Gear Harness Carabiner. Auto Release.

This tool allows you to lower an item, release it, and then retrieve your rope without unhooking it yourself. It spares you the back and forth. I started thinking of it while bringing Christmas decorations down from the attic. This is an entry in the BUILD A TOOL CONTEST. Check it out here.

It has been particularly exciting for me because industry professionals have contacted me about it. This includes a Cirque Du Solei style circus school, arborists, and a wind turbine technician.

The wind tech has a time sensitive job where this carabiner might help. His team of rope access workers are removing parts from a wind turbine then lowering them down. As of now, they require a tech to wait below and unhook the parts. I don’t know for sure but, I think they want to use these workers on as many towers as possible and not lose any to ground duty. Also, a drop hazard is preset for the worker below. I haven’t completed a production run yet but, the wind tech asked if I could send him three to evaluate them for this job.

I took a few prototypes and prepared them to ship out. This instructable shows how I went from a crude proof of concept to a working prototype.

My first thought was to create an "overbalanced" hook. That idea was based on a hook flipping over once tension was released. You can see a couple of my sketches in the last pictures. The problem here is that the hook must have enough clearance to rotate and the item being lowered might interfere. I moved on to making a "four point harness hook" which could be easily undone.

Thanks to my trusty stock of coat hangers, I could get an idea of how to go about this. So, I bent a section of wire into the letter "g". If anything, this crude prototype showed me that I could at least make a reliable harness from this shape.

I moved on to a making another small-scale sketch. This time I cut it out and super glued it to a piece of aluminum. Once I cut it out from aluminum, I was closer to the final design.

Thanks to Autodesk, I was able to create this design and modify it as many times as needed. It took a lot of rotating and off-setting.

I wanted a shape that was easy to grip so I settled on a 3" circle. I placed a square in the middle of it and continued the design based on 1/2" rope.

I added notches to the outer circumference to correspond with the valleys of the hooks.These notches were originally intended to allow this design to be used a gear tie (just like my fishbone design) but, it turned out, they would also allow this carabiner to auto-release.

Once I was happy with the design, I sent the file off to the laser cutter. A couple weeks later, I got a box with five aluminum blanks.

The production model will be anodized black. For the prototype I am using flat black paint. Coloring the frame adds to the look of the carabiner by highlighting the beveled after milling.

I sprayed the one side, waited for it to dry, and flipped it over to paint other.

I have been looking into hobby CNC milling machines and saw that they use a standard router. With this in mind, I thought I could use my router table to mill a few prototypes. However, I had to solve a couple problems before I could do this.

First, I had to reduce the hole diameter in the table. If not, the aluminum blank might accidentally be pushed below the table surface causing a dangerous jolting. To fix this I used a small piece of sheet metal with a hole just big enough for the router bit to poke through.

The other problem was that the surface of the router table was scratching the surface of the frame as I dragged it along the bit. Adding layer of cloth helped but didn't eliminate them all together.

I carefully chamfered the edge on both sides, removing about 1mm all around.

This part was fairly difficult since thick music wire is hard to bend by hand. I used 1/4" bar stock, vise grips, and an aluminum dowel drilled with a hole. The spring wire came from the hardware store (Lowes).

First, I measured and marked the wire at the mid point.
I placed the wire into a notch I filed into the bar and clamped it down with vise grips. This helped keep the wire perpendicular to the bends as I set them.
I bent the ends down, giving the wire a "U" shape.
Next I measured where I wanted the gate to land and marked one side.
I clamped it down, and put in an "L" shaped bend in one side.
From here, I placed the spring into the carabiner, marked the other side, and then bent that side down too.
I used a diamond wheel to trim the spring ends down to length and remove any burs.

To form the radius, I clamped the spring to a socket and used a special tool I made from electrical conduit to pull it around.

Finally I pried the spring open (so it will snap shut) and installed it in the frame.

This started out as a four point box hook. As I got further into it, I found it could do more. I wasn't sure how or if I could get this prototype to auto release but, I had to start somewhere. It's been fun to find different ways to tie this carabiner but more importantly, it has given me a starting point for a future design on a professional model.

Thanks for reading.