Wednesday, December 3, 2008

Black Friday Blues...

This gave me quite a chuckle. It's from CycleDog in OK.

The womenfolk were out shopping. I was bored. I could watch Eastern Yahootie State beat the snot out of Western Yahootie State, but why bother?

My commuter bike's computer had died. The battery failed - again. I decided to find a way around the problem. There was an old calculator with a solar cell in my junk box, but just for fun, I decided to try a bigger solar cell meant to charge a car battery.

Why stop there? The bigger array offered more power, so I could add a few extras.

Another junk box yielded an ancient TRS-80 type 200 laptop. The solar cell would easily power it, but for surges I decided to add a small battery too. With some Hall effect devices and strain gages, the computer could monitor speed, cadence, and various forces applied to the bike frame. I could actually measure the lateral stiffness and vertical compliance! Yes, it's real-world geekery, but I was bored. I fabricated brackets out of old bike parts, angle iron, and some bits stolen from kid's broken toys. It wasn't pretty, but for a quick lash-up it would do.

All that extra power only added temptation. I mean, what self-respecting electronics geek could ignore it? A few calculations revealed that I'd only be using about a quarter of the energy on hand, so I immediately added a few other goodies: a GPS system, a old video camera, and a cell phone for mobile Internet access. This all required more wiring and cables, of course, and the video camera needed a short mast since I wanted overhead shots.

So far, I'd stayed within the law as far as the FCC was concerned. The next step was going to be tricky. I wanted to rig up a proximity sensor that would switch on the camera as a vehicle approached from behind. I gutted my son's old toy baseball radar gun, but it was designed for very low power and short distances. More power would make it operate over greater distances, so I scrounged the magnetron tube from our old microwave oven. Now kids, don't do this at home. It's a job for a professional.

The maggie tube and power supply went onto the rear rack. I had to find a bigger battery and ended up with an old car battery back there too, as well as an inverter for the higher voltages required for the magnetron. An FCC inspector would have a heart attack if he saw this, and drafting closely could offer some hazards - like getting cooked internally. But this was just a quick lash-up.

A trial run was in order. I pushed the bike out of the garage and set off down the hill. It was immediately apparent that the extra weight caused problems. I wobbled wildly and steadily gained speed. The rear tire blew with a deafening bang! The wheel thumped a few times before all that weight on the front end caused the fork to collapse. I vaguely remember flying over the handlebars.

Witnesses said the following events happened in short succession. The bike had barely stopped moving when a short circuit caused the car battery to overheat and explode. Bits of casing peppered houses and cars. Someone called the cops, the bomb squad, the fire department, and presumably an ambulance in that order. The wiring and cables on the bike caught fire, resulting in a brief but intense blaze that actually melted the aluminum frame.

But like I said, that all came from various witnesses. I'm sitting in a cell at the local police station, waiting for an interview with Homeland Security about the alleged bicycle bomb. This is the bright side. At least I didn't have to go shopping.


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