Dynamo...

[JamesW]

strictly for what its worth - I wouldn't consider a rim type dynamo...

From the amount for negative feedback towards dynamos, and given my intial stated aims, I suspect that actually a rim/bottle type dynamo is the way to go as it does not need to be in contact and wasting energy until the battery is not fixed/not making proper electrical contact at which point it could be flicked on and a switch flicked to switch the lights from battery to dynamo power. Given that this would be an emergency solution for the most part after my warrantee has expired (in a few months) this seems to me to be the way to go as efficiency is not as important as actually having lights when it is dark!!!

James

P.S. For those still grumbling about a dynamo on an ebike - I did point out at the start that I was aware of the power issues involved but was not interested as this is more for the instances when my battery connections fail or I choose to cycle without the battery (which I do occasionally as I am still fairly young and like to enjoy the quite of no motor!)

P.P.S - If I have a front hub motor with 3 phase wires and no hall sensors, I should be able to use this as a "dynamo" when it is not being powered shouldn't I? Spinning a motor with no power creates power if I remember my basic physics lessons. Can I use this to my advantage to remove the need to fit a bottle dynamo entirely (i.e. can I draw power from the motor?)
- And If I can draw power from the motor, can I draw power in different amounts to create an electric brake to save my brake pads (KERS style)?

 

[flecc]

Just one more point of bottle dynamo disapproval James! I suspect you've never heard them in action, but you won't enjoy the quiet of no motor when a bottle dynamo is in action, they can create quite a din, especially at the interface of the tyre wall and dynamo wheel. My last one was very noisy, enough to make pedestrians turn their heads.

As for drawing power from the hub motor, most of them are internally geared and have integral freewheels, the motor isn't running when pedalling without power. Generally it's just the larger diameter direct drive hub motors that are engaged all the time.

The same applies to braking, none on freewheeled motors. There is one design in Japan of one specifically to act as a complete electrical brake, but for the most part the braking force on other permanently coupled hub motors is very low.
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[Deleted member 4366]

James, you need to take a big step back to look at the problem you're trying to solve.
IIUC, you want emergency lights in case you get a problem with your main battery. You're worried that if you had emergency battery lights, the batteries might be flat when you need them.

Why not buy two pairs of the Aldi lights and keep them in their packaging. I've had mine (and used them occasionally) for three years and the batteries are still OK. These lights are so small, you can easily keep two pairs in your pocket, and they cost and weigh a lot less than a dynamo. If you're still worried, buy three or four pairs. If none of them work when you need them, I'll personally send a taxi to take you home.

 

[KirstinS]

I carry two Usb chargeable back up lights

I also carry a small portable charger that contains a single 18650 cell. It doubles as a back up for my mobile and my cycle lights


My main bike pack also has a usb out

Cheap, easy, smaller than a puncture repair kit

 

[tillson]

I think he's made his mind up that the emergency lights are going to be powered by a dynamo. That's not going to change.

 

[neptune]

Bike dynamos, as we all know, are really permanent magnet alternators. I remember seeing reference to an early bike dynamo, that really was a dynamo, complete with commutator and brushes. Alternators are simpler and cheaper than dynamos. I think the OP really just wants to have a tinker, and there is nowt wrong with that. I would agree though, that with modern LED lights, dynamos and alternators have outlived their usefulness. I bought a pair of Aldi lights that clip on with rubber bands, I gave them to my grandson, and he is still using them after months.

 

[flecc]

I think he's made his mind up that the emergency lights are going to be powered by a dynamo. That's not going to change.

Or by the e-bike's motor generating power, which makes me think James wants a complex solution in preference to the simple and obvious.

Maybe a bottle dynamo generating power for a miniature motor to drive a tiny compressor pumping the tanks of two Tilley lamps would be ideal.
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[neptune]

Had to laugh at flecc`s comments. Back in the 1970s I had a bike made from found parts. The lights were powered by a rim type dynamo. But I had it mounted on the handlebar, powered by a twelve inch diameter wind turbine. When riding headwind the lights were quite good, but with a tail wind, things got very dim... It did tend to attract strange comments though.

 

[JamesW]

Or by the e-bike's motor generating power, which makes me think James wants a complex solution in preference to the simple and obvious.

Maybe a bottle dynamo generating power for a miniature motor to drive a tiny compressor pumping the tanks of two Tilley lamps would be ideal.
.

...Well my family have always said if there is a simple and a difficult way of doing something, I'll invent an even more difficult and complex one!!

Neptune is quite right - I just want to tinker and tinkering with lights is less dangerous than tinkering with most stuff!

 

[selrahc1992]

...Well my family have always said if there is a simple and a difficult way of doing something, I'll invent an even more difficult and complex one!!

Neptune is quite right - I just want to tinker and tinkering with lights is less dangerous than tinkering with most stuff!

for what its worth, im all for tinkering (bicycles can be a relatively safe way to do just that in my reality - and, to misquote that bloke form sin city, there is nothing one cant do to a bicycle) - i'd still rather have a look at vintage sturmey archer hub dynamos though..

