Paxton ActionLABS ® MECHANISMS Introduction The following information is very important for your safety and also your success in completing the Mechanisms Module. Make sure you read carefully and understand the proper use and safe techniques in working with all equipment. If you are ever in doubt about any operation, always ask your instructor for help. Mechanical Safety Maintain a clean, safe work area. Technology laboratories require good work habits. If you have questions about the safety of gear configurations, ask your instructor for help before applying power to the system. 1. The Mechanisms Trainer is motor-driven and powered by 115 VAC electric power. The system is fused and controlled by an On/Off switch. Get your instructor’s approval before activating the system. 2. The safety shield must always be in the down position whenever the motor switch is activated! 3. Rotating gears and chain drives can be dangerous if misused! Keep hands and clothing clear when gears are in motion. 4. DO NOT attempt to manually stop gears in motion or change gears while V. 3.0 the motor switch is activated! ® Copyright © 2006 Paxton/Patterson LLC - All Rights Reserved. All electronic materials in Paxton ActionLABS Learning System are 5. printed Keepandall components in their proper storage areas copyright protected including but limited to student guidebooks, graphics, tests, rubrics, when the trainer is not videos, and instructor and student orientations. being used. 6. Make sure you understand how to properly use all 1 Paxton ActionLABS ® MECHANISMS Introduction To Your Trainer Mechanisms work hand in hand with all other areas of technology such as electronics, fluid power, communications, and manufacturing. Industrial applications are changing each day, so it is important to continually update your knowledge in all areas of technology. This program will provide firm foundations and entry level skills that may help direct you to your future career. It is essential as you continue your education that you master reading, math, and science skills to support your technology training. 2 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 1 Day 1: Activity 1/Experiment Trainer Components and Functions Purpose: The purpose of this experiment is to familiarize you with the Trainer’s components, post adjustments, safety, and startup procedure. If you fully understand how the Mechanisms Trainer works, you will successfully complete the experiments. Materials Needed: The Mechanisms trainer with instrumentation panel includes the following: Spur gears - 50 tooth (6), 45 tooth (1), 40 tooth (1), 30 tooth (1) 25 tooth (1), 20 tooth (1) Sprocket gears – 30 tooth mounted on 50-tooth spur gear (1), 20tooth (1), 10-tooth (1) Post retainer collars (15) Small weights 8 ounces (4) Large weight 10 ounces (1) Spring scale 0 to 72 Oz. (1) Cone pulleys (2), one with handle Winch assembly with cable (1) Idler pulley (1) Roller chain (1) Lever arm (1) Inclined plane ramp (1) Gyroscope (1)-optional Hardware package consist of eye hooks (4), Allen wrench (1), weight coupler (1) Cable Set consists of long cable (1), short cable (1), and pulley block (1) Procedure: STEP 1: Study the instrumentation panel of your trainer that is shown in on V. 3.0 the next page. Each component is identified and its function is defined. 3 Paxton ActionLABS ® MECHANISMS DAY 1 STEP 2: Become familiar with each component and its location. Can you show your partner where each of the parts is located? Main Components 1. Component storage posts houses 4, 8-oz. weights, a cone pulley, sprocket, gears, and a winch 2. Spur gear mounting posts experiments for spur gear 3. Safety shield gear motor is engaged for protection while 4. On/off switch drive activates motor gear 5. Power indicator light activated indicates power is 6. Power supply module cabinet; supplies power found on rear of 7. Gear train mounting posts used to design various configurations; each post is adjustable 4 8. Motor gear drive drives gear configurations V. 3.0 9. Inclined plane adjustment post supports Paxton ActionLABS ® MECHANISMS DAY 1 11. Limit switch winch experiments 12. Sleeve bearing protects motor in used in pulley experiments 13. Ball bearing pulleys experiments used in pulley 14. Spring scale effort, and resistance measures force, 15. Weight car supports weights during inclined plane activity 16. Lever arm storage secured keeps lever arm Gear Post Adjustments and Retaining Collars STEP 3: Find the gear mounting posts that have Retaining Collar been fitted with retaining collars. These collars are locked or released by a set screw on the side Mounting Post and are adjusted with