Do Not Need , Do Not Want (a law school is so over joint)

A brief break from The Shocking Truth…

You’d hardly think it to look at me or my lifestyle, but I am genuinely trying to cut back on crap (seeCrap).

One of the ways I’ve decided to do this is to try to limit my “impulse” purchases, which tend to make up the bulk of my expenditures.  This is easier to do with in-person than with on-line purchases, for reasons that I will discuss briefly below. 

These days, I try only to be in a store when I need something.  That’s not rare–I may need a particular kind of bolt for a project I’m working on, for example, or a plastic box, or a tie (though gods know I have enough of those!).  When I’m in a store, all kinds of things present themselves.  Ideas emerge.

So I’ve started to think hard in terms of needing things.  And if I cannot find a present need for the object in my hand, I tell  myself that I do not want it.

Does it work?  Well, yeah.  If it’s something I can hold in my hand, I can do a pretty good evaluation.  Do I need it now?  Do I even have a place to put it, whatever it is?  If I do not need, the only justification for buying is because I want, and I have decided (in advance) not to want. 

It’s a lot harder with online purchases because they lack both the tactile feel of things and because the transaction itself is bloodless.  I don’t need to even hand over a card.  Heck, I can do “one click” ordering on Amazon.

I suppose one of the reasons I’m doing The Shocking Truth review is to somehow justify in my mind the money I’ve spent on various dynamos. 

Sad, really.

But I’m getting better.  Honest.  You’d be amazed at what I didn’t buy this week.

We now return you to your regularly-scheduled blargh..

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The Shocking Truth, Part 6: Rocking It Old School

Getting to the Bottom (Bracket) of Things

All of the other units tested here are currently manufactured. But it has been a couple of years, as far as I know, since the last bottom bracket generators were sold in the US. They were victims of the success of dynohubs in a way that nothing else could be, because—in many respects like the dynohub—bottom bracket dynamos were invisible.


Well, let’s consider what a bottom bracket dynamo is. It’s based on a small metal platform that fits between the chainstays ahead of the rear wheel. Extended behind and below the platform is a metal roller, often but not always coated with rubber. A lever, or in some cases a cable arrangement, allows that roller to be brought into contact with the tread, rather than the sidewall, of the tire. From the drive side of a given bicycle, a bottom bracket dynamo is invisible. From the NDS, it looks something like this:


 (Sorry for the photo quality–shot the day I was testing for wet-weather slippage.)

Pressed one way, the lever at the front (projecting WSW in the photo above) releases a catch and a spring presses the roller against the rear tire. Push the lever the other way, and the dynamo moves forward and locks away from the tire. You can see the white, rubber-insulated wire that connects to the ”hot” side of the generator coil snaking its way around the mount.

The bottom bracket dynamo is similar to, but superior in two important respects to the sidewall dynamo.

First, unlike the sidewall unit, it presents no risk to fragile sidewalls. It runs on the same tread that the weight of bike and rider applies to the road.

Second. It is tucked out of the way and is, as described above, practically invisible.

However, those advantages come at a cost: more than any other generator, the bottom bracket unit is exposed to the worst that the road can throw at it. It’s more likely than any other to encounter guck from the wheel and from the road. Ride through puddles? The bottom bracket dynamo is likely^H^H^H^H^H^H GOING to get wet.

 Interestingly, some users figured out ways to mount the dynamo in other places—for example, near the fork or at the front end of a front fender. This prevented slippage due to the roller getting wet and (in the case of top-mounted units) allowed for some attempts at integrated light-and roller units.

The heyday of the bottom bracket generator was probably the 1980s (I say probably because I haven’t found a good historical source; one may exist, but if so, I don’t know of it. This means that if you want to try something like this, you’re going to have to buy a used unit. Take heart—bottom bracket dynamos, the most common of which appears to be the Sanyo Dynapower shown in the photograph above, are fairly common on eBay and can generally be had for less than $50.

Costs Associated with Bottle Dynamos


If you want a bottom bracket dynamo, you’re looking at finding one used or, alternatively, “NIB.” Either way, there’s really only one place to go these days: eBay. Sometimes they’re out there, and sometimes they’re not, but bottom bracket dynamos seem to turn up nearly as reliably—if not as commonly—as downtube shifters. They are far less common than bottle dynamos, however.


You can either go cheap, or expensive. Cheap will mean used, $50 or less, and that’s fine. If you want expensive, that means you’ll be buying an NIB—“new, in box”—unit, and those can run up to $200 (which is, solely in my opinion, kind of ridiculous).


The Sanyo NH-T6 unit I have, complete with its cast alloy mounting base, weighs 254 grams. The NH-T10 that Peter White used to stock looks like it might be a tad bit lighter. So a bit more than a bottle dynamo (at least than the Dymotec) but no additional mounting equipment is required.



Here are three reasonably common bottom bracket generators, so you have a better sense of what I’m talking about:

Sanyo NH-T6 (also shown in the slippage photo above):

Sanyo NH-T10 (note the rubber cover on the roller):


There’s only one bolt—the one that clamps the upper and lower portions of the dynamo to the chain stays—but that doesn’t mean that this can’t be tricky. Bottom bracket dynamos are designed to sit in the “V” formed by the chain stays as they come together forward of the chainstay bridge (if one is present). Some bikes, I am told, have a mounting plate (probably the same one used for a kickstand) to which you can mount the dynamo. Mine fit just fine on two frames I tried, but I could see with oddly shaped stays, you could have a problem. And you wouldn’t want to clamp this onto carbon stays, it should go without saying, and, possibly, on some aluminum stays. Further, part of the clamping process penetrates the finish on the stays to ground the dynamo to your frame, so be aware!

