Safety Fork, the

This morning, I found myself thinking about the Science Museum of Minnesota. See, they have this exercise bicycle there, but instead of some sort of adjustable-resistance wheel, the pedals crank an electric generator. The generator powers a car radio, a fan, a dozen or so light bulbs, and—if one can turn the generator fast enough—a bell.

When I was at the Science Museum on March 4^th (for Sarah’s and Jenn’s birthday celebration), I couldn’t turn the generator fast enough, and that’s what I was thinking about. I’m pretty sure my problem wasn’t that I’m not capable of generating the two or three hundred Watts of electricity required. I’m pretty sure my problem was gear ratios.

Or rather, I’m pretty sure my problem was the lack of gear ratios. On a normal street bicycle, I have a multitude of ratios so that I can choose appropriately for low-rpm, high-torque situations like riding up hills or for high-rpm, low-torque situations like building speed on a level, all while turning the pedals at a comfortable speed. The generator bicycle had a single, fixed ratio which, I am now convinced, was the source of my difficulty. The pedals weren’t difficult to turn, there was just a point at which I couldn’t pump them any faster. I needed a higher gear ratio.

If I went back to the Sceince Museum with parts and tools, do you think they’d let me install a smaller sprocket on generator or a larger one on the pedals? I think they should. Better yet, they could add two or three more ratios to the permanent demonstration—they could teach lessons about power and gear ratios at the same time. That would be excellent.¹

¹Or, in my parlance of the 4^th, excellently.