gewichtweenie wrote:But bikes aren't made from single ply (=sheet) of carbon and the forces aren't aligned to the principle axes , meaning the anisotropy isn't fully exploited. The primary control in characteristic still being general tubing dimension and shape.
The real point being that unless a manufacturer truly and fully gimps 1 variant of their bike from the same mould (like, say, putting jello suspension, 14" tires, and 150hp motor on a porsche,), there is way more marketing value in saying "we used the best carbon in the best orientation in the best places" than there is in real appreciable differences.
did you watch the video i posted?
for fork as an example, if i use purely 45 degree carbon sheet in the video it would be very tortional stiff (won't rotate) but can flex forward and backward quite a lot.
In another extreme, if i use purely straight 90 degree going down carbon. it will not flex forward and backward but it can twist which is obviously bad.
Real fork will not make from single type of sheet of carbon, but how much of each type and where would it place will dictate how it perform even if it has the same shape.
Then stem is another very good example in other way.
Stem require stiffness in all direction so making a carbon stem will require quite a lot of carbon sheets in different directions that it will not be any lighter than aluminium stem. Unlike other place of the bike where designer can tune stiffness in only some way and leave it to flex in other and also save weight by doing so, Carbon stem only improve aesthetic as it can be made to look real cool easier.