It’s important to get the roller aligned properly with the tread of the tire, which the V-shaped nature of the stays makes comparatively easy. When it’s released, a spring will hold the dynamo’s roller against the tread. The only decent way I could find to adjust tension was to move the mount forward or back between the stays, varying the distance between the disengaged roller and the tread. That’s probably not ideal, but it worked well enough. I may be missing an adjustment somewhere. The NH-T10 can be remotely activated, in which case it would probably be cable tension holding the dynamo in place rather than a spring, but I cannot verify this; it’s possible the cable is set up simply to release the dynamo.


Bottom bracket units generally provide a single wire connection, since they ground the other side of the circuit to the frame. The weird thing about connecting them is that, of course, the bottom bracket is nowhere near either the headlight or the taillight. You can just run both head- and taillight connections to the bottom bracket and hook them up there in parallel, or you can run a wire up the seat tube (that’s how I did it) to connect things near the seat tube cluster. It’s not difficult, in any event, you just need a little more wire.


Overall Performance

Overall, I was quite pleased with the performance of this dynamo, especially given my earlier experience with an identical model (some ten years before). It may be a matter of finding just the sweet spot for mounting. The dynamo ran very acceptably with 28mm Pasela tires.

Wet Performance

My previous experience with bottom bracket dynamos was that they slipped, and badly. This one did not. I suspect several factors here. First, my prior experience was with incandescent halogen lighting, which needs a fairly constant flow of power (and a lot of it). With such a light, any slippage becomes instantly noticeable as flicker. With the eDelux headlight, on the other hand, a capacitor is charged by excess power from the dynamo and can “cover” small slippages. Further, when I rode in Wisconsin, a good part of my commute was over trails covered in limestone screenings—essentially dust, which turns to slippery mud when wet. By comparison, most of my wet miles during this test were run on asphalt surfaces, including extensive dips into puddles. I would guess that a combination of good surfaces—surfaces that didn’t put a lot of muck on the tire tread—and good adjustment were key. Again, I did not ride this unit into a downpour, but in moderate rain, with fairly extensive puddles, I had no issues.

Charging performance

Like the non-limited bottle dynamo, the bottom bracket unit—correctly adjusted— generates plenty of power.


While, as noted above, some units could be handled via a cable-and-lever assembly, with the NH-T6 you really need to dismount to turn the power on and off. There’s no other good way to reach under the bottom bracket!


If you’re not on the bike, the bottom bracket unit can appear very noisy. But once you’re riding., its placement makes it very quiet in operation. It’s about as far away from your ears as anything can be on a bicycle, and it’s not quite, but almost, behind you. It’s easy to leave the noise behind. Other riders, however, may suspect that you’re being boosted by a small electric motor.


I didn’t notice any significant vibration with this unit. Perhaps a little at very low speeds, but overall, anything that was there was drowned in road surface “noise.” Most bottom bracket dynos have either a light tread pattern somehow impressed into the metal roller, or else a rubber cover over the roller, and since this is running on virtually the same surface as the rest of the tire tread, it’s hard to pick it out even if you’re trying.

Subjective Resistance

Does the dynamo cause resistance, and can you feel it?

The situation is similar to that of a bottle—more than a dynohub. In addition to the magnetic resistance of the device itself (which is lower than that of a dynohub) there is mechanical resistance as the roller turns against the tire.

Can you feel it? Yes. This is particularly true at low speeds, but diminishes pretty rapidly as you spin up—likely because a greater proportion of your work is going into the contact between tire and road than between tire and dyno.

Like the sidewall dynamo, the bottom bracket unit can be completely disengaged when you don’t need it, so there is no wear and tear on tire or dynamo, and not resistance.

One thing worth mentioning at this point is that a bottom bracket dynamo frees you from concern about tire sidewalls. You can have concerns about sidewall fragility, but you generally trust your tread. The bottom bracket dynamo exploits this—both tust and tread. However, you are limited to tires with invert, slick, or minimal tread patterns. A bottom bracket dynamo will not do well with knobby cyclocross or MTB tires—for those uses, you need to find something else.



No parts are available. When you deal with a bottom bracket dynamo, you are dealing with “obsolete” technology and you’re on your own. If you’re good mechanically, you can carefully clean the roller and surrounding mechanical parts, but that’s about it.


Bottom bracket dynamos are tough. They have to bit, given where on the bike they live, and their comparatively higher weight probably reflects that. Given the number that are available on eBay, I would venture to say that most of us will be outlived by these units.   That’s not to say that they can’t be damaged, but that they seem to have established a long service life.

Attractive Nuisance?

If there is any dynamo less visible than a hub dyno, it’s the bottom bracket generator. From the drive side, invisible, and from the NDS, all but. Nor are they likely to invite “tweaking” from a malevolent passer-by; the dynamo is tucked, safely, well below eye level.

So, what’s not to like?

The bottom bracket dynamo is in a great position from the perspective of the rider, but a poor one from the perspective of the mechanism. It’s exposed to water, dust, mud, and—really—anything that the front tire throws up or that the rear drops in (the latter especially a factor if you’re using fenders). During testing, at one point the dynamo started to make a really awful noise. It turned out that a bit of twig was caught between the roller and its built-in “mini fender” and it sounded like the bike’s rear fender had been bent into the rear tire! (The mini-fender is there, by the way, both to provide a little protection for the bottom bracket generator from materials thrown back by the front wheel and the protect the bottom bracket area of the bike from any mess that the generator throws back.

Bottom bracket dynamos limit you in terms of tire selection, and they may—depending on the type of riding you do—be more likely to slip than any other kind of dynamo. This is especially a consideration if you ride on dirt or limestone (or other loose) paths.

Finally, they can make it harder to insert or remove a rear wheel, especially if you have horizontal dropouts, since they impinge–like fenders–on the tire’s space to move.


