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Old 23rd March 2005, 12:12 PM   #11
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Default Update

*Update*
I am now home and after some research did I give up the idea with building a good reflector out of segmented aluminum pieces. There is just too small angels and too hard to make it right. So this is what I did:
I went to my old gymnasium where i got a hold of a guy who can cnc mill it for me. I do not know the cost, but he seems like a nice guy . It will be in massive aluminium, but i doubt it will be very heavy. The next step in the procedure is to polish it, and that will be done in a lathe. I'll be back after the easter with some more info!
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Old 23rd March 2005, 04:55 PM   #12
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Holy CRAP! Well, I guess it depends on how big of a reflector you're talking about here. But in any case, that looks like a LOT of metal to remove. You'll start with a huge solid chunk of aluminum, then cut away most of it....

It doesn't matter how nice the guy is, unless he's doing it for free, it'll be in the hundreds.

There is much quicker and more economical way of creating hollowed rotated volumes. It's called metal spinning. What you do is place a big circular sheet of aluminum on the lathe, then chuck smooth or wheeled tools in the holder and start pushing the disc into the shape you need. Just compare to a profile cut out of cardboard or plywood as you go. Then, without removing the reflector from the lathe, you can polish it as it spins.
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Old 23rd March 2005, 07:20 PM   #13
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Yes I am aware of that technique but It is unfortuantly not an option availible to me here, nor do I have the skills to do it. The aluminium will be cut out from an 80mm(~3.92") axle and it will be around 70-80mm long so it won't be extremly expensive I hope. The piece will weight around 1kg not worked and that maybe equals 30$, I hope You can sell the aluminium that gets over to a decent price as well
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Old 23rd March 2005, 08:14 PM   #14
cbm5 is offline cbm5  United States
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Well, it shouldn't be too bad at that size. It depends on the alloy and treatment grade of the aluminum, too...some of that stuff can be difficult to chew through.

For that size of a reflector, casting could be a good option. Use the CNC mill to cut a form out of a wax cylinder, then use it for a lost-wax mold.
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Old 23rd March 2005, 10:08 PM   #15
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Default as long as you are milling aluminum

You could also have him mill out a spherical reflector with a hole in the middle. Then you can use them both to capture 100% of the light (minus light absorbed by the reflectors):
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File Type: jpg reflector.jpg (17.9 KB, 433 views)
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Old 23rd March 2005, 10:25 PM   #16
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Only problem with that idea is that it will be hard to cool and heat up the lamp which reduces lamp life.
The wax idea i assume might work, but when i got access to a cnc mill will this be the easiest way to do it, and most likely the one with higest accuracy. Note: he will only mill out the inner ellipsodial form and leave the outside as an cylinder. Only a shame that i still loose a lot of light due to the 16:9 lilliput screen.

Cheers! Time to go to the sports cabin and drink some beer, bath some sauna, jacuzzi and something called bath barrell(big barrel with water thats warmed up and then you sit outside in the snow) I'll be back on monday/tuesday with some results if i'm lucky.
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Old 23rd March 2005, 11:32 PM   #17
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let him mill out an intergrated heatsink as well

Quote:
Originally posted by Gilgamesh
Only problem with that idea is that it will be hard to cool and heat up the lamp which reduces lamp life.
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Old 23rd March 2005, 11:40 PM   #18
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Default heating and cooling

Yes, heat can be a problem with these reflectors. I think you would need to make the hole for the lamp large enough for some cooling air to be pulled over the lamp surface and out the space around the base of the lamp. But you will also have to do something to remove IR from the light. Aluminum reflects IR just as well as it reflects visible light. With an eliptical reflector, you can use a very small dichroic mirror right at the second focal point. Very nice.

>bath barrell(big barrel with water thats warmed up and then you sit outside in the snow

I used to love doing that after skiing: Sit in a jacuzzi or hot tub (that's what we call a bath barrell) until you get too hot. Then sit in the snow or go in the unheated pool (with the icebergs!) for a while. Repeat as needed. I also did the same thing at a hot spring right next to an ice-cold mountain stream.

Lots of hot water is the ultimate sign of civilization.
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Old 6th April 2005, 11:33 PM   #19
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I'll post an update soon I unfortunantly didn't get it done when I was home so I have to wait until summer to fix my projector. I'll be back with some pics of the polished reflector and such!

/Gilgamesh a bit drunk (uni you know )
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Old 10th April 2005, 07:46 PM   #20
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*picture update*

Alright things settled down a bit. Here a pic of the unpolished reflector this is how it looked when i got it from the cnc mill.
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