Check out this Popular Mechanics article
http://www.popularmechanics.com/home_journal/workshop/4217639.html?page=2
If you want more info see the thread below
https://www.hearth.com/econtent/index.php/forums/viewthread/9579/
http://www.popularmechanics.com/home_journal/workshop/4217639.html?page=2
If you want more info see the thread below
https://www.hearth.com/econtent/index.php/forums/viewthread/9579/