Engineering Vehicles

Mechanical engineers use scientific knowledge about forces, motion, and energy to design machines that use kinetic energy to do work. Hovercrafts are vehicles that solve the problem of friction by traveling over land and water on a cushion of air.

• Mechanical engineers apply the concepts of forces, energy transfer, and motion to design machines that use kinetic energy to do work..
• Vehicles are machines that move passengers or goods from one place to another.
• .Hovercraft are vehicles that travel over land and water on a cushion of air.

• What causes a hovercraft to hover above the ground?
• How does the structural system of the hovercraft support the craft as it lifts off the ground?
• What causes a hovercraft to move forward?
• What kinds of questions do engineers who want to design a hovercraft-like vehicle need to ask?

Misconception: Sustaining motion requires a continued force.

Fact: An object in motion will remain in motion unless acted on by an outside force. 

Hovercraft: a vehicle that creates a cushion of air to travel over land and water

Machine: a technology that uses kinetic energy to do work

Mechanical engineering: the field of engineering concerned with applying forces and energy transfer to design and build machines

Vehicle: a machine that moves passengers or goods from one place to another

Delivering Mail in Alaska

In southwestern Alaska, transportation is difficult. There aren’t many roads connecting the small towns and villages to one another. This makes mail delivery challenging, especially in the winter, when it is too dangerous to fly planes.

In response, the U.S. Postal Service began using a hovercraft to deliver mail in the late 1990s. A hovercraft is a vehicle that travels over land and water on a cushion of air. A vehicle is a machine that moves passengers or goods from one place to another. Bobsleds and race cars are also kinds of vehicles.

The hovercraft in Alaska carries mail year-round, except for six weeks when the water is just beginning to freeze and one week when the ice begins to melt in the spring. This is because the hovercraft needs a relatively flat surface to hover above.

Engineering a Hovercraft

A mechanical engineer named Christopher Cockerell was the first person to create a hovercraft. He used cat food cans and an air blower. He continued to test and revise his idea, crafting miniature hovercrafts out of balsa wood and fans. Mechanical engineering is the field of engineering concerned with applying forces and energy transfer to design and build machines. Mechanical engineers focus on using machines to solve problems. A machine is a technology that uses kinetic energy to do work.

Transportation Subsystems

Every vehicle is a system because it is made up of connected, interacting parts. Each vehicle is also made up of smaller subsystems that allow them to function properly. The key subsystems are a propulsion system, a suspension system, a control system, a guidance system, a structural system, and a support system.

Take a hovercraft. A mechanical engineer has to balance four forces to achieve movement. Thrust is what makes the hovercraft move forward. Thrust is generated by the propulsion system, which provides the force that moves a vehicle toward its destination. Thrust must equal or exceed drag caused by air resistance between air molecules and the hovercraft for the vehicle to hover.

While all vehicles are made up of the six subsystems, they are designed differently depending on whether they are intended for land, water, or air. For example, vehicles intended for land include cars, trucks, buses, and trains. They are propelled forward by engines supported by fossil fuels or electrical stations. Tires and shocks support the weight of the vehicle as they move across roads. Road vehicles are typically controlled by steering wheels.

Vehicles intended for the water include boats, canoes, and warships. They can be propelled by human power, such as oars, wind power with sails, or mechanical power with engines. The weight of a boat is suspended by buoyancy. Ships today use advanced navigation equipment that can determine the ship’s location, how close it is to land, how fast it is going, and possible underwater hazards.

Vehicles intended for the air include planes, helicopters, and jets. They are propelled forward by the action-reaction forces of turbines or the spin of propellers. The weight of an airplane is supported by the wings, which are kept airborne by lift. Airplanes also have advanced navigation equipment that help pilots determine their location, height, and speed. Air traffic controllers act as an additional airport guidance system.

For the hands-on activity, students engineer a prototype rescue vehicle that moves over land on a cushion of air to reduce friction between the craft and the ground. As part of this process, students first define the problem before they design a possible solution to the problem, given the available materials. Students test their prototype solution to see how well it solves the problem, and decide if they would refine or replicate any of their designs based on the data.