The final unit I will be reviewing is a philosophical and physical reworking of the bottle generator, manufactured by Velogical.  I’ve been riding with this unit for several weeks, and I have an interesting relationship with it.  Stay tuned!

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The Shocking Truth, Part 5: Bottle Generators

“This battle with the bottle is nothing so novel.”–Elvis Costello

 Elvis was right. There’s nothing really novel about bottle generators. They are so well-known that a non-cyclist will instantly know what one is, (thanks in part to the Simpsons),

Nor is it novel that they can work surprisingly well. In fact, the first thing I did when I got this idea about comparing dynamos was to check out the specifications on a series of bottle dynamos. On discovering that the Dymotec 6 was one of the best-rated, I did a quick check on prices and leapt to eBay–finding one that was in the US and was being sold for less than $50.


I also noted, in passing, that it came without a mount (bottle dynamos traditionally mount to bicycles that are intended to take them, but many or most modern bikes, certainly those sold in the USA, lack appropriate mounts, so you need to get your hands on the appropriate hardware.

Many bottle mounts look like bits of old Erector Sets (NB: I live down the hill from where the Gilbert family, of Erector Set fame, once lived). I didn’t want one of those, so I dug around until I found a mount that looked both minimal and strong. It came from England (there’ll always be an England!). But before it arrived, my patience had run out. The dynamo I had picked up turned out to be a left-handed unit…

Discursion: yes, dynamos are handed. A left-handed dynamo is intended to ride forward of the left-hand seat stay or fork; a right-handed dynamo runs on the other side. This has nothing to do with the internals of the dynamo, but rather has to do with the spring-loaded pressure system, which is designed to allow you to easily move the dynamo into contact with the wheel. If you look straight down through the roller, with the mount at the back, a left-handed dynamo will swing right to contact the wheel (and the reverse for the right-handed dynamo). This is not all that important. Most of the time!

…but, lacking an appropriate mount, my mind wandered to my workbench, and I suddenly remembered why I liked rack-mounting hardware so very much. I was able to quickly fashion a mount from a bit of steel rack strap. held down on one end by the front-rack mounting bolt, and tensioned across the fork (see illustration below). I protected the fork with a bit of helicopter tape.


Please pardon the messy shop in the background!!

This meant that the Dymotec 6 was mounted backwards–normally, for safety reasons, you’d want it installed ahead of the fork (so in case it came loose, you wouldn’t experience a sudden stopping event) but I was (1) in a hurry and (2) pretty danged sure of the mount, so I went ahead and installed it backwards anyway. Big Deal.

So. Did it work? Did it work?

In short, yes. I had good solid light front and rear.

What I also had was noise!

The tires I was using, Pasela blackwall 28mm tires, non-TG, wirebead, seemed to act like amplifiers. Remember when you were a kid and played with inflatable pool toys (if you did) and tapping one would make a kind of boom? Well, it felt like that’s what my tires were doing.

What’s worse, because (in spite of manufacturers’ best efforts) tires do not have a uniform shape, the sound varied a bit in frequency as the bottle (under pressure from its built-in spring) followed the varying shape of the tire sidewall.

Consequently, I tried something a little different, and moved the contact point from the sidewall to the rim.

Sidenote: This works because the roller on the Dymotec 6 is made of hard rubber, which provides some grip on a metal sidewall. There are other examples of this type of roller, but almost all low-priced dynamos have metallic rollers, which will slip on (and scrape up) alloy rims. You can (I am informed by others) put rubber grommets or O-rings on metal rollers to make them suitable for sidewall use, but that might take some experimenting.

Running the Dymotec on my rim seemed to improve the noise situation in terms of both the noise level and noise variation aspects.  

Having the dynamo mounted in front was also nice because it meant it was trivially easy to turn my lights on and off—the rubber-covered spring release was just inches away from my down tube shift levers. However, turning the dynamo off meant grabbing the body and moving it away until it clicked into its “off” position. Still and all, not too bad.

Costs Associated with Bottle Dynamos


There was a time when you could talk into any Target in the country and pick up a dynamo light set–and certainly any bike shop would have one. They might not have been good sets, but they would have them. It looks like that’s no longer the case, but you can go to Amazon and type in “dynamo” and find something pretty quick.

My research indicated that the best bottle dynamos was the Dymotec 6. This unit is fairly widely available–it can be obtained from Peter White Cycles, the Dutch Bike Co., Harris, and probably others, for less than $60.


While you’ll get the dynamo for $60 +/-, depending on where you go, you’ll also need to spend a little money on a mount, unless your bike comes with one built-in. Mine didn’t, so in addition to the mount I improvised from a rack mount, I spent $5 to get a seatstay mount from England. Now, $65 is not a trivial amount, but all told, it’s not bad for a light source. And…you don’t need to build or rebuild a wheel. That’s all to the good.


There’s a wide range of weights in bottle dynamos. The Dymotec 6, which has a plastic body, weights in at under 210 grams, mount not included (but not much more). Older dynamos, especially the beautiful and beautifully made Soubitez units, weigh a good deal more.



Here’s where I found things getting tricky. Remember that you have to take “handedness” into account when mounting, because you’re going to want to the dynamo to be able to move toward the wheel on its spring, once you release it from its standby position.

This required mounting the dynamo on the right side of my bike, behind the fork, using my improvised mount. In that position it worked well. I was able to reach the release button without endangering my hand, and turning off the dynamo meant grabbing the body of the dyno and moving it back to the locked position.

