Originally Posted by
Schwinnsta
It is doubtful that it puts the seatpost in tension. The tensile forces caused by bending do not get large enough to cause the tube to go into tension. You still get changes in loading so you still get fatigue. You are also adding to the stresses by the clamping forces.
as the seatpost is on a ~73deg angle, it is load towards the back consequently, the load distribution of the tube will be compressive on the back and tensile on the front. The oval hole believe as a stress raiser.
if you cut a small notch on a piece of branch perpendicularly the branch axis, if you apply a bending load setting the notch side in tension, it will eventually break.
do the same but putting the notch side in compression, it may break but if/when it does, it will be later