Shy,
In your engine all the forces can be held in balance by the fact that opposite to the piston force is a force acting on the cylinder head. By the way, why do you need any form of balancing if a rotating mass can't create lateral force at any particular instant in time?
Oh dear - I think you would benefit from some engine theory, unless of course this is a very thinly diguised attempt to "wind me up"
.
On a plain crankshaft the mass of the pistons and con-rods would cause severe out of balance rotational forces / vibration. The crankshaft is therefore shaped/forged with balance weights to counterbalance their mass - if this wasn't done the engine would shake itself to bits.
Unfortunately, the crankshaft balance weights also go through the lateral "fore and aft" positions during their 360 degree rotation and in those positions they themselves are not opposed by the up/down movement of the pistons and con-rods. This results in fore and aft vibration. For this reason, engine designers traditionally never fully balanced a crankshaft; they "left off" some balance mass as a compromise between allowing vertical and longitudinal vibrations.
This was very obvious on single cylinder or twin cylinder motorcycles up until the 1970s, where the engine was often bolted rigidly in the frame and the rider felt those out of balance forces through his most sensitive regions.
The BSA Goldstar (500 single) was a "classic" example. At idle, the bike can be seen to rock fore and aft on it's wheels as the crankshaft mass balance goes through the fore and aft positions.
These days engines are much more sophisticated and multi cylinders prevail but as far as I am aware, the basic rules of physics have never changed.
In modern engines, a balance shaft is sometimes fitted to oppose some of the lateral vibrational forces. My Honda four cylinder motorcycle has one, unless their designers and salesman have been conning me
