Bank Light

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This topic contains 56 replies, has 7 voices, and was last updated by Giulio TiberinI 3 months, 2 weeks needle.

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  • #10046

    marco95
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    Hello everyone ;-)
    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?

    #10052
    Massimo Marconi
    Massimo Marconi
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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.

    #10053

    marco95
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    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 you :good:

    #10061

    Bartolomei Mirco
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    • Messages 217
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    Hi Mark, a welcome from me… :bye:
    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:

    Primary 420 f/4.6 lightweight


    Although I haven't shown everything I've experienced, There's a little something… :good:

    #10067

    marco95
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    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”?

    #10069

    Bartolomei Mirco
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    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… :good: :-)
    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… :-) ):

    View post on imgur.com

    View post on imgur.com

    View post on imgur.com

    View post on imgur.com

    P.S: I live in the province of Vicenza, and I graduated I also in mechanical engineering, in Padua though… :good:

    #10070

    marco95
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    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 me

    #10071
    uraniborg
    uraniborg
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    but it is the first time you make a lens of a telescope?

    #10072

    Bartolomei Mirco
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    • Messages 217
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    Ah, Ok, I understood what you meant… :good:
    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:

    View post on imgur.com


    inside those cylindrical holes would then went to graft myself with some kind of PIN coming out primary cell.

    Or as I did here:

    View post on imgur.com


    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

    View post on imgur.com

    but I assume there are a thousand ways yet, You can really indulge with imagination… :good:

    #10073

    Bartolomei Mirco
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    • Messages 217
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    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… :good:

    #10074

    marco95
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    It is the first time :unsure:
    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.

    #10075

    Bartolomei Mirco
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    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)… :good:

    #10121
    Stefanosky
    Stefanosky
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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… B-)

    #10122

    marco95
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    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 mm

    #10123

    Bartolomei Mirco
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    No, the arrow is to 5,075 mm… :good:
    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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