Topic Simple machines Key Question What simple machines are found in an internal combustion engine? Learning Goals Students will: construct a working model of an internal combustion engine that has a piston, connecting rod, and shaft; identify the simple machines in the model; and determine the relationship between the diameter of the circle along which the lower end of the connecting rod moves and the distance the piston travels. Guiding Documents Project 2061 Benchmarks Science is an adventure that people everywhere can take part in, as they have for many centuries. Engineers, architects, and others who engage in design and technology use scientific knowledge to solve practical problems. Throughout all of history, people everywhere have invented and used tools. Most tools of today are different from those of the past but many are modifications of very ancient tools. NRC Standards Mathematics is important in all aspects of scientific inquiry. In most chemical and nuclear reactions, energy is transferred into or out of a system. Heat, light, mechanical motion, or electricity might all be involved in such transfers. Scientists and engineers work in many different settings, including colleges and universities, businesses and industries, specific research institutes, and government agencies. NCTM Standards 2000* Use geometric models to represent and explain numerical and algebraic relationships Recognize and apply geometric ideas and relationships in areas outside the mathematics classroom, such as art, science, and everyday life Science Physical science simple machines wheel and axle Technology Industrial revolution Internal and external combustion engines Engineering Mechanical engineering motion conversion Math Geometry circle diameter Measurement length Integrated Processes Modeling Observing Collecting and recording data Comparing and contrasting Materials Pushpins Hole punches ¼-inch Rulers Glue stick White glue Scissors Round toothpicks Plastic drinking straws, 15/64-inch diameter Paper fasteners, ½-inch Card stock patterns Background Information In this activity, students construct a working model of an internal combustion engine (ICE) of the type used in cars and trucks. The moving parts in the model are the shaft, the, the connecting rod, and the piston. In an internal combustion engine, the linear motion of one or more cylinder-shaped pistons, moving in a cylinder-shaped combustion chamber, is transformed into the rotary motion of the and shaft. This rotary motion is eventually transformed into the rotary motion of the driving wheels in the car or truck. 1 2010 AIMS Education Foundation
An internal combustion engine transforms the heat energy obtained by a burning mixture of gasoline and air into the mechanical energy of a moving piston, connecting rod,, and shaft. In an internal combustion engine, a fuel-air mixture is drawn into the combustion chamber. When the piston is at the top of its travel, a spark plug ignites the fuel-air mixture. The rapidly expanding gas produced by the burning mixture pushes the piston down the cylinder. The piston is attached to a connecting rod that is attached to the. The turns the shaft, converting the linear motion of the piston to the rotary motion of the shaft. The and shaft form a simple machine called a wheel and axle. (A machine multiplies a force or changes the direction of a force.) fuel-air mixture in connecting rod rotation circle spark plug exhaust gases out combustion chamber piston shaft Internal Combustion Engine The Industrial Revolution began in the late 18 th century and was powered by the technological development of the steam engine. A steam engine is an example of an external combustion engine. Water is heated in a boiler to make steam. The steam is then piped to a piston, the working part of the engine. In an external combustion engine, the source of heat is external to the engine itself. boiler steam in piston External Combustion Engine Two of the inventors that solved the engineering problems associated with the first practical steam engine and the first successful steamboat were the Scotsman James Watt, for whom the watt as a unit of power is named, and the American artist and inventor, Robert Fulton. In 1885, Karl Benz, a German mechanical engineer, designed and built the world s first practical automobile to be powered by an internal combustion engine. Today, the heat obtained by burning oil, coal, or the heat produced in a nuclear reactor is still used to boil water to make steam to spin a turbine to produce electricity for our homes and businesses. steam water turbine electricity generator Early automobiles like the Stanley Steamer were powered by steam engines. The discovery of oil and the development of an efficient and inexpensive internal combustion engine soon made these engines the standard for powering our cars and trucks. The model in this activity can be operated in two ways: 1) by moving the piston to turn the to model the actual