Upgraded Slackline A-Frames: New Design to Hold the Line Steady

My first set of Slackline A-Frames work fairly well. I’ve set them up and used them multiple times so far. However, one thing became clear after I started using them with people who do tricks – the ends of the Slackline are not held static where it passes over the A-Frame. This is an important feature to have: a steady, non-sliding line. I came up with a way to add the feature to my A-Frames.

IMG_2741First, I’ll describe the problem. As shown in the above photo of the original design, the Slackline passes over a piece of 1/2″ pipe. The pipe is 12″ long or so, and there is nothing to prevent the Slackline from sliding sideways (left to right). This happens predominantly when a slacker on the line does a move called “surfing”. They kick their legs out sideways and swing their feet back and forth in an oscillating motion. This action causes the Slackline to slide back and forth on the 12″ piece of pipe. The biggest downfall of this is that it abrades or melts the line just at the point where it crosses over the pipe. In addition, it makes for non-static ends on the Slackline. This is opposite of a tree-based Slackline, where the ends do not move left to right when in use, even while surfing.

The solution I came up with is fairly simple to implement. and can be made of parts from a hardware store. First, I made two of the U-brackets shown below. Each U-bracket is made from 1/2″ black iron pipe and some fittings. Each one uses the following parts:

  • four 90 degree elbows
  • two 4″ nipples (although any length under 6″ is OK)
  • one 3″ nipple
  • two 2″ nipples.

The only critical part is the horizontal 3″ nipple. The goal is to have 2″ (width of the Slackline) between the two 90 degree elbows once they are screwed onto the 3″ elbow. I was able to get the elbows to screw in 1/2″ on each end of the elbows, leaving 2″ for the Slackline. I used parts that I had laying around as well as pieces I bought at the store. Screw all the pieces together so they look like the picture below*.

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The second thing I did was drill two more holes in the top of each A-Frame to accommodate the U-bracket. These are 7/8″ diameter holes, to accept the 0.840″ outside diameter of 1/2″ black iron pipe. The holes go all the way through the plywood and the 2×6 legs – that way you can use longer nipples if you prefer (instead of the two 2″ nipples).

IMG_3616

The picture below shows the solution in use. The whole idea is to create a channel where the Slackline sits as it goes over the iron pipe. As you may notice, the channel I have created isn’t quite 2″ exactly in width. That is mostly because of the way black iron pipe is put together. Threads at the joints of black pipe are tapered. For industrial applications, fittings are screwed together until the tapered threads seal together. The joints are not an exact science, so the fittings don’t always end up completely seated, or even seated by the same amount. This is one flaw in my design, and it means I need to tighten my fittings a bit more (one or two turns, by the looks of it).

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In any case, the idea was to use off the shelf parts to create a steady point for the Slackline to pass over the A-Frame. Here is another picture of the setup in use.

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Of course, the length of all of the pieces of the U-brackets can be adjusted to fit your needs. As long as the Slackline clears the top of the A-Frame, things will be fine. I should probably shorten the 4″ nipple to reduce the leverage the U-bracket has on the A-Frame itself.

Hope you get the idea.

*You may have noticed that my 3″ nipple going horizontally in the U-bracket doesn’t quite look like a piece of black iron pipe. This is because I milled the 3″ nipple to remove the extra threads present once the 90 degree elbows are tightened to this nipple. You can get around this by wrapping the 3″ nipple with duct tape, or possibly by filing the threads down by hand. Otherwise, the threads will cut the Slackline and reduce its life.

Home Made Anchors

Today I have a couple pics of some anchors I made at home. I was able to procure some 6″x6″x0.25″ plates of 6061-T651 aluminum. I cut these down into 2″ strips, laid out some hole patterns, and drilled/milled the stuff until I was left with two pieces for each anchor.

A trip to the hardware store, and I put these together using shoulder bolts, spacers, and nuts. I still need to add some sort of strap to them for connection to the tree, my plan is to sew some dog-bone style straps to one end of the anchor.

Each anchor replaces a rap ring and a carabiner, and the eventual goal is to use this type of anchor on a longer line (> 100′).

So far, I’ve made three of these, and they work great for the 50′ lines I usually set up. I don’t have a method for testing their break-strength, but calculations show they are fairly heavy duty. Here are a couple photos:

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Expanded Fixed End Anchor Technique

Today’s post includes a video below.

Expanding on my thoughts about the “double-bight” line locker, I have modified the method I use to attach the fixed-end of my Slackline to a tree. Thinking about how this works, I was able to eliminate the water knot and replace it with a double-bight line locker

This method has one advantage, and one disadvantage as compared to using a traditional water-knotted anchor.

Advantage: there is no knot in the line. In general, knots tend to weaken the anchor. I am not sure how much, and I know the weakness is reduced if you use a third strand of webbing to beef up the knot. (See here)

Disadvantage: There is only one level of webbing going around the tree. With a traditional water-knotted anchor, the anchor is doubled around the tree. This puts less stress on the anchor itself. However, for shorter lines (< 100 ft), I am not sure how much of an issue this is. Here is a photo of a fixed anchor some guys made (red line) to secure a 70′ Slackline. It uses only one wrap around the tree (similar to my method) but uses a knot (which my method eliminates).IMG_2405

Below is a photo and link to a short video (1 min) describing what I’ve done.IMG_0965

I consider this an extension to my series on Anchors.

Anchor Basics Parts 2

Today’s entry includes video below.

This is the second entry in the series on slackline anchors. (click here for Part 1)

The Part 2 video below describes three types of anchor setups for the adjustment end of a slackline (the part where you tighten it).
Now, get out there and start slacking!!

Inspiration for this idea is taken from Adam’s “Strength of 3 men…” video on NWSlackline.

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Slackline Anchor Basics

Today’s entry includes a video below.

Today, I decided to add a video about Slackline setup. This is part one in a two part series on anchors. We discuss the anchor at the fixed end of the line (the end without the pulleys/tightening system).

Here is the short (2 min) video:

More Info:

Want to learn more about making anchor slings and water knots? Click here.

Want to learn more about Rap Rings? Click here.

Want to learn how to setup a basic primitive Slackline? Click here.

(again, thanks to Adam over at NWSlackline for these great instructional articles)