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.