However, before you get there, you need to align the dynamo (this is discussed in the Dymotec manual). Essentially, you want to position the roller of the dynamo perpendicular to a line drawn out radially from the center of the hub. This minimizes additional mechanical resistance, and keeps the dynamo from “scrubbing” your tire or rim. Getting the dynamo properly aligned and the mount properly tightened to keep it that way can mean that you need an extra hand or two, keep things in the right position and to hand you 5- and 6-mm Allen wrenches, screwdrivers, and so forth. It’s not extremely difficult, and if you’re careful you’ll only need to do it once, but you should be aware. Also be aware that most dynamo mounts are designed to puncture your frame’s paint job, so that the dynamo is grounded to the frame–many dynamos are built this way and grounded through the case. The Dymotec 6 needs one additional cable to ground to the frame (see the instructions). Many dynamo mounts, such as the very fancy Dynamohalter, have a screw designed to punch through the paint for electrical purposes. The screw also helps keep the mount from rotating, so if you’re committing to this kind of lighting, it’s worth biting the bullet and going through the paint. It’s painful, but, as I said, you only need to do it once. The Dymotec can be grounded to its mounting tab via an included cable, so there’s no need for additional wiring to take care of that. A final note here–to ensure proper running of the dynamo on the wheel, whether rim or tire, the manufacturer tells you to set the dynamo so that its roller is about 10mm away from its running surface when it is not running. The Dymotec includes a knob for fine tension adjustment as well.


Although I purchased a seatstay mount for the dynamo, I was unable to use it. My foot struck the dynamo as I pedaled. This is a situation created by a combination of factors: (1) I use a crank with a very narrow “Q” factor, or tread, so my feet are pretty close to the bike at all times; (2) I have size 13 feet, which means they project back quite a bit while I’m pedaling; (3) Traditional bottle dynamos, such as this one, occupy a space partially outside the triangle formed by the seatstays. Consequently, without contorting my body, there was no way for me to ride with the Dymotec rear-mounted. My bike doesn’t have particularly short stays, but it’s possible that this would not have been an issue on a full-on touring bike. I could also have tried mounting the dynamo on the right side (as I had done in front) , but that would have interfered with mounting panniers, and so I decided not to try it. Because of this, most of my comments below will be based on the forward-reverse mounted Dymotec.


The Dymotec provides two hot and two ground connections on the “bottom” of the bottle, and comes with a nice two-conductor wire, prepped with lugs, so it’s easy to connect. In fact, it comes with pretty much all of the wiring options you need.


Overall Performance

Comparing the bottle to a dynohub, I did not notice much difference in lighting performance. The Dymotec, which meets the StVZO standard, did an excellent job of supplying power to the lights on my bike, and of charging the standlights’ capacitors. Because of mechanical coupling issues, any bottle dynamo will be less efficient than a hub dynamo, but I would have no concern using this system to ride at night.

I experimented with the dynamo running on both the tire sidewall and the rim. In general, I think running it on the rim works better for three reasons. First, pneumatic tires act like echo chambers, and so it was considerably noisier to run the dyno on the tire than on the rim. Second, the rim is more likely to be consistent in diameter than is the tire: Any variation in the rim (dents, etc.) will be reflected in the tire diameter, but any variation in the tire (and let’s fact it, unless you’re buying very pricey tires and tubes, there tends to be some variation caused by tubes bunching, etc., inside the tire). Consequently, running the dynamo on the tire will cause more variation in sound (which I personally find a little irritating) than running on the rim. Finally, you will see some wear from the roller on your tire–much less on the trim.   While some tires have dynamo tracks that deal with this problem and that are designed to reduce wet-weather slippage (e.g., the Vittoria Randonneur), using the tracks may be difficult if you also use fenders.

Wet Performance

My great fear was that moisture would cause serious slippage of the rubber roller. Fortunately, I was able to test this because the Connecticut weather cooperated. We had several days where there was heavy rain at night followed by light showers during the day. I tested wet weather running by running through deep puddles and riding in moderate rain (note that my particular arrangement of handlebar bag and fenders protected the dynamo from rain coming down, leaving it most vulnerable to road moisture). I found that with position and tension properly adjusted, I experienced no slippage running on either the tire or the rim. This was true of riding in the rain and riding through 2″ and deeper puddles.

It’s worth noting that I was not riding in a downpour, but in light to moderate rain. Nevertheless, I was very favorably impressed. There is a special roller available for the Dymotec 6 that uses a wire brush instead of a rubber roller. Supposedly, this will ensure operation of the dynamo in all weather conditions; I did not test it. My understanding from reading up on the matter is that most riders find they don’t need this roller in wet conditions, and it is better-suited to riding in snow and ice.

Charging performance

Bottle dynamos come in two flavors–voltage-limited (to protect the bulbs of incandescent headlamps) and unlimited, which presume voltage regulation at the lights. The Dymotec is of the latter type, and, consequently, can produce plenty of power for charging batteries or electronic devices.


Note that switching a bottle dynamo on or off requires physically moving the bottle into or out of contact with the wheel. If you’re using a front-mounted system, this is easily done while riding. Bart Simpson to the contrary, I suspect that most riders who use rear-mounted dynos will want to stop and engage/disengage the unit. This is not a big deal, as you’re unlikely to be turning your lights on and off. I will say that I have on occasion been on rides that pass in and out of forested areas, and it’s nice to be able to switch on your lights as you enter one of these darker patches. That’s one advantage that dynamo hubs have, since they can be switched electrically. It’s worth noting that some French builders (in particular) used to add a fitting for a shift lever onthe seat tube that could be used with a cable to engage/disengage a dynamo while riding.


Bottle dynamos are noisy. I’ve mentioned this above and I’ll reiterate it here. Running a rubber-rollered dynamo on the rim reduces this noise, and it’s likely that a read-mounted system would have seemed quieter still–my dynamo was in the perfect position for me to hear it! But recognize that the mechanical interface of roller and wheel is inefficient, and so there’s going to be resulting noise and heat. The sound is, as some have pointed out, similar to that of a small electrical motor (which is not surprising since dynamos and electric motors are, in many respects, similar devices–differing mainly as to whether motion is generating electricity or vice-versa). Some people find the sound comforting at night, since it gives other cyclists and pedestrians a little warning. I don’t like noise from my bike, and I found it a bit irritating.


