DIY MH reflector?

[herpsandreefs]

Has anyone built a reflector that worked as well as a premade one? I need one big enough for a single 250 MH and 2 65 w PC. Also, if I was able to make one, should I bend it like my drawing (attachment) (1) to reflect each individual light source, or just have one big curve (2) for all three lights?

Any advice would be helpful,

Chris

 

[Fatal Morgana]

The first one (1) is better. For the PC, just use a flat back with two sides at a angle.

Reflector is more of an adjust-and-test than real science, but the rule of thumb is that the more and wider the light emitting areas (inner bulb of the MH, and the tube of the PC) you see, the better the reflector.

 

[herpsandreefs]

So can it just be one sheet with the angles bent into it. Would a flat sheet of stainless steel work?

 

[Bishop1]

Stainless works, it's an interesting beast to work with though... you would have to have it bent with a special piece of equipment as it would be a real B**** to do yourself without it.

Bendable Aluminum is easier to work with, you can bend it at home with a few clamps for simple angles, but for the parabolic curve you're looking at you would still need to have it bent on a tool to do it proper.

You could buy a sheet of bendable aluminum, sand it down with 400grit - 1000grit sand paper, then buff it with a polish to a mirror finish and have it bent pretty cheaply and easily at a local shop.

Considering the relative low cost of something like this from a mail-order shop (esp. in LA) I assume you're in this for the fun more than the price right?
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Lukumi Forum

 

[narkosis]

bishop,

I've got hold of several 4'X8' German polished Al sheets which I've been using to make T5 parabolics. If I wanted to do the same for MH, is there any website or S/W available that lets me figure out the facet angles, or better still for a smooth parabolic? It's a whole lot cheaper than buying Spiders this way.

Thanks

 

[Bishop1]

You can use the Law of reflection to compute the facet angles based on the position of the bulb vs the position of the reflector. I don't know of a specific program other than something like Optica would would be overkill...

Some graph paper, a ruler, and a pencil would be the easiest... or just get your hands on a spider light reflector and mimic it's angles.

You could also approximate it with 15deg angles every 2.5" or something like that.
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Honda CB550

 

[narkosis]

Right, much appreciated.

 

[Anonymous]

For non-image optic work, what I heard is that they don't usually use Optica or ray-tracing software to optimize the angle. It is still a craft involve nothing but bent-and-look (figuratively, off course) procedure for the most part.