Rear light for hub dynamo

For discussions about bikes and equipment.
ANTONISH
Posts: 1588
Joined: 26 Mar 2009, 9:49am

Rear light for hub dynamo

Postby ANTONISH » 2 Jan 2018, 2:15pm

Apologies for this being on the similar lines as another couple of threads.
Having acquired the edelux ii which has a convenient connection for a rear light I'm pondering what to path to take.
The edelux draws 2.4W - presumably at 6V R.M.S.
I have a number of rear lights and was thinking of using one with a 1W red led from Reflectalite. This of course would mean a 3.4W connected load - while I don't think this would overload the dynamo - the required terminal voltage would probably only be available at a higher speed.
I'm not sure what the effect would be on the headlight output at slower speed.
I would be happy with a 0.5W - which is available as a discrete diode but would require a rectifier as unlike the Reflectalite it is polarity sensitive.
Any ideas would be welcome.

Valbrona
Posts: 2224
Joined: 7 Feb 2011, 4:49pm

Re: Rear light for hub dynamo

Postby Valbrona » 2 Jan 2018, 6:16pm

Bonkers. You fit a permanent/battery light at the back, eg. B+M permanent and just use the dynamo for the front light.
I should coco.

User avatar
andrew_s
Posts: 4898
Joined: 7 Jan 2007, 9:29pm
Location: Gloucestershire

Re: Rear light for hub dynamo

Postby andrew_s » 3 Jan 2018, 12:49am

Valbrona wrote:Bonkers.
Not at all.

Not only is a dynamo rear light substantially more reliable than a battery light, you don't have to make a special stop to turn it on.

On the whole, I'd take the view that a modern rear LED light is better than an ancient rear light with a Reflectalite LED bulb retrofitted. Apart from anything else, you get the standlight (remains on for 3 or 4 minutes after you stop).

Valbrona
Posts: 2224
Joined: 7 Feb 2011, 4:49pm

Re: Rear light for hub dynamo

Postby Valbrona » 3 Jan 2018, 4:58am

andrew_s wrote:
Valbrona wrote:Bonkers.


Not only is a dynamo rear light substantially more reliable than a battery light, you don't have to make a special stop to turn it on.



You can get permanent/battery rear lights with automatic (daylight/motion sensor) function, just like you can get automatic rear lights that work off a dynamo.

Not sure how a permanent/battery rear light is any less reliable than a dynamo rear light when the top quality ones have indicators that show when battery life is low. But with modern LEDs the batteries run for ages - the big rack mounted B+M rear lights with built-in reflectors take big/long lasting batteries.

Not sure why anyone would want to faff around running cables to a rear light unless they were determined to want to make their bike look a mess.
I should coco.

User avatar
epa611
Posts: 78
Joined: 6 Jan 2007, 7:26pm
Location: Johnstone, Renfrewshire

Re: Rear light for hub dynamo

Postby epa611 » 3 Jan 2018, 6:34am

Valbrona wrote:
andrew_s wrote:
Valbrona wrote:Bonkers.


Not only is a dynamo rear light substantially more reliable than a battery light, you don't have to make a special stop to turn it on.



You can get permanent/battery rear lights with automatic (daylight/motion sensor) function, just like you can get automatic rear lights that work off a dynamo.

Not sure how a permanent/battery rear light is any less reliable than a dynamo rear light when the top quality ones have indicators that show when battery life is low. But with modern LEDs the batteries run for ages - the big rack mounted B+M rear lights with built-in reflectors take big/long lasting batteries.

Not sure why anyone would want to faff around running cables to a rear light unless they were determined to want to make their bike look a mess.
Rear dynamo lights are fit and forget. Some cabling is a minor concern


I'm a trendy consumer. Just look at my STF-L09 using Tapatalk

Tiberius
Posts: 485
Joined: 31 Dec 2014, 8:45am
Location: North East England

Re: Rear light for hub dynamo

Postby Tiberius » 3 Jan 2018, 7:11am

OP....I'm not sure if this answers your question, but just to say that I have two bikes running dynamo lighting systems. Both bikes have a SON 28 dynamo/Edelux 11 headlight/B & M Toplight Plus rear light which is wired into the Edelux 11 headlight.

I have no idea about current draw/lumens etc but I can say that both Toplights are good and bright and the stand light time is roughly five minutes. I can't see any difference in headlight output with the rear light attached or unattached. With both lights connected they actually come to life even when the bike is being moved around the garage.

The lights were fitted approximately three years ago. I swiched them on and I have never switched them off...the Edelux is switched to permanently on. I ride in all weathers and the lights have been 100% reliable.

