippage compared to a cool, dry day.
• The amount of use that each of these brakes has varies significantly. This could definitely affect the results of a test like this. This could be why the Sparrow performed so badly. I believe that once it has been used a few times, the friction will become better.
• IMPORTANT! All these tests exceeded the capacities of these braking devices. This should NEVER be done at home. It can have a very negative effect on the strength of the device and compromise its ability to hold much force. Do not exceed the working load limit of your gear!

Future Research

I would like to vary the sheath types and also the heat/humidity to get a better idea of how these devices perform across the board.

Here is a video of the test: