Introduction: Prototyping Magnetic Boots!
Walking across large, metal pipes in search of urban adventure, my inner voice joked, "Hey, magnet shoes would be handy right about now." Well, no arguing with that! Off to build my very own magnetic shoes!
This tutorial is an overview of my build process for a magnetic boot prototype in hopes of inspiring you to build and test your own fantastic, whimsical ideas! 'Cause seriously, making ideas come to life feels like a superpower.
Step 1: Design & Planning!
1. Plan out general shoe design.
To hang upside down safely, each boot needs to (approximately) hold my weight. I weigh about 130 lbs, so that means each shoe needs to hold 130 lbs. There are lots of ways to do this -- thirteen 10-lb force ("lbf") magnets, six 25-lbf magnets, etc.
After testing with 15-lbf magnets, I opted for 8-lbf magnets that were smaller, circular, and thinner.
2. Prototype, prototype, prototype!
The very first prototype was just a bunch of magnets on a piece of wood. This helped determine specifics of the project, like magnet placement, screw type, etc.
I also experimented with various shoe types and tried different ways of orienting the magnets to maximize the perpendicular magnetic field strength.
Step 2: Materials
-- Sturdy Boots
These had to secure my feet (aka no slipping out) and withstand my body weight. I found a pair of sturdy (although rather large) snowboard boots at a local thrift store which work as a first prototype.
-- Rare earth (neodymium) magnets
Small, thin-ish (< 1/4" thick) magnets with a 10 - 15 lbf rating (see previous step).
-- One screw per magnet (or per magnet hole)
Use screws with a length shorter than the sole of the shoe (so they don't poke your lil' feetsies.. or add some sort of rubber sole inside).
-- Suggestion: One washer per magnet
Supposedly, the washer helps increase the magnetic field of the exposed surface. I haven't calculated this or done any serious research, so at this point it's just a design suggestion.
Step 3: Tools
Step 4: Build Process!
1. Level bottom of the boot with a CNC router (or other available method).
Clamp the boots to the CNC table with the bottom facing up -- a piece of wood was helpful to keep the boots straight. Set the zero point of the CNC to be the lowest point on the sole of the shoe, then use a large bit (ours was 3/4") and level the sole of the shoe to the zero point.
2. Mark boot with tape for location of magnets.
3. For each magnet, drill in screw, magnet, and washer into the bottom of shoe.
Step 5: Testing & Observation!
To test the boot, I stuck it on a roof beam and pulled downwards. I added more magnets and repeated this until I couldn't pull the boot off by hand, then (slowly) tried to hang from it.
Lessons learned during testing:
1. I ended up using waaay more magnets than I thought, so it is probably worthwhile to calculate how the individual magnet fields are adding together.
2. Magnets need to be level to maximize the total magnetic field strength.
3. There is a limit to how close you can place each magnet depending on the shape and size of its magnetic field. Smaller, round magnets are easier to work with than large, rectangular magnets.
4. Don't place magnets close to parking passes (or other electronic devices). Also keep them far, far away from large containers of screws.
Step 6: Results & Next Steps!
At this point, my magnetic shoes are more magnetic "gloves" (lol thanks @jayludden :D). But! I can successfully hang from one boot, so the concept works!
The lessons learned from testing will help improve this prototype design. Currently awaiting more magnets for the second boot (used most of them for the first one), trying different magnet orientations, and searching for a spot to test them upside down.
Stay tuned, will have them up and running, er, well, hanging, soon!
Many thanks to: Tinker Tank at Pacific Science Center for being my build and test center, and to Richard Albritton for the CNC help!