the of the collar supplied Allen wrench as shown Allen Wrench below. Gear Train Mounting Adjustable Posts STEP 4: Find the gear mounting posts. To reposition a gear train mounting post, V. 3.0 loosen the post by hand, turning it counterclockwise about a quarter a turn; slide the post to the desired position. To 5 Paxton ActionLABS ® MECHANISMS DAY 1 STEP 5: A Spur Gear Identification Chart (like the one pictured below) has been provided in the back of the Module Guidebook to help you identify the spur gears provided with the Mechanical Trainer. Identify the spur gears by laying the actual gear over the outline. NOTE: All spur gears except the 20-tooth gear have their gear teeth count imprinted on the face of the gear. 6 V. 3.0 The Mechanisms trainer has features that provide a safe environment for students. However, some Paxton ActionLABS ® MECHANISMS DAY 1 NOTE: A safety shield has been provided to prevent your clothing or hands from making direct contact with moving gears. The safety shield is equipped with a safety switch that will not allow the gear drive motor to operate if the safety shield is in the up position. The winch assembly and limit switch are to be used only during the winch and gear ratio experiment. They are not designed for other uses. STEP 6: Turn the on/off switch of the Mechanisms trainer on and observe the movements of the gears. NOTE: The safety shield must be in the down position. STEP 7: With the gears rotating, lift the safety shield and watch the gears’ rotation stop. If the gear motor does not stop, turn the unit off and report the failure to your instructor. STEP 8: With the power off, lift the safety shield. Using the supplied Allen wrench, loosen the set screw on gear #3 and remove the retaining collar. NOTE: A quarter turn of the Allen wrench should be enough. STEP 9: Remove the gear or gears on post #3. Now replace the gear or gears on the post and secure the retaining collar. All collars will be removed this way when you use your Trainer. 7 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 1 STEP 10: With the power off, lift the safety shield and loosen one of the gear train mounting posts. Move it to a different position. Tighten the post. The four gear train mounting posts and the inclined plane post are all moved in the same fashion. Move them several times until you feel comfortable using the system. Refer to the illustration below. STEP 11: Examine all the components supplied with your trainer. STEP 12: Please clean up your module work area and make sure everything has been replaced. Conclusion: You have learned how to properly use the Mechanisms trainer and can identify its components. Remember that safety is always important when operating any equipment in the lab. 8 RETURN TO THE PAXTON ActionLABS PROGRAM. V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 2 Day 2: Activity 1/Experiment 3 Classes of Levers Purpose: The purpose of this experiment is to address three separate subjects with three separate but related parts — first, second and third class levers. A lever consists of a lever arm and a fulcrum. A lever arm is a rigid piece of material that transmits and modifies force, while a fulcrum is the support about which a lever turns. The three classes of levers all have advantages as well as disadvantages. Remember a seesaw or teeter-totter? This is a type of lever. Materials Needed: 1 Mechanisms Trainer 1 Large weight (approx 16 oz) 4 Small weights (approx. 8 oz each) 1 Spring scale Hooks for weights 1 Ruler Procedure: STEP 1: Read the following paragraphs about first class levers. All first class levers have one thing in common: The fulcrum is located between the effort being applied and the resistance (load) being moved. Refer to the illustration below. First class levers are useful for many jobs, such as when an increase in force is needed. The mechanical advantage of a first class lever is determined by comparing the length of the effort arm to the length of the resistance arm. The closer the fulcrum is to the resistance, the less effort will be required to move the resistance. You will use your Journal to record your answers during the following experiments. V. 3.0 9 Paxton ActionLABS ® MECHANISMS DAY 2 As we work with the three classes of levers, we will use a common formula to calculate the ideal mechanical advantage (IMA) and the actual mechanical advantage (AMA) of each class of levers. The two formulas are =IMA LENGTH OF EFFORT ARM FROM FULCRUM (FORCE APPLIED) Example: =5 (IMA) LENGTH OF RESISTANCE ARM FROM FULCRUM (LOAD) 10ft. 2 ft. =AM A ACTUAL LOAD (WEIGHT BEING MOVED) EFFORT (FORCE BEING APPLIED) Example: =5 (AMA) 500 LBS. 100 LBS. NOTE: You will not be working with precision weights or balances; therefore, many of your readings or calculations may have a variance of plus or minus 1/2” (.5) in distance measurements and approximately 1 to 2 ounces in weight measurements. 