Page "Bulldozer" Paragraph 34

By the 1920s, tracked vehicles became common, particularly the Caterpillar 60.

Rubber tired vehicles came into use in the 1940s.

To dig canals, raise earth dams, and do other earth moving jobs, these tractors were equipped with a large thick metal plate in front.

( The blade got its curved shape later ).

In some early models the driver sat on top in the open without a cabin.

There are three main types of bulldozer blades: a U-blade for pushing and carrying dirt relatively long distances, a straight blade for " knocking down " and spreading piles of dirt, and a brush rake for removing brush and roots.

These attachments ( home-built or built by small equipment manufacturers of attachments for wheeled and crawler tractors and trucks ) appeared by 1929.