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Introduction LEGODACTA® PulleySet
Contents
This booklet has been developed by teachers to support and guide you and your students through your exploration of the LEGO DACTA® Pulley Set, #9614. The booklet contains: • Information about pulleys • Simple hands-on pulley activities • Drawings of possible solutions
Activities
Activities for exploring concepts (pages 3-7), investigating principles (pages 9-11), and problem solving (pages 12-15) are included for elementary school students of varying abilities. The activities foster and enhance cooperative learning in teams of two students per building set.
Objectives
After performing the activities in this booklet, students will be able to: • Define a pulley as a wheel with a grooved rim for a belt or cord which can transfer force or speed. • Build a model which will increase speed. • Build a model which will increase force. • Arrange pulleys so that the driver turns in the same direction as the follower. • Recognize that the turning ratio of one pulley to another is determined by the size of the pulleys. • Build a model that will transfer force at a 90-degree angle. • Have fun with pulleys!
LEGO and DACTA are trademarks of the LEGO Group. Distributed by the LEGO Group, DK-7190 Bilkad, Denmark. 1997 The LEGO Group ISBN 0-91483144-4
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PulleyPatter A pulley is a wheel with a grooved rim which can be used to transfer force or speed or to turn another wheel. A single pulley changes the direction of the force in a belt or cord in the groove. The pulley at the top of a flag pole changes your downward pull on the rope into an upward pull to raise the flag. A crane uses one or more pulley wheels to raise heavy objects. Two pulley wheels can be connected by a belt. When one wheel is turned, the belt causes the other pulley wheel to turn as well. An automobile engine uses a belt drive to turn wheels on other devices, such as a water pump or an air conditioner. The photographs on the back of this booklet show additional examples of pulley wheels. Familiarize yourself with pulleys by working through activities on pages 3-7. Photocopy the drawings on pages 16-17 for easy reference, You may wish to provide these activities to your students as well.
Direction of Rotation • Build the base and model 1 shown on page 16. Predict what happens when you turn the handle. The wheel you turn (called the driver) causes the other wheel (called the follower) to turn also, because they are connected by a belt. The driver and the follower turn in the same direction. • Predict what happens if you grip the follower and turn the handle on the driver. The belt may slip. This is normal for belt drives.
MainIdeas: Two pulleys connected by a belt turn in the same direction. The belt may slip.
pulley wheel 0 bushing (used as a small pulley wheel)
PuleyPatter ChangingDirection of Rotation • Build model 2, shown on page 16. Predict what happens when you turn the handle. The driver and the follower turn in opposite directions. • Predict what happens if you grip the follower and turn the handle on the driver. The belt may slip. Slippage is a safety feature of devices which use bell drives, such as a drill press or a lathe.
MainIdeas: rnvo pulleys connected by a crossed belt turn in the opposite directions. The belt may slip.
DecreasingSpeed • Build model 3, shown on page 16. Predict what happens when you turn the handle. The belt drive causes the large pulley wheel follower to turn slower than the smaller bushing driver The driver and the follower turn in the same direction.
Mainidea: A small driver makes a large follower turn slower.
AdditionalInformation: The small driver turns several times to make a large follower turn once. This "gearing down" decreases the speed of rotation but increases the force. This is a common application for belt drives.
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small driver (fast)
large follower (slow)
PuleyPatter IncreasingSpeed • Build model 4 shown on page 16. Predict what happens when you turn the handle. The belt drive causes the small bushing follower to turn faster than the larger pulley wheel driver The driver and the follower turn in the same direction.
MainIdea:
small follower (fast)
A large driver makes a small follower turn faster.
large driver ( s l o w )
AdditionalInformation: A small follower turns several times in response to a single turn of the large driver. This "gearing up" increases the speed of rotation but decreases the force.
AtAnAngle • Build model 5 shown on page 17. Predict what happens when you turn the small handle. The rotational motion goes through a 90-cl4ree turn. The pulley wheel follower also turns slower than the smaller bushing driver
MainIdea: A belt drive can be used to change the direction of rotation by 90 degrees.
AdditionalInformation: This model contains examples of both changing the rotation by 90 degrees and "gearing down."
