Arhiiv kuude lõikes: June 2016

Optimizing a bike for commuting

The objective is to get from point A to point B every day, minimizing some combination of time, effort and cost. The objective is not to get exercise (in that case, take a longer route, make the bike heavier) or to win a sprint. If cost is not a concern, then of course get the best bike money can buy. It is still not obvious this should be the fastest road bike.

The total time spent on bike commuting includes maintenance, locking and unlocking the bike and any other unavoidable tasks. A high-end road bike with thin tires may save some time every day, but gets flat tires more frequently than a thick-tired mountain bike. Each occasion of a flat tire costs significant time, plus some money. The time cost occurs randomly, which for most people is worse than if it were predictable and could be scheduled.

Thin wheels get bent more easily than thick ones, again requiring maintenance. Thus the fastest commute is not achieved by the lightest, thinnest bike. Reliability is what influences both time and cost the most.

Wheel and tire width affects weight, aerodynamic resistance, rolling resistance, flat tire and wheel bend frequency and ride comfort. The lowest rolling resistance occurs when the tire pressure is such that vertical tire thickness drops 15% under load (F. Berto, Bicycle Quarterly Vol 5 No 1). Tire tread pattern has such a small effect on rolling resistance that it can be ignored for commuters. The tire thickness that minimizes rolling resistance is 22-23 mm ( The thinner the wheel and tire, the lower the aerodynamic resistance, but this effect is under 1% of effort, small enough to ignore for commuters ( Wheel weight and inertia have an even smaller effect.

The thicker the wheel, the less chance of it bending (other things equal – wheels of weak material or poor construction bend no matter what). More expensive wheels are on average stronger and lighter. The thicker the tire, the lower the probability of punctures and pinch flats. For a commuter, it is optimal to choose wheels and tires heavy and thick enough to never bend or get flats on normal roads (having some potholes, broken glass etc). In my experience, this means thicker than 25 mm road tires and thinner than 50 mm mountain bike tires.

Punctures are less likely than pinch flats even with 25 mm tires. Puncture probability can be further reduced with e.g. Kevlar-lined tires, which add less than 40 dollars to cost.

It sounds like I am advocating a hybrid bike – these have intermediate thickness wheels and tires and are supposedly designed for commuting. My experience with the one hybrid I tried (Apollo Trace 10) was very bad. Both wheels bent enough to hit the brakes in less than a month of half an hour per day riding and two spokes broke on the rear wheel. Looking closely at the wheel, the substandard manufacturing was obvious. My speculation is that hybrids may be low quality because they are marketed to people who on average are not bike fans, ride little and in flat road conditions. They thus cannot distinguish quality levels and may buy a bike mainly based on its flashy paint. Road and mountain bikes, on the other hand, may be bought by more knowledgeable customers. For these to sell, they may need some minimum reliability.

It would be good to have bicycle reliability statistics like there exist for cars. Then this would be the best source to base bike choice on, not recommendations from friends, forums or bike shops.

What matters for speed and ease of riding is first the fit of the bike to the rider and second the maintenance of the wheels and drive train. The weight and general flashiness of the bike are far less important.

I think that the best used bike for a given price is better than the best new for that price, because clueless customers go for new, and some people want to demonstrate their wealth by replacing their high quality used bike with new at short intervals. They sell a high quality used bike for cheap to make room in the garage. I got a great on a used bike: a like-new 2008 Giant OCR 1 for 350 AUD. But this is just one data point.

On reporting on the Syrian war

According to the media, there are no ordinary towns in Syria, only key towns, strategic towns and key strategic towns. The same holds for villages, highways, road crossings, border crossings etc. There are no minor skirmishes in the Syrian war, only major offensives, strategic offensives and similar very important actions in very important places. What the media calls major campaigns usually involve from a few dozen to a few hundred fighters. Entire cities are attacked and defended for months by some hundreds at most, with the media reporting major clashes every day.

A residential bike shop business model

There is an empty market niche for a neighbourhood mechanic who accepts a bike in the evening and returns it in the morning. The demand is concentrated almost entirely outside business hours – evening, early morning, weekend. Opening the residential neighbourhood shop at those times would target cyclists whose bike breaks down on the commute from work to home. An overnight fix means they would not miss their next morning’s ride and would not have to haul the bike to a city shop by some other transportation.

Currently the neighbourhood shops I have seen are open during regular business hours, perhaps close a little later and open also on the weekend. I have not checked, but they must be almost customerless in the daytime on weekdays. People go to work or school. I doubt there are enough stay-at-homes who bike enough to require a mechanic’s services frequently. People in the city may visit a city bike shop at lunch, but not a residential neighbourhood one. The local shops seem to be open exactly when the customers are not there.

Fixing a bike takes time, so cyclists leave it in the shop and come back later. It is important which time of the day the bike spends at the mechanic’s. Customers who use their bike a lot and thus need frequent service want the bike available and working mainly during rush hours, because many of them commute with it. A city bike shop open during business hours can accept a bike in the morning, fix it and give it back by the end of the workday. For the commuter, the bike is available both morning and evening. The shop does not need to store the bike overnight, so does not need to rent a large space, saving costs. In a suburban shop, customers could leave their bike one evening and pick it up the next evening, but they could not use their bike for one day’s commute then.

Load sharing between city and suburban bike shops is possible. Mechanics can work in several shops at different times. They can shift to accommodate peak demand, the timing of which differs by shop. The residential neighbourhood shop would get the most customers on the weekend or outside business hours. The city centre would get more on weekdays in the daytime (the cyclists whose bike breaks down on the way to work).

