what do the counterweights balance?

It has been said that the front one counter weights the eccentrics, while the rear helps balance the flywheel and anything else. Is this true?

Also if the eccentrics are 180 degrees offset then shouldnt they balance themselves out?

Can someone help explain this to me?

thanks
Rip

 

howstuffworks.com

and search PLEASE! Google anyone ?

 

The reason why I was asking here is because the questions I have are not explained in detail. I wanted to know if during the design of the counterweights what were they specifically trying to balance out. In cranks (different from eccentric shafts) I understand the need, but because of my inexperience with the rotary, and not seeing eccentric shafts been mentioned too often in articles. I wanted to ask. I've never seen a counterweight placed outside the engine (except old short blocks), rather harmonic dampeners. But a harmonic dampener is not a counterweight.

And searching this forum for "counter weight" seems to result in DIYs, and "which one to buy" questions. I did find one person said what I wrote in the post. I wanted to make sure this was correct. A little verification.

Rip