February 2, 2014
This is the plan, anyhow. N-1, I designed long ago, finally built, and with the exception of broken wires, a confuso (OVERFLOW vs OVERVOLTAGE), and a units error (4000Hz “ticks” versus 1Hz “seconds”), it appears to work. The only remaining mystery is why not all the zero crossings are detected; I went so far as to determine that the cause is on the analog side, and I think before I worry too much about it I will check to see if it matters, or if I can fix it in software.
So, why do I think this one is better? First, it is not sensitive to the LED load; it just runs whatever you put there, pulling the right amount of current form the hub. Second, it has a switchable doubler, so the lights come on at low speeds, but then the doubler turns off at high speeds for more efficiency and less need to limit current. Third, you can do whatever the heck you want with timing and flashing patterns. Fourth, on the advice of Wiley, it uses screw-down terminals, which is a good thing (most first controller just died, from a corroded+broken wire) and allows easier repairs in the field. Fifth, it has “everything”; it can be reprogrammed in place, it can supply at least a half-amp of 5V current for phone charging, it has an optional input for solar panels if that’s what you want, it has a shunt for overvoltage protection, and it has a switched optional input for batteries (or capacitors) for a standlight.
The prototype (which proved most of this would work) has several flaws; among them, I was still suffering from the delusion that I could stick it in side a frame tube. That’s not such an awesome idea. Making it in one compact lump allows all the capacitors to be lashed down tight, allows the screw terminals, and reduces the need for extra wires. The whole thing is relative compact — 5cm by 10cm, with a bit of the BuckPuck sticking off the end, and the capacitors piled about 3cm high.
And there’s a wee bit of software….
Read the rest of this entry »
December 23, 2013
A first effort at writing this up, if you’re interested and it’s unclear, ask questions.
I’ve never been 100% happy with the packaging on home-made lights, but glueing power LEDs to aluminum angle iron with a mirror on top works pretty well and gives you some options for mounting (for example, using long bolts to bell brackets). On a bike with a front basket, however, the basket itself is a natural place to mount not only the light, but also most of the wiring, so inferior packaging is not such a big deal.
To start, here’s what the bike looks like with lights installed, showing the basic arrangement of the basket, hub, wires, and tail light.
Note that there’s no off switch and no way to disconnect anything but the hub without wire clippers or a soldering iron. Why build it like this? #1, eliminating connectors and switches eliminates sources of failure. #2, daytime running lights turn out to be useful. From the OECD, Cycling, Health and Safety, p. 170 (pdf):
The safety effect of daytime running lights on bicycles was tested in a Danish study in 2005 (Madsen 2006). Nearly 2,000 cyclists in the town of Odense used the new induction lights (flashing type) for one year with, while 2,000 others continued with ordinary bike lights, which were only switched on during dark hours. The accident frequencies of the two groups (based on self-reported accidents) were then compared and analysed. … The main result was that use of daytime running lights was associated with a reduction of the number of crashes by more than 30%. The number of related crashes (crashes in daylight and with a counterpart) decreased by 50% approximately. Both results are statistically significant. There are indications that the study may have not controlled for all factors – for instance it is unclear to what extent the control group’s crashes included single vehicle crashes (this type of crash is hardly influenced use of induction lights). Also, the study makes no finding as to the safety effect of flashing versus steady lights.
The photo below shows the basket from the other side, and on Flickr it is annotated with notes on some of the parts, but the basic idea should be clear; there’s room under a basket, and plenty of stiff wires that can be used for mounting zipties. The little wooden stick is intended to adjust the level; ideally some of the light is visible to approaching traffic, but it is better if most of it is kept down low and out of people’s eyes. One problem with “beater bike” systems is that it’s not clear how much money to put unto them; for another $25, it’s possible to add a second set of LEDs on a switch that are aimed lower and with a color chosen not to be so deadly to night vision (e.g., amber, or perhaps warm white).
The photo taken from below in the front shows the LEDs, lenses, mirror, wiring, and aluminum angle on which the LEDs are mounted. Note that one lens is a spot, and the other spreads its light out horizontally. The goal for the spread lens is to ensure visibility from the sides and to fill in the near part of the road.
The “better taillight” is made from stuff I had lying around because “you never know, that might be useful”.
The clear tube is acrylic with one-inch inner diameter, and the round top is an acrylic hemisphere, held on with superglue. There’s a fancy holographic diffuser film in there from a sample sheet; not clear that is really necessary, some vertical sanding on the inside/outside of the tube might have been just as effective.
Lense holders are necessary for the headlights and their lenses.
PCB for rectifier/doubler.
Small capacitors: 1000 uF, 16V
Large capacitors: 6800 uF, 35V
Wire: I use marine-grade, 2-conductor, 18 gauge.
First cut mirror and aluminum angle. I sized the aluminum to fit to one side of the support under the basket — the middle seems symmetrical, but it will get dirtier there. A Next drill aluminum. Next glue mirror to aluminum, then drill through mirror. I always roughen surfaces before gluing and use 5-minute epoxy because I am impatient.
