Bottom Bracket Dynamos
 

Not sure if best posted here or in the Electronics section.

I noted yesterday that Peter White Cycles is importing Sanyo bottom bracket mount dynamos. IMO good replacements for those which have died on older bikes or even for a new dynamo lighting installation on a steel frame road or touring bike. Reasonably priced too by todays standards.

http://www.peterwhitecycles.com/sanyo.asp

I need a visual. Does anybody have a picture of the BB dynamo installed on a bike?

Sounds very interesting indeed!

These are very cool, but I don't understand why they call them "bottom bracket dynamos". They're not directly powered by the turning of the axle at the bottom bracket. Why aren't they just called "rear tire (or wheel) dynamos"?

They are affordable for sure. I wonder what the weight difference between a normal hub plus this dynamo is compared to a Shimano 3N-80 or SON. I would assume the rolling resistance from a good quality hub dynamo would be less than this dynamo. Am I correct in that assumption? It would seem to be more prone to problems (misalignment, dirt/water, etc) too. Then there are the little things like unsightly wire to the headlight.

They're called "bottom bracket dynamos" just because that gives the best indication of where they mount, as opposed to "sidewall dynamo." Both sidewall and BB dynamos are tire-powered, as opposed to "hub dynamo." You're right, of course, that it's not a very helpful name... but I can't think of a better one.

I had one for many years, and liked it because it didn't mess up the lines of the bike as bad as a sidewall dynamo. It seems very nicely made, and felt like a high quality unit in my hands. But in retrospect I must admit it wasn't actually a great dynamo. It was difficult (okay, impossible) to adjust the pressure of the spring, so on one bike there was too much pressure, on another there wasn't enough. If there wasn't enough, it would slip intermittently, especially in the rain when you most want it to be reliable. Of course you assume your wheel is round, but in practice it probably isn't; so you get flashes of light as you ride. As a result the dynamo spent most of its life in the parts bin. About five years ago I finally found a bike on which it fit perfectly (mounted to the kickstand bracket) and was happy to be using the dynamo... but the bearings conked out after about one mile of riding, and that was that.

That is exactly what I was thinking before I went to the provided link to Peter White Cycles as well. I thought it was the Gruber Assist design, but than the rider providing the power.

I also think that it is possibly better to have it touching the rear tire on the side to pickup less dirt and stuff.

Here is one the my Soubitez dynamos:
http://www.os2.dhs.org/~john/soubitez.jpg

How about "tread dynamo" as opposed to a "sidewall dynamo". Anyhow, it doesn't matter at the end of the day what it's called.

Did you have to modify the rear fender to use this type of dynamo? I imagine most cyclists who would use a dynamo would also want fenders; I do. EDIT: I think JohnDThompson's photo answered my question.

I'm still waiting to hear about this game changing dynamo they've eluded to over at the VO blog.

One of the problems with the side-mounted "bottle" dynamos is that if they get loose they can fall into the spokes with disastrous results.

It is also my experience that the chainstay mounted dynamos put less drag on the wheel, but I can't quantify this.

If you have ever seen one on a bike, BB dynamo is a pretty good name. That Sanyo hub dyno looks good too, I think I might get one for my daughter's bike.

No. Fenders typically do not extend below the chainstay bridge; the dynamo mounts below this. C.f. the picture I posted above (black fender is visible above the chainstays).

Right. The name communicates a reference to an object. If you know what that object is, you're good; if you don't, you may well think of something else. Bummer... but you'll get over it.

I did not. The rear fender had a J-shaped clip that hooked to that little frame bridge that connects the stays behind the kickstand mount; so the BB dynamo hit the tire just below the fender. I got lucky on that bike; my trek 720 had successfully resisted all my efforts to mount the same dynamo in the same place. But then again, as I said, my Sanyo BB dynamo failed almost immediately after I got it installed correctly (and I'd only had it 25 years at that point:rolleyes:), but I suspect the fender would have caused a problem had I ever used it in the rain-- collecting all that water and shooting it down right where the dynamo roller and the tire meet: right where you don't want it.

