Worm gear and worm drive: it can realize large speed ratio, self-locking, large friction coefficient and low transmission efficiency.

Suitable for occasions with large speed ratio and need self-locking.

Bevel gear: low friction coefficient, high transmission efficiency, adjustable transmission angle and no self-locking.

Suitable for places where the transmission angle needs to be changed.

This paper discusses the balance problem of mechanical system composed of crankshaft, connecting rod and piston. What kind of balance does it belong to? How to balance?

I think it belongs to dynamic parallelism.

How to balance?

Single cylinder: Parallel axis can be used for parallelism.

Multi-cylinder: reasonably distribute the combustion time of each cylinder.