Before I make anything, I always look for existing devices that already exist that I can model my project after. I knew clap-off bras clearly already existed somewhere (Syria). So, I looked all over the internet for a clap-off bra so I could see how the Syrians made it work. Despite hours of searching, I couldn't find a single instance of one that wasn't poorly 'shopped in 4chan
This lack of reference annoyed me, but by no means stopped me from my pursuit. My first though was to use a solenoid. This failed. It got too hot. I immediately wrote off all electromagnetic solutions as potential burn hazards. In retrospect, this was a horrible mistake.
My second thought was to build a tiny spring-loaded quick release mechanism. Of course, making a spring-loaded quick release mechanism is a lot easier to speculate about than actually build. This too ended in disaster. I took some time off from the project.
I then partnered with occasional collaborator Noah Weinstein
. We discussed various possibilities for opening the bra and finally decided upon exploding the bra off. Unsurprising, the initial test demonstrated that an exploding button in the front of a bra was going to end in disaster. Yet, this did give us another idea.
We finally decided that we were going to get a large metal button, coat it in nitrocellulose and create a brief incendiary event that would burn the thread away. Hence, when the thread burns away, the button would fall off and the bra would open. Fortunately for whatever poor girl who was going to have to wear this, that approach did not work either. No matter what thread we used, we could never get it to fully incinerate and release the button. This disheartened us and the project was laid to rest yet again.
A year or so passed and I decided to try an idea that Noah and I discussed in passing, but never executed upon. The fourth iteration involved pulling the pin out of the center of a hinge, such that by removing the pin, the bra would separate. We initially didn't want to do this because it would involve using a large motor attached to the bra and this didn't seem very 'classy.' Nonetheless, I figured I would give it a go.
I went out and bought the smallest servo motor I could find and on the first attempt to pull out the pin with the motor, I tore the gears apart and the weak little servo was destroyed. As it turns out, pulling out a pin that runs vertically using lateral force is nearly impossible. Once again, I found myself in overly-complicated mechanical quick release territory. I consulted 'ridiculous clothing' expert Rachel McConnell
and she surveyed the situation and surmised that my current approach was pretty hopeless. Normally I would just ignore the project for a few more months, but I was hell bent on just finishing the darned thing.
In talking to Rachel about my long list of failures, I recounted the one idea someone suggested to me early on that I had yet to try. Basically, this involved using a small electromagnet and a strong rare earth magnet and polarizing the electromagnet in such a way that it repels the rare earth magnet. Rachel supposed this would work and I supposed I would give it a try.
So, I went to Radioshack to get some magnet wire to wind an electromagnet. They didn't have any. I went to another they didn't have any either. I went to a third, and they too didn't have any. I headed back and had a moment of inspiration. An electromagnet is basically a coil with some metal in the middle. I just needed to find something with a coil. I tore apart my work station looking for a decent-sized coil of any sort, but to no avail. I finally turned to my office-mate - and all-around good guy - Paul Jehlen
, and said to him, "Hey, you wouldn't happen to have any solenoids or big relays or anything with a coil in it?" He produced a defective 5V DPDT relay. This was perfect as it is essentially just an electromagnet that controls a switch.
I carefully cut open the DPDT relay, an exposed the coil. I stuck a rare earth magnet to the end and then powered it up and tried to repel it. This didn't work. The magnet was too strong and it would just reposition itself.
Out of sheer curiosity I checked to see how strong the magnet was with a screwdriver that I had lying around. To my amazement, the electromagnet had a fair amount of pull and was able to lift the screwdriver at 5V. I got to thinking, "I wonder what would happen if I gave the 5V coil a full 9V?" So, I did just this an discovered that the coil didn't heat up as much as I had expected it to and the magnet got significantly stronger. It was now apparent to me that the simple electromagnet inside of a relay powered at 9V was going to get the job done.
Now that we know a bunch of ways not to make one, it is time to actually go ahead and get the job done.