Great idea, Hoop, and thanks for taking the time (and for what sounds like a proper test rig setup!). This will be a great reference and time-saver.
Could you share a photo of how you’re attaching to the gage arm?
Great thread Hoop!
One of the most important things in flashlight hobby.
A seemingly simple request, but my testing area has an unpainted wood ceiling with beams in the way. If I move everything into the house I could take ceiling photos. The granite surface plate is small so I can move it without much trouble. I think it’s worth doing to better characterize the optical behavior, especially since this kind of testing has not been shared on BLF before, as far as I know. Hopefully I can get a camera to portray the beam characteristics accurately.
I cannot answer this yet but it will hopefully become clear once I test a domed and dedomed LED of the same type with the same optic. It will be interesting to see the differences.
I measured the top surface of the OSRAM KW CSLNM1.TG to be .028” [.71mm] above the top face of the MCPCB. This suggests that the S2 reflector geometry terminates essentially at the focal plane, aka latus rectum.
I was not expecting the lux readings to be so symmetrical or for focus to be rather easily achieved across a range of points. There is a bit more loss to the right side of the graph, as the reflector gap increases.
As for your program, nice work there! I appreciate it, although writing down the lux values doesn’t take much time. It takes more time to adjust the height gage in .001” increments, as it’s easy to overshoot the mark or hit a .0005” value.
Also I was mistaken, my meter is an Extech EA30 model, not EA31.
I machined a clamp out of aluminum.
awesome!
IF, as a rule of thumb, the base of the reflector should be at a height slightly below the top of the dome.
as you said, at the latus rectum line:
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Then, to improve the dedomed beam on the left,
I should bring the reflector closer to the dedomed LED, by an amount equal to the height of the dome removed.
thank you very much for the brainstorming… really appreciate your measurements data… super helpful
I can't believe you posted a pic of someone's latus rectum!
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I don’t know about that. I can’t yet say how an LED’s silicone dome affects the focus. It will hopefully become clear after some more tests.
It seems that a spherical dome shape would capture and bend the light from horizon to horizon (+/- 90 deg or more from center).
If the dome is removed or shaved then a dead spot out the sides and edges (less than +/- 90 d) leaves the dark ring.
A round emitter seems the best shape; square emitters, even with a spherical dome, seem to have dark rings and artifacts.
But it could be that all might be “fixed” with the shims.
This is a great test Hoops, many thanks. Plus it gives me a good use for my old vernier height gauge.
Nice to see this
Added a study of centering ring geometry for the S2 + WF1 combination.
I had expected to achieve 100% lux from the initial centering ring design. When that didn’t happen, I experimented with different geometry in order to reach it.
Great data, thanks for doing those measurements.
Thanks for the clamp photo. I know it’s fairly simple for you to do but that’s really some nice extra effort to go to. Really interesting on the ears and geometry as well…hadn’t ever thought about that aspect. And then how the heck did you hold the G10 stock for that tiny machining! Machine the top and then slice off from the rod (assuming rod stock is available…I’ve only ever seen it in sheet). The #4 configuration…I suppose that depends on mass production accuracy with the reflector bases, or can it accommodate a little variation? Never measured but all but the cheapest reflectors I’ve held have seemed to be very well made.
The clamp took about about 3 hours to make in total.
The gaskets were machined from .062” thick G10 sheet in a cnc mill. The fixture base was an aluminum plate, machined flat in-situ. The G10 sheet was clamped to the aluminum plate with Kant-twist clamps at four corners, close to the machining area. I would not use this method for production, but instead would use a matrix of screws across the entire sheet, machining the gaskets between the screws.
Manufacturing variability of the component stack (reflector + LED) is an important consideration and it would require more samples and testing to evaluate.
The reflector is presumably machined in two operations. The repeatability between the ops should be pretty good but not perfect. It depends on how they are machined and held and transferred between ops. A dual spindle lathe which finishes both ops without human involvement might be used. This would make the most sense considering the quantities being produced.
The vertex opening of the S2 reflector is pretty much exactly 5mm, (.197”- PIN GO, .198”- NO-GO) which suggests that care is being taken in their manufacture, despite how rough the outside looks. The finish on the inside parabola is good.
Compressibility of the centering gasket material matters in this case as well because the surface area on the bottom of the S2 reflector is very small. The compression force would depend on how tight you install the pill into the head. I think Nylon 66 wouldn’t compress much more than G10, meaning very little, but a series of gaskets could be made out of different materials, with slight height variations, .001,.002, etc., then a pill installed in an S2 several times with each gasket, and lux values recorded and averaged, then all results compared.
If I were making my own light I would go through all of this trouble…. 
