Friction Weight=(D-U)/2

[Robert Scott]

I also take issue with Mr. Stern's article.

Mr. Stern states that if an applied force is not aligned in the direction 
of travel, then  there are energy losses.  He also claims that these energy
losses are due solely to the "vector" effect and are separate from losses 
due to friction. The fact is there are no inherent energy losses when a 
force is applied off-axis.  And unless there is friction involved, the force
will be the same for both directions of travel.  In the particular example 
of the capstan-heel cushion interface cited by Mr. Stern, there may indeed be
energy losses.  But these losses are due to the friction as the capstan 
slides slightly on the heel cushion.  This observation should in no way
detract from the practical value of Mr. Stern’s article, which is that 
the geometry of the capstan-wippen interface can affect touchweight.

-Robert Scott
 Detroit-Windsor Chapter, PTG