Because the dynamo is mounted at the rim, I found that it was primarily noise rather than vibration that was an issue. Certainly there is some vibration, but it was for the most part lost in the road noise of Connecticut chip-seal roads. Vibration is unlikely to be a major issue.

Subjective Resistance

Again, there are two questions: Does the dynamo cause resistance, and can you feel it?

Of course the bottle causes resistance, and more than a dynohub. In addition to the electrical resistance of the device itself, which is significantly lower than that of a dynohub (see note), there is mechanical resistance, because the wheel now has an additional load connected to it at the rim.

NOTE:   Why is the electrical resistance of a bottle dynamo lower than that of a dynohub? The reason is that the small wheel of the dynamo roller spins many times for each rotation of the wheel, which means in essence that it can use smaller coils and magnets to generate the same amount of power as a dynohub. Much more motion is going into the bottle than into the hub (one consequence is that hub dynamos generally have more magnets, so more weight).

Can you feel it? Yes. The resistance is not large (again, pace Bart Simpson) but it’s there. And, in all honestly, it probably seems like more than it is, simply because you can hear it.

On the other hand–and it’s an important hand–you can completely disengage the dynamo when you’re not using it. No resistance, no noise, no vibration. Your wheel is then subject only to the vicissitudes to which any wheel is subject.



The Dymotec is built to last (I have seen 10-year evaluations on the web). One of the reasons it can last is that, in spite of, or perhaps because of, its use of a rubber roller, it’s easy to replace the roller. Mine came with a replacement roller kit and, as I’ve noted above, you can get a special roller for winter conditions. Replacing the roller consists of (1) snapping off a protective top cap with a flat-bladed screwdriver, (2) pushing a c-clip off from a plastic axle, probably with the same screwdriver, through better tools are to be had (this requires a little care–you don’t want the clip to escape!), and (3) lifting off the roller. Assembly is, as they say, the reverse of disassembly. Replacement rollers are generally around $5-$10, a trivial amount in cycling (grin!).


You can probably smash a Dymotec without any trouble. That being said, it’s unlikely that this would happen in practice without seriously damaging the bicycle to which it’s attached. So long as you don’t run into the problem that I had with the dynamo interfering with pedaling, it’s likely to keep quite safe.

Attractive Nuisance?

The risk here is that the dynamo is one more obvious thing bolted onto your bike. A casually malicious person may grab it and give it a twist while you’re parked, necessitating readjustment. But it’s unlikely to be a target for thieves. Our culture has assigned bottle dynamos a place of worthlessness that operates to protect them. All things being equal, I would be concerned for my saddle, handlebars, and wheels long before I would be concerned that someone might walk off with my Dymotec.

So, what’s not to like?

There’s very little not to like about the bottle. Other than the rear position problem I had, and that not everyone will have, my main reservation is the noise factor. I simply do not like the sound that the thing makes. If you have a particularly sleek bicycle, anything that hangs onto the frame is going to break up the line, and that can be an aesthetic consideration. If you have carbon rims, you’ll probably find slippage to be more of a problem than if you have alloy rims, and I suspect you’d want to run on the tire in that case. I’m not a fan of running anything on a tire sidewall that can leave a mark. It may be psychology, it may be the tires that I use, but the idea of a tire failing from sidewall wear (especially in front) scares the dickens out of me. This may be a lesser factor if you use heavy-duty tires.

Tires become much less of an issue if you run your dynamo on the tread surface itself. That was the philosophy behind the bottle’s cousin, the bottom bracket generator. That’s the next chapter in our electrifying saga!

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They Often Call Me Speedo/Leaving the Bike Lane

Now, they often call me Speedo
But my real name is Mr. Earl

–Ry Cooder, on Bop Til You Drop, song originally by The Cadillacs



This morning I varied my routine a little.  I’m going to be teaching a class this fall at a local university, so I decided to take some time and visit the library and the general area.  I zoomed around town at a furious 48 MPH!

Well, no.  I was at a stoplight when I looked at my computer and saw the max speed reading, and then I noticed that I was still going around 48 MPH ad the signal light on my computer was blinking rather rapidly.  I’m guessing that I was stopped with the magnet sitting just on (or just off) the sensor, and the result was a series of high-speed signals to the computer.  Who knows?  But I sure looked fast.


Also this morning–this school has some very nice bike lanes along the roads on its campus.  Unfortunately, like bike lanes in many places (and alas, especially like bike lanes near universities and colleges generally) this one was liberally supplied with broken glass.

So I didn’t use it.

Here’s my shout-out to transportation planners everywhere:  Cyclists will use bike lanes if they don’t cause problems.  This lane was less a solution to traffic issues than a guarantee of flat tires.  Many of the lanes in New Haven put riders in the Door Zone.  Those are problems.

Oh, and a related shout-out to environmental planners in the Connecticut Legislature:  Thanks so much for putting a return fee on bottles.  I’ve been in states with, and states without, and Connecticut has much less glass on its roads because it has a bottle law.  But if you want to make it work a lot better, make it a lot more than five cents.  Make it a quarter.  Because $.05 isn’t that much anymore, and I’ve seen an increase in road glass over the past five years in the state.

Meanwhile, thanks for all the views, and stick around for more electrifying dynamo information–coming soon!

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The Shocking Truth, Part 4: Dynohubs

If you check around bicycle message boards, you will see that, prior to ten years or so ago, most cyclists in the US relied on lighting systems powered by batteries, whether these were comparatively small systems, operated by AA or AAA batteries, or more sophisticated systems, running on sealed lead-acid or Nickel-based rechargeable batteries. Generally, such lights used halogen-based incandescent bulbs or—in the case of the smaller lights—some used small white LEDs, as that technology began to grow.

