Compound Machine:       Two or more simple machines working together to make work easier. Examples: Wheelbarrow, Can Opener, Bicycle

Gears:        Two toothed wheels fit together either directly or through a chain or belt so one wheel will turn the other. Some gears may have a screw or a toothed shaft in place of one of the wheels. A gear may also be a combination of toothed wheels that produces a certain speed (such as a bicycle's top gear which makes the bike go fast, and the low gear for slow speed.)Examples: Clock, Automobile, Drill

Inclined plane:      A sloping surface, such as a ramp. An inclined plane can be used to alter the effort and distance involved in doing work, such as lifting loads. The trade-off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed.Examples: Staircase, Ramp, Bottom of a Bath Tub

Lever:      A straight rod or board that pivots on a point known as a fulcrum. The fulcrum can be moved depending on the weight of the object to be lifted or the force you wish to exert. Pushing down on one end of a lever results in the upward motion of the opposite end of the fulcrum.Examples: Door on Hinges, Seesaw, Hammer, Bottle Opener

Pulley:      A wheel that usually has a groove around the outside edge. This groove is for a rope or

belt to move around the pulley. Pulling down on the rope can lift an object attached to the rope. Work is made easier because pulling down on the rope is made easier due to gravity. Examples: Flag Pole, Crane, Mini-Blinds

Screw:      An inclined plane wrapped around a shaft or cylinder. This inclined plane allows the screw to move itself or to move an object or material surrounding it when rotated.

Examples: Bolt, Spiral Staircase   Simple Machine:      A machine with few or no moving parts. Simple machines make work easier.Examples: Screw, Wheel and Axle, Wedge, Pulley, Inclined Plane, Lever

Wedge:       Two inclined planes joined back to back. Wedges are used to split things.Examples: Axe, Zipper, Knife

Wheel and Axle:      A wheel and axle has a larger wheel (or wheels) connected by a smaller cylinder (axle) and is fastened to the wheel so that they turn together. When the axle is turned, the wheel moves a greater distance than the axle, but less force is needed to move it. The axle moves a shorter distance, but it takes greater force to move it.Examples: Door Knob, Wagon, Toy Car

Other Elements of Machines:Though these devices were also used in machines in Leonardo's time, he experimented with them and made changes to improve how they worked. He also combined them in many exciting new ways to create machines and inventions that had never been seen before.

GearsGears are toothed or pegged wheels meshed together to transmit motion and

force. In any pair of gears the larger one will rotate more slowly than the smaller one, but will rotate with greater force. Each gear in a series reverses the direction of rotation of the previous gear.

Bevel GearsGears that mesh at an angle change the direction of rotation.

Worm GearA worm gear is a combination of a gear meshed with the threads of a screw. This combination changes the direction of turning motion by ninety degrees. Worm gears also decrease the speed of turning from screw to gear and increase its force.

Rack and PinionA single gear, the pinion, meshes with a sliding toothed rack. This combination converts rotary motion to back and forth motion. Windshield wipers in cars are powered by a rack and pinion mechanism. A small pinion at the base of the wiper meshes with a sliding rack below.

CamA cam is a wheel with shaped bumps on it. Cams are often connected to rods, levers, or springs. In the gravity trip hammer shown here, the bumps on the turning cam push down on the end of the lever making it raise the hammer again and again.

Crank and RodThe crank is a wheel with a pivoting arm attached near its edge. The arm is attached by a hinge to a rod. When the crank turns, the rod is pushed back and forth. Alternatively, if the rod is pushed back and forth at the right speed, the crank will turn. The crank and rod shown here are part of giant steam engine.

Chains and BeltsA chain or belt connects two separated wheels so that one turns, the other will turn in the same direction.

RatchetA ratchet is a device that allows a wheel to turn in only one direction. The ratchet wheel has specially shaped teeth. A bar on a pivot called the "pawl" is fixed above the ratchet wheel. The pawl slides over the teeth of the ratchet in one direction, but blocks the motion of the teeth if the wheel turns in the other direction.

Classroom Activity: Sketching Gadget Anatomy

Main Idea: Close observation and sketching lead to a better understanding of how machines work.

Learning Objectives: Observe a machine closely from several angles while it operates. Identify the elements of machines combined in different gadgets. Show how the moving parts in machines relate to and affect each other. Create a clear diagram of how a machine works.

Time: about 30 minutes with one machine per group

Materials: paper pencils with erasers printed copies of the Inventor's Toolbox pages for reference. a selection of small machines with visible working parts (the more you have, the

better): egg beater, cork screw, car jack, can opener, garlic press, tongs, monkey wrench, hand drill, Vise-Grips, the mechanism from a music box, wind up toy, pencil sharpener, stapler.

Procedure: 1. Have students prepare to work in small groups (2-5). 2. Provide each group with one machine to examine in detail. Suggest that students

take turns operating the machine while the others watch to see how each part moves.

3. Challenge each group with the following questions to encourage thought and discussion. Invite them to investigate their own questions as well.

o What is the function of this machine? o How many moving parts does it have? o How are the moving parts connected to each other? o What does each moving part do in the machine? o Which parts are elements of machines?

4. Place the machine at rest so that everyone in the group can see it and distribute paper, pencils and erasers.

5. Students should begin sketching diagrams of their machines. They should draw the machine from their own point of view first. Later they can trade places and draw it from different points of view to show all working parts.

6. When the diagrams are completed, students should add arrows and written notes to indicate directions of motion for each part, label the elements of machines involved, and explain connections.

7. Have students display and explain their diagrams to other groups.

8. If time permits, give each group a new machine to investigate and sketch.

Teacher Tips: Encourage students to draw systematically, starting at one point and drawing each

part and connection in order. Emphasize that in this kind of drawing it is not important that their drawing look

exactly like the machine; instead it should show how the machine works. For example, getting the exact proportions for the parts is less important than showing how they connect to each other.

Encourage students to experiment with sketching enlarged views and cut-away views to show parts that are very small or obscured by other parts. Leonardo often left out the casing and structure surrounding machines in his illustrations so he could show the workings more clearly.

Many of the published Leonardo resources in the Bibliography contain examples of his work that students will understand better after they have tried this activity. They may want to see how other artists have created diagrams of machines. David Macaulay's book The Way Things Work contains many wonderful and whimsical examples.

Real World Connections:

Ask students to get their parents involved in helping them locate examples of machine diagrams from home. The instructions provided by manufacturers with bicycles, kitchen appliances, tools, and lawn mowers often contain explanatory diagrams to help you understand these machines. Auto repair manuals also contain dozens of these diagrams. Many construction sets such as Lego® and K'NEX® also have similar kinds of diagrams to help you build particular toy designs.

When you have several diagrams from different sources, ask the students to compare them and discuss them using the following questions as starting points:

What are some similarities and differences between different diagrams? Which diagrams do they think are the easiest to understand and the hardest to

understand? What techniques have the illustrators of the better diagrams used to make their

work clearer? What techniques can the students apply from these examples to make their own

machine diagrams more understandable?