kaesees wrote:
If the nominal circumference is 4.625 inches (average of 4.5 and 4.75), that gives a nominal diameter of 37.4mm =~ 1.48". I'm guessing they decided on a 1.5" diameter then made up the circumference tolerance to put that roughly in the middle of the allowable band.
Interesting to see metric measurements were included about a decade later and became the primary measurements about two decades later.
Interesting to see metric measurements were included about a decade later and became the primary measurements about two decades later.
On that web page they don't go into details about what the actual metric equivalents were in the rules. It would be useful to actually have the full rules for each year.
Yeah, if an inch is 25.4mm, then 1.5 inches is 38.1mm, makes sense they had 1.5 inch diameter balls in mind. When they specified the tolerances in mm they probably used the same tolerances they had for the 40mm ball (i.e. +/- 0.5mm). 40mm balls were all just a hair above 39.5mm (manufacturing tolerances being far tighter than rules tolerances, so the manufacturers made them as small as possible, most likely because people preferred smaller balls because the "play better")... this is what led to the "ball size increase". I wonder if most 38mm balls weren't really just over 37.5mm..
Iskandar