In the rest of the world, many cyclists continued to use dynamo-based systems. These were much lower-power, but had the advantage of not needing batteries (and so not being subject to batteries running out and/or the need to recharge. German law required lights on virtually all bicycles, and so it was there that lighting systems grew most sophisticated.

Then, and it’s not clear to me which came first, at some point 10 to 15 years ago, some American cyclists started to use European dynamo systems, and Peter White (of Peter White Cycles) began to import dynamo lighting gear that met the German standards.

This is my impression; it may have happened earlier, but that’s when I started to see more chatter about dynamo systems. I’m guessing the internet had something to do with this.

In any event, Randonneurs or Audax cyclists—folks who ride time-competitive events ranging from Paris-Brest-Paris on down—were among the adopters of dynamo systems. Their popularity in the USA might be traceable to the establishment of Randonneurs USA in the late 1990s. Randonneuring events often required equipment like fenders, as well as lights capable of running all night long, that were not part of the ordinary “racing” bicycles of the times.

Around ten years ago, a new (or rather, vastly improved) type of dynamo became popular among randonneurs. This was the hub dynamo, or dynohub, and it has probably supplanted all but batteries in the American bicycle power pantheon. Battery lights continue to be popular for their very high power output, useful in MTB night riding. With the advent of LED headlights, which are far superior to halogen or other conventional bulbs in turning power into light, dynohub popularity exploded.

This is because the dynohub has the highest efficiency of any dynamo system, and this is because it does not require any mechanical coupling to the wheel. Instead, the dynohub replaces the front hub of a bicycle, eliminating the need for any kind of roller, and the only coupling is electromagnetic, inside the hub itself. There, a set of magnets on the inside of the hub rotate around coils of wire which are fixed to the axle. The rotation generates alternating current in the coils, and this is brought outside to connectors on the hub.

The very sophisticated and popular SON dynamos, produced in Germany by Schmidt, are the best-known. However, Shimano also produces a wide range of hub dynamos at a significantly lower price, and these are held by most writers to be nearly as good as, quite a few just as good as, or (by a few) superior to the Schmidt units. My sense from reading over the material in this area and my own experience is that the Schmidt models are Dura-Ace to the Shimano’s Ultegra status. In other words, that the aesthetic and operational differences are marginal, while the price differential is not (Schmidt units cost two to three times as much as Shimano dynohubs). There are a number of other companies that produce dynohubs, but where they fall in the scheme of things is unclear, as none are as popular as these two. Generally, most dynohubs meet the StVZO standard, putting out (at least) 6 volts at 3 watts.

My primary experience has been with the Shimano DH-3N70, purchased and first built into a wheel in 2005. This is the unit I will discuss here, but it is reasonably representative of the class of dynohubs.

Cost Associated with Hub Dynamos


At the time I bought my hub dynamo, it was comparatively difficult to locate one, but that was probably because, being low on funds, I was looking for the Shimano rather than Schmidt units. Schmidt dynohubs have been available via web/mail order for some time, the most famous source being Peter White Cycles, who is also (unless I am mistaken) the North American importer for those hubs.

Pretty much any shop in the USA that deals with Shimano parts can order one of the Shimano dynohubs and build a wheel with it. Prebuilt dynohub wheels using Shimano parts are available through Quality Bicycle Products and often via eBay.


A good Shimano dynohub will cost around $100-150, depending on the model (the more costly units are somewhat lighter). There are lower cost units, but these often run at lower (sub StVZO) power levels or have have lesser bearings, solid axles, etc. A Schmidt hub will run in the $275-325 range.

Remember that this is the cost only of the hub. In addition, you will need a rim, spokes, and (unless you DIY) a builder. These items can add up, which is why dynohubs tend to be seen by maby as a high-priced spread. A wheel equipped with a Shimano dynohub will cost more than a good many low-end bicycles cost.


An ordinary Shimano 105 front hub (5500 series) weighs about 150g. The lighter and more costly of the Shimano dynohubs, the DH-3N80, runs 490g. (measured weights, Source here). The claimed weight for the SONdelux, Schmidt’s lightweight unit, is 390g. This means that going from a Shimano conventional hub to a Shimano dynamo hub costs you about 12 ounces.



Once it has been built into a wheel, installation of the hub dynamo is exactly the same (with one exception, see below) as installing any quick-release front wheel. The only exception is orientation:


Orientation is a factor because you will need to connect the hub to your lighting system any time you change a tire or tube, so you’ll need to make sure that the electrical connector is where you can get at it. Shimano uses a small plastic plug to connect wires to the hub; Schmidt uses tiny “spade” connectors. Both are easy to use, and take perhaps five seconds’ work to connect/disconnect (if, say, you need to patch a tube).


Overall performance

Overall, performance of the dynohub is outstanding. Its relatively high mass, large size, and robust construction mean that a dynohub can be extremely responsive.   As an example of this, when I walk the bike across the basement floor, both the headlight and the taillight flash brightly as the wheel turns. This is indicative of excellent low-speed performance. Indeed, although hub dynamos appear to be current-limited, in the sense that they will not put out more than 0.5 Amps (thus achieving the StVZO standard at 6v), they are capable of putting out a great deal more voltage. Indeed, this is one of the reasons that standlights work so well with hub dynamos; the extra power is stored in the light’s electronics and released to power the LED itself while the bike is stopped.

Wet performance

Because the dynamo does not require any mechanical coupling to the wheel’s rotation, there is no possibility of slippage in wet weather. Indeed, I have in the past ridden my bike through streets flooded by the Mississippi to the level of 10 inches or more, and while my feet got wet (and I moved plenty slowly!) the dynamo never failed me.

