Dynamo system choices

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Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Dynamo system choices

Postby Brucey » 14 Feb 2018, 10:23pm

Giles Pargiter wrote:This is where we disagree then Brucey.

Due to the extra around 500grams (approx, depending on exact dynamo, IRC the B+M weighs 120grams,) you always carry with a hub dynamo...


for £65 you can buy a hub generator that weighs between 360 and 390g depending on who you believe. This is only ~225g heavier than a fairly light conventional hub, not +500g. And only ~100g heavier than a bottle dynamo. Most folk have a £ per gramme saved when choosing parts that strongly indicates they don't give a monkeys about weight.


and the slight eddy drag of even the best, taking into account the fractional extra drag of a bottle dyno in operation you will find that you will need to be using lights at least 90% of the time for the best hub dyno's to be more efficient.

Your maths is broken. The best hub generators drag less than 1W extra (lights off) at touring speeds, but are ~5W less draggy when the lights are on vs the best bottle dynamo that you can presently buy (just). You would need to use the lights about 20% of the time to break even, not 90%.

Note also that this assumes that having yet another warty thing hanging off the side of your bike creates no aero drag, which is obviously wrong. I don't know how much it takes to push a bottle dynamo through the air but it could easily be 1 W.

I don't think the point about which tyre you choose is very relevant really as this is in no part dependant on the dynamo. You do not need a tyre with a dyno track whatever type of dyno you use.


I disagree and have witnessed the consequences first hand.

Not to mention that with all things considered hub dynos are enormously more expensive.


you can buy a bottle dynamo for £1.25 if you like. It will probably drag the thick end of 20W when you are using it, and have a very short life expectancy. Your favoured dynamo presently costs £35 (where you can find it NOS), which would enable you to have a choice of pretty reasonable hub generators.

The World has moved on; if bottle generators were so great we'd all still be using them and B&M would still be making them. My abiding memory of using them is getting to the end of any given journey with a sense of profound relief; relief that the blinkin' thing didn't just break (again) and relief that I wouldn't have to listen to a sound like a kitten being strangled any more, shattering the silence of the night and fraying my nerves to shreds.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

mercalia
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Joined: 22 Sep 2013, 10:03pm
Location: london South

Re: Dynamo system choices

Postby mercalia » 14 Feb 2018, 11:23pm

Brucey wrote:
Giles Pargiter wrote:This is where we disagree then Brucey.

Due to the extra around 500grams (approx, depending on exact dynamo, IRC the B+M weighs 120grams,) you always carry with a hub dynamo...


for £65 you can buy a hub generator that weighs between 360 and 390g depending on who you believe. This is only ~225g heavier than a fairly light conventional hub, not +500g. And only ~100g heavier than a bottle dynamo. Most folk have a £ per gramme saved when choosing parts that strongly indicates they don't give a monkeys about weight.


and the slight eddy drag of even the best, taking into account the fractional extra drag of a bottle dyno in operation you will find that you will need to be using lights at least 90% of the time for the best hub dyno's to be more efficient.

Your maths is broken. The best hub generators drag less than 1W extra (lights off) at touring speeds, but are ~5W less draggy when the lights are on vs the best bottle dynamo that you can presently buy (just). You would need to use the lights about 20% of the time to break even, not 90%.

Note also that this assumes that having yet another warty thing hanging off the side of your bike creates no aero drag, which is obviously wrong. I don't know how much it takes to push a bottle dynamo through the air but it could easily be 1 W.

I don't think the point about which tyre you choose is very relevant really as this is in no part dependant on the dynamo. You do not need a tyre with a dyno track whatever type of dyno you use.


I disagree and have witnessed the consequences first hand.

Not to mention that with all things considered hub dynos are enormously more expensive.


you can buy a bottle dynamo for £1.25 if you like. It will probably drag the thick end of 20W when you are using it, and have a very short life expectancy. Your favoured dynamo presently costs £35 (where you can find it NOS), which would enable you to have a choice of pretty reasonable hub generators.

