Front Light Height

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Carlton green
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Joined: 22 Jun 2019, 12:27pm

Front Light Height

Postby Carlton green » 14 Nov 2020, 2:07pm

I’m of the opinion that optically the best place for a front light is directly above the front wheel, there it can/might illuminate the road ahead and cast no shadows. For logistical reasons that option isn’t available to me, on one of my bikes I utilise a brazed on lamp boss on my front forks and on another I’m in the process of (gently and carefully) clamping a light mounting bracket to the front forks.

Light from the lamp already fitted shines both ahead and to the side, to the left side shines through the spoked part of the wheel but also has a shadow in it due to light hitting the front wheel rim and tyre. Short of mounting elsewhere there is no way around that shadow problem and all one can hope to do is limit it. I’ll likely keep the new light height near enough then same as that on my other bike (mounting bolt centre circa 22&1/4” from the ground ) but for front fork mounting is there an optimum or a better alternative height?

Jdsk
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Joined: 5 Mar 2019, 5:42pm

Re: Front Light Height

Postby Jdsk » 14 Nov 2020, 2:17pm

The headlamps on our tourers are in quite a wide range of positions because of bar bags, gadget bars and different types of fork crowns.

The lowest is on a fork at 520 mm from the ground to the centre of the lamp. I wasn't happy when I fitted it and it doesn't look right but it works fine on the road.

Can you add a photo of the fork crown so that we can see the problem?

Jonathan

thirdcrank
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Joined: 9 Jan 2007, 2:44pm

Re: Front Light Height

Postby thirdcrank » 14 Nov 2020, 2:39pm

The shadow of the front wheel was always a feature of the once-ubiquitous brazed-on lamp bracket. It never seemed a problem in those days,but thinking about it, the shadow is just where a driver emerging from the left would be.

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Mick F
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Location: Tamar Valley, Cornwall

Re: Front Light Height

Postby Mick F » 14 Nov 2020, 2:45pm

When I spec'd the Mercian frame in 1986, I had a front lamp boss on the RH fork leg.
I had no issues with my front lights. Yes, there was a shadow to the left, but I was fine riding along the pitch dark lanes on my way to work.

First battery lights, then a dynamo with a halogen bulb. The front lights were big. Two or three inches diameter.

Maybe, using the modern LED stuff, the front lights have more "coherence" and are laser-like, so the shadows will be sharper and more focussed and noticeable. In the old days with filament lights, the light output was fuzzier and softer.
Mick F. Cornwall

Brucey
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Re: Front Light Height

Postby Brucey » 14 Nov 2020, 3:50pm

I strongly advise you not to use a clamp-on bracket on the fork blades for the front light; reason being that

a) the thing might well damage the fork (esp if it is a CF fork)
b) if it comes loose it will slide down the fork and jam the front wheel
c) it is not very good as a lamp mounting position anyway.

You can mitigate the possibility of b) by using tape and/or zip ties just below the bracket so that if it comes loose it will tend to stop itself before it goes into the spokes.

If you can't think of a way of mounting the front light better than that I'd be surprised anyway. FWIW if I had no other option I'd fit a small front rack just to put the light on it.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Jdsk
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Re: Front Light Height

Postby Jdsk » 14 Nov 2020, 3:56pm

thirdcrank wrote:The shadow of the front wheel was always a feature of the once-ubiquitous brazed-on lamp bracket. It never seemed a problem in those days,but thinking about it, the shadow is just where a driver emerging from the left would be.

Good point, and it was one of my concerns. But at 520mm the lamp is well below the rim, brakes etc and only has the spokes in the way, and we use spoke reflectors.

Jonathan

thirdcrank
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Re: Front Light Height

Postby thirdcrank » 14 Nov 2020, 4:15pm

Once upon a time, many / most frames had a brazed-on boss on the RH front fork blade. A lamp of that era - typically a never-ready lamp with the specific cycle-lamp battery - cast a curved shadow of the front wheel. That was only when the light was working.

Re Brucey's advice not to use a clamp-on bracket:-

As a teenager, I once had to ride to Wyton Bar (near Hull and back at short notice (1961) In spite of the widespread fitting of brazed on bosses my Rotrax did not have one. With less caution than I have now, I whipped off a clamp-on bracket from our Saxon tandem (much heavier fork blades) and shoved it on. Give or take, it's something like sixty miles each way. Every few miles I reached down and tried to make sure it was ok. Several times I caught it. Halfway back the inevitable happened and I went over the top. Fortunately, things twisted round a bit so I landed more on my shoulder than my bonce.