Just to add that the scratty bit of dead thin cable that supplies the rear light does NOT make the bike look a mess.....one of the bikes is a TI Van Nicholas, God forbid that that bike EVER looks a mess.... :shock:

User avatar
mjr
Posts: 13759
Joined: 20 Jun 2011, 7:06pm
Location: Norfolk or Somerset, mostly
Contact:

Re: Rear light for hub dynamo

Postby mjr » 3 Jan 2018, 9:39am

Unless you're riding a fixed or coaster-braked single speed or kickback or automatic hub, the bike already has thick cables to the rear, so a thin lighting wire shouldn't make it a mess.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.

User avatar
Heltor Chasca
Posts: 3016
Joined: 30 Aug 2014, 8:18pm
Location: Near Bath & The Mendips in Somerset

Re: Rear light for hub dynamo

Postby Heltor Chasca » 3 Jan 2018, 9:50am

Two bikes set up with rear dynamo lights. One is a B&M Toplight, the other a tiny little Son. Very tidy. The wires are neatly routed along brake cables that are there anyway and hidden against the rack stays.

I don’t do messy. And I fully recommend rear dynamo lights.

User avatar
[XAP]Bob
Posts: 16896
Joined: 26 Sep 2008, 4:12pm

Re: Rear light for hub dynamo

Postby [XAP]Bob » 3 Jan 2018, 9:53am

Valbrona wrote:You can get permanent/battery rear lights with automatic (daylight/motion sensor) function, just like you can get automatic rear lights that work off a dynamo.

Do they automatically charge themselves or replace their own batteries?

Not sure how a permanent/battery rear light is any less reliable than a dynamo rear light when the top quality ones have indicators that show when battery life is low. But with modern LEDs the batteries run for ages - the big rack mounted B+M rear lights with built-in reflectors take big/long lasting batteries.

Working for 'ages' is, if anything, a disadvantage in terms of reliability - because you forget about it at some point.
My rear light doesn't work for ages - it works for*ever*. And that is a BIG difference.

Not sure why anyone would want to faff around running cables to a rear light unless they were determined to want to make their bike look a mess.

Brake cable, gear cable - there are already cables, and cable routes, to the rear of the bike. Adding a slim electrical cable isn't going to ruin the line of anything.


Battery lights cannot do the same job as a dynamo - because they must require maintenance.
My entire routine for my rear light is to glance at my cycle when I park up and check that the stand light is still on. A fair proportion of the time someone else will tell me anyway...
I have a second rear dynamo light on my RH mudguard, and I can see that from my seat, so that's easy to verify, and I can obviously see my front beam...

In winter I need about ten hours of lights per week - in weather that is decidedly not conducive to long lasting batteries.
In my early cycling days (you can probably still find my discussions and build decision on this forum somewhere) I ran battery powered home built lights - but that was a daily recharging routine - on a shorter commute than I now have...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

pwa
Posts: 10263
Joined: 2 Oct 2011, 8:55pm

Re: Rear light for hub dynamo

Postby pwa » 3 Jan 2018, 10:01am

My last experience of dynamo lighting was in another epoch when rubbishy bottle dynamos were the best you could get. Loads of faffing to get them half working in heavy rain. The technology has moved on and hub generators have removed the major reason I don't bother with dynamos. But one other thing that I found niggling back then was the wiring, which if I remember rightly involved having to penetrate the paint on your frame with a screw! I assume that no longer goes on. Another issue was fragile and vulnerable cables, easily damaged. That last concern would put me off a rear dynamo light. A long run of thin, vulnerable wire. (Not bothered about appearance too much).

User avatar
mjr
Posts: 13759
Joined: 20 Jun 2011, 7:06pm
Location: Norfolk or Somerset, mostly
Contact:

Re: Rear light for hub dynamo

Postby mjr » 3 Jan 2018, 11:29am

pwa wrote:My last experience of dynamo lighting was in another epoch when rubbishy bottle dynamos were the best you could get.

Last experience was before 1936? ;)

pwa wrote:But one other thing that I found niggling back then was the wiring, which if I remember rightly involved having to penetrate the paint on your frame with a screw! I assume that no longer goes on.

Lots of people seemed to do that, but I don't think it was ever required. You could always ignore the instructions and use twin-core instead of a frame earth.

pwa wrote:Another issue was fragile and vulnerable cables, easily damaged. That last concern would put me off a rear dynamo light. A long run of thin, vulnerable wire. (Not bothered about appearance too much).

Again, it was always up to the fitter what cable they used. I've mostly used very OTT speaker wire because I can't be doing repairing fragile wires or having them succumb to the weather more often than I'd recable anyway.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.