operation of an internal combustion engine, and 2) by turning the shaft to move the piston back and forth to model the action of a water pump or air compressor. Key Vocabulary Bottom of center: the lowest position reached by the piston in a cylinder Connecting rod: the rod that connects the piston to the Crank: the wheel on which the connecting rod is attached Crankshaft: the shaft connected to the to form a simple machine (see wheel and axle) External combustion engine: an engine for which the fuel is burned outside it Internal combustion engine: an engine for which the fuel is burned inside it Piston: a metal cylinder that absorbs the heat of the burning fuel-air mixture, moves up and down, and transfers mechanical energy to the and shaft Simple machine: lever, wedge, pulley, inclined plane, wheel and axle, screw Rotation circle: the circle traced by the end of the connecting rod attached to the Top of center: the highest position reached by a piston in a cylinder Wheel and axle: a simple machine in which the force can be applied to the wheel or to the axle 2 2010 AIMS Education Foundation
Management 1. Print all pattern pages on card stock. Each student or group will need one piston, one connecting rod, one, one support, one set of three shaft spaces, one cylinder wall guide, and one base pattern. 2. Step by step directions are included. They can be presented to students as handouts that require them to read and follow the directions. This also requires copies to be made for each student or group. The directions can be projected, still requiring students to read and follow them, but requiring only one copy. The drawback is that faster workers must wait for those who don t work as fast. The procedures can also be modeled using the construction video at http://aimsedu.org/stem or with you modeling the process. This method requires no copies of instructions, but it does require the wait time by faster workers. 3. It s important that students understand and follow the techniques described in How to Score, Cut, Fold, and Glue Card Stock. Those that do will easily construct a working model. 4. Plastic straws with a 15/64-inch diameter fit snugly into the hole made by a quarter-inch paper punch It is often easier to find these straws sold as flexible straws. If you use flexible straws, simply have students cut off the shorter, flexible end. 5. Take time to construct a model. Doing so will help you identify potential problem areas for one or more of your students and give you time to develop any appropriate strategies before doing the activity with your class. 6. Set materials in a central location so that students can get them as needed. Procedure 1. Show the students your model of the ICE. Explain to them that ICE is an acronym for Internal Combustion Engine. Tell them that they will be making a model to discover how engineers solved the problem of converting linear motion into rotary motion. 2. Ask the Key Question and state the Learning Goals. 3. Show students where the materials are located. Use one of the methods described in Management 2 for construction. Students should construct the model s components in the following order: the piston, the connecting rod, the, attaching the shaft to the, shaft support, and then putting the model together. 4. When models are finished, let students explore how they work. Invite them to turn the in one direction so they can observe the interaction of the moving parts. 5. Make certain that students notice the two diagrams on the model s base. Explain that the picture labeled Pump demonstrates the action of a piston pump. In a pump or air compressor, like one used to inflate tires, an electric motor turns the shaft that pushes the piston up and down pumping water or compressing air. Turning the shaft of the model demonstrates using the model as a pump. 6. Draw the students attention to the picture labeled Engine. Tell them that this illustrates how the burning fuel-air mixture pushes down on the piston to turn the. Have students put the piston of their model at top center (the highest position reached by the piston).tell them to move the piston to the bottom center (the lowest position). Let them see that the piston can go no further down, instead it moves back up. (The of an engine is designed to only turn in one direction so a large wheel called a flywheel mounted on the shaft stores energy to push the around and push the piston back to top center. Most internal combustion engines have more than one cylinder so that when one piston is at or near bottom center, another piston is moving down, which helps push the other piston up. The more pistons, the smoother the operation of the engine.) 7. Distribute the student page. Have students answer the questions. End with a discussion of observations and applications learned. Connecting Learning 1. What simple machine is evident in our model? [the wheel and axle] 2. In an internal combustion engine, the parts are not called a wheel and axle. What are they called? [The wheel is the, and the axle is the shaft.] 