In the case of gasket #4, the tolerances should be tight on the thickness of the center pocket area, I’d shoot for .0266” to .0272” probably, unless install and compression results proved otherwise. The outside ring of the gasket which centers the reflector matters less and is designed to be an interference fit. The edge of that ring has no chamfer and is kept sharp. With the forces involved in the install of the pill, the gasket is forced to stretch a bit around the taper of the reflector. This is why in the photo of the OP, the G10 ring is stuck to the base of the reflector. It bit into the aluminum a little. The height and ID of the outside ring of the gasket should be held pretty close. I don’t think there would be enough variability of the reflectors to affect the centering function of the gasket. Due to the interference fit, a little variation can be accommodated.
If the S2 reflector + WF1 were to be used in a device where there is no pill, no real compression force on the stack, a style of centering ring with tabs would be more appropriate than #4. A design which has 3 tabs 120 degrees apart instead of 4 at 90 degrees would still center the reflector, but block even less light. Based on gasket #3, but with three tabs instead of four, the resulting lux value should be 99.47% of optimal. An alternative way to center the reflector in this situation would be to utilize the outside diameter instead of the vertex opening, which would also be a “tabless” solution and so 100% lux should be achievable.
Interesting bits to chew on here. (speaking of that…is G10 rough on the cutters?) How do you suppose linen phenolic would do for this? It might have a little more compressibility than G10 but it’s still quite low. Machines well and isn’t terribly affected by humidity (would imagine that in a light head it would be a non-issue)…raw cuts and initial abrasive finishing sometimes leave it very slightly fuzzy, though. I don’t know how many people make the linen variety anymore but we used to have at least two mfrs here in the US. The canvas and paper are much more common (and both are cheaper, too). I’ve wondered about mylar, as a shim, too…never seem to find the mylar washers in quite the right sizing but I keep my eyes peeled (printers often have some of those on various guide bars and rollers)…not sure if it could handle the heat, though. Ceramic sure would be nice but based on the pricing of plain flat washers I don’t think most of us would spend the money on a fancy ceramic mini-widget if it could be made. 
I like the idea of micarta and what not but have not worked with it or tried to find specs. The specs will vary depending on what is used to construct it, both the cloth / fiber and the type of resin. Fabric cloth would make for less tool wear and better operator acceptability than fiberglass, I’m pretty sure. G10 is very abrasive to carbide tools and also to my sinuses. It contaminates the machine sump (coolant) a bit as well but doesn’t ruin it. The 10 in G10 means 10% glass content, I have read. There are grades of Nylon and other plastics that are 30% glass filled. The GF Nylon 66 has a higher working temperature than regular Nylon 66. Notice the “heat deflection at 264 psi” value. I have not worked with the stuff but it would be interesting to see how it machines and irritates compared to G10. G10 completely powderizes when machined. If the Nylon 30% GF made actual chips it would be nicer to machine.
I have not put much time into comparing gasket material properties but am starting to do so now.
Edit: Looking into material properties more, FR4/G10 is far superior to even 30% glass filled nylon 66 in its mechanical properties. It’s also much cheaper. FR4/G10 is what I will use to make gaskets going forward. I actually have a lot of experience machining G10, having made parts for the electrical industry. The downsides to working with the material can be reduced with certain machining strategies.
Great tests!
Would measuring the lux at a distance greater than 1m be better for focusing? With the luxmeter close to the reflector you could have a converging beam (fig. C) that at 1 meter reads higher lux than a parallel beam (fig A) but would perform worse at greater distances as it would start diverging past the convergence point. It probably doesn’t matter much with a small reflector but I think that’s why people like to test larger throwers at 10+ meters
Yes, good point.
Testing at longer distances (and installed in an actual light, if applicable) will be necessary to make a final determination about where the best focus is achieved and how thick a gasket should really be.
I am limited in the vertical distance at which I can test. I need to build a horizontal setup on an angle plate in order to test at long distances.
The S2 + WF1 test was conducted at 1.33 meters.
1 Thank
I think for most applications the G10 is the sweet spot. G12 and G15…seems like they only added long term resistance to moisture absorption, and the fire retardant grades seem the same but much more expensive. I lucked out and got some scrap pieces of several to toy with (abrasives, though, not milling). I worked a bit with various soft plastics and three grades of GF nylon (I think 6, 11 and 30% if I remember right). Certainly nicer to work with although static cling is a major feature…all do make chips but those chips travel further than I would have expected while using a router and the cling was…amazing. I think the 30% is what’s usually used in power tool housings, or thereabouts. There is some carbon-infused polypropylene that’s neat materal, too…much stiffer and more dense than any of the GF nylons. With the G10…yeah, all powder and it can be really irritating to the skin and mucous membranes, super bad news for the lungs, too (same for phenolic there). I’m not sure exactly why, but out of everything I toyed with it was the linen phenolic that was most impressive to me. Don’t see the linen version very much but it’s really a different animal than the usual canvas, and both are quite different than the micarta/paper grades. The linen was (maybe still is) used as some kind of washer in oil drilling rigs, which I thought was interesting…not sure where exactly it was used.
Added S21A + WF1 test. Added spill angle models.