Friday, 6 June 2008

I *did* pass thermodynamics - honest!

Bike: 37.2km @ 1h15 (Kanata loop)
- includes traffic lights - excludes a flat tire!

That's right - I flatted on this morning's ride. I was only 15min into it, and it was just before 6am, and I was in the middle of (urban) nowhere. I shouldn't complain, 'cause it's the only time I've actually got a flat during a ride.

What's ironic about all this is that I was planning on flatting a tire on purpose this weekend so I could practice using CO2 cartridges before my upcoming races. I guess my practice came a day early. So I took the tire off and attached the inflater to the cartridge without leaking CO2 (passed Test #1). Replaced tube and put tube and tire back on the rim without pinching the new tube (passed Test #2). Push the inflater onto the stem - nothing. Push harder - nothing again. Loosen inflater to see if cartridge has been punctured - gas spews all over, and I quickly close it off again. Crap.

So the engineer in me comes out (yes, I'm actually one, and I'm licensed) and I analyze the design of the adapter. At this point I realize that I'm using it wrong, and that the slider that opens the valve wasn't allowed to move the way I was holding it. Duh.

Now I hold the adapter and the cartridge (this is important for the next bit) and inflate the tire nice and quickly...and very cold-ly! It's at this point that I realize that my finger is frozen onto the cartridge! My first instinct is to rip it off, but past childhood winter experiences prevent me from doing that, and I suck up the pain a wee bit longer to try to thaw my skin off it (it worked). Tire inflated properly (finally) and all body parts are intact (passed Test #3).

It's at this point that I curse myself silly for what appears to be a frozen blister on the pad of my finger. Thankfully, just the upper layer of skin was frozen (solid) and it thawed nice and quickly (and it doesn't appear as though I got frostbite from it). But I keep cursing. Sure, I'm not a chemical engineer nor a civil engineer (I studied electrical engineering, as well as computer science) but every engineer-to-be learns a very simple formula in their first year of studies:
PV = nRT, where
  • P = pressure
  • V = volume
  • n = number of moles of gas
  • R = universal gas constant
  • T = temperature.
It's the Ideal Gas Law. You'll notice that pressure and temperature are directly related, which means that when you drop one, the other drops too. That's why the little cartridge got so damned cold when it went from some ungodly sealed pressure to about 90psi in one or two seconds.

For some reason, I can still remember the mass of an electron, Plank's constant, partial differential equation solving, and a multitude of other advanced topics, but not the Ideal Gas Law. Hell, I probably first learned that in high school.


But what's really important, and what was the real litmus test, was that the tire was successfully replaced and I was able to finish my ride (albeit a little shorter, since I still had to do this thing called "work").

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