Tarkus ja haridus ei taga tervet mõistust

Vähemalt kolme Yale doktorandi puhul kohtasin uskumusi, mis targa ja haritud inimese puhul on väga kummalised. Kõik nad lõpetasid edukalt ja said doktorikraadi. Esimene oli biofüüsika või mingi selletaolise valdkonna doktorant, kes oli kreatsionist, ehk selline kristlane, kes uskus Piibli iga sõna, sealhulgas et Maa olevat umbes 6000 aastat vana. Usklikke Yaleis jätkus ja pole ime, et mõni neist ka fanaatiline ja sõnasõnaline oli, aga biofüüsika peaks ju õpetama radiosüsiniku põhist asjade vanuse määramist, erosiooni põhjal planeedi pinnavormide vanuse mõõtmist, geneetiliste mutatsioonide põhjal liikide lahknemise ajastamist jne. Kõik sellised meetodid peaksid üsna lihtsasti Maa vanuse üle 6000 aasta olemist tõestama. Aga inimene jätkas uskumist ka pärast seda, kui temaga sel teemal räägiti ja uskumise üle nalja visati. Eks usklikud tunnevad uhkust “tugeva usu” üle, mis tähendab tõendite ja loogika eiramist.

Teine oli farmakoloogia doktorant, kes polnud usklik, küll aga enda sõnul “spirituaalne.” Ta uskus, et suudab tulevikku ette näha, mille tõestuseks tõi ta näite, et mõtles sõbrale ja kohtaski kohe tänaval seda sõpra. Ma katsusin ääriveeri uurida, kui palju on selliseid juhuseid olnud, kus ta sõbrale mõtles, aga sõpra ei kohanud, või ei mõelnud sõbrale, aga kohtas teda. Juhtisin tähelepanu, et tuleviku ennustamise võimet tuleks hinnata kõigi nende kombinatsioonide esinemistiheduse põhjal, võttes arvesse valikulist mälu. Nimelt on juhus, kui mõtled sõbrale ja kohe kohtadki teda, meeldejäävam kui alternatiivid. See argument talle ei meeldinud. Kui inimene tahab midagi uskuda, siis ta seda ka usub. Loogika ja statistika on siis võimetud.

Kolmas oli mehaanikainsenerinduse doktorant, kes oli kristlane, aga tema imelik uskumus polnud sellega seotud. Ta käis “hiina meditsiini” ravil, mida pakkus keegi valge mees, kes oli seda õppinud enda väitel Lõuna-Ameerikas. Kummaline kombinatsioon, aga meditsiin ise oli veel imelikum. Nimelt olid ravitsejal klaaspudelites erinevad ained, näiteks suhkur, sool, vesi, toiduõli jne. Ta käskis ravitaval ükshaaval iga aine pudelikese võtta ja seda sirge käega kehast eemal hoida. Kui ravitsejal õnnestus kerge survega patsiendi käsi alla suruda, siis järelikult oli pudelikeses olev aine patsiendile kahjulik ja selle tarbimist pidi vähendama. Kui ravitseja ei suutnud nõrga jõuga kätt alla suruda, siis võis ainet edasi kasutada. Selle meetodiga jõudis ravitseja järeldusele, et suhkur on doktorandile kahjulik, teised ained mitte. Mina ja üks arvutiteaduse doktorant avaldasime kahtlust, kas ravitseja mitte eri ainete puhul eri tugevusega ei surunud. Nii et käe allavajumisel poleks pudelis oleva ainega muud seost kui ravitseja suva. Soovitasime topeltpimendusega katset, kus ravitseja ega ravitav ei teaks, mis aine pudelikeses on. Lisaks võiks valim suurem olla kui üks inimene, sama ainega võiks mitu allasurumisproovi teha, käe külge võiks objektiivse kaalupommi riputada, mitte subjektiivselt suruda jne. Insenerinduse doktorant nõustus vähemalt, et asi oleks usutavam, kui katseid meie soovitatud moel teha, aga jätkas siiski selle hiina meditsiini järgimist. Ju siis süütuse presumptsioon dikteeris, et kuni pole tõestatud ravitseja petturlus, seni on ta aus inimene. Või püüdis insenerinduse doktorant meid lollikesi võltsi nõustumisega maha rahustada.

On electric bikes and science news

There is some debate on whether electric-assist bikes are good or bad. The argument on the negative side is that people will stop cycling and bike roads will be taken over by these (electric-)motorized vehicles. On the positive side, the claim is that electric bikes replace motor scooters, cars and public transit, which is good for the environment and perhaps health if people actually pedal their electric bike a bit. To summarize: electric bikes good if replace motor vehicles, electric bikes bad if replace bicycles or walking. It is an empirical question what the substitution sizes are.

There are many calls for scientists to communicate better, engage the public, present their results simply and interestingly etc. Whether more science news and popular science is good or bad depends on what it replaces, just like for electric bikes. If dumbed down entertainment science replaces the rigorous variety, this is bad. If science news replaces brainless news (celebrity gossip, funny animals, speculation on future events), it is good. It is an empirical question to what extent scientists switch to popular topics and crafting press releases if their evaluations rely more on outreach or policy impact. Also a question for the data is which news are left out of print to make room for more science news.

To maximize education of the public, there is a tradeoff between the seriousness of the science presented and the size of the audience. Research article level complexity is accessible to only a few experts. Entertainment is watched by many, but does not educate. The optimum must be somewhere in the middle.

Similarly, difficult courses in a university have few students taking them, but teach those few more than fun and easy subjects. The best complexity level is somewhere between standup comedy and a research seminar.