Yep, its time to do a pinned reflection guide
Maybe one can be sketched up among the guys that have had the most experience with the subject/PJ's?

Are you volunteering Joe?

You are certainly among the most experienced here. I don't have that kind of experience. The best that I would be able to do is a summary of each page of the reflector thread and post some links to what I believed was the most pertinate and effective.

To all you people who are saying you shouldn't have a full hemisphere because the only light that needs to be bounced back has to be the angle for the lens. Though this has a cerain logic, there is a fatal flaw. The lamps we are using can't even be be closely approximated as a point source. Say a stray photon from one side of the arch goes out and hits part of the mirror that wouldn't be in your diagram, now depending on which direction the photon has been augmented it will either go to one side or the other of the center path, if this angle is sufficient then it could reach the screen OR be bounced into the dish and then be reflected into the screen.

Pyrometman,

Haven't browsed this one in a while, but my question on your above reflector is this: Aluminum while it has a highter % reflection than stainless, oxidizes very quickly. Polishing would remove the surface coating of aluminum oxide(milky white layer), but that would return quickly... does this make aluminum the best material to be stamped into your (nicely designed and thought out) reflector? is there a heat resistant coating that you were planning on applying or having us apply after buffing?

You could powdercoat it chrome color then sand it with 600,1200, and 1500, then buff it with Meguiar's Mirror Glaze #9(available at an auto body store). Powdercoating is good to about 300 deg. Proly cost you at least $75 to have it powdercoated though.

Hemispherical mold, up to 2 quarts.

http://culinary-direct.com/catalog/category/cat66706.cfm

I have read a lot about the hemishperical molds, but didn't hear from anyone who actually bought and used one.

Typically, molds are quite thin and I am wondering if this thinness is a detriment to the reflector. Is this mold thin? Would the heat from the bulb warp the thin material?

Thanks for the response.

Sam

Since the molds are for baking they should be fine to at least 500 degrees.
Don’t see the PJ getting this hot. If it does, then, “Houston we have a BIG problem”

2 things first the molds are not shiney inside cause I was going to use it but found out is is brushed not polished...second the area of the bulb and reflector gets up to 1200 degrees cause there is not air flow

I would be happy to be a part of it and throw in my thoughts, but I don't think I'll be spearheading it. Anyone want to start? We cdould pass a doc around email to each other or start a private forum or something????

Obviously the commercial PJ's are using a parabolic reflector, but I am curious if that is to focus for a fresnel to pic up or is it to spread on the LCD directly. Anyone know?

I am very interested in the hemisphere molds. There are stainless stell so the max temp is extreme. The first prob likely would be the point when the metal starts to color. My first PJ that gets about 4-5 hours per day use is yellowing a bit on the stainless reflector. I am sure this could be avoided with controlled cooling.

I think if we polished the inside to a rediculous mirror the hemispheres they would work great. Who knows how to best polish these up?

Just got one in the mail today, you could turn this thing open side down and stand on it, good thick stainless steel. It isn't brushed it just looks like it was just pressed and then sent out. I am going to find a polishing kit to hopefully bring it up to a mirror finish. Will let you know how it turns out.

worldprojector,

Thanks for your comments on my reflector design. You make a very good point about oxidation of the aluminum, especially when it is right next to a heat source. Oxidation or aluminum is certainly a function of temperature and will be a negative when compared to polished stainless.

Now let me get to some of the ideas for providing "protection" for a polished aluminum surface:

1. Perhaps the best is an actual metal-ceramic coating such as AlSiO. There are others but I believe that this route will be expensive as Dom mentioned a few posts back. I am still researching this area but I don't think I will find a DIY'ers price that fits.

2. Anodizing is the next solution. Many, many reflectors are protected this way. Anodizing puts a thin layer of aluminum oxide (yes, the same thing we are trying to prevent) on the surface. The aluminum oxide layer is so thin (on the order of 10 thousandths of an inch) that it does not significantly cut down the reflectance of the surface. The key is that it provides a protective layer over 100% of the surface, significantly cutting down on the oxidation of the underlying aluminum metal. There are people out there doing DIY anodizing, so it is possible. I will continue to investigate this method as well.

3. The third method I've thought of is cooling. Since oxidation increases at higher temperatures, simple cooling should extend the life of the polished surface. This means that you will still have to take the reflector out from time to time to polish. You would just want to design your projector to make the reflector removal easy and so that you don't have alignment problems when you reinstall it. I think that the cooling would utilize a small computer case fan pulling in cool air and blowing directly on the back of the reflector.

Any other ideas would be welcome. This is DIY you know

Linens-N-Things Scrub Holder Stainless, 5-5/16" diameter.

I can't find it online, but they had a bunch instore. The picture doesn't do it justice, but it has a mirror finish inside. There are a few tiny dimples from the base being spot welded on, but i really doubt they'll be a problem.

