Definitions : Actually 'Butting' * is the thickening, the side effect is it allows thinning of the center,

or top in the case of seat tubes the upper portion..



the thinner center of the spoke reduces, the tensile strength,

but in weakening it, allows additional elasticity to be transferring stresses to the middle, relieving some from the ends..

but you can make up your own definitions.. they may be inaccurate, but you can use them ..

* Think of the 'flying buttresses' in the great cathedrals .. like Cologne..






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