This competes with cycling on the frozen River Wharfe a couple of years later as my daftest cycling antics.

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nick12
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Location: york

Re: Front Light Height

Postby nick12 » 14 Nov 2020, 4:50pm

I have just fitted my lights can't go on the fork crown due to uphanger for canti's .last year I fitted it on the front rack but have since removed the rack. I have a spa head stem bell as a spacer on the bike. I have unwound the bell and fitted the lamp into the spacer it seems pretty solid .cables are in the way but don't really affect the beam.
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Jdsk
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Re: Front Light Height

Postby Jdsk » 14 Nov 2020, 4:57pm

The more options the better. Could you have come forward under the straddle wire with one of these?

Image

Jonathan

mattsccm
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Joined: 28 Nov 2009, 9:44pm

Re: Front Light Height

Postby mattsccm » 14 Nov 2020, 8:47pm

Thanks for this. Just started to fit a B&M light and bracket much like the one in the pic with the red cables only to remember that the forks have no hole in the front of the crown. :( The Guards mount at the rear. Was pondering on this and the pic made me realise that I have something like a headset spacer with a thread sticking out the front .Yeah! :D

Jdsk
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Re: Front Light Height

Postby Jdsk » 14 Nov 2020, 8:54pm

The last one I did had an unthreaded hole in the fork crown, to my surprise. So I fitted a second bracket on the mudguard with the two brackets snug on either side of the fork crown. Bolt and nut through those. The hole in the new bracket further from the crown was riveted to the mudguard. The hole nearer to the fork crown was used for the light mount. Or something like that.

Jonathan

Carlton green
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Joined: 22 Jun 2019, 12:27pm

Re: Front Light Height

Postby Carlton green » 14 Nov 2020, 9:34pm

Many thanks for all of the responses received so far. All of the responses are appreciated and so is your time and trouble to respond.

I will try and take a couple of photos tomorrow and then see if I can post them on this forum.

Fitting a rack was mentioned. Yep, it would be the way to go but each time that I have tried to do so some subtle detail (that’s peculiar to the particular bike) has defeated me; of course I intend to revisit the obstacles encountered but in the meantime mounting off of the front fork seemed worth a try.

The danger of damaging the front fork was mentioned and I’m very much aware of that, my Heath Robinson arrangement gets around that crushing hazard and I have a better iteration of it in mind. The danger of something jamming in the front wheel is in my mind too.

I don’t have a handle bar bag fitted to the bike in question but I did want to leave that option open and hence a couple of alternative mounting points have been ruled out for now. Hence I resort to the ‘traditional’ lamp position of off of the front forks.

Coming back to lamp height (when mounted off of the forks) I don’t recall reading of an optimum yet ... 520 mm was mentioned in one of the earlier posts (thank you) and I must check that out.
Last edited by Carlton green on 15 Nov 2020, 4:31am, edited 1 time in total.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Front Light Height

Postby Brucey » 14 Nov 2020, 10:04pm

lamp height affects how easily you are going to be seen by other road users (too low and it can cause you not to be seen on an undulating road and of course there is the 'wheel shadow' problem too). However it also determines how easily you see potholes; with the lamp too low every small hole looks bottomless and if the lamp is set too high there are no shadows cast for you to see, and you will ride into quite deep holes without seeing them.

Hence most riders settle on somewhere between fork crown height and handlebar height as a happy medium.

If you are planning on a front bag a front rack seems even more appealing....?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

WOT
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Joined: 22 Aug 2019, 9:43pm

Re: Front Light Height

Postby WOT » 15 Nov 2020, 9:53am

Mounting at handlebar height gives a balance of light spread without casting annoying shadows.

B&M do a mount for this purpose but I had this one 3d printed to attach to the underside of my garmin.

Light is a Cyo-T.
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WOT
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Re: Front Light Height

Postby WOT » 15 Nov 2020, 9:57am

Jdsk wrote:The more options the better. Could you have come forward under the straddle wire with one of these?

Image

Jonathan


The width of the jaws on this part aren’t a perfect fit for some lights (B&M in my case) I bought one, modified it by spreading the jaws, didn’t like the result and it’s in the bottom of a spares box now.