# [Wet Thumb Forum]-reflectors for T8 lamps



## Roger Miller (Jun 19, 2004)

I've been looking into replacing one or more of my diy lights with newer fixtures. The lamps are mostly T8s and since the choice of PC lamps readily available in the US is pretty bad I'll probably stay with T8s. I've been wondering about building better reflectors into my DIY fixtures.

I can draw up profiles for the reflectors but I'm not sure what kind of material to use or how to get a nice specular finish on the reflectors. Any ideas?


Roger Miller


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## Paul Higashikawa (Mar 18, 2004)

Roger, would a reflector from AHS work? I am just wondering. If it does then it will save you time from making one. I've never tried one for NO lights. Wonder if it does make the output more efficient. 


Paul


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## Bob Hooper (Apr 10, 2004)

Roger,
You are the man I have been looking for!!! I'v posted on this board as well as many others and didn't get the response I was really looking for.
I have a large quanity of a material that is in my opinion, every bit as reflective a s the the material that the AH Supply reflectors are made from. It is available to me in very large quanities at a very reasonable price.I also have access to a brake so I can pretty much bend the reflectors into any configuration that I chose. What I lack, is the knowledge to configure the right design to work with NO tubes. AH Supply reflectors were designed to be used with compact fluorescent bulbs and leave a lot to be desired when used with regular tubes I would even bend you up a couple, send them over to you, and let you try them out. At no charge to you of course.
Thanks,
Hoop


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## Roger Miller (Jun 19, 2004)

Hoop,

What is the material? How long a piece can you bend? (not interested in more than 4 feet). Can you bend curves or do you need angles?


Roger Miller


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## Bob Hooper (Apr 10, 2004)

Roger, 
I can bend curves or angles, angles being the easier of the two. This is a mirror polished aluminum. I duplicated an AH Supply reflector using this material and installed them side by side in a DYI hood. For the life of me, I can see absolutely no difference what so ever between the two. They have both been in place over 6 months. I have been experimenting with this material for over a year now but could never hit on the right configuration for use with NO bulbs. 4 foot sections are not really a problem, but thought I would experiment on something smaller until I was satisfied with the result.
Thanks,
Hoop


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## Roger Miller (Jun 19, 2004)

Hoop,

Here is the general concept:








The picture is not quite to scale, so the angles are a little messed up. The lamp sits 0.1 inches in front of the center of the reflector. The reflector is not intended to focus the light, but to harvest the light that would otherwise go away from the water or restrike the tube. By design this reflector should get pretty much all of the light from the lamp and put it down toward the water.

The curves are ideal. I haven't quite figured out how to best simplify it to a few angles.

Roger Miller


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## Bob Hooper (Apr 10, 2004)

Roger,
You may not be able to simplify it down to a few angles. The curve may have been what I was lacking in previous experiments. Wouldn't you want the reflector to extend down past the bulb a little on the sides? Where the curves meet at the top of the bulb could you insert a flat spot, say about 1/2", for mounting purposes? Would this distract from the effectivness of the reflector?
Hoop


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## Nillo (Jun 11, 2005)

I put a variation of the double parabolic design in a community album because I couldn't figure out how to upload to image to this thread.


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## Roger Miller (Jun 19, 2004)

Nillo, where is the album?

Hoop, I stopped the reflector where I did because if I extend the same curve downward then it starts curling under the light. It might be possible to improve the effect by extending the reflector down a little, but I'm not sure about that.

I don't think a 1/2" flat spot right behind the lamp is a good idea. That would be half the width of the lamp itself and would just reflect a lot of the light back into the tube. The idea is to get that light reflected out from behind the tube. I expect that sheet metal reflectors would be mounted either at the top of the curve in the reflector or at the ends, not directly behind the lamp.


Roger MIller


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## Bob Hooper (Apr 10, 2004)

Roger,
When you say behind the tube do you mean directly above the tube? I Would love to see that double parabolic design that Nillo is refering to. How do I access the community album?
Hoop


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## Roger Miller (Jun 19, 2004)

> quote:
> 
> Originally posted by Hoop:
> When you say behind the tube do you mean directly above the tube?


Yes.



> quote:
> 
> I Would love to see that double parabolic design that Nillo is refering to. How do I access the community album?


It's in the thread named "reflector" in this forum.

Roger Miller


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## Bob Hooper (Apr 10, 2004)

Roger, 
I think your curved reflector is the better idea. You could always stop the curve at the exact base of the bulb and bring it down on a straight line till it is just past the base of the bulb this way it does not curve under the bulb. Correct? Just curious, did you arrive at this design through mathmatic computations?
Hoop


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## Roger Miller (Jun 19, 2004)

The curve is based on a mathematical calculation -- it isn't a "double parabola" though it may look like it. The idea was to trace a "ray" of light emitted from any point on the surface of the lamp (up to 90 degrees from the line perpendicular to the surface) and figure out where that ray goes when it is reflected. The rays should all either be going downward or they should hit the reflector and be reflected downward without restriking the tube.

The calculation involves a fairly complicated numerical integration that I have done in the simplest possible way. I don't regard it as being finished.

The problem with using the curve is that the shape of the reflector has be to be exact or the effect it produces won't be the effect that is intended. In that case it might actually be better to use a simplified version of the shape. Something like Nillo's sketch, though I think I would want the simpler version to be a little deeper than Nillo's sketch.

I'm not sure there's any advantage to extending the reflector profile straight down below the tube. If the reflecting surface is vertical then the light will be reflected back at exactly the same angle that it is incident on the reflector. Imagine a "ray" of light that comes off the tube at 10 degrees below the horizontal. If that ray is reflected off a vertical mirror then the reflected ray will bounce back still at 10 degrees below the horizontal but in the opposite direction. I guess if you want the light going left instead of right that is a good thing, but I don't have a particular preference that way. I just want the light going down and not restriking the tube.

As it stands there is an area on the lower part of the lamp's cross section where a ray of light coming off the tube at a sharp angle could end up missing the reflector and going upward. There may be some angles that will restrike. There's room for improvement, so I still need to look at it a little more.


Roger Miller


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## Bob Hooper (Apr 10, 2004)

Roger,
I suck at math so "your the man". Let me know when you have something you feel is close and I will start to fabricate it.Do you have some smaller tanks we could test run them on? I have a couple of 10's, a 5, and a 20 gal long, everything else is much larger.
Hoop


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## Paul Higashikawa (Mar 18, 2004)

Hoop, count me in on ordering one of such reflector when you make them from Roger's design. I am actually looking for an 8" reflector, much like the one from AHS 13-W kit. Its shape, however, is not the one I am looking for. I much rather prefer the parabolic shape they have for the 36-55W kits, but they do not have smaller size. The reflector they have for the 13-W is an "M" shape. Feel free to e-mail me about the price and the like whenever you have time. Thanks!

Paul


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## cdnburt (Feb 24, 2005)

I've been looking into this subject and doing some research online. From what I've found, the reflector design shown here: http://aquabotanicwetthumb.infopop.cc/groupee/forums/a/tpc/f/8006023812/m/112107675/r/112107675#112107675 should work well, but extending the "skirt" down below the bulb would be better.

The following article on reflector design is interesting reading.
http://www.1stsourcelight.com/pages.cfm?pageid=38


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## cdnburt (Feb 24, 2005)

Boy that was an exercise trying to get the links to work! 

I am very interested in having someone make up some 48" reflectors for me. I am working on a built in aquarium display housing 2 x 90g and plan on using 6 T8 tubes over each tank. Decent Reflectors would be a nice addition.


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