What's new
TerraForums Venus Flytrap, Nepenthes, Drosera and more talk

Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!

48" parabolic mirror reflectors

Has anyone come across any 48" parabolic mirror reflectors?

Previously I invested time & $$$ into AHS outfits (which I liked alot) but found that the lamps burned out at erratic times (usually just after I left for a 3 day weekend). I'm probably going to be adding an additional rack of lights in the basement for more intermediate-highland growing space & would like to have the parabolic mirrors w/ T-8 lamps. If I'm unable to find these reflectors I may give in and try the T-5's since I continue to hear good things there - & I believe they have the reflectors...
 
Ron,

I don't know if the reflectors can be readily bought individually, but this is where I got my high bay T8 fixture: http://www.contractorlighting.com/h....html?osCsid=7476936ebb9f7e0ea8badffb7a2e7158

It comes with lights and a built-in 95% reflector (make sure you order a three prong cord too).

If you look elsewhere, go for the ones marked high bay. High bay lights are typically designed for high ceilings, and direct light downwards strongly. On the growrack this is desirable, as all your plants are located directly below the lights. You will minimize light waste this way.

Jason
 
A parabolic reflector over 48" fluorescent tubes? I am not familiar with any other than the ones used with a HPS or MH bulb. There are some very good aftermarket reflectors you can get to place over fluorescent tubes but they are not parabolic. I would think that a parabolic reflector would only work well with a very bright point source light source. Perhaps we are thinking of different things?

Tony
 
A parabolic reflector over 48" fluorescent tubes? I am not familiar with any other than the ones used with a HPS or MH bulb. There are some very good aftermarket reflectors you can get to place over fluorescent tubes but they are not parabolic. I would think that a parabolic reflector would only work well with a very bright point source light source. Perhaps we are thinking of different things?

Tony

Tony,

The reflector that comes mounted to my light fixture is curved along the length of each individual bulb. I suppose that curvature function is described either spherically or parabolically, just not with the same parabolic function that is used in HPS and MH reflectors.

Jason
 
Ron,

Just for academic purposes, the "ideal" fluorescent lamp reflector design would be shaped like the McDonald's arch or the letter 'M"

This would eliminate the deadzone inherit to a pure parabolic design. Parabolic designs work best when the area within the parabola is free of obstruction and the energy source being focused is external of the reflector.

The double arch design greatly reduces this section of reflector that would normally be blocked by the bulb itself. However, from a marketing and manufacturing standpoint this design is not cost competitive.

But if we reduce this area (with smaller diameter bulb) this inefficency is greatly decreased, hence the big advantage of the T5 format

:)

Av



Butch
 
hey Ron,

I've had these sitting around here for a while. They originally came from 2'x2' troffer lights(ceiling grid fixtures) you put them side by side and you have the 2'x4' mirror reflectors. they are a little dusty but still very reflective. let me know if you're interested.

100_0817.JPG

100_0818.JPG

100_0819.JPG


~billy
 
Just for academic purposes, the "ideal" fluorescent lamp reflector design would be shaped like the McDonald's arch or the letter 'M"

That's interesting. I might have to do some ray tracing for a double arch design. It doesn't seem like that would be much more expensive to create. Do you know how the normal parabolic reflectors are molded? Perhaps on a press?

Jason
 
jason,

I would imagine so, but most "quality" fluorescent reflectors are actually faceted, not true parabolic. I would think the problems with the double arch would be the design of the die used in production plus the resulting mounting issues. Both of which would result in a production cost increase.

What is ideal is not always what is practical.
Av
 
Thanks to everyone for all the helpful, informative replies. :hail:

A parabolic reflector over 48" fluorescent tubes? I am not familiar with any other than the ones used with a HPS or MH bulb. There are some very good aftermarket reflectors you can get to place over fluorescent tubes but they are not parabolic. I would think that a parabolic reflector would only work well with a very bright point source light source. Perhaps we are thinking of different things?
Tony, I suspect that Jason explained it already. The only real difference in the parabolic reflectors for the 2 applications, is as you mentioned: one is for a point source and one is for a line source. For others who aren't aware of the benefits of these units, here's a pic:
Parabola.jpg
(pic borrowed from Wikipedia - hope that's ok) With a parabolic reflector, all light coming from the lamp will be focused toward the area we want it (as Av described, in reality the lamp blocks some of the reflected light and some also strays out of the target area). High bay lights or others designed to get the light to one area focus the light better than most available fixtures (like shop lights) which are designed to scatter the light over a broader area.
That's interesting. I might have to do some ray tracing for a double arch design. It doesn't seem like that would be much more expensive to create. Do you know how the normal parabolic reflectors are molded? Perhaps on a press?
While I've never been in one of the lighting manufacturing facilities, based on the design (using multiple facets to approximate a parabola) and having worked with 'tin-knockers' on hvac ductwork, I would hazard a guess that they are bent with a piece of equipment called a 'brake'. As with any process, the more steps, the higher the cost - which is why we probably haven't seen any of the 'McDonalds M' shaped reflectors. As can be seen from Billy's pics, manufacturer's don't usually try to use too many facets to duplicate the curve (although I have seen more than Billy's show).
 
  • #10
jason,

I would imagine so, but most "quality" fluorescent reflectors are actually faceted, not true parabolic. I would think the problems with the double arch would be the design of the die used in production plus the resulting mounting issues. Both of which would result in a production cost increase.

What is ideal is not always what is practical.
Av

I might try and make my own some time then. My idea is to create a mold surface from ABS 3d printing, then vacuum mold plastic over that. Then I could adhere mylar to that plastic with the help of a few people to keep it from creasing. I should have access to such facilities here at my community college and at my transfer college. The reflector in my T8 fixture is removable, so if I made the same mounting pattern, I could swap it out with a custom one.

Jason
 
Back
Top