Are bottle-dynamos directional?

[Chris S]

My bottle-dynamo gives much more light when I spin the wheel backwards instead of forwards. Is there anything that I can do about this?

 

[glasgowcyclist]

My bottle-dynamo gives much more light when I spin the wheel backwards instead of forwards. Is there anything that I can do about this?

Mount it on the other side?

I guess the difference in output will be down to the position of the spring tensioner that's holding it against the tyre. In one direction it will be acting against that spring (more drag and brighter) and in the other direction it will be working with the spring (less drag and dimmer).

I'm sure someone will be along shortly with diagrams and a clearer explanation.


GC

 

[Sharky]

Ride backwards?

Can the dynamo be fitted to the other side, then it would rotate in opposite direction?
Keith

 

[Richard A Thackeray]

From what I recall of using them many years ago; when it was in the stowed (not on the tyre) position, it was held in place by an sprung-loaded mechanism
When released to rub on the tyre, it sprang in, under tension.

Surely this indicates the relevant seat-stay to mount it on?

 

[raleighnut]

From what I recall of using them many years ago; when it was in the stowed (not on the tyre) position, it was held in place by an sprung-loaded mechanism
When released to rub on the tyre, it sprang in, under tension.

Surely this indicates the relevant seat-stay to mount it on?

You could mount it upside down to normal, it'd never know.

 

[Ian H]

My guess is that it's brighter when the wheel is spinning to pass the roller towards the bracket and dimmer when spinning past the roller away from the bracket. In which case fine-tuning pressure and/or alignment should solve it.

 

[sight-pin]

The spring pressure is adjustable iirc,(at least it was when i used one in the 70's)
You'll probably find the grip on the dynamo wheel is worn smoother in the normal direction so slippage is the problem, Hence why it's brighter in the other direction as the wheel has more grip, i should think?

 

[glasgowcyclist]

You could mount it upside down to normal, it'd never know.

Don't be daft - all the electricity would fall out.


GC

 

[I like Skol]

My bottle-dynamo gives much more light when I spin the wheel backwards instead of forwards. Is there anything that I can do about this?

Really, in this day and age? I would just junk the dynamo and buy some LED lights and a couple of rechargeable batteries. Far more versatile, will easily swap from bike to bike, stay lit when you stop, bright and not very expensive. My front light is from a cheap Reebock branded set that I bought about 4 yrs ago and seems to be indestructible and the rear lights are a pair of smart lights which again have been in use for a couple of years in all weathers.

Batteries last weeks between charges and I carry a couple of spare batteries just in case but they start to noticeably dim long, long before they stop working so I have yet to stop and change batteries out on the road. lights cost less than £25 and batteries are not dear either. I use Sanyo Eneloops as recommended by others on this forum.

 

[sight-pin]

Don't be daft - all the electricity would fall out.


GC

He may be able to claim back from the national grid then

 

[Chris S]

Ride backwards?

Can the dynamo be fitted to the other side, then it would rotate in opposite direction?
Keith

Unfortunately there is just one mounting-lug on one side of one fork.

 

[tyred]

Really, in this day and age? I would just junk the dynamo and buy some LED lights and a couple of rechargeable batteries. Far more versatile, will easily swap from bike to bike, stay lit when you stop, bright and not very expensive. My front light is from a cheap Reebock branded set that I bought about 4 yrs ago and seems to be indestructible and the rear lights are a pair of smart lights which again have been in use for a couple of years in all weathers.

Batteries last weeks between charges and I carry a couple of spare batteries just in case but they start to noticeably dim long, long before they stop working so I have yet to stop and change batteries out on the road. lights cost less than £25 and batteries are not dear either. I use Sanyo Eneloops as recommended by others on this forum.

Dynamo lights are always there when you need them, if the electrical connections are made properly they will always work and the headlamps for dynamo systems are designed as such so put their light on the road where I want it. They are pretty much fit and forget (I have bikes from the 30s with original dynamo systems in working order) and because they are bolted to the bike, they won't fall off or get pinched.

As for the OP, check the alignment of the dynamo. If you hold a straight edge along the axle of the spindle/roller, it should bisect the front wheel nut of the bike.

 

[DRHysted]

Really, in this day and age? I would just junk the dynamo and buy some LED lights and a couple of rechargeable batteries. Far more versatile, will easily swap from bike to bike, stay lit when you stop, bright and not very expensive. My front light is from a cheap Reebock branded set that I bought about 4 yrs ago and seems to be indestructible and the rear lights are a pair of smart lights which again have been in use for a couple of years in all weathers.

Batteries last weeks between charges and I carry a couple of spare batteries just in case but they start to noticeably dim long, long before they stop working so I have yet to stop and change batteries out on the road. lights cost less than £25 and batteries are not dear either. I use Sanyo Eneloops as recommended by others on this forum.

Ahh I hear the words from someone who has not experienced modern dynamo lighting. Admittedly mine is a dynohub not a bottle dyno. But I am so impressed that next year I will be having my main commuter converted as well. They knock the socks off all my other lighting (including magic shine), stay on for four minutes after I stop, and the rear has a smart brake light (this function will not work with a bottle dyno).

 

[I like Skol]

Ahh I hear the words from someone who has not experienced modern dynamo lighting. Admittedly mine is a dynohub not a bottle dyno. But I am so impressed that next year I will be having my main commuter converted as well. They knock the socks off all my other lighting (including magic shine), stay on for four minutes after I stop, and the rear has a smart brake light (this function will not work with a bottle dyno).

I hear what you are saying and I am sure that quality modern set-ups are 'light' years ahead of the stuff most of us are basing our opinions on but, how much does such a set-up cost (including having a wheel built with the dedicated hub)?

The OP sounds as though he is struggling with a product straight out of the 70s or 80s and based on that assumption I will stand by my advice to chuck it in the bin and get some 'light' modern LED lights.

 

[DRHysted]

I hear what you are saying and I am sure that quality modern set-ups are 'light' years ahead of the stuff most of us are basing our opinions on but, how much does such a set-up cost (including having a wheel built with the dedicated hub)?

The OP sounds as though he is struggling with a product straight out of the 70s or 80s and based on that assumption I will stand by my advice to chuck it in the bin and get some 'light' modern LED lights.

The lights were £160 from Germany, that was a rack mount rear with smart brake light, a seat stay rear, and a absolutely cracking from light with a beam pattern to die for (the light goes on the road exactly where you need it, no overspill at all). All needed as I ride country roads without street lighting at very unsocial hours.
The wheels were being replaced at the time due to excessive rim wear. My local did a deal of £205 for custom built front, and an off the shelf rear that matched.

I could have done it cheaper, as I didn't go for the cheapest hub, or the cheapest lights. But they really are that good.