On Bicycles, and.... what else is there?

Chris Horner published his blood values on his web site . I didn't have much interest in this. Indeed, I was much more interested in the America's Cup then in the Vuelta. It's not because I'm not interested in bike racing. Rather it was because it all seemed so unreal, so "not normal", that I just wasn't interested. Horner won. Curious. The data were published in raster form, and would require transcription (or OCR) to do anything interesting with. I didn't have the interest + time to do this. But then I saw this blog post which links to a spreadsheet with the transcribed data. Back in 2009 I made the following plot, which I posted to my blog the following year, showing the reticulocyte percentage in Lance Armstrong's blood, which he published online, plotted versus his hematocrit. It's generally considered a sign of transfusion when the hematocrit increases with a low reticulocyte percentage. Reticulocytes are the young blood ce...

Governor Brown, after vetoing two, finally signed a 3-foot passing law for the state of California: AB1371 . Hats off Jim Brown and the California Bike Coalition for their dedication and persistance to this issue. It was very much on my mind this year as I experienced several close passes by heavy vehicles. With the status quo of "no blood, no foul", these passes were effectively legal, since what constitutes a "safe pass" is so vague. Here's the text of the bill-now-law, which I'd like to review here. Note I'm an engineer, not a lawyer, so I'm just interpreting the language, without any insight into lawyer-specific knowledge: SECTION 1 . Section 21750 of the Vehicle Code is amended to read: 21750 . (a) The driver of a vehicle overtaking another vehicle or a bicycle proceeding in the same direction shall pass to the left at a safe distance without interfering with the safe operation of the overtaken vehicle or bicycle, subject to the limitatio...

I live in San Francisco and was at the race. I was glad every race Oracle won until the final, because the racing was absolutely incredible, and I wanted it to continue. But it's clear New Zealand came into the finals better prepared, and racing should be about the best competitor winning, not about opening the spending floodgates to gain an advantage. So good job to Jimmy Spithill and crew for sailing an excellent race in the end, but I feel for the New Zealand fans who saw the advantage of their superior preparation squandered. I hope the rules are streamlined before the next iteration to reduce the influence of big money. I was amazed at the number of Kiwis who made the flight to watch in person. It was a difficult series for that, since the schedule with the strict wind limits was so indeterminate. If fan support could directly contribute to boat speed, Emirates Team New Zealand would have won the race.

After my last post, I commented that my analysis was obviously flawed, because it would lead to the conclusion the winning bidder had a 100% chance of winning. There were two obvious points of weakness in that analysis. The first is I assumed the expectation value of the number of bidders was the number of bidders, not counting my friend. I don't count my friend because his presence wasn't random (I specifically picked this auction because he was there; I didn't pick it at random). However, that assumption is obviously just a guess. But lacking other information, it is the best I can do. The next approximation I made was that the chance a random bidder was better than my friend's bid was the number of bidders who ranked better than my friend. This was 25%. This seemed a reasonable assumption, until I apply it to the case my friend wins the auction. In that case the result would be 0%. That's obviously wrong. So what I assume is all bids can be mapped onto...

A friend of mine big on a condo and lost, ending up 3rd/9. The friend was convinced the bid had been too low. I wasn't so convinced: after all, what if the two people who'd bid higher hadn't bid, and no other higher bidders had shown up? It's an inherently probabilistic process. If the goal was to win at all cost, you'd just bid the most you could possibly spend every single time. So to estimate the chances that bid would have won the bid requires estimating two probability distributions: the probability distribution of the number of bids and the probability distribution of the values of those bids. Without any information available on these, it's necessary to guess. The first approximation is that bids are uncorrelated: whether someone bids, and how much, is independent of how many others do so. The next approximation is that the bids are statistically representative of the probability distributions. So not counting the friend, there were 8 other bids...

The last time I considered the constant cadence approximation as it applies to circular chainrings. Recall the principal issue is that the constant cadence approximation makes the following assumption for each pedal stroke: = × where ω is the angular velocity of the pedals, τ is the propulsive torque, and brackets signify a time-average. The error from this approximation is obviously: × − which is fairly trivially shown to equal: − ) × (ω − )> which is proportional to the correlation coefficient between torque and angular frequency, where a positive correlation results in an underestimation of power. Angular frequency is proportional to what I refer to as "instantaneous cadence": the rate at which the crank arms are revolving. So the issue comes down to whether the instantaneous cadence is correlated with applied torque, or similarly, if it's correlated with applied power (assuming applied power fluctuations are due more to torque changes than cadence c...

A big issue with power accuracy is to not only get the force versus time accurate but also to get an accurate cadence versus time. Power is the instantaneous product of propulsive force times pedal velocity, pedal velocity being proportional to cadence multiplied by crank length, and therefore errors in cadence translate directly to errors in power. It is typical in the power meter business that cadence is approximated as constant over a full or perhaps half pedal stroke. Indeed, Garmin has announced they are using this approximation on the Vector. This is of course technically incorrect: cadence varies over a given pedal stroke just as it varies from one pedal stroke to the next. Ideally cadence would be sampled at a sufficient rate to get multiple points within a half-pedal-stroke, so the variation in pedal speed between the strong and weak portions of the pedal stroke would be captured. I have previously looked at this issue and I concluded the power error would be proportion...