Was just thinking...... how do you balance an engine that has a counter balance shaft ???????
Its a matter of counteracting Physics. Engineers have been trying to change the constants in Physics for 100's of years..lol
I assume you understand the basics/purpose of balancing of the reciprocating parts of an Internal Combustion Engine(I-C-E), keeping each independent assembly equal in weight as possible.
Its more complicated but I'll try and provide a Cliff Notes version of the purpose of a Counter Balance Shaft.
In certain engine designs, (especially In-Line designs) these engines produce a vibration caused from the motion of connecting rod assembles, (because all the piston/Rod Assemblies are not always symmetrical during crankshaft rotation), which causing a secondary vibration, (sometimes referred to as Second-Order Rolling Couple).
But you cannot change Physics. This is also why most V-8 engine designs have a "Harmonic" Balancer on the front of their Crankshaft.
Bottom Line; Vibration = Loss of Performance/Efficiency in an I-C-E
The Counter Balance Shaft design dates back to the 1900's.
Btw, this was one of the reasons that Mazda focused on developing their Rotary I-C-E instead of their In-Line 4 cylinder Automotive Engines.
The only engine design that defeats this secondary vibration issues are the Flat Four and Flat Six designs, (Porsche/VW and Continental General Aviation Engines etc).
Why no Secondary Vibrations in the Flat 4/6 Design? Because when one Cylinder is at Top-Dead-Center the other balances it out at being at Bottom-Dead-Center.
I hope this helps.
DR