Archive for July, 2013

Sparkle Pony

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!

Roll Bounce

So in the past year I’ve built two more freak bikes.

The first one, which I’m calling Roll Bounce, looks like a normal bike at first glance:


It started as a trashed full-suspension Pacific frame and fork. I stripped off the useless parts (most of it), cleaned off all the stickers with naptha and greased up all the bearing surfaces that were salvageable. What goes well with suspension? More suspension! Asking around, digging through spare parts bins and some generous donations landed me a suspension seatpost:


a suspension stem:


and even suspension handlebars. That’s a vibraslap being used as the bell:


The result is a very floppy and suspended ride, which helps a lot because:

The hubs are not in the center of the wheels! They are offset by one centimeter. The reason why isn’t the point — the point is — how?

Loads of thanks to Gideon Weisz for the innovation that made this possible. Gideon is a jeweler and, among other things, makes rings. He was creating ring modeling software when I mentioned my off-center wheel project, and Gideon offered to modify his ring modeling software for spoke calculations. When building wheels, it’s important to know how long the spokes should be — too short, and they won’t reach the rim; too long and they’ll poke into and puncture the inner tube. However, all other spoke calculators assume that the hub will be in the center of the wheel. Gideon’s spoke calculator can apply an offset to the hub and calculate individual spoke lengths! Wicked cool.

With the spoke lengths in hand, I collected 72 spokes of varying lengths over the course of a few weeks. Not all spoke lengths are readily available, so this involved scrounging some from parts bins, extending the threads and trimming spokes when I found close matches, and hunting for others from local bike shops. I also had a few spokes custom cut at Paramount Bicycle; thanks Tyler.

Then I built the wheels, lacing them with a standard three-cross pattern. They came together surprisingly quickly and the spoke lengths worked out perfectly.

Riding this bicycle is like riding on a slowly undulating, rippling surface. It is pretty comfortable but the constant bobbing can get disorienting after a while, and it’s a pretty rough ride when bombing down hills. I took meclizine for motion sickness the first time I rode it for a few hours but have ridden it a few times since without chemical assistance and had no problems. Huzzah!

I’ll blog about the next build in another post.