Eamon Burke
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[video=youtube;hSxk9fa92l0]http://www.youtube.com/watch?feature=endscreen&NR=1&v=hSxk9fa92l0[/video]
What gives?
What gives?
It's a pretty darn good way of finding defects.
Back in the dark ages when I worked on the Atlas Centaur rocket program, the rocket had a nose cone (fairing) made out of fiberglass honeycomb sandwiched between solid sheets of fiberglass. The air in the honeycomb is at sea level/atmospheric pressure, and when the vehicle was launched, as it moved into space and external pressure approached a vacuum, the air in the honeycomb would push outward against the fiberglass skin. If there were large enough areas where the skin wasn't attached well to the honeycomb, the fairing would tear itself apart.
There was a lady with a well-trained ear that they used to fly from Houston to Cape Canaveral to do a "coin-tap" test--basically rap the entire fairing with a hammer and listen for voids where the skin wasn't attached to the core. Not high tech, but effective.
It's a pretty darn good way of finding defects.
Back in the dark ages when I worked on the Atlas Centaur rocket program, the rocket had a nose cone (fairing) made out of fiberglass honeycomb sandwiched between solid sheets of fiberglass. The air in the honeycomb is at sea level/atmospheric pressure, and when the vehicle was launched, as it moved into space and external pressure approached a vacuum, the air in the honeycomb would push outward against the fiberglass skin. If there were large enough areas where the skin wasn't attached well to the honeycomb, the fairing would tear itself apart.
There was a lady with a well-trained ear that they used to fly from Houston to Cape Canaveral to do a "coin-tap" test--basically rap the entire fairing with a hammer and listen for voids where the skin wasn't attached to the core. Not high tech, but effective.
I've no idea how long natural stones may take to wear down through sharpening use - if ever - but maybe someone experienced with this can get a feel for if there any inconsistencies within a stone, and thus judge quality based on how a stone wears? Certain stones might also have hidden cracks/lines inside and not seen on sides, and even be more liable to crack over time through use when given pressure or not supported well when sharpening?
.. I'm just speculating, but interesting to think about. I've just got one nat stone and am wondering what to expect from it over time.
I believe the stones are tested for cracks when they are still slabs before cutting, the sound when tapping can give some idea of hardness.sorry,my bad. when we work with stone, we always check for the soundness of the stone by tapping it with a hammer. just assumed he was doing the same thing . sorry for my misinformation.
Yes, that is the question that is in my mind. When you use a stone over the years, will the figure change significantly? Does Renge or karasu figure change as you go a few mm deeper? And will this change the way a stone works?
How about non toxic surface lines, will they become more 'toxic' past the surface if their mineral composition changes?
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