Charging performance

Dynohubs put out plenty of power for charging devices (like smart phones) while you travel. A number of companies make devices that turn the hub’s AC into USB-level output more suited for the diet of small electronics. This is nothing to sneeze at; a cell phone provides multiple functions that can be useful on tour(though my preferred approach is to charge an external battery, and use that to charge the phone later—belt and suspenders!).


One important difference between the dynohub and all other forms of dynamo is that with a dynohub, which is always rotating, turning your lights on and off is done with an electrical switch rather than by removing the dynamo’s contact with the wheel. (At least one company produces a dynohub that can be physically disengaged, but I have neither seen nor tested one). This means that the control for dynohub lights can be located anywhere you want it to be—e.g., in a small box on your handlebars, on the light itself, etc. This is not a huge deal, but it’s nice to have the option.


Hub dynamos are essentially silent. This is because the source of noise and vibration in dynamos is almost entirely the wheel/roller interface—and here, there isn’t one. Consequently, any nois from a hub dynamo is indicative of a defect in the product (I once bought a wheel with a Shimano hub dynamo that made a “wiping” sound as it rotated, and I returned it.


While noise should be a non-issue, I have experienced (as have others) a small amount of vibration when the hub is powering a light at certain speeds. The amount is fairly trivial, and seems to have to do with some electromagnetic resonance. Different hubs appear to generate this resonance at different speeds, and I experienced it at around 28 MPH with my particular unit. In general, the more power drawn by the load, the greater the vibration (hence, a halogen bulb connected to a dynohub is more likely to cause vibration than an LED headlight). This is not a major issue for all riders, but could be disconcerting if it happened unexpectedly during a high-speed descent. This is a good reason to get familiar with the operation of your lighting system, whatever it may be, during daylight hours.

Subjective Resistance

There are two questions here, really. Does the dynohub cause resistance, and can you feel it?

The first question is objective, and the answer is that yes, it does. This can be seen easily by spinning the wheel off the bike next to a wheel with no hub installed, or by holding the axle and turning the wheel. You’ll feel a definite “notchy” quality. As the wheel turns, one magnet is leaving and another engaging with a particular coil (actually, this is happening in several places in the hub at any given point). Thus, magnetic resistance will tail off as you turn the axle away from one magnet, and increase as you turn it closer to the next. The wheel will want to remain in a “stable” configuration. It is important to emphasize that this is not mechanical resistance, but an artifact of the generator. However, it is easily overcome on the bicycle. Note also that this resistance is greater when the dynamo is connected to a light.

But can you feel it? This is a subjective matter. Prior to undertaking this project, I would have said no. However, at that point I had been riding with a dynohub for almost ten years. I tended to leave it on at all times, so as to make myself conspicuous in traffic. I’ve done centuries this way, and did not notice any resistance. However, the first step in this project was to replace the front wheel with one using a conventional hub, and the bike did feel slightly livelier than it had before. It is possible that this was due to the twelve ounces or so that were gone from the front wheel. I do not appear to be any faster! But I would say that subjectively, you can sense a small amount of resistance.



In theory, dynohubs cannot be serviced, and places that sell them will warn you not to try. In fact, you can find videos on the internet that show you how to service dynohub. I have not tried this, and don’t plan to. Mine has served for 10 years, and I expect modern dynohubs are better built than when mine was produced. Once concern has been raised by Schmidt about moisture, because a typical hub dynamo contains a great deal more air and ferrous metal than a normal front hub. Consequently, sudden temperature shifts can cause air to move into and out of the hub through the bearings and seals, and that air can bring moisture into the hub, which can in turn cause internal rusting. Schmidt claims that its hubs have a system for equalizing pressure so that this does not become an issue. I have lived in places like the American Midwest and Northeast that have significant temperature and humidity swings, and have not experienced problems like this with my Shimano hub, but if it is a concern, the Schmidt units might be worth a look.


Dynohubs are as strong as any normal front hub. They are unlikely to be damaged by potholes, and no more likely to lose a chunk of flange than any other front hub. They are directional, and electrical connections are generally made on the hub’s drive side (in theory, running the hub backwards can cause the generator to “unthread,” but I have never heard of this in practice. (Schmidt now produces a hub that doesn’t need to be plugged into the bike’s electrical system; instead, custom faces are placed on the dropouts that connect when the hub is inserted—this does, however, require a custom fork at a minimum.)

Attractive Nuisance?

Your hub will probably not attract thieves. It is significantly larger than most front hubs, but it’s just a hub. At first, because in my younger days I had had a front wheel stolen, I was extremely nervous about leaving the bike locked up. However, other things on the bike are more likely to be stolen (a Brooks saddle, a nice headlight, a pump) and so I gradually lost my paranoia. Correct locking procedure will protect your front wheel in any event.

So, what’s not to like?

Some people think that dynohubs are ugly. Here’s a regular front hub (a current 105):


And here’s a dynohub (the model I use):

 DH-3N70 001

(The grey and black object obscuring the drive-side end of the skewer is the connector for the dynamo’s electrical output.)

The dynohub is clearly fatter, with much larger flanges (on the other hand, shorter spokes!).

Dynohubs are also significantly heavier than standard front hubs, as discussed above. Because the weight is at the hub rather than the rim, it shouldn’t have much impact. However, it’s clearly there when you pick up the bike.

You’re limited in terms of wheels. If you’re the kind of person who likes to switch wheels a lot, having your dynamo built into one of them can be an issue. Alternatively, if you’re happy with the wheelset you have, converting the front wheel to a dynohub may be costly—or impossible. Low spoke count wheels in particular will have problems with dynohubs, which typically come as 32- or 36-hole units.

Over time, however, a typical commuter will probably save money by running a dynohub instead of batteries. It cost me roughly $130 to have the hub and spokes of a wheel replaced with a dynohub; ten years later, it still works, which means it has cost me around $13 each year to have instant, no-charge, no-battery power.