It’s good to clip the LED hexagons to a heat sink while you are soldering them, except for the tab being soldered. That protects the LED from being overheated (I ruined one that way once, though I didn’t ruin about a dozen others being careless).
Use nail polish on all the exposed electrical connections (but not on the LED lens itself) to help protect against the elements. It’s not required, but it helps.
Glue the hexagons and lenses in one operation, clamping the entire assembly. The lenses have a larger diameter than the LED pucks, this prevents you from gluing them on too close to the mirror. Be aware of the orientation of the oval beam lens — you want it wide from side to side, not from top to bottom.
Work some tape in around the headlights to help keep water splashes off the LED.
When wiring, always think about strain relief. Vibration on a bicycle is the enemy of all electronics, including wires.
The taillight is always ad hoc and depends on what your mounting options are. Gluing hemisphere to tube uses superglue in a pretty large quantity, and the superglue vapors tend to fuzz the acrylic surface (which is okay for a taillight). A bare LED works, but a little protection from bashing and the elements is better, and a larger-than-point light source is also better.
December 15, 2013
Cambridge is taking the somewhat bold step of continuing Hubway rental bike service through the winter. Unfortunately, they failed to get the message through to enough people in public works to be sure that good places to ride these bikes will exist. There’s a cycletrack on Concord Avenue from Belmont to the Fresh Poond rotary that curves on around Fresh Pond. They plowed one side pretty well (and it was nasty snow; first it snowed, then it rained, then it turned really cold and a little windy; anything not removed in a very timely fashion got very hard to remove.
First, a plow driver clearing the Burger King parking lot found a convenient place to dump his snow. The wide lanes that cars use would have been most convenient, of course, but instead, he chose the cycle track:
Further on, they did a moderately good job of clearing the snow off the path, and left a nice hard surface to ride on. Unfortunately, it was nice hard ice:
Yay studded tires, today they were useful and not just a noisy morale and power suck.
Crossing Fresh Pond parkway, I stopped to take a photo of something that has recently puzzled me — the curb cut for the crosswalk is tiny. Why? What’s the point of making the pedestrians (and bicycles) fit through such a tiny space?
My crossing experience was enhanced by some bozo in a car (but I repeat myself) attempting to make a prohibited right turn on red, right across the crosswalk that I was ready to use (making my way on foot across the uncleared-and-partially-frozen piles of snow that had been left for my enjoyment). When I pointed out “no turn on red, the sign, right there” he, instead of responding with the eminently sensible “oops, sorry”, asking if I had been looking where I was going. Well duh, yeah, I saw him not turning, and I thought I should make it clear that I knew what my legal rights were.
Then, time to ride on the less-awesome side of the Concord cycle track. Oops.
So, I rode in the street, and because the frozen ice wall is not that safe for me, I ride a good distance from it. I also didn’t ride that fast (didn’t know it would be a problem when I left, I planned to use the cycle track) because I spent a good chunk of the morning shoveling snow and scraping ice. It was hard work, I ache in a lot of places, I was actually riding the bike to help give my joints some low-intensity recuperation (sitting still afterwards, I just get stiff).
If Cambridge wants to show that they’re serious, instead of setting things up for failure by leaving no place for anyone except the boldest cyclists to ride, they need to find someplace other than their shiny new cycletracks for storing snow, and they need to ding plow drivers just as hard for dumping on the bike facilities as they would for dumping in the street, and they may need to look into selective use of chemicals and/or sand on bike paths (Arlington and Lexington seem to leave their paths untreated, but they also appear to use a real plow and scrape it down to the asphalt). I realize that Fresh Pond is both a park and a reservoir so that may limit use of chemicals, but it’s a big reservoir and it’s one little cycle track — it might not require that much salt, it might be small enough to allow the use of more expensive chemicals (calcium chloride, magnesium chloride). Even a little sand embedded in the ice is a surprising help (perhaps because of the relatively high pressure of bike tires, I’m not sure why) — I was out a few days ago on normal tires in the first cold weather and experimentally tried to break the rear end loose on some dirty frozen surfaces, and there was enough traction to go, stay upright, and stop (which is all you should expect in the winter, even with studs).
November 10, 2013
is a comment containing this link
to a study by Kenneth D. Cross and Gary Fisher which is cited by John Forester in Effective Cycling to support his claim that accidents where the cyclist is hit from behind are not a large risk, and thus we should not be afraid to ride with traffic and even somewhat in the part of the road where automobiles commonly travel. I believed this claim for decades, because presumably he would represent that study fairly, and not cherry pick or distort the data to support his position.
What can I say, I was young and naive, right?
Surprising to me, when you read the cited statistics, you discover that things are not exactly the way Forester claimed. Accidents in which cyclists are hit from the rear (Problem Type 13, p. 33) cause 23.4% of the fatalities. That’s not at all the impression you would get from reading Forester. It is true that 70% of these fatalities occur on narrow, rural roads at night, and alchohol is often involved, but that still leaves 7% of all fatalities in the non-narrow+rural+night case of hit from behind.
Is 7% large? Probably. Riding against traffic poses a significant risk of injury (p. 174, a factor in 20.1% of injuries) but only a 4.8% risk of a fatal injury.
