Hi Hezz,
I have version 5.1. I just got a mailer the other day for 9.0. I can get it for $169 if I order before 1-30-04.
Have you thought of setting your oven 10 deg over the melt point of your plexi and melting it like that? I've done that to soften Lexon sheets that I had to bend around a radius. It worked very well.
John
I just had a thought. Your casting looks like a stone wok. I remember seeing/reading something about a wok is part of a sphere. Some ancient religious reasoning about focused energy.
I'll go check it out.
I have version 5.1. I just got a mailer the other day for 9.0. I can get it for $169 if I order before 1-30-04.
Have you thought of setting your oven 10 deg over the melt point of your plexi and melting it like that? I've done that to soften Lexon sheets that I had to bend around a radius. It worked very well.
John
I just had a thought. Your casting looks like a stone wok. I remember seeing/reading something about a wok is part of a sphere. Some ancient religious reasoning about focused energy.
I'll go check it out.
u wouldnt happen to have a pocal point on that engergy would ya doon? lol
Hezz great work, i can see u are realy getting somewhere with this.
Trev
The one on the left is a semi-spherical wok. The one on the right is a full spherical that is within .005" true. the outside diameter is 355mm.
If you lightly coat the inside with a high-temp spray grease and fill it with the pellets. then put it in an oven with the temp between the melt and boil point of the plastic you would end up with your lens. Right?
John
If you lightly coat the inside with a high-temp spray grease and fill it with the pellets. then put it in an oven with the temp between the melt and boil point of the plastic you would end up with your lens. Right?
John
Attachments
Scratch the grease idea. If you place it in the freezer after it's cooled to room temp the pan will contract and probably pop the lens out.
John
John
Doon1,
In the early days of this project I thought about the WOK but it is hard to find one that isn't flat for a small area on the bottom. Even so, finding a wok with the correct radius curvature is even harder. A good wok with a totally round bottom would work but the wok would not be safe to use after for food.
I am not locked into any one lens configuration. If I need a lens with a different focal length I can make another blank for about $20.
Ace3000,
Thanks for the Kudos. I hope I can pull this off. I think that I am going to buy a dial indicator and make a sphereometer so that I can have an idea on how round the lens is before I commit to the final finish. I think I will gel coat the mold to make it smoother and easier to get out of the mold. If it has a glass like finish it will be very easy to remove from the mold with a little PAM sprayed on.
I'm leaning towards sand casting for the first try because it is easy. I'm going to make a small wood frame like you suggested and then get some fine mortar sand and vegetable oil to prepare the sand. They have some special oils that they use to mix with the sand for casting but some of them make it less easy to dispose of. With vegetable oil I can just dump the used sand out in the garden when I am done. I will post a model of what the casting form will look like.
Hezz
In the early days of this project I thought about the WOK but it is hard to find one that isn't flat for a small area on the bottom. Even so, finding a wok with the correct radius curvature is even harder. A good wok with a totally round bottom would work but the wok would not be safe to use after for food.
I am not locked into any one lens configuration. If I need a lens with a different focal length I can make another blank for about $20.
Ace3000,
Thanks for the Kudos. I hope I can pull this off. I think that I am going to buy a dial indicator and make a sphereometer so that I can have an idea on how round the lens is before I commit to the final finish. I think I will gel coat the mold to make it smoother and easier to get out of the mold. If it has a glass like finish it will be very easy to remove from the mold with a little PAM sprayed on.
I'm leaning towards sand casting for the first try because it is easy. I'm going to make a small wood frame like you suggested and then get some fine mortar sand and vegetable oil to prepare the sand. They have some special oils that they use to mix with the sand for casting but some of them make it less easy to dispose of. With vegetable oil I can just dump the used sand out in the garden when I am done. I will post a model of what the casting form will look like.
Hezz
Doon1,
Were you talking about TurboCad earlier. If you don't need the radiosity scene rendering you can save a lot of money by getting the standard version. I think it's only about 70 - 80 USD.
I would be interested in seeing your results with a wok but I found that I couldn't find a wok with a close enough size radius. If you could make a rough lens within .005 - .010 you would have a good start on the final lens.
I am still sticking to my method as I am as much trying to create a repeatable method for making the lenses as I am trying to make the lens. Also I found that woks are about 90 - 130 USD. I felt that was too steep for a form that wouldn't give me the exact curvature I desired.
Hezz
Were you talking about TurboCad earlier. If you don't need the radiosity scene rendering you can save a lot of money by getting the standard version. I think it's only about 70 - 80 USD.
