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Re: [ATM] Pictures
Anthony,
You have my respect for your efforts, but it seems to
me that on Speculum versus Aluminized glass, there is
really no need to re-invent the wheel or to try the
experiments again - that was all settled over 150
years ago!
Guy
--- Anthony Stillman <atmer@flash.net> wrote:
> Speculum Metal Mirrors
>
> advantages
> -no need to aluminize
> -can test with a faint light sources
> -the tube balances close to the mirror
> -faster than glass thermal equilibration
> -something different (bragging rights)
>
> the down side
> -low reflectivity ~60 percent
> -temporarily blindness when testing with a bright
> light source
> -the mirror is really heavy
> -huge thermal expansion ratio
> -hard to obtain a decent polish
>
>
> I alloyed the metal, 110 grams at a time, from tin
> (most given to me by
> Richard Schwartz) and scrap copper, using an
> oxy-acetylene torch.
>
> Annealing. The 62mm mirror (sixth casting) was not
> annealed. The second
> 90mm blank, the one that broke while roughing out
> the curve, was. The
> metal is very brittle and somewhat weak.
>
> I haven't done enough experimentation with rapid
> solidification to effect
> grain size. The last three blanks were frozen
> slowly while the torch was
> played over their faces. In comparison to my early
> efforts these blanks
> are practically free of porosity. I think this is a
> far more significant
> issue than grain size in obtaining a good figure.
>
> Why bother? I like to try different things and,
> reviving obsolete
> technology using modern techniques appeals to my
> idiosyncratic iconoclasm.
>
> Next post I'll report my successes.
>
>
> Anthony
>
>
> cives censent, servi non facent
> Citizens vote, slaves don't.
>
> The Latin "v" is pronounced as an English "w." The
> "i" sounds like a long
> "e." The "c" is always hard. And yes, I think
> ATM's are far more likely
> to vote than not. Saddly, not everyone is an ATM.
>
>
>
>
>
>
> >At the attached addresses are images of my most
> recent speculum metal
> >mirror failures.
> >
> >First 90 mm casting. The casting investment
> vented steam through the
> >liquid metal. Like visiting "Yellow Stone", on Io.
> One of these vents,
> >split in two, is visible on the right two pieces.
>
><http://www.atmlist.net/contrib/atmer-at-flash-dot-net/Vented.jpg>
> >
> >Second 90mm blank. Broken while using an every so
> slightly unbalanced 220
> >grit grinding wheel to smooth the curve roughed in
> by a balanced 100 grit
> >grinding wheel.
>
><http://www.atmlist.net/contrib/atmer-at-flash-dot-net/Broken.jpg>
> >
> >Close up of the second blank's broken face.
>
><http://www.atmlist.net/contrib/atmer-at-flash-dot-net/CloseUp.jpg>
> >
> >
> >
> >Anthony
> >
> >
> >cives censent, servi non facent
> >
> >
> >_______________________________________________
> >ATM mailing list http://www.atmlist.net/
>
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>
=====
Guy Brandenburg
Washington, DC
My home page:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
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