What is a tachometer and how it works?

A tachometer is a sensor device in a car used for measuring the speed of an object. Predominantly, they are used for measuring the rotational speed of a mechanism which is mainly the engine shaft in a car.  To help out readers understand tachometers better, Jsk Automotive has put together a blog explaining everything there is to know about a tachometer. 

Source: https://goo.gl/qiDqa1

 

Crankshaft harmonic balancer reduces engine vibrations

A crankshaft harmonic balancer is an important engine component that is attached to the front of an engine’s crankshaft, which is generally built into the crankshaft pulley. The primary function of a crankshaft harmonic balancer is to alleviate and absorb the vibrations caused due to the rotation of the crankshaft.

Source: http://www.jskautomotive.co.uk/blog/symptoms-bad-crankshaft-harmonic-balancer/