grins 8th annual old lumens machine made entry

Subscribed and really interesting build! I'm eagerly following along.

Wow, that’s ambitious, making your own reflector. I love it :+1:

:beer: everyone
Last year I took a gamble on a very different heatsink it paid off. This is a bit of a gamble not so much the main mirror but the hyperboloid Im not sure how accurate it has to be. There are a few things that might stump me. But it has to be different it has to stand out. For the OL challenge I want to build something I have thought about but havent done before.
Anyway the 180mm billets turned up today and I had just got the geometry right.


So I cut that out and glued it to acrylic and roughed out the billet

I take the ridges off with a lathe tool then use 40grit emery between the profile and billet.


Few hours later it is starting to take shape I will make a new profile because the first is worn out.

:+1:

You have a lot more patience than I grin. :smiley:

Well what a mission after nearly 24hrs I have this. The outside edge is a bit low but will be trimmed. Hot spot lookes good in the sun.

Chopped k75 in a testing jig


About 50m

OOooh shiney…!

That spot looks really well focused. Good job :+1:

Thanks PP,
I am surprised at how simple it was but I knew it was going to take time. I had it roughed out by sunday spent all sunday fine grinding/sanding from 8am until 11pm with a few hours break, then 6 hours polishing this morning. My arms feel like they are going to drop off. Started with 40grit emery then 240grit, then went to wet and dry 320 400 600 800 1200 1500 2000 then calico wheels first grey compound then brown and white, last was mothers aluminum polish. If there were any marks not removed I repeated the step before. I think the calico wheels would remove more of the finer scratches that are hard to see.

I love what you do grin. :slight_smile:

Awesome work, great job!
It looks fairly easy, but i know it isnt

Thanks, anyome can do this if they are determined enough. But it is pretty exciting being able to make custom one off reflectors. I have also been thinking of ways to manufacture parabolic mirrors to make them more available to people with smaller budgets. Soon I may have the space to setup a dedicated workshop to do it.

Wow! What a marathon polishing session. :+1: :beer:

i thought the use of a plastic template was a brilliant idea. How did it survive all the sanding operations?

Impressive. Took as much time to polish as I spent cleaning out my garage (though I spread that across a week)

So true Agro. Could not have said it better. :beer:

The first one I ran into the job a few times which caused the damage to it. The second one didnt wear at all. The profile doesnt actually touch the mirror it is just to push the paper onto the job. Once the tension on the paper is even as it moves between the profile and mirror it is time to move to the next grit.

So the primary mirror is just about done so I will leave it at that for the time being. Next I turned the billet around and cut a bit Of material for the drum and bezel.

The light comes through the vertex of the primary and there needs to be something to condense the light for the secondary hyperboloid. A lens would work but I have chosen to use a 50mm hemispherical reflector because I have a bit of practice cutting them and I cant grind a lens. Yet. :smiley: a few pics will explain how I do it except handle sanding 8t with 1500 and 2000grit.




I cut the chatter marks out turning the lathe by hand and end up with this.

And ready for final polish.

That’s a beauty.

i have a cutter bit like that with one side ground down so it’s not trying to cut both sides at the same time. That is a huge contact surface to cut, but it sure turned out great with all your pro tricks.

That chatter reminds me of the reflector surface in a Convoy, like they put some chatter marks in the reflector mold that shows up in the plastic part.

Nice. :beer:
More black fingers to come.