Here it is with the handle and base cut off.

Oooo... nice find. Where are the welds at?

Here it is with the notches cut. All I can say is YAY!!! I'm happy. I didn't think I'd find anything as good as a norpro after they went away.

So, final verdict as far as I can tell:

- 5-5/16" diameter
- Will work with both Ushios listed in LL store
- Appears to be a perfect hemisphere, no flat spots
- 2 dimples on the side to hold scrubby rack, but they're not in the way
- 4 tiny dimples on the bottom(about 1mm diameter) where the base was spot welded on

My Ushio is broken as you can see in the pic, so the envelope isn't sitting in the right spot. Waiting on a replacement from LL.

...start with 600 wet, wipe it dry so you can see how much you've sanded...you don't want to get flat spots...then move up the line of grits...1000, 1200, then 1500. The most important part is the sanding. You want to be very thorough with each subsequent grit or else you will end up with swirls that will never go away. Also just use little pieces while sanding instead of folding the paper because the folded corners can cause extra swirling.

Buy some rouge or tripoli at Home Depot in the buffing section, I don't remember which polishing compound you are supposed to use with stainless but it says on the back of the packages what you will need. Put the arbor and buffing pad on a drill or whatever and go to town. Be careful to cover the nut on the arbor with some masking tape or whatever so if you accidentially bump the metal it won't ding it all to hell.

Then finish up with Mother's metal polish or whatever they have at the auto parts store for chrome...a scratch and swirl remover...

It's really easy to get fantastic results with the sanding/polishing compounds...you will surprise yourself if you havn't done it before. I polished my hammer to a mirror shine.

Pulsareous,

Great find! Can you post a side view so we can see the hemisphere shape and where your arc tube is sitting (broken arc tube notwithstanding)

Thanks!

I saw this at TJ Maxx today.

I bought an aluminium hemispherical cake pan at micheals today. It was like $7 and it polishes up nicely.

You get a complimentary picture of my hand to go along with it :-p

BTW, I feel obligated to give credit for this find to my GF She didn't like how my last PJ kept me out in the garage for all hours of the night, but when I said I needed a reflector, she lined up a bunch of stores for us to check out and even clipped me some coupons!!!

That's what I got for my reflector. I also bought it from Linens-N-Things. Yet, I haven't started doing anything with it due to the weather is too cold.

Just got done cuttin the pieces for my box in the driveway. Temperature around 10 degrees F.

Indian reflector, 2" deep and 4.5" in diameter. $5.

I went to an Indian grocery store in New Jersey and found a bowl that can be used as a reflector. Norpro bowl seems to be out of sight and this can be a replacement. It cost me $5. I do not live near an Indian store, so you may need to hunt one.

As you see in the pictures, I did not removed the labels or cleaned it. The reflecting surface is very good and close to Norpro. It is about 2" deep and 4.5" in diameter.

I have not used my projector yet. It has been sitting at my friend's workshop for the last one month. I am not sure if high heat would scorch and damage our reflector's polished surface and this cheap fix can definitely be an advantage for us.

I can see you guys lurking around Indian stores now. Tell them why you are buying them

Ronjon

Puls looks like you may have found it just your bulb is almost sealed by it so hope you dont build up too much heat. Id love to see how it looks on a lcd to see the brightness

Ronjon (how's the surf shop?)

That reflector looks good. I just took it into photoshop and overlayed a couple perfect circles. Even though the photos were not a pure profile, the overlays look good. You will note it looks like the pot has less than half the sphere, so plan accordingly before cutting it.

Just got done cutting and polishing my bowl from jb prince and it turned out very good. Just polished it by hand with a good metal polish and some flour. Sorry no pics, I dont have a digital camera. Only problem is with jb prince there is a minimum of $25 order, so I ended up with a spoontula as well.

The surf shop is probably doing OK. Never been there.

My projector is done. These reflectors are spares, in case the Norpros are burnt (I have one spare Norpro too).

You are right, I do not have to cut much.

Ronjon

Pulsareus,

One more question please. How did you remove the base and handle? Did you pry them off -- I'd be worried about warping the shape of the bowl?

Thanks again!

The base was spot welded in 4 spots. I mounted it by the handle in a vice and used my angle grinder to grind through the 4 welds. You have to be careful not to get it too hot, or grind too far. If you get it too hot it will discolor. I used the same method to get the handle off, spot welds again. Very little to no prying should be necessary.

didnt find the one you guys got at linen n things. I did buy one that is 4 3/16 wide (inside measurment) as far as I can tell its perfectly round on the inside 2 1/16 deep. its double walled INSIDE is perfectly round but the outside is flat bottom its double walled.

