3. By keeping a centre distance of 91.5mm and a transmission ratio of 2 with a deviation of +- %10, for the same rating

[answerhappygod]

3. By keeping a centre distance of 91.5mm and a transmission
ratio of 2 with a deviation of +- %10, for the same rating inputs
(including service life of 20,000 h), size a spur gear set with a
contact ratio of 2 and the minimum weight possible. Required
contact (flank) and root safety factors (for ISO/DIN calculations)
≥1. (Hint: set minimum and maximum teeth range from 9 4 to
90, facewidth/normal module range from 6 to 20, and use minimum
weight for rough sizing. You might also need to re-set the
facewidth for fine sizing)). Critically compare the theoretical
contact stiffness for this geometry and the non-optimized one,
analysing the reasons for the differences in the results, based on
your knowledge of gear design.