i was all ready to go today. got a NOS stewart warner "cadet" speedo, and calibrated the odometer to my wheels (the directions say "for 24" and 26" wheels," yet there's no way to change between the two.)
to calibrate it, i marked a spot on my tire, rolled it through a full revolution, then measured that. installed the speedo and put a zip tie on one spoke, then hooked up a drill with a skateboard wheel as a friction roller, and let 'er rip.
counted how many times the ziptie spoke hit the fork as the odometer spun through a mile. (don't even ask how long that took.)
then i took the revolutions, multiplied it by the tire dimension, and was surprised that i was only about 100 feet off. given that this wasn't under load (which won't make that much of a difference) and i coulda missed a turn (or twelve), and i dunno if the numbers on the odometer where exactly zeroed out, that's pretty freaken close.
if the odometer is correct, i'm pretty satisfied that the speed would be correct, but i wanted to do some timed runs to make sure.
so, i was pretty satisfied with a 100' discrepancy in a mile, so i took off to my secret testing spot. the Santa Ana river trail. it's a bike trail with mile markers, there's some almost straight mile runs, and it's nice and smooth. ignoring the fact that motorized bikes are prohibited (anything for the sake of science) i had a stopwatch mounted to my handlebars, within easy access on my left grip.
my plan was to make some timed speed runs, calculate the times against the speedo reading, take some pictures, and post some proof.
BUT...
the speedo stopped working 2 blocks from my house, my camera fell out of my jacket pocket and the battery door broke off (still works with some tape,) and i ended up just going to get a burrito.
turns out, my NOS speedo cable snapped. i mean, it was 60 years old. i already figured out how to fix it but i need to go to the junkyard for a drive cable from a car, then the liquor store for a pack of smokes and a 6pack (that's about how long it takes to calibrate it.)
so the only times i have to post, are these:
burrito store's about a half mile, took me about a half hour there and back, including the time it took to make me a carnitas burrito.