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Old 09-27-06, 12:24 PM   #1
guruguhan
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The guy at my LBS suggested a Sanyo bottom bracket over a dynohub...thoughts?

Hi all,

I was planning on getting a dynohub for lights on a tourer, but after speaking to my LBS, I don't know anymore. I had thought that when the light was off, a dynohub had no resistance (thought there was some kind of clutch), I was told that there is always resistance (does it increase when the light is on?). The guy at my LBS said he used a bottom bracket (Sanyo) in the past and that he preferred them, because there was no resistance when not needed.

how many of you prefer the hubs over the bb? How much resistance am I looking at with the hub? A hub setup, wheel and all, would be quite a bit more expensive, but I'd be willing to do it if over the long term I'd be happier. Any thoughts would be greatly appreciated.

Does the position of the bb ever cause problems?

Thanks
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Old 09-27-06, 01:02 PM   #2
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I've used my lights on tour once (in about 8 months of touring). Does anyone ride at night?

Thread hijack.... Are those generator things worth it? Can you use them to power a battery charger for your Ipod & phone?

They sure seem cool...
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Old 09-27-06, 01:04 PM   #3
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I've used my lights on tour once (in about 8 months of touring). Does anyone ride at night ?
I ride early AM and use my Cygolight all the time.
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Old 09-27-06, 01:36 PM   #4
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I have both types of generators. I have the Sanyo BB on my Giant Excursion and an older Dynohub on a 3 speed. The hub type does have some drag even when not being used but I consider it minimal. The drag does increase notably when the lights are on. The Sanyo generator works fine in most condtions, the worst being mud, snow or ice then it has a tendency to slip. It has no drag when not being used. If you are only going to need lights occasionally I would go with the Sanyo, it will prove to me more cost effective. If you are going to be riding in the dark every day the hub would be the way to go.

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Old 09-27-06, 01:58 PM   #5
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If you are going to use lights only occasionally, get battery LEDs.

If you are using your bike as a commuter as well as for touring, get the dynohub. The LBS guy is dreaming and isn't up with the latest technology. The drag with a SON dynohub in off is the equivalent of around 1 foot of climbing in a mile. About the same as riding up and over a gutter crossing. The drag with it on is, IIRC, around 3 feet per mile -- the same as riding up and over three gutter crossings. The older Shimano dynohubs had somewhat more drag, but the higher level models are now approaching the SON efficiency, although the drag, I believe, remains the same whether on or off. There are some technical differences between the SON and Shimano varieties, to do with wiring.

If matched with a good light, such as the Busch and Mueller Ovalplus, you get highly efficient optics that the powerful battery lights simply don't match, and you are burning only a 3W globe. There are LED lamps that are coming out of Germany that really are very, very good as well, largely because of the excellent optics.

You have your power source permanently on your bike, and you don't have to worry about whether your batteries are up to charge or not, and you just never know if you will be caught out late one afternoon still 30km from your camping destination.

I have never used a BB generator, but I did use an S6 sidewall generator, and if you want to talk about drag, then the sidewall will give you an extra workout. The BB generators are rated as not being much better, and certainly much, much worse than the dynohubs when engaged. Plus, a BB generator need a long run of wire to get to the front light, and we all know what happens with those types of wires -- the get snagged and eventually break.

By the way, people who "test" the freespin on my front wheel with the SON always walk away with doubtful looks on their faces. I even had one guy inform me after a 1200 randonnee that I desperately needed my bearings checked out. The fact is, at finger-twirl speed, the magnets in the dynamo are trying to overcome their reaction to reach other (like poles repel, opposite poles attract, etc). When ridden, the inertia of the rider overcomes this push-pull reaction and the resistance fades away to almost nothing when there is no power being drawn, and almost-almost nothing when a light goes on.
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Old 09-27-06, 02:33 PM   #6
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I bought a dynamo hub for commuting and left it on for a tour last May. The resistance is almost unnoticeable, whether the light is on or off. I only needed lights twice on that tour (one tunnel, and one pre-dawn ride to the airport to get home, but it sure was nice to just switch on the light and go without worrying about batteries, etc. I won't do another tour without a light if I can help it. Any tire driven generator (including bb generators) is going to slip on a wet tire, and rainstorms are a good time to have lights on your bike whether it's daytime or night time.
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Old 09-27-06, 05:52 PM   #7
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SON it is, thanks for the help
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Old 09-28-06, 04:29 PM   #8
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Ahh, I had to have a google search for that. It sounded interesting... the one I saw was $70! For a BB generator. And it came with the lights too. Oh, wait BB MOUNTED... contacts the rear wheel. Doh! Hey, they have a dyno in the hub, why not a dyno in the BB
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Old 09-28-06, 11:25 PM   #9
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I just spoke to a tourer who I met in Old Riga about this. He regularly rides all summer from Holland to wherever. Her mentioned problems with sand a dirt foulling up his BB generator. Currently he uses a hub generator and is much happier.
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Old 09-29-06, 12:53 AM   #10
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For touring I found the light was pretty useless, except off the bike for camping. With the new LEDs it's pretty hard to kill them so it isn't all that likely I will be out of light. The flashing LED are awesome. Though the white ones can do more harm than good.