User avatar
[XAP]Bob
Posts: 16896
Joined: 26 Sep 2008, 4:12pm

Re: Rear light for hub dynamo

Postby [XAP]Bob » 3 Jan 2018, 12:21pm

pwa wrote:My last experience of dynamo lighting was in another epoch when rubbishy bottle dynamos were the best you could get. Loads of faffing to get them half working in heavy rain. The technology has moved on and hub generators have removed the major reason I don't bother with dynamos. But one other thing that I found niggling back then was the wiring, which if I remember rightly involved having to penetrate the paint on your frame with a screw! I assume that no longer goes on. Another issue was fragile and vulnerable cables, easily damaged. That last concern would put me off a rear dynamo light. A long run of thin, vulnerable wire. (Not bothered about appearance too much).


Why would the wire be vulnerable? It's tied to brake cable most of it's length, then along the rack arms.

What on earth is going to give it any damage...

I need to replace my rear cable at some point - because I've rearranged a few things, and the current cable is a fraction short. I might take the opportunity to upgrade the rear light to one with a built in brake light.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

User avatar
andrew_s
Posts: 4898
Joined: 7 Jan 2007, 9:29pm
Location: Gloucestershire

Re: Rear light for hub dynamo

Postby andrew_s » 3 Jan 2018, 1:18pm

[XAP]Bob wrote:Working for 'ages' is, if anything, a disadvantage in terms of reliability - because you forget about it at some point.
My rear light doesn't work for ages - it works for*ever*. And that is a BIG difference.

A common problem with battery rear lights is that the user checks the light looks OK when they turn them on at the start of the ride, then forget about them.
Unfortunately, batteries recover when rested, and a light that looks bright when you turn it on can be as dim as a very dim thing a couple of minutes later. At least with a fully manual battery light, there's the chance to see the dimness when you turn it off, even if you then proceed to forget about it, but an auto on/off battery light loses that check.
How many PoBs do you see riding round with glow-worm rear lights?

A battery rear light loses the main advantage of dynamo lights, which is that they are there, and just work, without having to think about them at all after installation. Set up a new bike with dynamo lighting, turn the lights to sensomatic, and that's it for the next three years or so, unless you want to turn the lights on for daytime fog or something.
Provided that you make a decent job of the installation, you'll only ever touch the lights to make some change - a newer, better front light, change from a mudguard light to a rack light, replace the mudguard, redo the cable ties when you change your brake cables, or whatever.

If you use decent wire and route/attach it well, it's no more liable to damage than any other part of the bike. The best wire is the coaxial cable that SON/Schmidt use (available from Spa/SJSC etc). It's pretty much immune to the insulation chafing through, and lies nice and straight against the frame or other cables.

User avatar
andrew_s
Posts: 4898
Joined: 7 Jan 2007, 9:29pm
Location: Gloucestershire

Re: Rear light for hub dynamo

Postby andrew_s » 3 Jan 2018, 1:32pm

[XAP]Bob wrote:I need to replace my rear cable at some point - because I've rearranged a few things, and the current cable is a fraction short. I might take the opportunity to upgrade the rear light to one with a built in brake light.

The first rule of dynamo wiring is to always loop up some spare cable somewhere, for just such changes.

I've got one of the lights with a brake light. I've no idea if it works or not - you can't see yourself, and no-one else has seen fit to remark on it.
I did ride behind someone with one once, a local on a Belgian cycle track, and it seemed vaguely useful for me, as an indication that the next corner might need braking for.

User avatar
[XAP]Bob
Posts: 16896
Joined: 26 Sep 2008, 4:12pm

Re: Rear light for hub dynamo

Postby [XAP]Bob » 3 Jan 2018, 1:53pm

andrew_s wrote:
[XAP]Bob wrote:I need to replace my rear cable at some point - because I've rearranged a few things, and the current cable is a fraction short. I might take the opportunity to upgrade the rear light to one with a built in brake light.

The first rule of dynamo wiring is to always loop up some spare cable somewhere, for just such changes.

I've got one of the lights with a brake light. I've no idea if it works or not - you can't see yourself, and no-one else has seen fit to remark on it.
I did ride behind someone with one once, a local on a Belgian cycle track, and it seemed vaguely useful for me, as an indication that the next corner might need braking for.


It's not the first such change ;)

I don't know how effective it will be either - but I can see that there is a benefit in an additional signal for braking. The fact that it requires no additional wiring or special brake levers etc makes it a fairly low 'cost' additional signal which isn't likely to be detrimental...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.