In contrast, sidewalk riding in the presence of driveways (Problem Type 8, p. 31) is not nearly as dangerous as portrayed by Forester — no fatalities! (Yes, there are injuries, 5.3% of the total).
And thus my opinion of Effective Cycling takes another lurch downwards. The study itself is interesting; what I read there makes me feel happy about my decision to equip my bike (and all my kids’ bikes) with hub-powered lights that are always on when the bike is rolling; again and again, visibility is a factor.
November 10, 2013
In a comment exchange on some random liberal blog, a transit advocate was mysteriously opposed to bicycles-as-transit. He never completely explained why, but I think he was making assumptions about road damage and congestion that assumed a linear relationship to weight. However, that’s just not so. Damage-per-wheel is at least proportional to the cube of the weight on the wheel, if not the fourth power. It’s very non-linear, and non-intuitively a heavy vehicle with many wheels can do less road damage than a lighter vehicle with just a few.
Turns out, a city bus can do a LOT of damage, and per-passenger, it does over twice the damage of even a single-occupancy SUV. A plan-loaded city bus is almost as bad for roads as a fully loaded semi truck, and a crush-loaded city bus is worse. Whether you calculate it as marginal damage per passenger, or average damage per passenger, a bus passenger is hundreds of times more damaging to the road than even a fully-loaded cargo bike, and thousands of times more damaging than someone merely carrying themselves on a bicycle. Even the marginal road-damage cost of the first passenger to board a bus is a little bit worse than the road-damage cost of a single-occupancy SUV.
I’m not at all sure that these costs are rolled into the published “costs” of transit. Note that these are not the only costs; there are congestion costs, parking space costs, fuel costs, risk-to-others costs, risks-to-rides costs. But the road damage costs are really large.
(And if someone knows more about this than I do, do please check my math, I am working from published sources and conservative estimates. This was surprising to me.) Read the rest of this entry »
November 10, 2013
Standard US anti-cycling claim: “We’re too spread out, not like those dense European countries.”
Here’s the copy-and-paste from Calca:
density(area, population) = population/area http://en.wikipedia.org/wiki/New_York_metropolitan_area NYCMetro_area = 13,318 NYCMetro_population = 23,508,600 density(NYCMetro_area, NYCMetro_population) => 1,765.175 http://en.wikipedia.org/wiki/Netherlands Netherlands_area = 16,039 Netherlands_population = 16,819,595 density(Netherlands_area, Netherlands_population) => 1,048.6686 http://en.wikipedia.org/wiki/Massachusetts Massachusetts_area = 10,555 Massachusetts_population = 6,646,144 density(Massachusetts_area, Massachusetts_population) => 629.6678 http://en.wikipedia.org/wiki/Denmark Denmark_area = 16,562.1 Denmark_population = 5,602,536 density(Denmark_area, Denmark_population) => 338.2745
And if you notice, there’s a whole lot of Western Massachusetts that’s relatively empty (and also relatively hilly), but that works against the “we’re spread out” claim; if the west is sparse, then the east must be even denser.
And no, we do not have a uniform transit policy across the nation — how many subways are there in Montana or Alaska? We do what’s locally appropriate.
October 21, 2013
Or, rules for breaking the rules.
When I go grocery shopping I often ride to Fresh Pond Mall in Cambridge. Getting there on Concord Avenue is easy; there’s a nice cycle track that’s almost entirely unbroken, adjacent to a sidewalk, together they are 12 feet wide.
Unfortunately, on the return I’m supposed to ride on the other side; the “cycle track” there is cut by many driveways, usually full of dirt and debris, and just plain less pleasant. So instead, I salmon on the nice side. I have a two-part logic to justify this. First, 12 feet wide is the same width as the Minuteman Trail (in places the trail is only 10 feet), which accommodates bidirectional walking and cycling with only an instruction to “keep right” (which is even vaguely followed), so it should be possible here, too. However, because some Bright Boy at the Cambridge Planner’s office decided to invent their own rules and post them (and even encode them in asphalt and concrete), people often follow posted rules that make suboptimal use of the space. Second, I have rules for breaking rules that make it “okay” (okay if you subscribe to my rules, that is).
Rule #1 is that when salmoning, you yield to everything, because you’re breaking the rules.
Rule #2 is that other people should not even imagine that they need to break the rules to accommodate your breaking the rules.
Rule #3 is that when in doubt, give priority and deference to pedestrians; if any crash should occur, it’s not the pedestrian bringing energy and momentum to the crash.
Rule #4 is that you can stop if it is necessary to maintain rules 1-3.
So, normally you ride in the cycle track, not the walkway, since pedestrians should not even need to think about what you might do. If there’s an oncoming bicycle, no pedestrians, then you use the walkway, leaving plenty of room for the bike. If there’s oncoming bike AND pedestrians, then you stop, in the walkway (now you are a pedestrian, and you are where you belong) till the traffic clears. And if there’s an oncoming bicycle in the walkway, maybe you stop, because two wrongs not only doesn’t make a right, it does make the chances of a crash through misunderstanding a good deal higher.