10 V. 3.01 Paxton ActionLABS ® MECHANISMS DAY 2 STEP 2: Using the Mechanisms trainer, set up the lever arm as shown below. To mount the lever arm, loosen and slide the inclined plane mounting post to the top position. Unscrew the retainer screw, place it through the center hole position of the lever arm, and mount it on the inclined plane mounting post as shown below. Do not tighten the retainer screw; it only needs a few clockwise turns. 11 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 2 STEP 3: Locate these components and have them ready: 1 Large weight (approx. 16 oz.) 4 Small weights (approx. 8 oz.) 1 Spring scale Hooks for weights Ruler STEP 4: For Lever Setup 1, use the two small (8 oz.) weights. Slide the hooks over the lever arm until it balances as shown below. Do not place the hooks through the holes in the lever arm. The resistance arm is the distance from the fulcrum to the load on your right. The effort arm is the distance from the fulcrum to the point of the force-applied weight on the left as shown below. 12 STEP 5: Once the lever arm is balanced, measure both the resistance arm and the effort arm from the fulcrum to the points where the weights hang and record the findings in your Journal. V. 3.0 STEP 6: Weigh each weight with the spring scale and Paxton ActionLABS ® MECHANISMS DAY 2 STEP 7: For Lever Setup 2, use the 16-oz. weight on the resistance side and an 8-oz. weight on the effort arm side. The large (16oz.) weight will be inserted into the lever armhole as shown below. The small (8oz.) weight will be hooked over the effort arm so it can be slid along the arm during the experiment. STEP 8: Slide the small weight along the lever arm until it balances. Note how the smaller weight has controlled the larger weight. STEP 9: Measure both the resistance arm and the effort arm and record the findings in your Journal. STEP 10: Weigh each weight with the spring scale and record the results in your Journal. Calculate the AMA and IMA and enter those findings as well. STEP 11: For Lever Setup 3, place the large weight and three small weights on the resistance arm side of the lever arm. A small weight will be hooked over the lever arm on the effort arm side as shown below. 13 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 2 STEP 12: Once the lever arm is balanced, measure both the resistance arm and the effort arm and record the findings in your Journal. STEP 13: Weigh each individual weight with the spring scale and enter that data, as well as the AMA and IMA, in your Journal. STEP 14: Read the following information about second class levers. Second class levers provide an easy way to increase force without changing direction. In all second class levers, the resisting weight is between the fulcrum and the effort as shown below. Fulcrum Effort 250 lbs. Resistance 500 lbs. A common example of a second class lever application is a wheelbarrow, shown below. The wheel’s axle serves as the fulcrum; the pan holds the Resistance resistance; and the effort is applied on the handles. Fulcrum Effort 14 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 2 STEP 15: Set up the lever arm as shown below. You will use the 16-oz. weight and the spring scale to perform this experiment. STEP 16: For Lever Setup 1, place the weight and spring scale on the lever arm as shown below. Resistance (Weight) Fulcrum Effort STEP 17: Pull upward on the spring scale and observe the scale reading while keeping the lever arm horizontal. Record the effort (force used) in your Journal. STEP 18: Measure and record the distance between the effort and the fulcrum in your Journal. STEP 19: Measure and record the distance between the resistance and the fulcrum in your Journal. STEP 20: Calculate the AMA and the IMA using the proper formulas. Record this V. 3.0 data in your Journal. 15 Paxton ActionLABS ® MECHANISMS DAY 2 STEP 21: For Lever Setup 2, assemble the lever arm as shown below and repeat STEP 17 through Step 20. Record all the data in your Journal. STEP 22: For Lever Setup 3, assemble the lever arm as shown below and repeat STEP 17 through STEP 20. Record all the data in your Journal. STEP 23: Now that we have looked at the second class lever, let’s move on to the third-class lever. Read the following paragraphs about third class levers. In third class levers, the effort is located between the fulcrum and the resistance as shown below. 