Dynamo wiring

[johnt]

I am thinking of having a bottle dynamo bracket brazed behind the R/H fork blade of my touring bike (531 Galaxy) prior to enamelling. I am considering running the cable through a small hole drilled underneath the bottom head lug, through the down tube and out through another small hole under the bottom bracket, then via a spade connector and cable glued to inside of mudguard to rear lamp. If possible I would like to use small rubber gromits in the holes ( does anyone know where to get them?). Has anyone done this? Any advice or suggestions welcome.

[Steveo2020]

I have a bike with the cable routed under the mudguard - I found silicon bathroom sealant the best thing for sticking it there and it sealed up the holes neatly too.

Cheers

[alicat]

I would get a hub dynamo and rig a front light to it. I would use a battery lamp at the rear.

I have two bikes with hub dynamos, both with rear dynamo lights with the cabling running to the rear rack. I always have a slight concern that the wiring has pulled out eg with the front wheel swinging round and there is no light at the rear.

[mercalia]

RHS dynamo? You should be sure you can get a RHS one. I know BM do one Also you need to get the bottle dynamo before you get a braze on to make sure the bracket is the right length & height for the dynamo and tyre you intend to to use. My Dawes 1-Down has a bottle dynamo bracket brazed on from new but is too short & low for the BM S6 and Schwalbe 1.75 marathon tyres, so I use a bracket that bolts on the brake bosses( not many of them now? ) This pi**ing about is what makes bottle dynamos a relic from the past

[NetworkMan]

As aluded to by mercalia the trouble is that there is no standardisation for dynamo mountings. You could have a braze-on to suit dynamo X but when that fails and you can no longer buy a new one you'll find that dynamo Y won't fit.

My Nordlicht is mounted on a Zinkens dynashoe along with the B&M headlamp, and the rear carrier lamp is battery operated. This means that there are no cable runs anywhere and I can remove the dynamo/lamp by undoing one large bolt if I don't need it during the summer. I suspect however that the dynoshoe is no longer available.

If I were starting again I'd go for a dynohub. Won't the cost of the brazing/painting get close to the cost of one?

[mercalia]

what makes it worse even if your bottle still fine, if you change the tyre - differnt side wall height the bracket may not allow the dynamo to go up hi enough ( as in my case with the brazed on one ). I dont use night time lights to justify any thing else and my front wheel is in fine condition so cant justify wasting a perfectly good wheel to replace with a hub dyno

[ukdodger]

I am thinking of having a bottle dynamo bracket brazed behind the R/H fork blade of my touring bike (531 Galaxy) prior to enamelling. I am considering running the cable through a small hole drilled underneath the bottom head lug, through the down tube and out through another small hole under the bottom bracket, then via a spade connector and cable glued to inside of mudguard to rear lamp. If possible I would like to use small rubber gromits in the holes ( does anyone know where to get them?). Has anyone done this? Any advice or suggestions welcome.

One word of advice is to use two wires to each light rather than one wire and the frame as the return. The frame isnt an ideal path for electricity. Over time the connection between the bottle and the frame and between the lights and the frame deteriorates and causes fluctuations in the current. At worst the light goes out or constantly and annoyingly goes on and off and if you're using the 6v filament bulbs the bulbs will eventually blow.

[[XAP]Bob]

Dynamo light at rear here, but hub rather than bottle...

The security of always on, reliable, lighting is worth it.

[Mick F]

One word of advice is to use two wires to each light

Absolutely!

The earth return relies on an electrical contact, and that in turn relies on bare metal.
Dunno about anyone else, but bare metal on a steel bike is asking for trouble.

Yonks back, I had an excellent bottom bracket dynamo. It was a superb bit of kit - Soubitez, not the rubbish Sanyo version - and it was clamped onto the chainstays immediately behind the BB. The power came up a single wire and split two ways - rear and front.

In order to get a good earth return, you had the clamp very tightly to crack the paintwork.
I re-designed the system to two-core wires so the earth return wasn't required.

[Brucey]

if you want to keep your options open, I'd suggest having a couple of M5 threaded bosses brazed into the fork centreline on the inside of the blade. This arrangement can be used with a simple bracket (which SJS amongst other sell) to mount a bottle dynamo very securely. Should you ever change to a hub dynamo or choose to run without the bottle dynamo, everything can be removed and the braze-ons are quite unobtrusive when there is nothing in them.

This arrangement can also be used with a RH or LH dynamo with equal facility.

cheers

[johnt]

I know that hub dynamos are excellent, but don't do that much night riding and can't justify the expense when I have a perfectly good front wheel. I like the "anti theft" aspect of bottle dynamo. The frame needs enamelling anyway. I was planning to use a dynamo bracket with a slot to allow for different makes of dynamo, which I have on other bikes. It was more the drilling of the lugs and routing of the cable I was concerned with, as well as the availability of rubber gromits. Thanks guys!