Dynamo...

[Alan Quay]

to add to d8veh comment, the "dynamo" is almost always a 6v ac alternator. when rectified you get just over 4.2 volts dc, that is why if you look closely the dynamo bulbs are always 4.5 volt, becuase that is the "effective" voltage (root mean square) of 6 volts ac. if they were 6 volt bulbs they would be underpowered and dim. So to get up to 12 volts dc you would need 3 of them all very cleverly mounted & isolated as I mentioned before

Instead of three dynamos, you could rectify it, then use a dc-dc converter to bring it up to whatever voltage you like.

 

[VictoryV]

Instead of three dynamos, you could rectify it, then use a dc-dc converter to bring it up to whatever voltage you like.

remember you only have about 1.5 watts to start with!!

 

[JamesW]

Ahh slight problem then. 10w banggood led light cannot be powered especially if rear light is added to circuit.

 

[selrahc1992]

Ahh slight problem then. 10w banggood led light cannot be powered especially if rear light is added to circuit.

how about this http://www.atob.org.uk/bicycle-accessories/top-draw-dynamos-bush-muller-dymotec-s12-dynosys-lightspin/
£300 is a bit steep, but evidently it can be done

 

[Deleted member 4366]

That's a good link. Interesting what they say about dynamos. A 3w one knocked 1.4mph of their speed. A 10w one (if you ould find one) at about 60% efficiency would drag you back with 16w, which is about 1/4 of normal pedalling power. You'd feel it like a brake.

 

[JamesW]

The 10w I am quoting is the bangood light you linked to in the start of the lights again thread last year. It doesn't dip and draws about 1A at 9-12V. So you think that would act like a brake Dave?

 

[Deleted member 4366]

The 10w I am quoting is the bangood light you linked to in the start of the lights again thread last year. It doesn't dip and draws about 1A at 9-12V. So you think that would act like a brake Dave?

It would slow you down a lot. Unfortunately, you can't get something for nothing. What a lot of people don't realise is that with no load, a dynamo or alternator will spin freely, but, when you take power from it, it becomes much more difficult to turn.

 

[RobF]

No detectable load from the Alfine front hub dynamo/B&M lightset on the Rose.

The front light is adequate, but a commuter or someone doing forest trails at night would want more.

If I were commuting, I would probably deploy an extra rear light as well.

 

[JamesW]

No detectable load from the Alfine front hub dynamo/B&M lightset on the Rose.

The front light is adequate, but a commuter or someone doing forest trails at night would want more.

If I were commuting, I would probably deploy an extra rear light as well.

And this is my problem, my commute is approx. 20miles down unlit country lanes so when I need my backup lights, then they must be BRIGHT and reliable!! I was hoping just engaging a dynamo would sort this it is looking like it might not!

 

[Alan Quay]

And this is my problem, my commute is approx. 20miles down unlit country lanes so when I need my backup lights, then they must be BRIGHT and reliable!! I was hoping just engaging a dynamo would sort this it is looking like it might not!

Hmm. Has anyone mentioned that dynamos might not be the best way to go ?

;-)

 

[flecc]

And this is my problem, my commute is approx. 20miles down unlit country lanes so when I need my backup lights, then they must be BRIGHT and reliable!! I was hoping just engaging a dynamo would sort this it is looking like it might not!

Even the best dynamo lights are really only good enough for you to be seen. They aren't very good for you to see the way ahead and are especially poor on unlit lanes for seeing potholes, downed branches etc in good time. For that you really need todays good LED lights or torches with mounting adaptors.
.

 

[Deleted member 4366]

As I said before, you're making the problem much more difficult than it is. For unlit roads, you want one of those single or triple Cree T6 LED lights with a 4 cell (8.4v) battery pack - about £15 - £25 from Ebay. You put the light charger next to your ebike charger, and charge both together every night. You keep the Aldi lights in your pocket for emergency use. They give out a surprising amount of light - OK for emergencies, but not ideal for unlit cycle paths.

 

[Deleted member 4366]

No detectable load from the Alfine front hub dynamo/B&M lightset on the Rose.

The front light is adequate, but a commuter or someone doing forest trails at night would want more.

If I were commuting, I would probably deploy an extra rear light as well.

Turn your bike upside down and spin the front wheel as fast as you can. Time it to slow to a stop. Switch on the lights and repeat. Could you post the two times here?

 

[Kenny]

I bought a secondhand step through Panasonic Agattu recently and have been upgrading it ready for, hopefully, some better weather.

As it was already fitted with hub dynamo I just upgraded the light to a Busch & Muller 80 Lux Cyo, which is pretty close to the top of their range.

I'll try it out soon on some unlit roads and report back if it's good enough or not.

I may be wrong but I thought the Cree lights although, exceptionally bright, just put out a wide flood of light which could annoy other road users, whereas B & m are designed to shine the light only where it's needed.

 

[Deleted member 4366]

I may be wrong but I thought the Cree lights although, exceptionally bright, just put out a wide flood of light which could annoy other road users, whereas B & m are designed to shine the light only where it's needed.

The single emitter ones or the triple emitter ones set to one, give a nice beam with a bright patch for seeing the road and a bit of a spread beam for seing the kerbs. The beams are directional enough not to annoy other road users, provided that you point the beam correctly. The aluminium Banggood one with rhe horizontal fins also has a nice beam. When you put the multiple emitter ones on full, they flood the road with a much wider spread. The Banggod cylindrical one with multiple emiters gives about as much light as the single T6 ones, but it's more spread out. Both of those might be annoying for anyone other than the rider. For completely unlit roads and cycle paths, I think two of the single T6 ones would be ideal.

 

[Kenny]

Thanks for the info Davy. I'm definitely going to have a tinker with these lights sometime.

My Pro Connect headlight is DC so I might give the Banggood a try, it's a real bargain.

 

[the_killjoy]

Just use your bike battery to keep your rechargeable lights charged; then when the bike battery fails you will have a set of charged lights to get you home. Or is that to simple ?

 

[JamesW]

Just use your bike battery to keep your rechargeable lights charged; then when the bike battery fails you will have a set of charged lights to get you home. Or is that to simple ?

Ahh killjoy, you obviously missed the post where I said I don't do simple. I like complicated and interesting. Simple is for meerkats!
James

 

[RobF]

Ahh killjoy, you obviously missed the post where I said I don't do simple. I like complicated and interesting. Simple is for meerkats!
James

Charging the light while using it is not recommended by Lezyne for their USB rechargeables, so killjoy's idea may not work.

 

[lowranger]

Just to add my experience of a modern Dynamo set up (on Kalkhoff). It won't help you James as its a front shimano hub system BUT sorry to contradict a few comments on here. There is no detectable resistance in the hub ( yes I know by definition it's using energy, but I can't detect it and, with the massive range of the bike its immaterial) the front led light is more than up to riding unlit bridle paths at night and the rear led is very bright. There is a Capacitor or suchlike built in, the lights go onto a marker light setting whilst stationary for about 5 mins. So if there is rear hub Dynamo system out there james then it will work for you, but I guess at quite a cost.