The most recent odd bicycle that I built is Sparkle Pony. The base was an old Schwinn BMX frame that had been discarded and was found leaning on a dumpster at an MIT loading dock. I extended the front fork to make it more chopper-like, which gives it a bit more style and groove when riding:

But the real innovation was this improvement to the rear caliper brakes:

Heck yeah! It shoots sparks when the rear brake lever is engaged. There’s a coaster hub on the rear wheel, so the caliper braking system isn’t necessary, it’s just redundant.

So, how? The core component is a rod of mischmetal, also known as firesteel. It’s a blend of metals that sparks easily when struck by a hard object.

First I sanded and scored the sidewall on the rear rim to remove the paint and rough it up. Then I coated the sidewalls in superglue, and shook coarse sandblaster media onto them, making an abrasive rim. When I spun the wheel and pressed the mischmetal rod to the abrasive rim, it shot sparks. Great!

Then, I cut two small pieces of mischmetal rod with a hacksaw. It cuts just like regular metal, only with lots of sparks. This also has the side effect of leaving some metal bits caught in the hacksaw blade, which causes some slight sparking the next few times the hacksaw is used.

I drilled a small hole in one end of each piece of cut rod and threaded the hole with a tap. This allowed me to attached the mischmetal rod to the slot that normally holds the brake pads. I carefully adjusted the “brakes”, orienting the mischmetal so that it strikes the center of the sidewall on the rim when the brakes are compressed, and this was done!