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

The Senate has posted an analysis of SB910, the bill which would impose a 3 foot minimum passing distance for motor vehicles passing cyclists. There is now on AroundTheCapitol an analysis, dated Thursday 28 April. First, I'll jump to the end: SUPPORT : Office of the Mayor, City of Los Angeles (co-sponsor) California Bicycle Coalition (co-sponsor) Amgen Cycling Club Channel Islands Bicycle Club Humboldt Bay Bicycle Commuters Association Sacramento Area Bicycle Advocates Santa Cruz County Cycling Club Silicon Valley Bicycle Coalition 47 individuals OPPOSED : AAA Northern California Automobile Club of Southern California Just in case any cyclists out there are members of AAA, please quit now. Try Better World , for example. AAA members are supporting the AAA's car-centric legislative agenda, opposing every attempt to improve the rights of cyclists on the roads. It is incomprehensible to me that any member of any bike coalition would be also a member of AAA. ...

Yesterday I hit refresh on my screen yesterday morning, and I saw this ( link )... the text of SB910, the bill supposedly requiring a 3 foot passing buffer when drivers pass cyclists, was revised. Changed from: 21750.1. (a) (1) The driver of a motor vehicle overtaking a bicycle proceeding in the same direction shall pass to the left at a safe distance, at a minimum clearance of three feet, at a speed not exceeding 15 miles per hour faster than the speed of the bicycle, without interfering with the safe operation of the overtaken bicycle. To: 21750. 1. (a) The driver of a motor vehicle overtaking a bicycle proceeding in the same direction shall pass to the left at a safe distance, at a minimum clearance of three feet or at a speed not exceeding 15 miles per hour faster than the speed of the bicycle, without interfering with the safe operation of the overtaken bicycle. Wow -- talk about flip flop from replacing a comma with an or. So it's now considered safe to blow by a c...

Back to the boat puzzle... I freely admit this is perhaps among the most boring topics ever posted to a blog in this history of the Intenet. But I feel the irrational need to put some sort of closure on this. I proposed that all solutions to the arbitrary boat puzzle could be reduced to the simple example of Mac-Nadia-Flannel. It was first proposed to me that if there is at least one member not a part of a maximal independent set incompatible with no more than two members of the maximal independent set, the problem can always be solved. This is true: just leave everyone else on the boat and solve the simple Mac-Nadia-Flannel-cans problem with the one remaining seat. But there's a more general approach, in which each elemnt of the "Mac-Nadia-Flannel-cans" puzzle is represented by a group rather than an individual. First, identify which animals which are going to go across on the first trip (the rest are a maximal independent set). Then bring the rest across. T...

The California State Senate is considering SB910, the latest in a long-running series of bills requiring a minimum passing margin for cyclists. The text of the bill is here . The key text: 21750.1. (a) (1) The driver of a motor vehicle overtaking a bicycle proceeding in the same direction shall pass to the left at a safe distance, at a minimum clearance of three feet, at a speed not exceeding 15 miles per hour faster than the speed of the bicycle, without interfering with the safe operation of the overtaken bicycle. I'm a huge fan of a 3 foot passing margin. It really changes nothing, since any rational observer would conclude passing with less than a three foot margin is unsafe, and it's illegal to pass at an unsafe distance. But this codifies that less than 3 feet is de facto unsafe, removing the burden to prove it. For example, presently a driver could pass with a two-foot margin, hit a cyclist, then claim it was the cyclist's fault for veering to the left. T...

I'm working my way backwards through Bicycle Quarterly and am currently at the Fall 2007 edition. There's a very interesting article there: Jan Heine went to the wind tunnel to test his Alex Singer Randonneuring bike with various options. One of the tests was the effect of a front fender. As he expected, the front fender appeared to reduce wind resistance. He used a telescoping fender to test the effect of length. I plot the result here: "N" corresponds to no fender, "S" for short, "M" for medium length, "L" for long, "XL" for extra-long, and "MF" for a mud-flap on an extra-long fender. There appears to be an optimal length: the fender blocks the wind from entering the brake area, then going longer than that is counter-productive. Jan dismisses the effect as relatively small. However, ignoring his "repeatability" tests to establish error bars, I'll plot the naked numbers of the difference ...