16 Resistance 100 lbs Effort 500 lbs Fulcrum V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 2 A typical application of a third class lever is the common shovel. The principle of the third class lever is also evident in the design of heavy construction equipment, such as the large industrial shovel shown below. Effort Resistance Fulcrum Hydraulics can be used to power a lever system. We will set up two third class lever systems of our own and compare them to the first and second class levers. You will use the large (16-oz.) weight and the spring scale to perform this portion of the experiment. Record the findings in your Journal. STEP 24: For Lever Setup 1, assemble the lever arm and components as shown below. STEP 25: Pull upward on the spring scale and observe the scale reading while keeping the lever arm horizontal. Record the effort (force used) in your Journal. STEP 26: Measure and record the distance between the effort and fulcrum in your Journal. V. 3.0 STEP 27: Measure and record the distance between the resistance and the 17 Paxton ActionLABS ® MECHANISMS DAY 2 STEP 28: Calculate the AMA and the IMA using the proper formulas and record this data in your Journal. STEP 29: For Lever Setup 2, assemble the lever arm as shown below and repeat STEPS 25 through STEP 28. Record all the data in your Journal. STEP 30: After recording all of your data, disassemble the weights and place them in their proper storage areas. Please clean up your module work area and make sure everything has been put away properly. 18 Conclusion: You have used all three classes of levers and have discovered that each class has its own applications. You also learned that all lever systems move around a pivot point called a fulcrum. Through the use of simple formulas, you can calculate both the actual mechanical advantage and the ideal mechanical advantage for each type of lever. You can therefore state that the main purpose of a lever system is to provide a mechanical advantage to the user. This can also be called force multiplication. You have V. discovered that you use lever principles daily. Look 3.01 around your school and see how many lever Paxton ActionLABS ® MECHANISMS DAY 2 Day 2: Activity 2/Experiment Single and Double Pulleys Purpose: The purpose of this experiment is to understand how machines today use single pulleys or double pulleys in combination to lift a weight in a different direction with or without reduced force. Both simple and complex applications use some form of pulley combinations. A complex application would be a large construction machine and a simpler application would be an engine hoist. Materials Needed: 1 Mechanisms trainer 1 Large weight (approx. 16 oz) 2 Small weights (approx. 8 oz each) 1 Spring scale 1 Block pulley unit with cable attached Procedure: STEP 1: Read the following information about single and double pulleys. Pulley systems, an inexpensive solution for moving heavy items, are efficient when using low friction ball bearing pulleys such as those on your Trainer. Many formulas are used to determine mechanical advantage figures for pulleys. However, since this is our first exposure to these devices, we will use one = AMA formula that will provide us with actual mechanical advantage (AMA). Our formula is: =2 ACTUAL LOAD (WEIGHT BEING MOVED) EFFORT (READING OF THE SPRING SCALE) V. 3.0 100 LBS. WEIGHT BEING MOVED 50 LBS. OF FORCE REQUIRED 19 Paxton ActionLABS ® MECHANISMS DAY 2 STEP 2: Open your Journal. You will record all your answers here. STEP 3: Locate the material components needed for this experiment and have them ready. Spring Scale STEP 4: Weigh all 3 weights as a group with the spring scale as shown below. STEP 5: Record the weight in your Journal. STEP 6: Set up the single pulley system as shown below. 8 oz. 8 oz. 16 oz. 20 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 2 STEP 7: Slowly lift the weights as shown on the previous page. Observe the spring scale reading while lifting the weights. Record the Effort to Lift Weight in your Journal. STEP 8: Now set up the double pulley system as shown below. SAFETY NOTE: You must maintain weight on the effort side or the weights will fall. STEP 9: Slowly raise the weights. Observe the spring scale reading. Record the Effort to Lift Weight in your Journal. STEP 10: Using the actual mechanical advantage (AMA) formula found under Step 1, Day 2, Activity 2, calculate the AMA of both pulley systems. Record both answers in your Journal. STEP V. 3.0 11: Compare and contrast the two systems’ AMAs in your Journal. 