Crunching the Numbers

Author: Harv

Every time I swing by the Bicycle Kitchen, turning from Melrose onto Heliotrope, I flash back to my student days at Los Angeles City College which is a few blocks away. Back then, there were no messenger bags and very few back packs available. My book bag was a war surplus (World War I, that is!) saddle bag. On damp days you could still smell the horse. Just kidding, it was NEW surplus. In it were my engineering text books and my slide rule. Every engineering student had the requisite slide rule for cranking out the answers to those number-laden math and physics problems. It would be a few years before pocket digital calculators were available and affordable.

I moved on to Cal State University at Los Angeles and graduated to take my place in industry. I had been taking computer design courses and could see the future of slide rule calculations becoming as popular as penny-farthing bicycles. I passed my slide rule on to another student and entered the world of IBM main-frames and punch cards.

What does all this have to do with bicycles? For me, plenty. The only slide rule I have today is a cheap, small, plastic unit missing its cursor. But I use it constantly for calculating gear-inches, wheel diameters, gear teeth requirements, road speeds, cadences, etc. It actually is much simpler and more direct to use than a desktop or pocket digital calculator. You can set up ratios on the C and D scales and pick off the various values of the above parameters by moving the cursor to that new wheel size, tyre size, chain ring tooth count, or cog size. Inch to Metric conversions can be made with the same ease. Since my little slide rule does not have a cursor, I just eyeball the various values without moving anything. With a digital calculator, you have to punch in the values, one digit at a time, and all the operands (+, -, /, = ) for each option. Then repeat to get new optional values. Tedious. Boring.

You can still get slide rules cheap on ebay. An old aluminum Pickett is 5 or 10 bucks plus about 5 for shipping. I am thinking about a new-old-stock Pickett for $20. This would be about a foot long and with a nice cursor to save my old eyes from squinting at those tiny scales on the pocket-sized plastic jobbie. Unless you are going to use the log-log-decitrig scales, slide rules are quite easy to learn to use. Think of how you will impress your friends and how quickly you can whip out those gear-inch calculations for tyre size changes and various chain ring/cog setups. As I am constantly experimenting with these components on my test-mule bikes, I have to make these calculations frequently.

I am looking forward to the new year, crunching those numbers on my new analog slip-stick. As you may have suspected, I still prefer DOS (5.5) to Windows and I program in command line mode. I composed this blog in a DOS programmers text editor called Q-Edit. But I havemanaged to advance beyond Edlin. :-)

MENU