•
large follower (slow)
small driver (fast) ,
PulleyPatter CompoundBeltDrives • Using the drawing and diagram on the right, add another axle and belt drive to model 3 from page 16 to form a compound belt drive. (Note: This model does not appear on page 16 or 17.) Predict what happens when you turn the handle.
follovver 2
The first follower turns slowly. The second follower turns even more slowly
MainIdea: Pulley wheels of two different sizes on the same axle can be connected to other pulley wheels to build more extensive gearing down (and gearing up) arrangements. s m a l l
follower
driver
FixedPulleys • Build model 6 shown on page 17. Note the use of six black connector pegs in the handles. Make sure your axle can spin freely. If it seems to be "sticky," pull outward on the bushings a little to reduce the friction. Attach a load to the hook. Predict what happens when you pull on the string. The string lifts the load when you pull on. it.
MainIdea: A fixed pulley can change the direction of a lifting force to a more convenient angle.
AdditionalInformation: Fixed pulleys are used at the top of flag poles and in venetian blinds, for example.
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fixed pulley
PuleyPatter MovablePulleys • Build model 7 shown on page 17. Make sure all axles can spin freely. Attach a load to the hook. Predict what happens when you pull on the string. The string lifts the load when you pull on it. The load is easier to 10. However, you have to pull the string farther with a movable pulley than with a fixed pulley.
MainIdea: A movable pulley can he used with a fixed pulley to lift a load with less effort than with a fixed pulley alone.
fixed pulley
AdditionalInformation: A system of a fixed pulley and a movable pulley is called a block and tackle. Sometimes such systems include several pulleys. Because two strings are supporting this movable pulley, you have to pull twice as much string to raise the load compared with the fixed pulley alone. However, you need only half the force.
PulleySummary Pulley wheels connected by a belt turn in the same direction. Wheels connected by a crossed belt turn in opposite directions. The belt may slip. A small pulley wheel makes a large wheel turn slower (gearing down); a large wheel makes a small one turn faster (gearing up). Belts and pulley wheels can be used to change motion through 90 degrees. Pulley wheels of different sizes can be mounted on the same axle for more extensive gearing down or gearing up arrangements. A movable pulley requires less effort to raise an object than a fixed pulley.
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Assessment ExamplesofPulleys
May be photocopied for student work. See pages 3-7.
Processand InquirySkils
Cause and effect Predicting Observing Hypothesizing
CriticalThinking Skils
Gathering and recalling information Understanding and interpreting data and information Applying what is learned to solve problems in new situations
Measuring Problem Solving Inferring Communicating
Analyzing a problem into its component parts Synthesizing various aspects or components into a new whole to solve a problem Evaluating one's own work
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NotesforBuildingCardI Students can investigate belt drives, gearing down, compound belt drives, and changing the direction of rotation using Building Card l from their Pulley Set. Instructions for your students appear below. Answers ate shown in parentheses.
• Build the model, following the instructions through step 5. Predict if the top will turn faster or slower than the handle. Then test your prediction. (The top turns slower because of the gearing down arrangement. The-smaller bushing driver turns the-larger-pulley wheel follower.) • Determine how many times you have to turn the handle to make the top turn once. (They have to turn the handle three to four times, The gearing down ratio is between 33 and 4:1.) • Change the model by moving the belt from the top pulley wheel to the bushing. Predict what happens when you turn the handle. Then test your prediction. (The top turns faster than before. This is because a small driver is no longer turning a larger follower The top turns about as ! l• Change the model as shown in step 5A. Predict what ahappens when you turn the handle. Then test your prediction. s(The top turns slowly as in step 5. Both signs turn in the same tdirection and at the sante speed because they are connected by a abelt drive with pulley wheels of the same size.) s • Investigate different belt drive combinations and predict their t behavior. For example, cross the belt on the left, but leave the h belt on the right as shown in step 5 A. Predict what happens e and test your prediction. h (The signs both turn in the opposite direction of the handle.) a Next, cross the belt on the right, but leave the belt on the left n as shown in step 5A. Predict what happens and test your d prediction. l (The top sign turn in the same direction as the handle. e The bottom sign turns in the opposite direction.) , e• Add a face, eyes, and mouth (see page 18) as shown xin step 5 &Turn the handle and watch the eyes and mouth cchange. Design other faces, eyes, and mouths. e p
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NotesforBuilding Card2 Students can investigate fixed and movable pulleys and the concept of the pawl and ratchet using Building Card 2 from their Pulley Set. Instructions for your students appear below. Answers are shown in parentheses.