21 Paxton ActionLABS ® MECHANISMS DAY 2 STEP 12: Disassemble the weights and place all components in their proper storage locations. Conclusion: You have constructed both a single and a double pulley system and have measured the effort required to move a weight system. You have seen that the effort is far less when using a double pulley system than when using a single pulley system. By using the AMA formula, you were able to calculate the AMA of both systems. RETURN TO THE PAXTON ActionLABS PROGRAM. 22 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 3 Day 3: Activity 2/Experiment Simple Gear Trains; Gears for Changing Direction of Force Purpose: The purpose of this experiment is to understand how gears work together. Gears are actually spinning levers (see below) and were probably one of the first methods of rotary work conversion. A torque, or force applied to one gear can move a second gear or more. You will be working with the spur gear, a roundtoothed wheel. Force Fulcrum Materials Needed: 1 Mechanisms trainer Various spur gears Procedure: STEP 1: The spur gear is the simplest and most fundamental gear design. Look at the illustration below to see how gears are used to reverse direction. If power is put into one gear, the output from the other will be reversed. Reverse direction. Third gear returns direction to input direction. 23 Three gears are locked and can not be rotated. V. 3.0 gears rotate freely. All Paxton ActionLABS ® MECHANISMS DAY 3 STEP 2: Lift the safety shield from the face of the trainer. STEP 3: Loosen the retaining collars on gears 2, 3, 4, and 5. Remove these gears, leaving only gears 1 and 6 as shown at the left. STEP 4: Note the small reference dots on both the gears and the face panel. Line up gears 1 and 6 with their respective reference dots as shown above. STEP 5: Rotate gear 6 clockwise and observe the direction of rotation of gear 1. In what direction did gear 1 rotate as compared to gear 6? STEP 6: Add gear 5 back onto the proper mounting post as shown at the left. STEP 7: Secure the retaining collars on all three gears and note that you have engaged gear 5 with the motor drive gear. The motor drive gear always rotates clockwise. Knowing this, which way do you think all the gears will rotate? STEP 8: Lower the safety shield and activate the power switch. Observe the gear’s rotation and confirm or correct your rotation estimate. Was your prediction correct? 24 STEP 9: With the motor drive gear as the input force and an application requirement stating that the end result of the gear configuration V. 3.0 must be a clockwise rotation, what do you have to do to obtain Paxton ActionLABS ® MECHANISMS DAY 3 STEP 12: Lower the safety shield and watch the gears closely as you activate the motor. Try it several times. What have you observed? The movement you observed is called ―backlash‖ or ―play.‖ This type of action in a moving machinery piece causes wear and loss of energy. When an engineer designs a piece of equipment, he or she is greatly concerned with this action. STEP 13: With the motor off, replace all gears and secure them with the retaining collars. STEP 14: Lower the safety shield and turn on the motor. Observe the direction of travel of each gear. STEP 15: Turn off the system. STEP 16: Please clean up your module work area and make sure all parts of the Mechanisms trainer are placed back in their original positions. Conclusion: You have experienced spur gears changing directions. You should have determined that the direction of rotation is determined only by the placement of the gears. You also observed that every other gear travels in the opposite direction regardless of the number of gears in the system. RETURN TO THE PAXTON ActionLABS PROGRAM. V. 3.0 25 26 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 4 Day 4: Activity 1/Experiment Gear Trains and Speed Change Purpose: The purpose of this experiment is to understand how gears, when used in the proper combination, can be used to increase or decrease speed. Materials Needed: 1 Mechanisms trainer Various spur gears Procedure: STEP 1: Read the following information about spur gear speed and speed reduction. Gears can increase or decrease speed. Common applications for this type of speed control are in bicycles, fishing reels, and car transmissions (seen below). You will often hear the term ―drive gear‖ in relation to mechanical systems. This gear is the driving energy force within the gear train. Automobile transmissions make use of numerous gear combinations to obtain the correct torque and speed. The speed at which a gear travels is measured in RPMs, or revolutions per minute, the number of revolutions a gear makes in one minute. 