While thousands, perhaps millions, of spindle whorls are found in 
archaeology digs, the modern spinster seldom experiences the Technology 
of the Removable whorl.  
REMOVABLE WHORLS -WHY??????
Modern
 spindle sticks have glued-on whorls.  They are NOT removable, like 
those found in ancient times.  The modern spindle is very balanced when 
well turned on a wood lathe as a single, integral object.  Perfect 
balance and long spin is the Modern Holy Grail.  
But, 
what if you could change the whorls on the spindle sticks?  The spindle spinning experience when making 'singles' yarn 
changes significantly with the constantly changing build up of stored yarn on the spindle. The spindle becomes much heavier; spin time slows down. 
 With a glued-on whorl, the dynamics of weight and spin time cannot be 
altered.
- CHANGE OF WEIGHT as spinning progresses 
Swopping out a removable whorl for one of different weight 
(lighter and lighter as the yarn stored increases from nothing to 1-3 
ounces (28 grams - 84 grams or so), ending up at the higher weight with 
NO whorl in use at all, as the yarn cop itself functions as the whorl.
- BOTTOM WHORL WEIGHTS VS TOP WHORL WEIGHTS
Top whorl weights generally need more weight for comparable 
revolutions compared to bottom whorl weights. One spindle shaft can 
sometimes be used in both configurations, but the whorls need to be 
different.
- DIFFERENT SHAPES for DIFFERENT YARNS
What if you  could change the shape of the whorl?  A spherical 
whorl riding close to the spindle shaft spins fast with a lot of quick 
twist delivery: Great for skinny yarns with high-twist needs.  A wide 
disc-shaped whorl twists more slowly, but for a longer time.  Better for
 heavier yarns or fiber preps that require more manipulation at the 
transition point from fiber to yarn.
Throughout history, various 
locations show preferences for different shapes of whorls.  The Curious 
Spinster wonders Why Why Why.