The World has moved on; if bottle generators were so great we'd all still be using them and B&M would still be making them. My abiding memory of using them is getting to the end of any given journey with a sense of profound relief; relief that the blinkin' thing didn't just break (again) and relief that I wouldn't have to listen to a sound like a kitten being strangled any more, shattering the silence of the night and fraying my nerves to shreds.

cheers


well mine b&m has never broken down in nearly 18 years or so the sound is a low whine of an electic motor. the only thing that would concern me is the extra effort that is in short supply thse days, why i prefer a battery system- changeing the tyres not really possible as i spend too much time on bad surfaces. by the way batteries rule in london, rarely see a dyno of any kind. the way ahead is a lamp with a separate powerbank

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[XAP]Bob
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Re: Dynamo system choices

Postby [XAP]Bob » 15 Feb 2018, 9:22am

My B&M bottle only handled one summer - it was fine through the winter, because it was constantly in use. In the summer it was rarely in use, but still got wet occasionally. It had completely seized by the next winter...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

SA_SA_SA
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Joined: 31 Oct 2009, 1:46pm

Re: Dynamo system choices

Postby SA_SA_SA » 15 Feb 2018, 10:58am

I meant to get a hub generator when my Nordlicht bottle wore out....years later, .it hasn't
IsGood ? :) : :(
I may just retire it early I suppose.

I don't really mind the whirr from a bottle* which I suppose just proves everyones different
*(but I like kittens/cats and don't hear any link fortunately) :)
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mercalia
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Joined: 22 Sep 2013, 10:03pm
Location: london South

Re: Dynamo system choices

Postby mercalia » 15 Feb 2018, 11:11am

[XAP]Bob wrote:My B&M bottle only handled one summer - it was fine through the winter, because it was constantly in use. In the summer it was rarely in use, but still got wet occasionally. It had completely seized by the next winter...


well did you try using some wd40 to unseize it? flush out the rubbish. I have done that once when the spring action became tardy and that did the job

since the last few contributions have dismissed bottles as unreilable what about problems people have with hubs? what are their experiences?

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Dynamo system choices

Postby Brucey » 15 Feb 2018, 11:22am

an issue if the generator is seized is that the shaft may be corroded where it passes through the bushings/bearings. IME if this is the case then should you manage to free the thing off so it turns again, the subsequent rate of wear in the bearings may be very high so that it will fail shortly anyway. At least one of the several generators that have failed on me failed in this way.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

mercalia
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Location: london South

Re: Dynamo system choices

Postby mercalia » 15 Feb 2018, 11:23am

SA_SA_SA wrote:I meant to get a hub generator when my Nordlicht bottle wore out....years later, .it hasn't
IsGood ? :) : :(
I may just retire it early I suppose.

I don't really mind the whirr from a bottle* which I suppose just proves everyones different
*(but I like kittens/cats and don't hear any link fortunately) :)


Mybe Brucey has a bad habit of running over cats all the time :wink:

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Dynamo system choices

Postby Brucey » 15 Feb 2018, 12:10pm

mercalia wrote:
Mybe Brucey has a bad habit of running over cats all the time :wink:


so far only badgers and squirrels, neither deliberately. :wink:

cheers
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[XAP]Bob
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Re: Dynamo system choices

Postby [XAP]Bob » 15 Feb 2018, 6:12pm

mercalia wrote:
[XAP]Bob wrote:My B&M bottle only handled one summer - it was fine through the winter, because it was constantly in use. In the summer it was rarely in use, but still got wet occasionally. It had completely seized by the next winter...


well did you try using some wd40 to unseize it? flush out the rubbish. I have done that once when the spring action became tardy and that did the job

since the last few contributions have dismissed bottles as unreilable what about problems people have with hubs? what are their experiences?

I did try at the time, I should open it up, it’s still sat in a drawer.

It’s the rotor that won’t turn, at all... I’ve grabbed each end quite firmly and tried to twist, but there is no hint of movement at all, even when I go full gorilla ;)
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

mercalia
Posts: 10535
Joined: 22 Sep 2013, 10:03pm
Location: london South

Re: Dynamo system choices

Postby mercalia » 15 Feb 2018, 6:27pm

[XAP]Bob wrote:
mercalia wrote:
[XAP]Bob wrote:My B&M bottle only handled one summer - it was fine through the winter, because it was constantly in use. In the summer it was rarely in use, but still got wet occasionally. It had completely seized by the next winter...


well did you try using some wd40 to unseize it? flush out the rubbish. I have done that once when the spring action became tardy and that did the job

since the last few contributions have dismissed bottles as unreilable what about problems people have with hubs? what are their experiences?