27 V. 3.0 continued… Paxton ActionLABS ® MECHANISMS DAY 4 If a 24-tooth gear operating at 100 RPMs is driving a 12-tooth gear, what will the RPMs of the 12-tooth gear be? The formula for this calculation is Driving Gear x Driving Gear RPM = RPM of Driven Gear Driven Gear 100 RPM – 200 RPM You will hear the term gear ratio; this is determined by the number of teeth of the gears in question. For example, a 10-tooth gear driving a 30-tooth gear would be a 3 to 1 ratio. It would take the 10-tooth gear 3 revolutions to turn the 30-tooth gear 1 revolution. A simple gear train consists of two or more meshed gears where the gear shafts are parallel and only one meshed gear is on each shaft. The illustration below shows a simple gear train with two meshed gears. 28 V. 3.0 continued… Paxton ActionLABS ® MECHANISMS DAY 4 A compound gear train consists of two pairs or more of meshed gears with parallel gear shafts as shown below. A machine can be made more complex by adding gears. However, this is not always a good solution when designing a machine. Gears cause increased friction and energy loss. The amount of friction can be controlled with a well-engineered design; however, a poor design will result in an inefficient machine. You will record the data from this experiment in your Journal under the entry Spur Gears – Speed and Speed Reduction. STEP 2: Remove gears 4 and 5 and set them aside as shown below. 29 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 4 STEP 3: Locate the gear train mounting posts and the 40-, 20-, and 45-tooth gears. Adjust the gear train mounting posts so the 40-tooth gear on post #1 is engaged with the unit drive gear and the other two gears are engaged with the 40-tooth gear. All gear counting indicator dots should be at the 12 o’clock (top) position. STEP 4: Lower the safety shield and turn on the motor. STEP 5: Count gear rotations, starting with the smallest (20-tooth) gear and using the 40-tooth gear as the driver gear. Record the gear rotations for the 20-tooth, 45-tooth, and 40-tooth gears in your Journal. 30 STEP 6: Turn on the motor switch to rotate the 40tooth (#1) gear 10 full revolutions while counting the number of revolutions of the 20-tooth (smallest) gear. Turn off the motor and record the number of revolutions of the 20-tooth gear in your V. 3.0 Journal. Paxton ActionLABS ® MECHANISMS DAY 4 STEP 8: To see a bigger speed difference, remove the three gears (40-, 20-, and 45-tooth) from the gear train mounting posts; place a 50-tooth gear on mounting post #1 and a 25-tooth gear on mounting post #2. STEP 9: Adjust the 50-tooth gear so it engages with the drive gear; the 25-tooth gear should engage with the 50-tooth gear. NOTE: The gear counting indicator dots should both be at the 12 o’clock (up) position. STEP 10: Place the retaining collars on the mounting posts and secure them with the supplied Allen wrench. STEP 11: Place the safety shield in the down position. STEP 12: Turn on the motor switch and rotate the 50tooth gear 5 full revolutions. Count the number of revolutions that the 25-tooth gear makes and record your answers in your Journal. STEP 13: Reverse the gear positions and use the 25tooth gear as the driving gear. Rotate it 5 full revolutions and count the 50-tooth gear revolutions. Record your results in your Journal. See if our gear calculation formula gives you the same answers that you recorded. STEP 14: Please clean up your module work area and make sure all parts of the Mechanisms trainer are placed back in their original positions. V. 3.0 Conclusion: Today, you learned how gears used in proper 31 32 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 4 Day 4: Activity 2/Experiment Multiple Speed Reductions Purpose: The purpose of this experiment is to understand that multiple speed reductions use a series of gears to decrease or increase the speed of the end working device. This type of configuration is called a gear train. A gear train can also provide variable speeds from one drive gear source. Materials Needed: 1 Mechanisms trainer Various spur gears Procedure: Multiple speed reduction gear trains are found in automobile transmissions, home appliances, and electric tools. In fact, the motor used on your Trainer is a geared motor that is reduced to 4 RPM. STEP 1: You are going to build a gear trainer that will give the end gear the lowest possible speed. Select 45-, 30-, 25-, and 20-tooth gears and two 50-tooth gears that have engagement collar (1) lugs protruding from the drive gear Over View collars (2) center of the gear assembly. 