Dynamo Lights

I'd check all the wiring to see if you have a short circuit, ie. Pos / neg wires touching somewhere

Thanks for suggestions. Have connected everything to the dynamo hub on my commuter and after some fiddling have confirmed that everything works, so it must be the hub on my touring bike that has the fault. Not sure what has happened to it or what I can do to fix it though!

Both the same type of hub? You're unplugging from one hub and plugging into the other and it goes from working to not working?

Yup, seems to be

Okay so the hub seems to be behaving as if it is not a dynamo hub - spinning freely in the axle with none of the usual resistance that I would expect. Anyone encountered this before?

.

Picked up a B&M My, Mew? tail light to replace a slightly tatty old Secula. It is TINY! Hope it throws out lots of light, it’s probably ott for my commuter and I might miss having a reflector, but this would be a good minimalist light for Audax/road bikes FYI

1 Attachment

bright enough for the most occasions.

I have one mounted on my rear mudguard and it's been great so far!

In your opinion, what is the best place to mount a rear dynamo light?

I'm going to see a framebuilder this Saturday to make some modifications on my rear triangle. They will modify the fender mounting points and add rack mounts.
I believe I should seize the opportunity to figure out where to mount my future rear dyno light, as well as the cabling. I plan on using a Son rear light.

I'm torn between several options. I'd like to avoid mounting it anywhere on the seatpost, as I might be using some sort of saddlebag from time to time. I'm thus left with :

1°) Mounting it on the dropout, Fairlight-style. I live in France, so it would be on the NDS dropout.
Pros : Barely any modification needed, I can run the wire along the brake hose.
Cons : The light would sit very low to the ground, so I'm afraid I won't be visible to cars.

2°) Mounting it on the hidden mudguard mount inside my seatstay (see picture below).
Pros : Slightly higher than option 1°), less exposed.
Cons : Slightly uglier cabling than 1°).

3°) Having a mounting point added high up on the NDS seatstay.
Pros : The most visible out of the 3.
Cons : Can't figure out any kind of cable routing that wouldn't look bodgy as hell. This would be solved with fully internal routing, but I'm hesitant to do that as I'm not having the bike repainted.

If I wasn't so afraid about visibility, option 1°) would be a no-brainer. What do you think?

1 Attachment

That looks excellent! Going on the list.

I personally think that dropout mounting is too low.
Under saddle? There's Seatposts that allow you to go through. And have a connector somewhere so you can move the light when you put a saddlebag on.
And apart from cabling, No 3 is great.

Or just get mudguards.

If you're getting rackmounts, just mount it on the rack?

On the rack or at 3.
Use Invisitape type stuff to run the cable on the underside of the top tube?

That's also what I thought about the dropout mounting. Any experience with a light mounted that low?

Under saddle isn't an option as there's a Di2 battery in there. Cable routing would also be problematic, I want something clean and durable so that'd probably mean internal, which isn't ideal, as I'm not having the frame repainted. The framebuilders will just touch up the areas they modify, so I'm trying to avoid drilling holes everywhere.
But I will talk to them to see if we can figure out anything about mounting it there.

I run full metal mudguards 95% of the time, so I was also considering that option (with a connector near the BB for easy removal). I wanted something that was independent of mudguards for the last 5%, so that I never have to worry about light even when removing mudguards, but it might be my best option so far.

@M_A_X : I don't actually plan to run a rack, the mounts will be there "just in case".

@Grumpy_Git : Ok so consensus seems high that 1 or 2 are shit for visibility!

If you're adding rack bosses for flexibility, put some semi-permanent joints in the cable also for flexibility: https://www.amazon.com/OliYin-Plated-Female-Connectors-Battery/dp/B071X4L38R/ref=sr_1_1?keywords=2mm+banana+plugs&qid=1657896527&sr=8-1 (don't buy them off amazon, naturally)

I went for option 3, attached to a rack mount, on my recent Surly Trucker rebuild.

