Light Project part 3
 

http://bikeforums.net/attachment.php...hmentid=282713

Because the light engine only drives these to 80%, four of these only total about 2,800 lumens after lens effeciency losses, which is short of what the Lupine Betty 12 claims - but ...... the run times and heating issues of the Betty never impressed me anyway. Apparently the latest 3,600 lumen Betty R version required a complete battery pack and system redesign to handle a 5.5A draw AND .....will only run on 100% at a speed of 25 km/h AND an ambient temperature of 20 degree Celsius or less and will dim down if slower/hotter. You're kidding - right? Summer nights in Montreal are hotter than that!

So can you really notice a difference between mounting two lights, three lights and four lights or more? Yes and no. If you're looking for more brightness to increase the REACH of any light - then thats relationship is exponential and you'd need 1, 4 or 9 lights to get twice or three times the reach of only one.

But that's assuming the lights are identical. Combining wide angle lights with narrow spots will give a beam that combines the characteristics of both, and the narrow beams will have more reach than the floods.

That works fine offroad, where there isn't automobile traffic to deal with. in the city, or bike paths a high powered array will dazzle traffic. The solution of course, is to angle the lights downwards. The problem with that is that because of the vertical coverage of a flood - it doesn't change anything and you've compromised the reach of the spots. Incidently - the problem is the coverage and not the power output. A floody 500 lumen light will dazzle just like a floody 2,000 lumen light.

If you run an array using only narrow spots and angle them down, there is much less of a glare and dazzle issue. But the coverage and reach are compromised. So the solution is an array with some of the spots using spreader lenses for more coverage, and some of the spots angled differently to give more reach. About 5 degrees seems to do the job. So the central top 2 lights in an array of four or more can be mounted independently of the others and will give more reach. Very much like a high / low beam run together. And for exactly that reason - they should have a seperate switch because they WILL be a problem for oncoming traffic.

Since this is a mtb, the array has been aimed for optimal use off-road eith the suspension in use. I can also use the lock-out on the suspension to further adjust the array, so that when the suspension is locked out (as it will be for most city driving) the array is further dipped and the 'low beams' can be made more traffic friendly. 'High beams' are off. The reach is further compromised but there are streetlights in the city so its very incidental.

In most cases found that 4 of those elliptical beams is plenty under normal conditions, since most of the light actually goes on the ground. Even a helmet light is superfluous. Running multiple lights is also where the higher voltage / lower amperage draw of these lights starts to pay off. Most in-line switches are only rated for 5A and won't even let you link TWO of the most common bike lights. With these - I can run 100W of lights with only 2 in-line switches and no relays. Each light draws less than an amp. Have run with up to 100W of lighting gives a wide beam with a usefull reach of about 250 feet and is probably pretty close to daylight on a cloudy day for the first 100 feet.

http://bikeforums.net/attachment.php...hmentid=284250

This may look huge, but looking down from the bars - it has such a small form factor you can't even see it past the brake / shifter controls. Its actually barely 8 inches across - something that might not be apparent since I've cut down the bars to a minimum. It also puts out more light than most sane people would need, was only occasionally used for some high speed descents, and the output (about 7,000 lumens) is more suited to MX racing than bicycling.


And after reading about reviews of P7 bicycle lights that included comments that the lights got quite hot on 'high', and personally experiencing that with some XML emitter bike lights, I was expecting similar issues with these units. Nope! So far these have never gotten anything more than slightly warm.

If you check out the MTBR backyard beamshots for the Lupine Betty there was a bicycle in the background. http://reviews.mtbr.com/2012-bike-li...ty-26-degree-2
So I took a couple shots myself just to have an idea. This daytime shot was taken with 35mm lens and that large tree is a measured 75 feet away - the same distance the backyard is in those MTB beamshots. And if you look closely - you'll see a bicycle leaning against it.

http://bikeforums.net/attachment.php...hmentid=282709

And needing a distraction during that storm last week - I went out and took some night shots. The 4 x 15/45 elliptical beam array clearly gives more spread than the Lupine Betty 26 degree beam, and ...... most of the light is on the ground, where its actually useful.

http://bikeforums.net/attachment.php...hmentid=282710

Nawwwww ... that might be the same exposure settings they're using, but it isn't representative of what I was looking at. And that's the problem at this point. A ONE second exposure works for me. A 4 second exposure might sell lights - but has little to do with reality. In dim lighting both contrast and color saturation decrease and consumer cameras are designed to boost both to give pictures more 'punch'. But things don't really look like that.


This might sell lights:
http://bikeforums.net/attachment.php...hmentid=282711

But this is closer to reality - not to mention being a reasonable amount of light to drive a bike by.

http://bikeforums.net/attachment.php...hmentid=282712

Equivalent to riding with your own personal, portable street lamp. One spot is more than enough to drive by brightness wise. Its the added coverage that makes me prefer the ellipticals. And spreading the same light over an area three or four times as large means, of course, that it'll take three or four lights to do the job. Two elliptical beams are actually enough. Four is just ..... a little better.



Will pick things up later

A number of the shots look plenty bright but seem to be wasteful of the lumen by spashing too much light to the sides which would annoy or blind oncoming drivers. Will you later parts begin to discuss how to focus the beam in various ways? For reference, I am thinking along the lines of the HL-2000 beam pattern pix on Peter Whites site...

Looking forward to Part 4 and beyond!

Thank for the input! I wasn't actually planning on doing a tutorial - was hoping more on starting some kind of discussion on what cyclists would like to see in a headlight. Can't think of a better place than a forum to do that!

The beam spread I'm currently using is a personal choice and not necessarily a general recommendation. On several ocassions on my commute home late at night I've had kittykats with racing stripes (skunks) amble across the path - resulting in near misses for both of us. The broader beam picks them out easily and gives me lots of warning. Lots of worms in the grass late at night and I guess thats what they're after.

There is some scatter from the light, but the majority of the output is constrained to 15 degrees which, when aimed downwards - puts almost all the light on the ground. It has the added advantage of being brighter over a wider angle of view than a plain 15 degree light.

I gess we could start a discussion on how to aim lights but we'd have to start by deciding what the optimal beam pattern is - off-road and on-road. I'm thinking different people may have different preferences. But I certainly have enough lights here if anyone wants to make suggestions on optimal combinations.

Based on your earlier comment I'm thinking that a combination of two eliptical beams with one or two regular spots might be more to your liking. Lets see where the post goes with the rest of the forum. :beer: