Dynamos - Hub or Bottle?

[Cyril Haearn]

A hub dynamo is FaF, fit and forget
I fear there is a black market in them, my front wheel was stolen once
Now I lock both wheels and frame to the stand

[Mike_Ayling]

Apologies if it has already been mentioned but are the "bottle"dynamos that fitted under the bottom bracket and drove from the topsurface of the tyre still around?

Mike

[Brucey]

Apologies if it has already been mentioned but are the "bottle"dynamos that fitted under the bottom bracket and drove from the topsurface of the tyre still around?...

you occasionally see them NOS on ebay. But offhand I can't think of any that are actively being made/marketed new.

They suffer from the problem that the part of the bike they use to drive the roller is the one that is first to be both wet and dirty, so wear and slippage are never far away. When you are not using the thing it just sits there collecting crud. Amazingly the mounting position collects crud from both the front and the rear wheels at the same time; a neat trick!

cheers

[Greystoke]

When I was a young lad someone I knew fastened the roller dynamo in front of the rear brake to avoid this. He had to cut the mudguard etc....it solved one problem but created others

[SA_SA_SA]

When I was a young lad someone I knew fastened the roller dynamo in front of the rear brake to avoid this. He had to cut the mudguard etc....it solved one problem but created others

The official version of that (but for front wheel) was the Union Maus(mouse cos it scurries along the top of the tire )...

I have just made one from a old sanyodynopower and and a threaded M6 rod with spacers for a folder:

it requires carrying a toothbrush to clear it of any sticky mud from country roads...
when it slips it squeals high....
After the 1st test ride I had to build a little mudguard for the roller to stop spray of gunk...
I think I now know why no one imported them to the UK...

Interesting I never had much trouble with a bottom bracket soubitez (but this only drove a front lamp as I used the entire output of a separate 3W bottle for a thirsty car-like wide beam rear filament lamp......).

[mjr]

A hub dynamo is FaF, fit and forget
I fear there is a black market in them, my front wheel was stolen once
Now I lock both wheels and frame to the stand

I think it far more likely that someone else parked near you and locked only their front wheel. It's pretty common around Cambridge for a casual thief to steal an unsecured frame and a nearby unsecured front wheel, especially a QR front wheel, but I have been told of cases even in King's Lynn (which has little cycle theft except for just before the start of the universities/colleges year).

[Cyril Haearn]

A hub dynamo is FaF, fit and forget
I fear there is a black market in them, my front wheel was stolen once
Now I lock both wheels and frame to the stand

I think it far more likely that someone else parked near you and locked only their front wheel. It's pretty common around Cambridge for a casual thief to steal an unsecured frame and a nearby unsecured front wheel, especially a QR front wheel, but I have been told of cases even in King's Lynn (which has little cycle theft except for just before the start of the universities/colleges year).

Kings Lynn, the Hanseatic University?
..
Quite possible
I am ashamed to admit, I thought for a moment, only a moment, of nicking a front wheel
Walked an hour home, bike rolling on the back wheel. Drove to the cycle shop next day, spent a lot on a new wheel, learnt my lesson

[Cyril Haearn]

My hub dynamo stopped working, checked the wires myself, still not working, getting the LBS to check it tomorrow, may have to use my other bike with a bottle dynamo
..
A bottle dynamo can be bought for pocket money and can be fitted in a few minutes

If the hub dynamo is faulty I shall probably buy a new one and rebuild the wheel myself, much more expense and time

[Brucey]

My hub dynamo stopped working, checked the wires myself, still not working, getting the LBS to check it tomorrow, may have to use my other bike with a bottle dynamo
..
A bottle dynamo can be bought for pocket money and can be fitted in a few minutes

If the hub dynamo is faulty I shall probably buy a new one and rebuild the wheel myself, much more expense and time

You don't say what make it is so this is a moan rather than a request for help? Hub dynamos -all makes- do go wrong occasionally but this is vastly outnumbered by the incidence of bad lights and/or (especially) crap wiring.

An easy way to check a hub dynamo is to fit a dead short between the terminals and try to spin the wheel; if the hub is working then it will not spin easily/for very long at all, by comparison with spinning the wheel with nothing plugged into it.

cheers

[Cyril Haearn]

A moan and a request for help, both
No light front or back
Not sure if the hub seems to spin more freely now, I thought a dynamo always dragged a bit

Shimamo
DH-3N31-NT

[Brucey]

you have two hub dynamos so you can apply a dead short to each and compare them. BTW it is very clear if you try and turn the axle on a loose wheel with and without the dead short (or other load). You can of course swap wheels between bikes too...?

cheers

[Cyril Haearn]

I only have one dynamo wheel
Just spent a happy half-hour disassembling and assembling the connector, got the wires in exactly the right place at last, seems to work now and I understand a bit more how it is built, just wish the connector was more robust

Thanks again Brucey

[Stradageek]

Now a hub convert!

Picked up an old Schmidt dynohub for £15 at a bike jumble, a bit of wiring some diodes and resistors and parts from two disassembled pound shop lights later I have a smooth, powerful, pretty much drag free and quiet all weather LED lighting system for less than £20.

And of course there's the fun of building the dynohub into the wheel.

No more noisy slipping bottle dynamos

[Brucey]

IIRC pound shop battery front lights draw ~100mA @ ~5V DC and rears a similar current at about half the voltage. I would imagine that they might have a very short life expectancy if you drive them using a rectified output from the hub dynamo; in the broadest terms you need some way of dissipating the other ~2 or 2.5W power you are not using.

If the load draws a fixed (low) current then you can expect the voltage to go ballistic.
If the load normally draws current at a fixed(ish) voltage then you can expect the current to vastly exceed 100mA.

If the load is neither fish not fowl, you may get more current and more volts in the lights than you would like. If you have a good scheme for avoiding problems, do share.

cheers

[andrew_s]

Apologies if it has already been mentioned but are the "bottle"dynamos that fitted under the bottom bracket and drove from the topsurface of the tyre still around?...

you occasionally see them NOS on ebay. But offhand I can't think of any that are actively being made/marketed new.

They suffer from the problem that the part of the bike they use to drive the roller is the one that is first to be both wet and dirty, so wear and slippage are never far away. When you are not using the thing it just sits there collecting crud.

The advantage of a roller (BB) dynamo over a bottle dynamo was that you could fit lightweight tyres which were considerably faster than the heavyweight tyres that had dynamo tracks.
Bottle dynamo drive wheels tended to slip more on a tyre sidewall, and it didn't take that much misalignment (eg as a result of a parking knock) before they would cause damage.

I used to carry a small screwdriver, so I could poke out the mud that had packed between the roller and its mounting and dried there. They would last me 2 or 3 years before the muck got too much and they died.

If you look at ebay...
The Union 8601 was the commonest in the UK. OK, but more drag than a properly set up bottle.
The earlier Soubitez were probably the best, but later models (after 1994?) had the bearings replaced by nylon (?) bushes that failed at ~40 mph.
The Sanyo Dynapower was the most powerful (3.8W nominal), was prone to blowing bulbs, and had a rubber drive "tyre" that was more prone to slip than the textured metal of the others, and would sometime come loose.