Reasons:

• not going to have a rack this time, not permanently anyway, so rack mount not an option
  
• bought the Fairlight mount, looked at it before finalising the wiring and decided it was much too vulnerable to damage down there as well as being not great for visibility
  
• just to add another point, the Schmidt website says not to mount their rear light vertically, and having played around with it can confirm that it’s a wide flat beam when correctly orientated. Probably annoying for following riders if vertical.
  
• didn’t want the dynamo wire on the top tube so ran it alongside the rear brake hose, intermittently heat-shrunk together.
  
  

So I elected to run the wire up the back of the seat tube. Because I won’t always have mudguards on this bike, I wanted to be sure the wire wouldn’t be vulnerable to damage from small stones etc so I used 3M adhesive cable clips and ran the wire inside some 3mm internal diameter plastic hose. Thought about the helicopter tape option instead but preferred that method.
I also have two Supernova gold connectors near the light at 3 in case I change my mind about the rack - I can easily add a short length of coax thus avoiding undoing the existing wire routing.
The bike is 1x11 so admittedly the lack of front mech makes it easier to get it tidy going up the seat tube.
I used another small bracket to allow me to make use of the piss-takingly expensive Fairlight mount. It’s a good location that will work fine under my seat pack (not shown).

1 Attachment

Old bikes were using the frame as a connection, and were running only one wire. If you want to make it as clean as possible, you could go also this direction.

Thanks for your reply, it was super helpful. I had those exact questions about the Fairlight mount and the Son rear light beam pattern.

I saw the framebuilders yesterday, and ended up sticking with the mudguard solution after talking with them. On their own bikes, they tend to mount it at the dropout, for the same reasons as Fairlight, i.e. it's compatible with all configurations. However, they tend to use Supernova rear lights - whose beam pattern is apparently better for vertical mounting -. As I have an Edelux at the front, using a Supernova for the rear light would mean loosing the standlight function, which I'm not keen to do.

I also hadn't realised how big an area brazing damages : adding braze-ons or holes to have some sort of clean routing towards position n°3 would have meant repainting the whole seattube.

@Five-Hats : I'm going to use a Son coaxial connector between the BB and the mudguard, to make mudguard removal easy. I assume that's what you meant?

@Julien1A : I've heard of that, but I'm not sure it changes much : Son coax is a single "wire".

Julien1A’s post refers to using the frame as one conductor (with the light body being grounded to the frame) and a single wire as the other.

SON coaxial contains 2 conductors - the central wire surrounded by an insulator, and the ground wire wrapped around that in a spiral.

Adding the SON coaxial connectors requires soldering, and personally I found them fiddly little bastards but had no choice but to use them at the hub, so I could use the connection block, and to allow my charger to connect to the female coaxial connector as fitted on my Edelux. Elsewhere, I think crimped connectors are a better job.

Oh, believe me, I know about coax cables ;) This is why I wrote "wire" in quotes.

I'm also familiar with what @Julien1A alluded to, though :
1°) I've always heard it was a fairly unreliable method to replace the neutral wire.
2°) I don't want to bother with that because it wouldn't make it cleaner than using a single SON coax cable.

I really like the cleanliness of SON's coax connectors, the crimped connectors look very unsightly in comparison. I'm confident enough in my soldering abilities to use them, we'll see how it'll turn out. But first, I need to put my hands on a pair of connectors.

I've always heard it was a fairly unreliable method to replace the neutral wire

Well, headset bearings aren't designed with low electrical resistance in mind.

I have the Klite mtb system with Son connector and USB charging block. Any recommendations for something to change to (road only)? The mounting option is limited to handlebar or bar extension.

Didn't bother thinking that one through but yeah, that might be the reason :)

wouldn't make it cleaner than using a single SON coax cable.

Ah, got you now.

Yes you’ve got that double barrel look with the crimped connectors but it’s acceptable enough for some locations, tucked away somewhere under a seat or rack tube and not intended to be disconnected often.