I did try at the time, I should open it up, it’s still sat in a drawer.

It’s the rotor that won’t turn, at all... I’ve grabbed each end quite firmly and tried to twist, but there is no hint of movement at all, even when I go full gorilla ;)


well mine didnt seize up but I did in the end flush it out with lots of wd40 as when it turned it started to grate and grind so there was muck inside. Has been fine ever since.

cycle tramp
Posts: 504
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Re: Dynamo system choices

Postby cycle tramp » 15 Feb 2018, 6:56pm

Brucey wrote:The World has moved on; if bottle generators were so great we'd all still be using them and B&M would still be making them. My abiding memory of using them is getting to the end of any given journey with a sense of profound relief; relief that the blinkin' thing didn't just break (again) and relief that I wouldn't have to listen to a sound like a kitten being strangled any more, shattering the silence of the night and fraying my nerves to shreds.

cheers


I wouldn't say that the Whole World has moved on.. bottle dynamos are still popular in Germany and the Netherlands and i believe still being made by companies like AXA....
...bottle dynamos still represent a cost effective way of achieving a fit & forget lighting system whereby all the parts can be replaced without too much issue...
...admittedly a level of care has to be used to get the best from them.. i always use an earth wire as well as a live and use 5 amp spade connectors at the end, as well as solidly mounting the dynamo to the frame..
...Probably less than 5% of my riding is done at night... so i remain content with my bottle dynamo & halogen bulb set up (& the box of spares that i've purchased 2nd hand from fellow riders looking to set their old equipement through this forum after upgrading to dynamo hubs) :- )

pete75
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Re: Dynamo system choices

Postby pete75 » 15 Feb 2018, 7:39pm

Brucey wrote:The World has moved on; if bottle generators were so great we'd all still be using them and B&M would still be making them. My abiding memory of using them is getting to the end of any given journey with a sense of profound relief; relief that the blinkin' thing didn't just break (again) and relief that I wouldn't have to listen to a sound like a kitten being strangled any more, shattering the silence of the night and fraying my nerves to shreds.

cheers


B+M are still making them - certainly they are listed on their website. Methinks you're over exaggerating by a biggish factor in your description of bottle dynamos.


http://en.bumm.de/produkte/mehr/fahrrad ... tec-6.html

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interestedcp
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Re: Dynamo system choices

Postby interestedcp » 15 Feb 2018, 8:54pm

pete75 wrote:
B+M are still making them - certainly they are listed on their website.
http://en.bumm.de/produkte/mehr/fahrrad ... tec-6.html


I think they just haven't updated their English site. The Dymotec 6 is gone from their German bumm.de site. According to the the US B&M importer they stopped making the Dymotec 6:
http://www.peterwhitecycles.com/dymotec.php

The sales must have been reduced to practically nothing for B&M to discontinue the Dymotec 6, since they have the rather commendable habit of continuing making older products as long as they sell, even when they technically have been superseded by newer versions. So they are still making and selling halogen bulb front and rear lights, whose basic design must be around 18 years old if not older.

(Edit: corrected S6 to Dymotec 6)
Last edited by interestedcp on 15 Feb 2018, 9:23pm, edited 1 time in total.
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Regards

Brucey
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Re: Dynamo system choices

Postby Brucey » 15 Feb 2018, 9:22pm

they stopped making the S6 and S12 models some years ago, and have more recently stopped making the more basic Dymotec 6 model. It is still in stock at some retailers; I provided a link to it upthread.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

mercalia
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Location: london South

Re: Dynamo system choices

Postby mercalia » 15 Feb 2018, 11:45pm

I get the impression that the major stockists we might use in Germany dont have any now. I am just glad I got my self a spare at a low price afew years ago