*edit its not 4 2/8 wide like I posted its 4 3/16 i changed that. and the inside was hard to measure but it seems like its exactly half deep(half of diameter)

$2.99 to bad I have the more round bulb and not the s400

one more pic to show the bottom and the tags. once again the inside wall(the reflection surface) is round and the outside wall is flat on the bottom

also the top of the bar code tag says SB-1 and the tage under that says "DoubleWall stainless steel...blah...dishwashersafe...blah...(11.1 cm) diameater" the 11.1 is the outside measurement and inside measures shorter

The original Norpro. They only have the 4.2 Qu version. It's big but I think it'll work great. Again, this would only work for larger projectors. My interior dimensions are 11.5"x15". It's also a tad expensive. I'm happy with it though.

Norpro

This is the bowl from amazon
Steeltek

It appears to be the exact same bowl as RHopper posted above.

Here are the specs
Depth 2 inches
Inside Diameter 5 1/8

thats not the same mine was a little over 4in and the outside is polished also I dont think its a steeltek. I ended up getting the one pulsareus found cause i have the bigger buld. bivoauc made a good find I think aswell. the one I found and posted on would be perfect for the s400 I think.

bivoauc you should meausere the inside dimensions and depth so people know for shure if that will work to

Tags for both bowls at linen and things (4 3/16 bowl and 5 1/4 bowl)


5 1/4- tag
"ah, here's the tag.... it's made by steeltek, www.steeltek-home.com on the tag is "SCRUBHLD-1", part number "097889672565" and part number "9788967256" -pulsareus (irc)


4 3/16 tag
The smaller one I found at the same place the tags are hard to read is "9788968079" and "097889680799" for part number

here is the bowl after the outer section is cut away and a notch cut out for bulb, i used it in a vertical projector about 3 months ago.

I understand using the collimater lenes to lumenate the entire LCD panel,and with the reflector behind the lamp you get more light,but my question is if your able to direct all of the light toward the LCD wil the collimater lens be needed and is thee such thing as tamperd mirror. The gray area would have a mirror finish

If I understand things correctly, the collaminator fresnel helps to provide an even light distribution across the entire lcd. It takes all light originating from the point light source located 220mm away and bends it into parallel beams that enter the lcd. Although your proposed lighting schematic will direct most of the light towards the lcd, if the light isn't travelling perpendicular to the lcd, you will not get an even image, because the collector fresnel will not be able to collect all the off-angle light.
This would result in a dim image with a hot spot in the middle, since the only perpendicular light passing through the lcd would originate from the center of the bulb.
If I have made any mistakes in the above, someone please correct me.

Rhino

Rhino17,

You are correct. It is also the same reason that only spherical reflectors work, only spherical reflectors will reflect the light back through the arc (as long as the arc is placed at the radius of the reflector), thus focused by the collimator.

Ed

reflector alternative to the norpro, i bought this about 2 months ago from linins and things.. 6 1/4" Dia. Double Wall Stainless Steel serving bowl. 1st pic is put back together after cutting along rim and you can see the notch cut out for bulb, same as pics above.

seperation of double walls

I just bought that same style bowl too joe. I think i got the one one size smaller which to my recollection had 5 1/2" diameter. I will be using the S400DD. I am planing on cutting away most of the walls except for the needed arc to reflect the light the width of the monitor, which has been suggested several times. Although this has been suggested several times has anyone done this and posted pictures. I looked but never saw any. I will post pictures when I start.

Hi all,

I've been reading a lot about reflection and have a question I haven’t been able to find answered in the forums. I have found a Norpro 3 qt bowl for sale and would like to know if this is to big for the Ushio 400W T-15 bulb. The bowl is 10" from edge to edge and 4.5" tall. There is reference to this bowl in the first few pages of this thread but no say on if it would work or not.

Thanks for the help

Lucas
Sitka, Alaska

Deathray,

Following your image from an earlier post, I am getting the S400DD bulb and have already found a reflector from linens n things that is spherical and 5.5in in diameter. How can I figure out what arc length I need to project across the whole 15in.

In other words using this diagram can you tell me how I can calculate the amount I can cut off the bowl and still get the full use of the reflector.

i'm not sure how much has changed with the different bulb, but i believe with the previous shapes and a norpro, ~60% of the norpro was useless in terms of contributing useable light and only focusing extra heat onto the lamp itself...

i have 2 norpros right now and am thinking of cutting both of them in half and selling 2 of the 4 halves... but not sure if anyone would want to buy them.

Just layed it out in cad. The very smallest in dia of a 5.5 in dia spherical reflector is 3.6" in dia or about .7" thick. It works out to be a minimum of 82 degrees. THat will cover a 15" diag screen.

90deg will give you plenty with not much overage, so that's about half of the bowl. Pretty easy to measure that out.

If that makes sense.

Yeah thanks for the help. Looking at other projects, I haven't seen this done much. Is there a reason why besides possible laziness?