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rloginunix
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Polish This  
« on: Nov 15th, 2016, 8:18am »
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Polish This
 
 
Somewhere deep in the bowls of the former Soviet technical inventions patenting system there, presumably, lies (dormant) a patent that is the answer to this puzzle and that was implemented and used in practice some time prior to 1979.
 
Puzzle:
 
- polishing large (meters in diameter) lenses/mirrors (just "lenses" onward) was done with a solid brick of an abrasive which, while removing the layers/molecules of a lens, produced friction, which in turn generated heat. The temperature differential could cause lens's surface warping (or even cracking in extreme cases) rendering it optically useless
 
- cold liquid (water) was poured on an abrasive which solved the problem but poorly - the water could not get through the solid brick rendering this type of cooling not optimal
 
- holes were drilled in the abrasive brick and cold water delivered through them - the cooling was now effective but polishing - not since the magnitude of the square area of the abrasive material in contact with the lens was much reduced (it is difficult to polish with nothing)
 
 
Solution:
 
was eventually found, patented, implemented and used in real life. To find it there is no need to know how to solve differential equations, no need to know the formula of the lens - none of that.
 
The solution is childishly simple and it has to do solely with the abrasive, which has to possess two seemingly mutually exclusive properties: grit/emptiness. I would wager that most of us saw the solution when we were kids (me - definitely).
 
See if you can take a crack at it.
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dudiobugtron
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Re: Polish This  
« Reply #1 on: Nov 15th, 2016, 10:10am »
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Is it also the same thing you use to scour dishes?
 
Another option might be sandpaper; although I don't know how well that performs when wet.
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rloginunix
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Re: Polish This  
« Reply #2 on: Nov 15th, 2016, 1:18pm »
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If by scour dishes you mean bristles of a brush(?) then - no, the brush does possess the two above properties but not enough grit.
 
Sandpaper is also negative - too thin and not tough enough to withstand the wear and tear.
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rloginunix
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Re: Polish This  
« Reply #3 on: Nov 16th, 2016, 7:57am »
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I was a bit in a hurry yesterday, so if it is not clear from the outset, I would like to make the following explicit:
 
the solution involves only those objects and substances that are mentioned in the problem statement.
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Grimbal
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Re: Polish This  
« Reply #4 on: Nov 21st, 2016, 3:43am »
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Instead of cold water, use boiling water.  The lens will expand uniformly.  Any excess heat will be consumed in the phase transition to vapour, which in turn is evacuated through the porous brick.  So the temperature remains stable.
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rloginunix
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Re: Polish This  
« Reply #5 on: Nov 21st, 2016, 1:18pm »
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Grimbal is on the right track, in more than one way.
 
He correctly identified the solution's both key components (water/abrasive) and a type of an operation applied to these components. What remains to figure out is what type of operation goes with which component.
 
Don't forget the childish hint. Assuming that Grimbal grew up where I am assuming he did, and recalling my recent flight directly above the peaks of Swiss Alps, the latter looked quite ... to me.
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Grimbal
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Re: Polish This  
« Reply #6 on: Nov 21st, 2016, 1:46pm »
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You are hinting at ice .
I have trouble imagining that an abrasive made of that will keep in shape and that it will not cause warp in the lens due to temperature differences.
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rloginunix
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Re: Polish This  
« Reply #7 on: Nov 22nd, 2016, 5:14pm »
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on Nov 21st, 2016, 1:46pm, Grimbal wrote:
You are hinting at ice .

Yes, you got it.
 
How they managed to evenly distribute the abrasive particles within the brick of ice the text does not say (that's a different puzzle perhaps) but apparently that was the solution - I would think that there is no need for it to keep its shape - it is supposed to melt away in the process thus providing the required cooling.
 
The way I understood the problem is that with the brute force approach the efficiency of cooling times the efficiency of polishing is a const - a gain in one means a loss in another. The above solution seems to provide a reasonable balance, no?
 
Also, granted - the scenario is taken completely out of the bigger manufacturing process context. But I have shared with you, guys, everything there was to share - pretty much verbatim (subject to translation into English).
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