the best cheap optics for the best cheap light?

My first thread start!

A good friend of mine has just spent all of his dough building up a nice touring bike with the best of everything including a very nice dynamo wheel. I think he's now broke so I'd like to build him a nice front light with a standlight in it. I know what I need to do having built several already. However I'd like to do it a bit differently this time.

I have discovered these great Feckelmann (sp?) German-made aluminium spice tins with clear plastic window lids for $2 at the local kitchen shop. They are about 55mm diam. and around 45mm deep. Ideal for you-know-what!

What I want to do is build a 2 LED front light using 'budget' everything and as cheap as possible. So I would like advice about optics please. I am aware of the small 8 degree optics available at DX - the ones that come in a 5-pack and have the lens encased in a conical white holder that snaps onto the rectangular base of the Cree XR-E.

These work fairly well and I have a few of them to hand, but I wondered if there are any others available that fall into the 'budget' category and might be worth using for a headlight. Maybe some knockoffs of the Ledil Smooth Spot? Any advice most appreciated.

Sam P.

Savvas said:

I am aware of the small 8 degree optics available at DX - the ones that come in a 5-pack and have the lens encased in a conical white holder that snaps onto the rectangular base of the Cree XR-E.

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I have used these in three or four builds and they are great for a road light.
Cutter do different beam angles in the same optic too.

It's Fackelmann, and the ones I've seen are stainless steel. Not good for LED use, stainless makes a poor heatsink.

panicmechanic said:

It's Fackelmann, and the ones I've seen are stainless steel. Not good for LED use, stainless makes a poor heatsink.

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Hope they are abvailable in Al. Likely SS, though.

55 mm dia x 45 deep so 45 x 55 sides plus 22.5*22.5* pi = 6.3 sq inches. 3 XP-Gs @ 500 mA about 4.5-5.2 watts. About 1.2 sq.in. /watt.

OK if AL and 1/8" thick walled (unlikely). Thin stainless won't move heat along itself fast enough even if 1/4 inch thick.

With a full tight, 1/8" thick AA'd aluminum liner to counter the high thermal resistance of the SS and move the heat under the entire shell so it only need move through the thin SS to air (the thermal resistance is per unit thickness, so the shortest path is best if the coeffient is high, it might be enough. Stainless also does not shed heat to air as well as AL. I'd bolt polished Al IC head sinks to top and sides for the old )streamlined look maybe a round LED heat sink on back too, to keep the look. Troutie showed a table saw setup to cut fins in AL stock and not lose fingers on the MTBR DIY Light site.

There's a choice of AL housings in your local drugstore, or even in the recycle bin:
get some inspiration here.

panicmechanic: "It's Fackelmann, and the ones I've seen are stainless steel. Not good for LED use, stainless makes a poor heatsink."

Panicmechanic: Yes - Fackelmann - that's the one. I was all set to say 'They are definitely aluminium' when I thought I'd better find a magnet. And you are correct! Although they are very light, non-shiny and look just like aluminium, unfortunately they are not! Although they'll probably be fine for a dynamo light which won't generate much heat. They wouldn't suit anything with batteries and powerleds. Shame.

Znomit: Thanks for the positive comment regarding the cheap DX 'Cree' optics. I think i'll go with them.


Sam.

Savvas said:

Although they'll probably be fine for a dynamo light which won't generate much heat. Sam.

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I hit max output well below my usual riding speed with triple XP-G's. Something around 450-600 mA into 9-9.3 Vf. Say 4-5.5 watts. So 5 to 8 sq in. So they will just do if you don't depend on heat moving along the housing through the thin steel. Thats why they'd need an Al liner or fewer LED's. A magnet will not work on all SS, so that was a break that yours does. But it sure won't on Al!

Znomit: nice tip: I think I say a possible container... er light body in the trash if Al....

I too have used the DX TIR reflectors that you mention ...They work OK but I think the AL metal reflectors are probably better as they don't "leak" any light from the side and back the way the plastic ones do.

I built a Troutie/Citizen Kane/Hammond dynamo light that works really well, and pretty cheap too.

2 xp-g's, 2 reginas (or choice of optics under 20mm), hammond case and a few components. Links for ideas, circuits and standlight a bit further down the page from my components photo.


http://www.singletrackworld.com/forum/topic/diy-700-lumen-batteries-inside-light/page/26


Estimated 400 lumens at moderate speeds, with flickerless light above 5mph and plenty to see by or be seen from that speed upward. Good road light by adding a little hood to tame the spill in oncoming drivers' eyes. I used one of these hoods (this shot from battery driven version of dynamo light).