Ex Bibliotheca

The life and times of Zack Weinberg.

Saturday, 4 October 2003

# 6 PM

I'm sitting in Cafe XO eating lunch and watching people go by. There seem to be a lot of women not much older than me (guessing) with babies or small children. No accompanying men; are they all glued to the baseball game? Or are these single mothers? Lesbians? All are possible, this being San Francisco.

The Muni J-Church line runs down this street. Muni's modern streetcars have air suspension, you can see these big disk-shaped rubber air bladders between the wheel clusters (there's an official word for these things but I can't remember it, argh) and the undercarriage. Every time I see one go by I have this worry that they're going to blow out. How can a rubber bladder possibly support that much weight? This is silly, of course. I don't have the same reaction to the tires on trucks, and that's exactly the same thing. Perhaps the difference is orientation. We tend to think objects are stronger against compression forces if they're fatter. A tire on a truck looks fatter in the direction of the load, because it's oriented that way. The suspension bladders are lying on their flat sides and look awfully thin.