3. How does the model convert the direction of motion? [When you turn the shaft (rotary motion), the piston moves up and down (linear motion). You can also move the piston up and down to turn the.] 4. How is the model like a real internal combustion engine? [The model shows how the piston, connecting rod,, and shaft convert the direction of motion.] 5. How does your model differ from a real internal combustion engine? [A real ICE often has more than one piston, is made of metal, has to have oil to lubricate the moving parts, etc.] 6. What relationship did you find between the diameter of the where the connecting rod is attached and the distance the piston travels? [The distance the piston moves is the same as the diameter of the circle the end of the connecting rod traces.] 3 2010 AIMS Education Foundation
7. If the distances you measured were not the same, what could explain the differences? [The paper fasteners do not fill any of the holes. This means the parts don t fit tightly together, thereby introducing error.] 8. What would you need to do if you wanted to make the piston move a greater distance? [Use a larger.] 9. What are you wondering now? Extensions 1. Challenge interested students to do a research report on James Watt, Robert Fulton, Karl Benz, or Henry Fold. 2. Ask students if they have a relative who has old engine parts they would let the class borrow to see actual components. * Reprinted with permission from Principles and Standards for School Mathematics, 2000 by the National Council of Teachers of Mathematics. All rights reserved. 4 2010 AIMS Education Foundation
Key Questions What simple machines are found in an internal combustion engine? Learning Goal construct a working model of an internal combustion engine that has a piston, connecting rod, and shaft; identify the simple machines in the model; and determine the relationship between the diameter of the circle along which the lower end of the connecting rod moves and the distance the piston travels. 5 2010 AIMS Education Foundation
How to Cut, Score, and Glue Card Stock dotted line Do not cut along dashed or dotted lines. dashed line snip snip Cutting to a Corner Every piece of a card stock pattern will be outlined in solid, black lines. The pattern may also contain dashed and/or dotted lines. Always cut along the solid, black lines. Never cut along dashed or dotted lines. Whenever possible, cut to a corner. This prevents you from accidentally creasing or folding the piece and makes for easier cutting. Scoring It is easy to neatly fold card stock if the line along which you wish to fold is first traced over with a ballpoint pen or pencil. (Ballpoint pens that are out of ink are ideal for this purpose.) Use a ruler to score along straight lines. mountain fold valley fold line to be scored ballpoint pen piece to be folded Gluing ruler white glue toothpick wet but not white! glue tab glue clinging to tip of toothpick toothpick For large areas, using a glue stick is the fastest and easiest way to glue card stock. Be sure to press hard on the glued sections. If possible, use a paper clip to clamp the pieces together. For small areas or where maximum strength is needed, use white glue. Nothing will ruin a project faster than the application of too much white glue. Put a bean-sized drop of glue on a piece of card stock left over from cutting out the pattern. Dip the end of a round toothpick in the glue, and apply only the glue clinging to the end of the toothpick to the piece to be glued. Use the tip or tapered end of the toothpick to spread the glue evenly over the surface of the piece. 6 2010 AIMS Education Foundation
ICE Pattern Pieces connecting rod apply glue here valley fold dashed line mountain fold dotted line apply glue here piston apply glue here cylinder wall guide shaft spacers 7 2010 AIMS Education Foundation
Crankshaft Support Patterns top brace top brace top brace top brace 8 2010 AIMS Education Foundation
spark plug water or air out Pump water or air in Engine rotary to linear cylinder wall guide combustion chamber steam or gasoline linear to rotary fuel-air mixture in spark plug exhaust gases out combustion chamber piston shaft support connecting rod rotation circle shaft Internal Combustion Engine 9 2010 AIMS Education Foundation
Construction Instructions Constructing the Piston, Connecting Rod, and Crank Materials needed: piston pattern piece connecting rod pattern piece pattern piece ruler scissors pushpin hole punch glue stick 1. Use the pushpin to score along the dashed and dotted lines on all three pattern pieces. 2. Cut along the solid lines. piston apply glue here 3. Valley and mountain fold the pattern pieces. 4. On the piston piece, apply glue to the shaded face and the face behind the piston. Press flat and punch a hole in the bottom of the piston. connecting rod apply glue here 5. On the connecting rod piece, apply glue to the shaded face and the face behind the connecting rod. Press flat and punch two holes as indicated. 6. On the piece, apply glue to the shaded face and the face behind the. Press flat. apply glue here 7. Cut out the circle. Cut along the shorter dark line. Carefully bend down the edge, and punch the two holes in the. 8. Heal the cut by gluing a piece of card stock scrap over the cut. Trim along the edge of the. cut and punch center hole scrap of card stock 10 2010 AIMS Education Foundation
