Can you solve these physics riddles? ft Simone Giertz - Part 1/3

Hi Diana,
I never know which way via lefty loosey righty tighty as i could neve determine the reference start point for rotation, instead i just use the RH curl rule for a RH thread.  LH threads are also used on combustible has bottles like acetylene, propane, mapp gas etc.

I'm an electrical engineer and diy'er do I'll use terms sometimes found in field theory to reference the face planes and join RH curl rule to RH threads; ie a rh thread obeys the rh curl rule and similarly a lh thread obeys the lh curl rule.

The way i think about pedal rotation is to put yourself in the reference frame of the crank as viewed in both cases with the bike frame behind the crank. such that both viewing planes point away from each other.  Then transpose the pedal rotation into that reference frame.  The slight difference in diametre of the pedal and crank threads along with the radially rotating force due to the push on the pedal will cause a precession so that the spindle will try to rotate opposite to the pedal rotation.  Hence the spindle threads are cut to tighten the spindle into the crank in the opposite rotation as the pedal.

Let us consider the rh pedal in the crank reference frame as viewed from the plane that points away from the bike.  The pedal is rotating counter clock wise.  Hence the precession will cause a cw rotation of the spindle.  This cw rotation must be into the crank so as not to loosen the pedal.  CW in is RH thread via RH rule.

LH pedal as viewed from the lh crank reference frame rotates ccw.  Therefore precession will cause the spindle to rotate cw.  this cw rotation must be into the crank to tighten which is lh thread as given by lh rule.

I appreciate this is a very physicsy/engineering answer and not all will follow.