Here at PRT labs, we’re constantly working to make our highlines higher and liner.
The ideal, simplified setup looks something like this:
If you’ve got big trees and loads to be transported between the spar trees, this works.
We’ve had to make some modifications to accommodate cliffs:
Yesterday, I finally got to implement a lot of parts of a different system for highlining rocks. Here’s the diagram:
Breaking that diagram apart, left to right:
On the Griphoist end, the Black Rat pulley turns the system into a 2:1. Which means the 1-ton Griphoist can now pull a 2-ton load safely.
I was worried that the 2:1 would make taking tension take twice as long. Well, it does, but we still got rocks in the air pretty rapidly.
Next big part of the system – A Climbtech removable bolt:
Instead of wrassling and slinging a rock, I just drill (and thoroughly clean) a 1/2″ hole somewhere near its center of mass. This is a big step forward for the way we place steps – we can lower/raise/tune/repeat, and when the rock finally is set, we don’t have to mess with lifting the rock to get straps out of the way.
Eventually, we’ll go to the swivel anchor – but using the removable bolt was a good proof-of-concept.
It should be noted that working one’s hiney off and enjoying scenery like this is very good for the soul.
Last piece: The port-a-wrap.
One of my crew thought it was a t-post pounder. It’s a fair guess – that’s a lot of steel. It’s critical because it terminates the Amsteel without knots. It’s also really easy to adjust.
Quick summary: I hiked two totally untrained volunteers up about 800 vertical feet of challenging trail. We carried all the gear and then fiddled around with setup and adjustment for a few hours. Once it was all set up, we moved about 2,000 pounds of rock in about 2.5 hours total time.
Pros (in addition to what’s covered above):
- All of the individual components are of manageable weight. A 7/16″ 200′ steel cable would be less than fun to carry up. A bigger griphoist would be less fun to carry up, and would still need the bigger blocks.
- The removable bolt worked like a charm. It’s frustrating to wrap a rock and then watch the highline do nothing but pull slack out of the wrap while the rock stays on the ground. The removable bolt is a much more “direct” connection to the skyline – not a lot of wasted energy flying the rock.
- When steel cable breaks, there are pretty unpredictable results. When Amsteel breaks, it loses that energy really quickly – it just kinda puffs up and falls to the ground. Safer for the crew.
- The bigger blocks are heavy
- Amsteel is kind of delicate. Care should be taken to keep it away from abrasive edges.
- Amsteel can get caught between the sheave and the housing (so can steel, but I’m a lot more worried about a pinch on Amsteel). Diligence is required.
- Removable bolts are like any active climbing hardware. They can be tricky to get out.
- The distance between the Griphoist and the first spar tree is critical. Without enough distance, it will be hard/impossible to pick up or lower rocks.
- If the Griphoist and the termination aren’t adequately separated, the Black Rat can spin 180 and make the cables into an “X”.
A side note: My nephew Daniel came to help with this. He’s a 17 year-old that is currently reading tomes about Robert Moses and Deng Xiaoping. For fun. On summer break.
Despite the death march up the hill, he had a good time.
Sometimes, we trail types like to talk ourselves down (it helps ease the blow of what some others say about trail guys). Days like this remind me that trail people are usually pretty intelligent people who’ve figured out that working outside, working hard, and doing work that will last is about as rewarding as can be.