• Build the model, following the instructions through step 4. Position the crane so that the hook hangs down over the edge of your desk. Attach a load to the hook. • Predict what happens when you turn the handle. Then test your prediction. (The crane lifts the load.) • Release your handle. What happens? (The string unwinds and the load falls.) Can any of you suggest solutions to the problem? (Accept student suggestions.) • You may wish to build your solution. Or you could try this solution. Change your model as shown in step 4A. Predict what happens when you turn the handle and release it. Then test your prediction. (The crane lifts the load. When the handle is released, the load does not fall. This arrangement —called a pawl and ratchet — allows the gear to turn in only one direction.) • Now change your crane so that it has a movable pulley, as shown in step 48, Predict what happens when you turn the handle. Then test your prediction. (It is easier to turn the crank to lift the load. However, you have to wind up twice as much string to lift the load as far as you did with only the fixed pulley.)
AdditionalInformation: An arrangement including fixed and movable pulleys is called a block and tackle. The photograph of the crane on the back of this booklet shows an example.
IC
Building CardExtensionIdeas BuildingCard I Invite your students to make up other imaginative types of signs for their models. Challenge students to create a device with sign boards which turn in opposite directions. (Use a crossed belt drive.) Ask students to suggest other uses for their pulley mechanisms. The example in the drawing is a device to pull two fish up from a pail. The fish are wound up on opposite sides of the device.
BuildingCard2 Experiment with many different loads. What is the heaviest load one crane can lift? Connect several student cranes to a single heavy load and raise it. Discuss with the students why it is easier to lift the load with several cranes. (Each of the cranes lifts a portion of the weight) Invite students to design and build different containers to raise objects. For example, how would they use their crane to raise water or marbles? How would they raise a priceless statue? The drawings show only two of the many possibilities.
PackagePile-Up
Sandy has to' stamp the packages by hand and then push them along the table. They pile up too quickly for her. Sheneeds help. Design and build a conveyor belt system which: • carries packages one at a time • uses a belt drive.
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SOLVINGCOPYMASTER I
Notesfor:PackagePile-Up BuildingHints
Sample solutions are shown below. Arrange the rubber bands side by side so that the belt drive functions as a conveyor system, Make sure the bands are not stretched too much.
ExtraMaterials
Bring dice or extra bricks for packages.
TestingtheSolution
Measure how far the packages move. Judge how easy the conveyor system is to operate.
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Extension
Place the conveyor systems from several student groups end to end. Can the students move a brick along all of the conveyor systems? How far? How fast?
Stowaway
Chris has to pull the boat out of the water and drag it to the storage area. Isn't there an easier way? Design and build a boat mover which: • winches a boat up onto the shore. • does not allow the cord to unwind by accident.
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SOLVING COPYMASTER 2
Notesfor:Stowaway BuildingHints
Use a pawl and ratchet arrangement to prevent the cord from unwinding. The model in the sample solution below uses a single movable pulley on the hook
ExtraMaterials
Invite students to bring in model boats. Provide wood or cardboard for the ramp.
TestingtheSolution
How far does the boat move when you turn the handle 10 times? Judge how easily the boat can be removed from the water.
Extension
Suggest that several student groups use their winches to pull the same boat at the same time. By working together, they can move much heavier objects,
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PuleyConceptModels IDirection of Rotation
2ChangingDiredion of Rotation
3Decreasing Speed
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MAYBE PHOTOCOPIED FOR STUDENT REFERENCE
6[bedPulley
See also step 3 of Building Card 2.
MAYBEPHOTOCOPIEDFORSTUDENTREFERENCE
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OD
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Building ElementSurvey 9 each, bushing, 111a 3 each, pulley wheel, u gray g r a 1 each, crane hook, y gray 2 each, I x 2 beam, red 1 each, I x 4 beam, red
4 each, 1 x 16 beam, red a l 4 each, connector peg, gray 8 each, friction connector peg, black
2 each, I x 4 Sate, e y er : yellow l e I each, 2 x 4 plate with l 2 holes, yellow oe wa 2 each, 2 x 8 plate with c — h o l e s , yellow h I each, 2 x 10 plate, , re d 2 x 4 each, I x 2 wall 2 element, yellow p l element, black a 1 1 4 each, 1 x 2 wall t 2 each, two-bladed rotor, e gray ,
t o o I each, axle 2 studs long, black 4 each, axle 4 studs long, black 3 each, axle 6 studs long, black 1each, axle 12 studs long, black 2 cS e a c h , 1 x 2 plate, yellow e , 2 e a c h , I
gray
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l a 4 e 0 a , c g h r , a 2 y x 2 r o u n d
brick, red 1 each, crank, 1 each, 24-tooth spur gear, gray 2 each, rubber band, black each, string, black
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