Light mounting using stays

[stewartpratt]

Wondering if anyone's tried this and had success (or failure)…

Consider a fork which has no forward-facing hole at the crown, but which does have a rear-facing one, and which also has bosses on the fork legs.

The usual means of mounting a dyno light (via the forward-facing hole) is out, but it would be possible to support its weight using a pair of steel rods running from the bosses on the fork legs to the mounting point on the light.

This leaves the requirement to anchor the light to the crown, without the need to be load-bearing. So some sort of bracket that connects to the rear-facing hole would seem to be in order. The issue here is that clearances will be fairly tight, and a metal (or indeed any) part in contact with the underside of the carbon crown itself would be undesirable.

Alternatively, maybe simply tidily Sugruing a small bracket to the top of the mudguard would work; but would an SKS P35 be stiff enough to keep the light stable at speed given whatever movement might be left to control after the stays are in place?

Any experience? Or any other ideas for getting a dyno light mounted to a carbon fork with no forward-facing crown hole?

[beardy]

This question has been asked and answered before on the forum, but finding that thread.....


What sort of bosses is it on the CF forks that you are planning to use, Cantilever, rack or mudguard bosses?

There are brackets available to mount dynamo lights on cantilever brake bosses, if you could live with it there instead of at the crown.

[Audax67]

Like the man said, it's easier if you don't start from there.

You could maybe try a drop-down bar extender such as the Topeak one: http://topeak.com/products/Xtras/BarXtender. My dynamo light is crown mounted but I have a battery lamp on one of these alongside it.

[stewartpratt]

The fork I'm specifically considering at the moment has mudguard bosses on the insides of the legs at roughly the same height as lowrider bosses. Disc brakes, no canti (ugh) mounts. Definitely want the light in the conventional position rather than to the side of the wheel.

As for bar mounts: thanks, but no. Need/want the bar space and also ends up too high. Also fugly Likewise spacer-mounted extenders.

[beardy]

For a dynamo light like a Cyo and with your requirements, I would be seriously considering kissing the fork guarantee goodbye and using araldite to fix something rigidly to the front of the fork crown, possibly with some back-up support from the mudguard.

[tatanab]

Even a lightweight lamp will cause the mudguard to flap around and the light beam to stray all over the place unless you brace the front of the mudguard should you choose to mount a light there. 20 years ago I ran mudguard stays from the lowrider bosses up to the front of the mudguard where I had fitted a bridge to accept them, I then mounted the light on that bridge. It was pretty neat. A problem is that the light is in the ideal position to collect all the muck thrown back from the mudguard leading edge.

[531colin]

Even a lightweight lamp will cause the mudguard to flap around and the light beam to stray all over the place unless you brace the front of the mudguard should you choose to mount a light there. 20 years ago I ran mudguard stays from the lowrider bosses up to the front of the mudguard where I had fitted a bridge to accept them, I then mounted the light on that bridge. It was pretty neat. A problem is that the light is in the ideal position to collect all the muck thrown back from the mudguard leading edge.

While you are putting an extra set of stays there, you could also extend the mudguard.....somewhere on here is a photo of R2's Genesis Longitude (?) where he has fitted a rear 'guard to the front to control the spray from the front end of the front 'guard.

[PH]

Without seeing the fork it's hard to say. A possibility might be to use a fork bung inserted from the underside and an L shaped bracket, a spacer should take care of keeping it just below the crown to avoid touching. Another alternative is a piece of plastic tubing inside the steerer and protuding enough to drill a hole and mount the light convertinally. Either of those methods rely on there being clearance to spare under the crown. Or fit SS mudguards which are strong enough to support a lightweight light.

[stewartpratt]

No hole in the underside of the crown, by the way.

[Audax67]

Sounds like a right crappy fork.

[MikeF]

Any experience? Or any other ideas for getting a dyno light mounted to a carbon fork with no forward-facing crown hole?

I've come to the conclusion that it's best to mount the front ("dynamo") light from the handlebars. It keeps it free from muck, and the on/off switch is easy to use.

[CREPELLO]

Does the fork have good clearances? If so, a bracket made from metal plate that fixes at the rear fork crown mount and runs under the fork could work*. In front of the crown, bend the plate to 90 degrees, drill a hole to mount a standard lamp bracket. Good clearance would ensure you can use a suitably thick plate for strength/rigidity.

Edit:* It would probably help if you use mudguards, to help brace the bracket. Otherwise just over-engineer it to reduce fatigue failure.

[stewartpratt]

The old "under and up" approach had occurred to me, but clearances are probably too tight, manufacturing a suitable bracket isn't trivial, and cantilevering a Luxos from an M5 bolt in a carbon crown doesn't seem brilliant.

I did have a viable idea, though: a pair of 3mm steel struts running up from the mudguard eyelets (which happen to be inboard and a few inches up the leg) to the light, with suitable eyelets at each end. Then two holes drilled in the sides of the mudguard and a pair of the SKS stay daruma bolts attaching the struts to the sides of the guard, with the nuts on the inside facing the tyre. That might well work, provided it's laterally stable enough—which I think it should be.

[CREPELLO]

Sounds viable. I hadn't appreciated that it was the big Luxos that you were fitting. It's certainly a challenge you've got there.

[stewartpratt]

Well, I don't need to do it. Just broadens my procurement options