Bulldozer

[|Bulldozer] - a crawler (continuous tracked tractor) equipped with a substantial metal plate (known as a blade) used to push large quantities of soil, sand, rubble, or other such material during construction or conversion work. The tracks give them excellent ground holding capability and mobility through very rough terrain. Wide tracks help distribute the bulldozer's weight over a large area (decreasing ground pressure), preventing it from sinking in sandy or muddy ground.

Bulldozers have transmission systems designed to take advantage of the track system and provide excellent tractive force.

There are lots of construction projects that start with moving dirt and rocks. In the past, men with shovels did this work. Bulldozers are designed for this work.
 * What's the problem?**
 * **Ask** - Making a machine that can move tons of dirt and rocks starts with a vehicle that can travel over uneven ground and move material by using its engine's power to push the material. How can the engine power be used for pushing? How can the bulldozer move easily to maneuver and still push against heavy loads?
 * **Imagine** - Keeping the bulldozer pushing forward against tons of dirt is a difficult job. How can the bulldozer be designed so it won't move backwards as it pushes against a heavy load?
 * **Plan, Create** - Using tracks is a good solution to the mobility problem. Tracks can carry heavy loads, and distribute the weight of the bulldozer over a large area. How does the track prevent the bulldozer from being pushed backwards?
 * **Improve** - Over time, track designs have been improved for better traction. How was this accomplished?


 * That's engineering**
 * [|Hydraulic press] - moving the weight of the blade and the material being moved. The addition of power down-force provided by hydraulic cylinders instead of just the weight of the blade made them the preferred excavation machine.

> traction, ground holding, mobility, power, horsepower, torque, force, transmission
 * Engineering ideas**

Challenges for you to work on...
 * Do It**
 * design a series of blades to move material and run tests to compare the designs. Use LEGOs to build the mover and blades. Material can be dirty, sand, beans, as appropriate,


 * News, updates**


 * Learn more...**
 * [|Truck Video for Kids - Bulldozer] - video, song and narration

..1e