17 July 2017 at 10:14 #10046
I'm going to start writing my thesis and I decided to design a telescope from top to bottom then I will open several discussions in different sections.
The first obviously concerns the Blank: I will build a plaster mould in order to create a blank of about 30 mm/35 mm thick and 400 mm in diameter (F5) with hexagonal cavity in the rear to make it as light as possible; also I will try to create the mold so that the glass has already reached the desired ball curvature.
someone has already done something and managed to give me advice/information/opinions?17 July 2017 at 10:34 #10052
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Hi Mark, what you're majoring ?
About the fusion of glass there is a trial of Mirco with borosilicate glass, http://www.grattavetro.it/forums/topic/primario-420mm-foca/ He will definitely give you all the information you need, but I believe it is a job that goes a little’ beyond the “normal” DIY.17 July 2017 at 10:59 #10053
in mechanical engineering, that is, I'm still missing one year, but I think the designs require the entire time; I thought I'd ask for help from Professor of Mechatronics for the frame, to that of geometric modelling for all part of CAD, to material science and finally to that of turmoil regarding precisely the turbulences in the pipe. And of course the help of all of you17 July 2017 at 12:36 #10061
Hi Mark, a welcome from me…
mechanical engineering, well, where ?
Then complete a blank fusing glass is not easy and I'm telling you because I made quite a few’ of evidence, go all more or less OK, once for a reason once for another…Anyway, This allowed me to gain experience and understand that, Obviously, as in all things, need the right equipment and machinery, otherwise the result nevermake…
That said I'm very interested to read and understand how you intend to make your project, that if you want to, can I somehow, try to give you some tips for what little experience I gained.
Meanwhile if you want to see here:
Although I haven't shown everything I've experienced, There's a little something…17 July 2017 at 13:24 #10067
In Udine. Anyway I read your article and I must say you've done a job complex! My first problem was to create the back so you have backers to support but after seeing your coming to a resolution. As for the merger but I didn't understand, you created the mold and then melted the glass inside or the two pieces were carved and then “glued”?17 July 2017 at 14:25 #10069
Then, I state that I did not understand what you mean by: “create the back in order to have the supports to the support”, "from anything though…
As for glass melting, I first realized the plaster mould, and then I loaded it with glass beads, that with temperature merged.
But here I should open a whole chapter about the difficulties I encountered, the imperfect merger of slivered due to inadequately high, at the time of holding that is saying, the air bubbles that are trapped in, mold resistance, to cracks that result in cooling etc…
Because of all these and other problems, that still wouldn't be able to prevent with certainty, at the end I was directed towards the process of softening more than pure fusion.
Here are a few pictures of the first race I'd done (lots of hours of work, for a negative result. But the game is so and you have to accept it… ):
P.S: I live in the province of Vicenza, and I graduated I also in mechanical engineering, in Padua though…17 July 2017 at 14:55 #10070
I mean that, being the back of blank consisting of a series of pits I was a moment difficult to figure out how to best position the “legs” for primary support (I don't know if I explained). As for fusing I intend shortly to take a ride in the Murano glassworks. Even if they treat the glass to make artistic works I think will help me17 July 2017 at 15:08 #10071
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but it is the first time you make a lens of a telescope?17 July 2017 at 15:29 #10072
Ah, Ok, I understood what you meant…
EH, There may be many ways to do this, as you can see in the picture above, the plaster mould has a whole range of straight cavity inside which will form the ribs, that then converge in “nodes”, where are those fine and long cylinders of chalk. In this way I would get a blank with a back like this:
inside those cylindrical holes would then went to graft myself with some kind of PIN coming out primary cell.
Or as I did here:
in which I predicted in the back, a series of perforated discs, in that hole I had glued plastic threaded inserts, on which then I went to anchor with the screws that I predicted the triangles of primary cell
but I assume there are a thousand ways yet, You can really indulge with imagination…17 July 2017 at 15:32 #10073
in well, There is no doubt, to speak with someone who handles and melts glass all day can only help you.
Although I'm not in the industry of astronomical mirrors their experience will definitely be able to provide valuable indications…17 July 2017 at 15:38 #10074
It is the first time
Anyway I was thinking of making hexagonal cavities mirco initially as I have seen in many of the very light glasses. at this point I would say (as advised me tiberini) leaving from the design of the support with Guiplop and try to find a way to bring together the heads of the figures forming the cavity at the points where you have to find the pivot of support.17 July 2017 at 15:50 #10075
Yes, This can be a proper way to do, in fact, both the small cylinders of chalk in the mold, both the discs drilled the second example that I brought, they're all exactly positioned in 18 support points suggested by Gui plop. Then the ribs I drew from these fixed points.
No one forbids you to do differently and use a schema with hexagons, squares, triangles, then you have to figure out where to best place the support points…
In short, the viable ways are many, It's up to you to choose the one that you think is right and also easier to do (that is not something to be underestimated)…18 July 2017 at 12:11 #10121
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You could make the positive with a 3d printer, then do the negative in plaster and then fill it with powdered glass…18 July 2017 at 12:41 #10122
To be honest it was what I wanted to do from the beginning, especially for the creation of “Dome” that would give to the mould and therefore to drive the bend that I needed, but I think I'm quitting because 3D printing only of the dome is expensive.
Anyway I was starting to get the first accounts: It seems fair that a 406mm arrow has to dig about 10 mm f5? because in that case the thickness of the glass without the part with the “cavity” I'd do 15 mm18 July 2017 at 14:10 #10123
No, the arrow is to 5,075 mm…
The formula (approximated) to use is:
r ^ 2/(4*Focal length) or r ^ 2/(2*Radius of curvature)
where the radius of curvature = 2 * focal length
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