Bottle dynamo in the rain

[Chris S]

My bottle dynamo gives a good light in the dry but in the wet it barely produces a flicker. Is the drive slipping on the wet tyre or do I have a short somewhere?

 

[mrandmrspoves]

Sounds like it's slipping. It may just need pushing in a little to enable it to grip the tyre better. Check the wheel head of the dynamo - if it has done many miles it could be worn smooth. Now't that a Dremel couldn't sort - but replacements are fairly cheap.

 

[andrew_s]

If it's electrical, you would likely get no light as all, so I'd bet on slipping.
Replacement rollers are available for Axa or Nordlicht bottles at the same place as this generic roller cover, or B+M produce a wire brush style roller for wet weather.
Slippage can also be reduced by making sure that the dynamo is accurately aligned, with the dynamo axis intercepting the wheel axis. This is especially important when using the B+M all weather roller, or tyre damage may ensue.

 

[amasidlover]

My experience of the B&M roller dynamo was not good; I eventually tried the wire brush style roller as linked above, but that ate through the dynamo track of the tire (a marathon plus I think, but it was a few years ago). Its possible that neither myself nor the bike shop that I bought it from ever had it set-up properly...

But, I gave up after the wire roller ate through the tyre and switched to a hub dynamo, which just worked, and with that being the goal of having a dynamo set-up (not having to mess around worrying about running out of batteries etc.) I would never go back to a bottle dynamo.

 

[Davidc]

I used bottle dynamos for many years, and slipping in the wet was the most common problem. I took to setting them up to run on the tread which worked best. They put wear on the tyres, but not enough to reduce service life.

I bought a hub dynamo (Shimano) some years back. So far total reliability*. That one's now done about 30,000 miles and is on the round-town bike. Bought another one about 4 years ago. It's on the tourer and has done about 4,000 miles.

Because I'm cautious with lighting I always have reserves, front and rear, so the occasional loss of power from the bottle dynamos never left me unlit. With hub dynamos it's always been the battery second set that's had any problems.

*I do check the bearings and adjust and grease them about every 10k miles, with extreme care because there are some fine wires inside.

 

[Chris S]

I've just noticed that the wheel is quite a lot out of true - it would exert a different amount of force on the dremel at different point in its rotation. I think I'll sort this out first. Thanks.