Previously I described the boat puzzle and how it's provided some mental exercise for my train commutes. The traditional example is the Mac-Flannel-Nadia case: The solution, as I described, is to identify a maximum independent set, in this case Mac and Nadia. Then you need a number of seats on the boats sufficient to transport the rest, in this case Flannel. So: 1. Flannel taken from shore A to shore B. 2. return with empty boat. Next step doesn't matter, as Mac and Nadia are identical in this problem. I'll pick Mac: 3. Mac taken from shore A to shore B. Now Mac and Flannel are together. I need to return with Flannel on the boat, as I cannot leave the two, or Mac will turd. 4. Flannel taken from shore B to shore A (leave Mac on B). But then.... 5. Take Nadia from A to B (leave Flannel alone). Nadia is now with Mac, and they lick each others faces, so that's fine. 6. Return with empty boat. 7. Bring Flannel from A to B. When I add in the can...

Jym Dyer sent notice of this gem along the SF Bike mailing list: APRIL 21, 2011 BUILDING & OPERTATING COMMITTEE TO DISCUSS 10 MPH SPEED LIMIT FOR BICYCLES (sic) Here was my response, which I emailed to the Golden Gate Bridge Transportation District : I have read the consultant’s report and the corresponding proposal to introduce a 10 mph speed limit on the bridge. The statistics do not justify such an action. Collision rates (per rider) have been decreasing over time, even with an enormous increase in the number of inexperienced cyclists (renting from Blazing Saddles and other agencies) crossing the bridge. And only a minority (39%) of collisions are labeled with “speed as a factor”. This is in spite of the fact that virtually all experienced cyclists ride in excess of 10 mph across the bridge (there are plenty of data available on Strava.com). Checking my own data, 25 kph is a typical speed even when riding alone in a relaxed, noncompetitive fashion. There isn’t...

I'll now continue my discussion of the boat puzzle in which the goal is to get cats across a river in a boat, where there are fewer seats on the boat than cats, and certain cats must not be left with each other unsupervised. For the first trip across the goal is simple: to leave no two incompatible cats back on the first short. For example, consider the following problem, with cats Mac, Nadia, and Flannel, where I spiced it up slightly with the requirement to also transport a supply of cat food cans: I want to find a group which has no mutual connections to leave back on the shore. Ideally, my boat should require no more seats than the number of cats + objects to be transported in that first trip. Thus I want this group without mutual connections to be as large as possible. The largest group without connections is called the maximal independent set . Here is the maximal independent set for the graph shown above: The only element not in the maximal independent set is...

A few more plots on the Scott Foil comparative windtunnel data... First VeloNews. Both Cervelo S and Felt AR frames were tested by both VeloNews and Scott. VeloNews tested the Masi Competizione, which they claim is similar to a Trek Madone. Scott tested the Trek Madone, so I include the results from these tests as well. VeloNews' tests were with Zipp 404 wheels except for the Masi which was tested with Fulcrums. However, I adjusted the VeloNews data based on the (considerable) improvement the Zipps had on the Ridley and Cervelo in their test, which were each tested with both the Fulcrums and the Zipps. VeloNews tested at positive and negative yaw, while Scott reported only wind from one side of the bike, so I averaged positive and negative data from VeloNews. In each case, both for the North Carolina windtunnel used in the VeloNews test, and in the Mercedes windtunnel used by Scott, I assumed an air density of 1.2 kg/m³ to convert from force (VeloNews) or power (Scott) to...

Scott just released a new bike, the "Foil" , their entry into the "mass-start aero frame" category. This bike has been around in the pro peloton for a year now. Mark Cavendish famously rode it in the first stage of last year's Tour de France, where he had a disappointing result. When he switched back to his previous bike, a beefed-out Scott Addict (the consumer Addict is under 800 grams, Mark's custom bikes are reportedly close to 1200 grams with a Pinarello-like excess of carbon fiber), he started winning races again. But the rest of his HTC Columbia team continued to ride the bike, including Mark Renshaw and the rest of the lead-out train on which Mark relies so heavily for his wins. Interestingly, until this consumer release it has been called the F01. Very clever: the F01 becomes the F01L, or the "FOIL". Scott wins the bike naming game against Specialized with the latter's recently-released Venge. The differentiating factor with ...

Another puzzle... actually I spent quite a few train commutes thinking about this one. There's a classic puzzle where a farmer needs to get a fox, a sheep, and a cabbage across a river on a boat. I don't have much experience with transporting fox or sheep, and cabbage aren't very exciting, so I'll recast the problem in terms of cats. Consider I want to transport three cats across a river on a boat. I can watch over the cats while they're on the boat, but when they're on one shore or the other, they need to get along. The names of the three cats are Mac, Flannel, and Nadia. If I can watch them they're fine, but if Nadia is left unsupervised with Flannel, Flannel will harrass Nadia. who needs her rest. And if Flannel is left unsupervised with Mac, Mac will turd, so we need to be careful not to let that happen. On the other hand, if Mac and Nada are left with each other, they'll just lick each others faces, so that's fine. The challenge is...