Yeah, sounds interesting. They're pretty stingy with details, eh?

It solves some problems and creates some more. I believe it is more energy efficient, i.e. it can create less kinetic drag than a sidewall generator creates. But that's under ideal conditions.

Maybe it would help to experiment with adding a temporary surface on the drum of this dynamo. You might be able to make one with silicone glue, such as Shoe Goo.

One chief problem is that this is a very dirt-prone area of the bike. That's probably what did in rhm's generator.

It'll probably produce little to no resistance, be super shiny, cost less than $100 and power multiple mobile devices in addition to the lights. Soon after its release one or more in use will explode and maim or kill someone or perhaps worse cause cancer or dementia with little exposure. :rolleyes:

Also relatively few tires have a bottle dynamo roller drive strip molded on the sidewall any more. Most Schwalbe city tires do but few others. Without that a sidewall dynamo can be rough on a tire.

BB dynamos had the reputation of being more efficient than sidewall dynamos but I have not seen it quantified. I suspect they disappeared as common equipment in the USA when mountain bikes took over 90% of the market as they will not work with knobby tires. They also require good wiring sealing as they sit in probably the wettest and dirtiest possible position on a bike.

The hub dynamo is almost certainly the most reliable version but it has the major disadvantage of requiring a new wheel be bought or built to install it. The BB dynamo is a reasonably priced alternative IMO for occasional use that I intend to try out.

We need a 12v, eye splitting, hub dyno that is 90% efficient. And comes with all the accessories to power smart devices, for $100

Now that would be game changing.

Yes, you would think that; but for all the miles I rode while I owned that dynamo, in fact it I don't think I had it installed for more than a couple hundred miles. Maybe less than 20.

Having used both extensively, I can't see why anyone would choose a bb dynamo when such good hub dynos are available so inexpensively. Admittedly, bb dynos are an improvement bottle dynos, but that wouldn't take much, IME. But, again, when something even better is available, why bother?

Oh yes - there is the old red herring of "added resistance when the light is off", which might be meaningful if you were racing, and if the difference was actually measureable. I'm running a Shimano DH-3N71 on the front of my recumbent. This is a dyno designed for a 26-28" wheel being used in a 20" wheel, which should theoretically add even more resistance. As it is, my cruising speed is about .3mph (three tenths) slower - with the light ON! With it off? Suffice it to say that I keep track of my commute times, and I'm currently going faster than ever.

So yeah, bb dynos were pretty cool 25 years ago, but now they're just a retro curiosity. No functional reason to use one instead of a decent hub dyno.

SP
BEnd, OR

Yeah, I have to agree. I've been tempted to get one to use on my touring tandem, only because it has Phil Wood hubs; I don't know if a hub dynamo would hold up as well as them. That's the only reason for the BB dynamo for me.

My Velo Sport came with one of these and internal wiring.

http://i23.photobucket.com/albums/b4...0/DSC01966.jpg



http://i23.photobucket.com/albums/b4...0/DSC01973.jpg


http://i23.photobucket.com/albums/b4...0/DSC01972.jpg

Very cool! I am soo tempted to drill little holes in all my frames and run the dynamo wires internally. What could possibly go wrong....

I had to double check that I was on the Classic & Vintage list and not Electronics & Lights.

tcs

rhm, if you used SKS chromoplastic fenders, you could use the fenders as wiring. There is an insulative plastic strip down the middle making the two sides into two conductors.

FWIW, I've ridden mine in plenty of rain and other foul weather and it's never had a problem.

These days you're probably right. When I bought my Soubitez dynamos (about 30 years ago), there weren't many good hub dynamos. Sturmey-Archer made one of course, but it was heavy as sin and had pretty low output. The Soubitez is relatively light, and came with halogen head and tail lights. It's been plenty bright for my commuting needs over the years. If/when it ever dies, I'll probably replace it with a modern hub dynamo. Do they come with brakes as well? My commuter is set up with front and rear drum brakes for reliable all-weather braking.

Carbide