 

[flecc]

Neptune is quite right - I just want to tinker and tinkering with lights is less dangerous than tinkering with most stuff!

I agree James, I'm all for individuality and we've long been famed for our eccentricities. Same is easy, but same is boring too.
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[Croxden]

Neptune is quite right - I just want to tinker and tinkering with lights is less dangerous than tinkering with most stuff!

I thought that but my job as a lighthouse keeper didn't last long.

 

[JamesW]

well I did hear that those old WW2 search light mirrors were pretty good and mounting one of those on the front of your bike with a few bangood lights in the middle should make you more visible than Beachy Head on a foggy night. - As I said I like simple, now off to find the mirror on fleebay.....

 

[JamesW]

well I did hear that those old WW2 search light mirrors were pretty good and mounting one of those on the front of your bike with a few bangood lights in the middle should make you more visible than Beachy Head on a foggy night. - As I said I like simple, now off to find the mirror on fleebay.....

Ahh - found one :
http://www.ebay.co.uk/itm/WW2-GERMAN-ARMY-RARE-PART-OF-THE-HAND-SEARCHLIGHT-SYSTEM-WITH-A-GENUINECASE-/371217528146?pt=UK_Collectables_Militaria_LE&hash=item566e49f552

or maybe this one - far less than a haibike and much more beautiful
http://www.ebay.co.uk/itm/ANTIQUE-BRASS-SEARCHLIGHT-WWII-1939-FIRE-ENGINE-SEARCHLIGHT-ON-STAND-/201257604948?pt=UK_Antiques_AntiqueFurniture_SM&hash=item2edbe35754

 

[Deleted member 4366]

OK, if you want a dynamo, so be it. A word of warning though. Some dynamos are not dynamos. They give out a/c instead of d/c. Sometimes it doesn't matter, but if you use LED lights, it does. Also, you might need some sort of regulator to avoid blown bulbs/LEDs. It would be best to buy a dynamo with its matching light set, but that will probably be quite expensive.

 

[KirstinS]

Ok, lets do this overcomplicated thing . Some other overcomplicatwed but non dynamo ideas

Alternative Option 1)

Buy a cheap wind up torch with internal lithium battery. Take it to bits and keep the crank and the PCB only. Mount the crank to the top tube of your bike and run wires from the PCB output to your bike lights.

http://www.factorycarparts.co.uk/led-wind-up-torch-a50565.html


Alternative Option 2) Buy a windup up charger with a USB output for your backpack.

Something like this - http://www.amazon.com/ForeverBattery-KA710-Wind-up-Portable-Rechargeable/dp/B00B4H3K50


Alternative Option 3) Build a piezo electric energy harvester ! (you're on yer own here though)

 

[JamesW]

OK, if you want a dynamo, so be it. A word of warning though. Some dynamos are not dynamos. They give out a/c instead of d/c. Sometimes it doesn't matter, but if you use LED lights, it does. Also, you might need some sort of regulator to avoid blown bulbs/LEDs. It would be best to buy a dynamo with its matching light set, but that will probably be quite expensive.

Wheatstone bridge to rectify + smoothing cap could I then run this into a 4x 18650 (or whatever the laptop cell type is) as a charge buffer?

Not convinced that there are gears in my motor - it is at least 4yrs old, probably more, I'm guessing it was made 8 yrs ago by various stickers on the kit and it's very big (15cm dia). How could I tell if my hub motor is geared and connected all the time?

 

[JamesW]

Ok, lets do this overcomplicated thing . Some other overcomplicatwed but non dynamo ideas

Alternative Option 1)

Buy a cheap wind up torch with internal lithium battery. Take it to bits and keep the crank and the PCB only. Mount the crank to the top tube of your bike and run wires from the PCB output to your bike lights.

http://www.factorycarparts.co.uk/led-wind-up-torch-a50565.html


Alternative Option 2) Buy a windup up charger with a USB output for your backpack.

Something like this - http://www.amazon.com/ForeverBattery-KA710-Wind-up-Portable-Rechargeable/dp/B00B4H3K50


Alternative Option 3) Build a piezo electric energy harvester ! (you're on yer own here though)

Alternative Option 4 - have something almost exactly like this phone charger already...
http://www.banggood.com/USB-Hand-Power-Dynamo-Torch-Charger-For-Cellphone-p-80039.html
Connect to crank shaft and must pedal to get lights?

 

[flecc]

How could I tell if my hub motor is geared and connected all the time?

Internally geared hub motors have been around for over a decade and are by far the most common.

To check, turn the motorised wheel forward and then try turning it backwards. If it's much easier forward than backwards, it's geared with an internal freewheel.
.

 

[VictoryV]

OK, if you want a dynamo, so be it. A word of warning though. Some dynamos are not dynamos. They give out a/c instead of d/c. Sometimes it doesn't matter, but if you use LED lights, it does. Also, you might need some sort of regulator to avoid blown bulbs/LEDs. It would be best to buy a dynamo with its matching light set, but that will probably be quite expensive.

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