If you take the weight of an object and gravity into account then apply a force via a small axe, calculating it's momentum, one should be able to predict the effect on the log. So with the very large 40" butt log at 40' in length, it shouldn't move at all, that is just a lot of mass. On the other end of the equation it is the small ones that have a more pronounced effect from the axe's momentum, which can be slowed down by having a nice radius in the blade of the axe, in which the force can be, in scale, gradually placed into the log. In other words keep a nice sharp axe, too. I think I could have added centripetal force in there some where.
I have seen it depicted in books, this method of leaving the butt attached, it may be stretching things a bit. I wouldn't completely rule it out, I guess it may have a bit to do with the species and the timber one is wanting from the tree. The depictions I have seen were for cedar railroad ties. Leaving the top on would produce a wobble in the log I would not want to deal with. An other point with small stock or ties, how accurate did these pieces need to be? Did they spend any amount of time snapping lines and keeping them plumb, and everything else we do to them, could they have just winged it by "crack of eye"?
Tim
