grins 8th annual old lumens machine made entry

Ok lets not think of this as a competition but a challenge. Now as most probably know ere I like lights that give you that crazy grin. :sunglasses: The best thrower would have to be a recoil but the big disadvantage is cooling the led that is on a spider. So I have been thinking you could go off axis, extremely expensive and near impossible to grind. The way I want to get around this is a reflex or cassegrain system. I know this works as I have a small plastic optic with this design. The reflex system has a primary parabolic mirror, a secondary hyperbolic mirror, it also needs an optic to shape the beam from the led for the secondary optic this this can be a reflector or lens. The other drama is matching the elements. So I want to see if I can build a reflex spotlight with matching elements. I am waiting for a drawing board to get here so I can do better drawings. I havent plotted the hyperbola yet but here is the basic geometry of the planned build.

The bezzel will be 180mm and under 200mm long. Light will come from SBT-90 and K75 driver so the battery pack can be 4s6p 30Qs.
So my personal aim is to learn a new skill and do something I havent done before. It also has to be a challenge because there is the opportunity to have input from some very switched on people.

Current stage the light is at

Whoa, this is pretty fantastic all by itself! Looking forward to the complete entry…

Wow! How long did that take?

I have spent a few hours working out a process to cut them these ones are contoured, then smoothed with a radius tool and finally ground with a profile clamped in a tool holder. I have some high speed steel blanks that I intend to make a profile from to get a more accurate cut. Over the weekend I will see if my coating will be any good. I will update it this weekend

So I cut a hemisphere from aluminium and polished it up this sits over the led and acts as a stop/aperture/shutter to shape the light for the hyperboloid secondary mirror. Because I am hand making the mirrors need to have some way of protecting them with a coating. So a bit of research turns out that “mothers” ceramic auto paint protector is silica dioxide and titanium dioxide. I think a hotplate and vacuum is the go I have the vacuum pump butt no hot plate. But see how it goes.

The initial finish it will be repolished when I adjust the height and aperture.

That’s a nice entry, bravo.

We are all Grinning :smiley:

Yes to this.
Is 180mm diameter correct grin?

Good size grin :slight_smile:

Thanks for encouragement :+1:

I had a 170mm borosilicate 3D printer base for front lens and I can get 180mm diameter aluminium bar. Another reason I wanted the hyperboloid to be a decent size for making it.

Have you considered cutting one of your huge mirrors to create off-axis parabolic mirror?

I did. But an off set parabolic mirror is a section of a full mirror and so even cnc they are offset in the lathe chuck. These have been ground with an acrylic profile and emery cloth moved between the mirror surface and profile like a feeler gauge creating the curve. So it is not possible this way. If this technique works well I will get a profile tool professionally made later because cutting them seems more accurate.

Oh Don. :blush:

This is the result of my practice parabolic reflector.
One of the reasons to build a custom reflector is so that it can be tuned to the light source. Like if you were for some reason decided to cut your w30 up.

So now I wait for the 180mm billets to turn up. Tomorrow I will start on the heatsink and driver housing.

So are the beam shots in pics 3 and 4 from the 75mm parabolic reflector with the emitter source held on a stinger as in picture 2? That puts a crazy grin on my face.

How did you do the polishing of the parabola? Aluminum oxidizes immediately when cut but our polisher folks can get a fairly nice finish using a pitch lap with alumina slurry.

The reflector in the photos is 140mm diameter and the beam shots are from the same one.
I sand it with a profile to 2000grit then use a buff once it is polished etch the surface with caustic then repolish. I am still not completely happy with the polish but it just takes a lot of time. I was looking at the laps just incase this wasnt going to work but it appears fairly accurate. So I dont think I will need it.
For a coating i have been experimenting with mothers car polish with silica dioxide and titanium dioxide. I also have the pure dioxides ordered and will expirment with baking them on under vacuum.

Wow! This is a true laser beam. :open_mouth:

Awesome idea and really nice test results, grin.

Did you run the SBT90 with the full current already for the fotos?

Da beam is killa :+1:
and great handwork

Regards Xandre

It Is a chopped W30 in the photos. The SBT-90 reflector has a much shorter focal length. You can see the difference between them.