Construction Instructions Attaching the Crankshaft to the Crank Materials needed: plastic drinking straw pushpin 2 round toothpicks hole punch 3 shaft spacer pattern pieces glue stick ruler white glue scissors 1. If you have a flexible straw, cut off the shorter, flexible end and discard. 2. Measure 1/8-inch from the end of the straw and use the pushpin to poke through the mark and out the opposite side of the straw. 1 8-inch pushpin 3. Push the toothpick through the holes and break the ends to form a short shaft through the end of the straw. 4. Cut out the three shaft support spacer patterns. Cut, score, fold, and glue the three spacers. Punch a hole on the circle face of each spacer. toothpick shaft support spacers 5. Glue two spacers over the center hole in the back of the piece and use the toothpick end of the straw to center the spacers before the glue sets. 6. Look at the front face of the and check if the end of the straw extends past the face of the. If so, remove the straw and glue the third spacer over the first two. 7. Set the toothpick end of the straw in the spacers. Use the tip of a second toothpick to apply white glue over the ends of the toothpick in the straw. The white glue will form a strong bond between the wood in the toothpick and the card stock. 8. Set aside to dry. spacers apply white glue here 11 2010 AIMS Education Foundation
Construction Instructions Attaching the Crankshaft Support and Putting the Pieces Together Materials needed: shaft support pattern ruler base page scissors pushpin 2 paper fasteners hole punch glue stick cylinder wall guide pattern 1. Score, cut, and fold the support piece and the two brace pieces. 2. Apply glue to the face under the printed holes, and press the faces together as shown. apply glue to bottom face with printed hole 3. Apply glue to the insides of the bottom tabs and press each tab in place. 4. Glue the top brace pieces in place and punch the holes in the sides. brace pieces apply glue to insides of tabs 5. Apply glue to the bottom of the shaft support piece and set the piece on the shaded area in the bottom right corner. punch holes 6. Use the two paper fasteners to attach the connecting rod to the and piston. 7. Insert the end of the straw through the two holes in the support piece. 8. Score along the dotted and dashed lines of the cylinder wall guide pattern. Mountain fold and valley fold the pattern. Glue the pattern to the shaded area on the base labeled cylinder wall guide. Check that there is a center groove in which the piston can slide. 9. Insert the piston in the cylinder wall guide. Adjust the straw in the shaft support so that the, connecting rod, and piston are in line. Turn the straw to see the model in action. piston connecting rod 12 2010 AIMS Education Foundation
1. Sketch and label the simple machine found in this ICE. 2. Measure and record the diameter of the lightly shaded circle that is inside the larger circle. cm 3. Top Center is when the piston is at its highest point. Bottom Center is when it is at its lowest point. Turn the shaft until the piston is in the top center position. Make a mark on the cylinder wall guide to show where the top of the piston is. Turn the shaft until the piston is in the bottom center position. Make a mark on the cylinder wall guide to show where the top of the piston is in its lowest position. Measure and record the distance between the two marks. cm 4. Describe the relationship between the diameter of the circle along which the lower end of the connecting rod moves (the inside circle) and the distance the piston travels. 5. Compare the two measurements. If they are not the same, explain why they may be slightly different. 13 2010 AIMS Education Foundation
Connecting Learning 1. What simple machine is evident in our model? 2. In an internal combustion engine, the parts are not called a wheel and axle. What are they called? 3. How does the model convert the direction of motion? 4. How is the model like a real internal combustion engine? 5. How does your model differ from a real internal combustion engine? 14 2010 AIMS Education Foundation
Connecting Learning 6. What relationship did you find between the diameter of the where the connecting rod is attached and the distance the piston travels? 7. If the distances you measured were not the same, what could explain the differences? 8. What would you need to do if you wanted to make the piston move a greater distance? 9. What are you wondering now? 15 2010 AIMS Education Foundation