This year Cervelo overhauled its road bike geometry, merging the previous R and RS series into a single unified R. I plot head tube angle versus reach for 2010 and 2011 series: the 2011 R series goes from R-like at small sizes up to RS-like in large sizes. On Sunday, Garmin-Cervelo's Johan Van Summeren produced an epic win at Paris-Roubaix riding his modified "R3". Johan's a tall guy: reportedly 2 meters in height, and rides the largest-size Cervelo. From the plot you can see this bike has a 22.5 cm head tube, 2 cm longer than the comparable bike from last year. And you can see every cm of this length in photos of Johan's bike, borrowed from VeloNews: Impressive. Johan is at the limit of the frame's geometry with a slammed -17 degree stem (of course he could have used a retrograde stem to get even lower, but this is generally considered undesirable). This seems to support Cervelo's geometry. But it got me thinking: is this the longest hea...

Both the VeloNews aero bike test and the Tour aero bike test (my discussion of that test is here ) examined the Cervelo S and the Tour AR. In the case of VeloNews, the bikes were tested "stock" with the exception both used Zipp wheels. Cables were installed and there was no rider. Tour on the other hand used a dummy rider (the only way to get a reasonably consistent position) and Mavic wheels. The Tour article is in German, so the finer details are beyond my comprehension. But they didn't use bar tape, while VeloNews used whatever bar tape the bikes had installed. Same deal with the saddle: the VeloNews bike tested bikes with "stock" saddles, while in the Tour test, the saddle was less important due to the use of a "rider". Despite differences you might think conclusions about which bike was faster would be fairly consistent. But comparing the only two bikes tested by both magazines, this is not the case: I averaged the positive and negati...

I've been spending a lot of train time playing around with puzzles, doing "work-work", and even reading the newspaper following recent world events. Time to get back to those VeloNews frame data. VeloNews plots its drag force in grams. Grams is not a standard unit of force. A "gram" of force is defined as the force exerted by a standard gravity on a one-gram mass. But with wind resistance, we're probably most interested in power. And to get watts from force we want the standard metric unit of force, which is Newtons. Newtons multiplied by meters/second equals watts. So I converted their data to Newtons. But even then, Newtons are good only for the relative wind speed at which they did the test. Actual force depends on relative wind speed and air density. Wind resistance force is generally proportional to the product of air density and the square of the relative wind speed. I don't know the air density, but I can guess it was close to 1.2 k...

Strava has really gained traction among the San Francisco Bay area cycling community. In some group rides, in particular competitive non-racer groups like Mission Cycling and SF2G , typically 3/4 of the riders will upload rides, all the more remarkable considering it requires an expensive GPS-enabled cycle computer (although the price of entry gets lower with each new generation of Garmins, as the users dump their old units). Here's the Marincello trail page for cycling (which includes both mountain biking and road biking). As I write this, 99 users have uploaded rides which include this segment, ridden a total of 567 times. The top time, by David Beldon, was with a VAM of 1194 meters/hour, quite impressive for a gravelly dirt fire road. I'm ranked 24th. But Strava isn't just about cycling. Basically any activity which involves transport by human power is compatible. Strava activities can be categorized in a number of areas, and of course running is one of thes...

Previously I described a puzzle of prisoners and hats. Each of 100 prisoners had a 50-50 chance to pick his number from his 50 picks from hats. For any prisoner to survive (puzzles tend to be violent; it's true), every one of the 100 prisoners needed to succeed with his 50-50 chance. Simple probability says the chance of the prisoners surviving is essentially zero: you can't flip a fair coin 100 times and get heads every time. The key, it turns out, is to use a rigged coin.... Go to that link now if you don't want to see a really big hint. Move below the cute kitten photos to proceed... Okay, enough of that. Here's that big hint. For simplicity, I'll assume 8 (not 100) prisoners and 4 (not 50) hats. I show two sequences: one which wins, the other which loses. The winning sequence: 4, 6, 3, 0, 2, 1, 5, 7 The losing sequence: 4, 2, 3, 0, 1, 6, 5, 7 These sequences are permutations: various orderings of the same elements. The key insig...