I just found it pointless to drive places I haven't been with a small bike light. It's not the same as driving around the hood with lights on, or comuting.

I do like generator systems because they can be pretty cool. I have a nice german one on my recumbent.

Last edited by NoReg; 09-29-06 at 01:06 AM.
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Old 09-29-06, 01:04 AM   #11
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Some of my brevet buddies have SON's and they love them. I have ridden at night with a guy that had one and he powered two fork-attached flood lights with it. They were so bright they were like headlights on a car! I'm looking towards getting a wheel built around a SON this winter.
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Old 09-29-06, 06:06 PM   #12
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"Thread hijack.... Are those generator things worth it? Can you use them to power a battery charger for your Ipod & phone?"

Yes you can, more info can be found on the bikecurrent fAQ at http://www.burrow.ca/cyclist/bikecurrent-FAQ.html
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Old 09-30-06, 08:22 AM   #13
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Thanks bentbaggerlen!
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Old 09-30-06, 09:46 AM   #14
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I use a sidewall generator on my tourer, mainly for getting from the hostel/campsite to the pub in the evening. 3w output is enough for riding on dark lanes and people remark on the power compared to their small battery lamos.
Sidwall units may be preferable to hubs for occasional short duration use but hubs have it for reliability and all-weather performance. The key to efficient sidewall generators is in the mounting system. Clamps are useless, you need a braze-on tab or a brake mount unit.
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Old 09-30-06, 08:01 PM   #15
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Quote:
Originally Posted by valygrl
"Thread hijack.... Are those generator things worth it? Can you use them to power a battery charger for your Ipod & phone?*...
I would rather say "yes you could". It seems to be a rather complex process. Unless you have the spare parts around, I think that you will save money, weight and technical problems by investing in a small quick charger that you would plug on occasions. This Summer, I charged my camera and rasor batteries that way while eating in a restaurant.
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Old 09-30-06, 10:12 PM   #16
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Yeah, I just carry my wall chargers... I was just curious, actually. I don't like riding at night, so I don't think the investment would be worth it.
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Old 10-06-06, 07:20 AM   #17
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I am very happy with Shimano Generator Hubs. I have two bikes that came stock with Shimano: '05 Specialized Globe (good hybrid bike but heavy); Bianchi Castro Valley ( lighter commuter 10kg);

Yes, there is a noticeable drag when the lights are on. With lights off there is no discernable drag.

Why would someone need a generator hub? Commuting into work from September thru April, at 5:45am is dark. I tried rechargeable battery powered lights but there was too much to that routine.
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Old 01-07-10, 08:03 AM   #18
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BB Generator VS Hub Dynamo

In the eighties I was a huge fan of the Sanyo BB generator. I commuted everyday and at night as well. The biggest advantage of a BB generator is that with such a large driving pulley, (the wheel) it can turn at a very high speed. This provides more light than a hub system at the same speed. The hub turns slower than the rim, more correctly the hub travels less "distance" that the rim. Anyway I killed at least 3 of the Sanyo generators because of snow and rain. UNTIL I mounted it on the seat stays! Not only was it easier to turn on, had a shorter wire, but lasted until I sold the bike in Germany. I did have to cut a hole in the fender but it worked. I liked the system because it was cheap and always worked.

Today however I am using a modern Sturmey-Archer front hub for my commuter bike. I have to say that the drag is really un-noticable. I am using the Planet Bike lights front and rear and of course an additional LED blinking light on my messenger bag.