I would be interested in seeing your results with a wok but I found that I couldn't find a wok with a close enough size radius. If you could make a rough lens within .005 - .010 you would have a good start on the final lens.
I am still sticking to my method as I am as much trying to create a repeatable method for making the lenses as I am trying to make the lens. Also I found that woks are about 90 - 130 USD. I felt that was too steep for a form that wouldn't give me the exact curvature I desired.
Hezz
no problem bud, when u want a hand with lining up the male mould give me a shout cos i can help u out in that, its easier then u think. Im actually thinking in doing the same thing your doing but with the sand casting at a later date, its fun casting things lol
Trev
yeah thats the right idea hezz, tell me, the lens u are making is it a plano convex? also in your pic u will need a top plate, the reason i say this is that if u make a top plate once poored if u are fast enough place a top on it to compress it slightly to have a nice flat bottom of the lens meaning less clean up and a truer lens.
Trev
Trev
Trev,
Yes the lens is a plano convex. What you mentioned is a good idea. Actually gravity is pretty good at levelling things off but it will probably leave a menicus around the edges that will have to be removed. This is no big problem as I will be hand lapping the flat side also and polishing it up to high standards. Probably with a large piece of plate glass.
I want to be able to mount the LCD directly to the flat side of the lens because the closer it is the more paraxial the light path will be through the lens. Also the lens will act as a big heat sink with air rising up and out the enclosure and moving all around the big lens.
Hezz
Yes the lens is a plano convex. What you mentioned is a good idea. Actually gravity is pretty good at levelling things off but it will probably leave a menicus around the edges that will have to be removed. This is no big problem as I will be hand lapping the flat side also and polishing it up to high standards. Probably with a large piece of plate glass.
I want to be able to mount the LCD directly to the flat side of the lens because the closer it is the more paraxial the light path will be through the lens. Also the lens will act as a big heat sink with air rising up and out the enclosure and moving all around the big lens.
Hezz
Hezz
ya thats right and also for a tip u can use cut back polish to cut back the surface of the lens to clean it up, ive been fooling with polishing this stuff up but becarful not to get one with any harsh chemicals as it will deteriate the acrylic.
here is a link to some proper acrylic polish, there are 3 grades, there is a harst cutback being the number 3 to the just polishing being the number 1
http://www.americanacrylics.com/polish.htm
Drop me an email for a better price
Trev
ya thats right and also for a tip u can use cut back polish to cut back the surface of the lens to clean it up, ive been fooling with polishing this stuff up but becarful not to get one with any harsh chemicals as it will deteriate the acrylic.
here is a link to some proper acrylic polish, there are 3 grades, there is a harst cutback being the number 3 to the just polishing being the number 1
http://www.americanacrylics.com/polish.htm
Drop me an email for a better price
Trev
Thanks for the info Trev,
By the way your projector is coming along nicely.
The wether has been pretty wet and snowy around here lately. There was 24 inches out on the side lawn a couple of days ago. As such I havn't done much in the last week or so. Maybe in a few days the wether will clear so that I can go outside and work on the lens. I will keep posting when progress occurs. Also I need to get a dial indicator because the plunger type that I now have isn't the best for what I need to do.
Hezz
By the way your projector is coming along nicely.
The wether has been pretty wet and snowy around here lately. There was 24 inches out on the side lawn a couple of days ago. As such I havn't done much in the last week or so. Maybe in a few days the wether will clear so that I can go outside and work on the lens. I will keep posting when progress occurs. Also I need to get a dial indicator because the plunger type that I now have isn't the best for what I need to do.
Hezz
A long time ago I wanted to use that setup. I decided to try out a high bay reflector because its working in the same way as you want, but it just didnt work as I would have liked. I would have had to place the LCD way too close to my 400 watt metal halide.
Dont get me wrong, this type of reflector is probably the best for bulbs like these, but currently we have no way of getting them, unless we start a venture to have a manufacturer make some for us, like for the 15" fresnels....
What we need is a reflector with the right focus and small enough that the opening can fit a reasonable size condenser lens, which we can in turn apply to the fresnel and get the best result. I doubt anybody can hand craft a reflector to those specifications, unless you are a professional and have design tools for the job.
Good luck tho!
Dont get me wrong, this type of reflector is probably the best for bulbs like these, but currently we have no way of getting them, unless we start a venture to have a manufacturer make some for us, like for the 15" fresnels....
What we need is a reflector with the right focus and small enough that the opening can fit a reasonable size condenser lens, which we can in turn apply to the fresnel and get the best result. I doubt anybody can hand craft a reflector to those specifications, unless you are a professional and have design tools for the job.
Good luck tho!
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