I think this is a "glass half empty"/"glass half full" argument...
One of you is saying that a butted tube is a thick-walled tube that has been thinned in the middle.
The other says that a butted tube is a thin-walled tube that has been thickened at the ends.
Unless you're in the tubing business, who cares which it is
? The point is that a well-designed butted tube can achieve a desired strength with less weight than an unbutted tube (of the same length and diameter).
PS- The way a butted tube is made isn't by actually adding or removing material from a unbutted tube. I believe the way they do it is by putting a mandrel with slightly tapered ends inside an unbutted tube. Then it's drawn through a die to squish down the ends against the mandrel. See this thread:
http://groups-beta.google.com/group/...ec5ff948d5f3ec
Originally Posted by Don Cook
The flutes act in the same principle as the corrugation of cardboard in a cardboard box. The flutes add strength. One other point is that if the seat tube wall thickness is uniform throughout it's circumference, the flutes also add weight. Why? Because the total linear measurement of the tube circumference is greater when it's fluted. It could also be that the seat tube maker was using a "thinner" than usual alloy and employed the flutes for strength. In this case many would say that the flutes reduced weight. Not true though, it is the thinner alloy that reduced some weight, but the flutes cancel some of that weight savings. This is similar to tubes that are butted. A tube maker uses a thinner tubeset. That reduces weight. But to add strength to the thinner material they butt the ends. This increases the tube thickness, adding weight. But, many would say that butting reduces weight. Not so. The thinner tubes provided a weight reduction, and some of that weight savings is cancelled by the neccassary butting.
Originally Posted by Dirtdrop
Removing material reduces weight. The wall thickness of a fluted seatpost is not uniform throughout its circumference it's a tube with grooves machined out of it.
Butted tubes are not thickened at the ends, they're thinned at the center.