That’s a lot to like.

I’m going to wait a few days before posting my next shocking truth, so if anyone has any questions—or wants to point out an inaccuracy J–feel free. Next up, we take a walk into the past, and spend some time battling the bottle.

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We Live in Public

And now, for a brief break from The Shocking Truth.  Potentially NSFW below.  Don’t say I didn’t warn you…






I have not seen the film We Live in Public.  But I want to steal its title, because we do.

This morning, in fact, I was sitting outside a coffee shop working on my notes about the Velogical rim dynamo (article forthcoming in the Shocking series).  I like this coffee shop because it opens at 6:00 AM, and I can just lock up my bike, walk in, buy a cookie, then sit down at one of the tables outside and read, work on my notebook, or (as this morning) work on note on my phone until it’s time to go to work.  I’m on a first-name basis with the staff, and we have nice conversations.  If it wasn’t facing a strip mall parking lot, it would be pretty ideal, but you can’t have everything.

This morning, as I was working on my notes, I heard a loud, exasperated voice nearby.  A woman was walking along the sidewalk just beyond the coffee shop’s enclosure saying (and I quote without censorship and with approximately the emphasis in the original):

“That’s fucking why I asked you the fucking question, you fucking dumbass!”

Now, let me be clear.  She was not saying this to me.  Nor was she saying it to anyone in the vicinity, or even to anyone who might be far enough away that her volume was merited.  She was wearing a cell phone headset, of course, and speaking to the person on the other end of the line.


This raises two concerns.


Now, when I was a teenager, I tended to talk that way (as did many of my friends).  But this woman was manifestly within three years, either side, of thirty.  Not a teenager.  By the time I was that age, (I’m 56 now) I had learned that this was inappropriate language in public.  And I learned that the people I respected most–coworkers, friends, people like that? didn’t use that kind of language in public.

But she, of course, wasn’t in public.  She was in the world of her phone call (hint:  it’s pretty inappropriate language for private conversations also, but what the hell).

This is the nub of my gist:  we live in public.  When you’re talking on a cell phone, you’re communicating not just to the other person on the line but to the other people around you.  When you work on a notebook, it’s not just you seeing the screen–it’s other people around you.

Observe yourself.  What kind of image do you want to project?


The constant use of “fuck” or “fucking” has devalued the the word.  It’s likely that the person on the other end of the speaker’s line didn’t blanch, because they were used to it from this source.

Now, I use words like that on occasion.  Pretty much everyone does when exasperated enough (even my wonderful spouse, shhhhh).  Such words significantly intensify a sentence and have the effect of conveying extreme frustration and anger.  They’re a spice, and, like cayenne, they can also be used in comedy because they represent extremity.  My favorite example of the moment:

(Available here.)

But if you use a spice or a word too much, it loses its flavor.  It becomes just another word, much as Woodie Allen complains about the devaluation of the word “love.”  (In (I think) Annie Hall, he points out something along the lines of “how I can I say I love you?  People love a car, a movie, a floor wax” (Allen then invents “lurve” as a substitute)).

Look, there is a shortage of decent intensifiers in language.  This is a particularly powerful one.  Use it sparingly.  You might surprise people.


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The Shocking Truth, Part 3 (Introduction, Believe it or Not!)

I’m about to start publishing an impressionistic comparison of various dynamos. It seemed like a good idea to write a technical introduction, so…

 A few days ago, I drafted two single-spaced pages of electrical theory. Then I realized just how unnecessary that was. So here’s a quick overview of what you need to know before I dive into the dynamos. Ready?


  1. All of these dynamos work the same way. They use magnets and coils of wire to turn a fraction of the rotating motion of a bicycle wheel into electricity.


  1. All of these dynamos meet the same standard, defined—for reasons beyond the scope of this introduction—by German standards known as StVZO. Each must generate enough power to run a 2.4-watt, 6-volt headlight. Here’s a useful side-bit: almost all modern headlights intended for use with dynamos fit this definition. Why 2.4 watts? Because traditional taillights used 0.6 watt bulbs. So: all of these dynamos are designed to put out 3 watts (at 6 volts).


  1. But they aren’t really dynamos. A dynamo puts out pulsating direct current (DC). These are actually generators, because they put out alternating current (AC). But I’m going to call them dynamos anyway, since most of the world does.


  1. But (2) is what a dynamo puts out. No dynamo is 100% efficient. The less efficient a dynamo is, in general, (a) the nosier it will be; and (b) the warmer it will run. Noise and heat are evidence of wasted energy. If a dynamo makes a lot of noise and runs warm, it may be putting out 3 watts—but it may be using 15 watts of your power to do that. A silent dynamo that runs cool might be using only 6 watts of input to create 3 watts of output. Consequently, a nosier and hotter dynamo will usually be a draggier dynamo (see: Bart Simpson).


All of that being said, I’m going to be looking at four different ways of building a dynamo:


  • Hub dynamos (as represented by the Shimano DH-3N70—since replaced with newer versions that seem to be functionally equivalent);


  • Bottom-bracket dynamos (as represented by the Sanyo NH-T6—no longer manufactured; replaced with the NH-T10, which was sold until a few years ago. There is a photo and brief discussion of the NH-T10 here—scroll down a bit;


  • Traditional bottle (sidewall) dynamo technology (represented by the Dymotec 6, widely acknowledged as one of the best bottles ever produced); and finally,


  • Updated sidewall dynamo technology in the form of the Velogical Trekking Model.


I have developed a set of categories within which I will rate each dynamo as Excellent, Satisfactory, or Poor (you may remember this system from elementary school). I will also have some miscellaneous comments on each unit. Each will be covered in a single post, and I will end this series with a discussion of the pros and cons of each.


Now, wasn’t that better than two pages of electrical theory?

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