These other guys are right. If you want cheap go with a BB generator but mount it on the seat stays. (up near the rear brakes) If you are riding in the dark everyday get the front hub system it is well worth the effort.
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Old 01-07-10, 08:08 AM   #19
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Have used my lights on tour plenty of times. For me it depends on where im riding, when I am riding, and what the weather is like. My touring partner and I made up 30 miles (from a late start) by riding at night. It was actually one of the nicer pieces of the tour, but it was slightly sketchy as it was just woods on both sides, pretty much the whole 30 miles.

You might find, in the desert you will ride more at night than during the day. Also true in the early summer and late spring. I use a Blackburn Quadrant headlamp and a helmet light (all LED of course). More importantly are the red blinkee lights. These are what keep you alive and seen by vehicles.

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Old 01-07-10, 08:15 AM   #20
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Just got a Shimano Afline dynohub, I have noticed no increase in resistance - of course there is some, but it is unnoticeable. I leave the lights running all the time.
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Old 01-07-10, 05:52 PM   #21
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Quote:
Originally Posted by guruguhan View Post
I had thought that when the light was off, a dynohub had no resistance (thought there was some kind of clutch), I was told that there is always resistance
There is always resistance since there are unavoidable losses in the generator itself (IR heating of the coil wires, magnetic eddy current losses, etc) and more importantly, the generator acts as a motor that acts to stop itself. Even with no load the generator will actively resist movement (causing drag). More sophisticated generator hubs try to minimize this drag but it cannot be eliminated without a clutch.

Quote:
Originally Posted by guruguhan View Post
(does it increase when the light is on?).
Yes, it varies depending on the quality of the generator and your speed. Peter White's website has a nice chart from SON that shows actual data for various hub generators vs speed and load. It's in german but it looks like W of drag are on the y-axis and speed in kph is on the x-axis. There is a reference to 28" on the x-axis so I assume these data are for 700c wheels.

Quote:
Originally Posted by guruguhan View Post
How much resistance am I looking at with the hub?
With a 3W generator you will get 3+W of resistance. The '+' part depends on the quality (efficiency) of the generator and your speed. There is a tradeoff between how much voltage you get from the generator at low speed vs how efficient it is at higher speed. Generally, getting higher output at low speeds requires wasting more power at higher speeds. The only way to change this for a given generator is to change the wheel size since this affects the rotational speed of the generator at a given road speed. From the SON data referred to above, you can expect roughly 7-10+ W of drag at 20mph.

Hope someone finds this interesting.... I just find dynamos, ie generator/motors kinda cool.

Last edited by Iowegian; 01-07-10 at 06:30 PM. Reason: added real data, thanks SON!
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Old 01-07-10, 06:41 PM   #22
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I would rather say "yes you could". It seems to be a rather complex process. Unless you have the spare parts around, I think that you will save money, weight and technical problems by investing in a small quick charger that you would plug on occasions. This Summer, I charged my camera and rasor batteries that way while eating in a restaurant.
I do too, but I also have a cheap (ebay, < $10) 4-AA charger that will give me at least one complete iphone charge. Plus I use AA's in camera, rear tail light. Busch and Miller make an AA charger that runs off a hub.

Clearly the cost of a SON28 (~$260) plus the charger (~$125?) means that it isn't *worth it* in most cases, especially if we're talking about touring (commuting might be a different matter). I've been dithering for a year about getting one nonetheless. It's just so freaking cool...
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Old 01-07-10, 07:14 PM   #23
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it's obvious when you ride in the rain that the Sanyo is slipping. It's really not the time to have light flicker out. I wouldn't do hub dynamo unless you can hook it up to a high output LED. I've got a Son wheel with Schmidt halogen light and as reliable as it is it's not worth it for the light output compared to the average high output LED set up.
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Old 01-07-10, 08:37 PM   #24
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it's obvious when you ride in the rain that the Sanyo is slipping. It's really not the time to have light flicker out. I wouldn't do hub dynamo unless you can hook it up to a high output LED.
Well that is definitely doable.

http://www.sheldonbrown.com/harris/l...motec-hub.html
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Old 01-07-10, 09:57 PM   #25
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yes, for only another $108 on top of the $500 I spent for a Son Wheel and Schmidt headlamp, I could have bought two high powered battery systems that put out more light. I wonder if one can put in one of those LED replacement bulbs in the Schmidt headlamp?

Last edited by LeeG; 01-08-10 at 12:22 PM.
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