Re: Re[4]: [ATM] Glueing plate glass

[Ken Lowther <hermit@outofoptions.org>]

Yes, and if I drink 500 gallons of water all at once, it will kill me.  
But NONE will kill me too!  Ken

Quoting Richard <cnc@cncservo.co.uk>:

> Hi Ken,
>
> Wednesday, February 23, 2005, 5:45:06 PM, you wrote:
>
>
> KL> My question for some time has been:
>
> KL> If you grind the two pieces against each other for good contact, do you
> KL> really need to glue them?  Just edge supports to keep them from
> KL> slipping...
>
> Yes.
>
> Imagine a stack of two or more thin pieces, and imagine a force
> applied so that they visibly bend. What do you see at the edge?
> The answer is a staircase - slipping of one layer over another.
> The reason is that for each piece, the top surface is in
> compression and has decreased in length, the lower surface is in
> tension and has increased in length. Your stack therefore tries,
> at each bond, to stop one surface from compressing and the other
> layer from tensing.
>
> Unless you can bond the layers with very strong resistance to
> shear then you will have a weak mirror. The strength of a single
> layer mirror will go with the cube of its thickness. Unless you
> resist shear the individual layers will each have a strength
> proportional to the cube of their individual thickness. Without
> that bond, a mirror of given thickness has relative strength
> proportional to 1/N^2 where N is the number of layers it is
> laminated from. (N layers each contributing 1/N^3 to the bending
> strength).
>
> Fuse it or forget it!. Better still, if you have the furnace to
> fuse it then you may as well start with cheap broken glass and cast
> it.
>
> --
> Best regards,
> Richard                            mailto:cnc@cncservo.co.uk
>
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>

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