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.
Step 1: Proof of Concept
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.
Step 2: Auto-cad 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.
Step 3: Painting
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.
Step 4: Milling
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.
Step 5: Spring Gate
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.
Step 6: Finding Uses
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.
slobokv made it!