50-tooth NOTE: The 20STEP 2: Set up the gear train as shown below. Use Side View and 30-tooth 50-tooth the gears gears are selected in the gear train mounting posts. colla mountedSTEP on 1 on 45r 25-tooth tooth the mounting Past 1 Past 4 posts opposite the other 20-tooth gears Past 2 30-tooth Past 3 V. 3.0 33 Paxton ActionLABS ® MECHANISMS DAY 4 STEP 3: Engage the 20- and 30-tooth gears with the 50-tooth gears with the engagement lugs protruding. STEP 4: Secure the retaining collars on all gear train mounting posts. STEP 5: Lower the safety shield. STEP 6: Turn on the motor switch and rotate the 25tooth gear 10 complete revolutions while counting the revolutions of the 45-tooth end gear. STEP 7: You have reduced the speed of the end gear through the use of a multiple speed reduction gear train. To attain a more dramatic speed reduction, remove all the gears from mounting posts 2, 3, and 4 and place the 45-tooth gear on mounting post 2. 4525Engage it with the 25tooth tooth tooth gear as shown. STEP 8: Lower the safety shield. STEP 9: Turn on the motor switch and rotate the 25tooth gear 10 complete revolutions while counting the revolutions of the 45-tooth gear. Note the speed difference of the 45-tooth gear. 34 STEP 10: Now use different gear combinations and try to achieve the slowest speed possible for the end gear. V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 4 STEP 11: Answer the following questions in your Journal. You may refer to the glossary if needed. a) Define RPM. b) What is the ratio of a gear train using a 10tooth gear as the driving gear and a 50-tooth gear as the driven gear? c) What is the formula for calculating RPMs? d) How would a small gear be affected if it were driven by a larger gear? STEP 12: Please clean up your module work area and make sure all parts of the Mechanisms trainer are placed back in their original positions. Conclusion: Gears and gear trains increase or decrease speed. When single gears are used in tandem with each other, we refer to them as a simple gear train. The gear train you constructed is called a compound gear train — it consists of multiples gears used together with some rigidly connected. The mechanical advantage of either depends only on the number of teeth on the driver gear and the end gear. The intermediate gears between the driver and the end gear do not affect the mechanical advantage. Gears are in common use throughout industry, so it’s important that you understand them. RETURN TO THE PAXTON ActionLABS PROGRAM. 35 V. 3.0 36 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 5 Day 5: Activity 1/Computer Program Crazy Contraptions Purpose: The program you will be using in this activity is a wacky game and construction kit that will allow you and your partner to be creative in solving contraptions and building simple machines. There are many areas to explore including some pre-made contraptions. As your ability in machine-making increases, you can design and construct your own. You should spend about 15 minutes completing this activity. Materials Needed: Hoyle ® Puzzle Games Software featuring Crazy Contraptions Procedure: STEP 1: MINIMIZE THE PAXTON ActionLABS PROGRAM. Double-click the Puzzle Games desktop icon to start the program. The program will take a few minutes to load. STEP 2: Select the New button. Start by typing your name in the sign-in box. Click OK. The FaceMaker option will appear giving you the option of creating a face to use with your player or selecting a pre-made player. Click OK when done. STEP 3: Click on the Crazy Contraptions program title. Click Play Contraptions. Enter your name in the sign-in box and click the red, Next arrow. If a new window pops up: This name does not match any on my list. Are you a new user? Select Yes. In the Select V. 3.3 Contraption type box, choose Tutorial and click Next. Choose a tutorial contraption and click Load. 37 Paxton ActionLABS ® MECHANISMS DAY 5 STEP 6: At the Main Menu screen, click How to Build Contraptions. Work through the tutorial to learn how to build your own contraption. STEP 7: When you are finished with the tutorial, see if you and your partner can build a contraption of your own. STEP 8: When done, click the Main Menu button on the left side of the screen. Click Yes when asked if you want to continue. STEP 9: At the Main Menu screen, click Exit to quit the program. Click Yes when asked if you want to quit the program. To completely quit the Puzzle Games program, you will need to click the program title in the taskbar. Choose File, then Exit Puzzle Games. Click Yes when asked if you want to quit the program. Conclusion: Today you and your partner learned to be creative solving contraptions and building simple machines. RETURN TO THE PAXTON ActionLABS PROGRAM. 38 V. 3.3 Paxton ActionLABS ® MECHANISMS DAY 5 Day 5: Activity 2/Critical Writing – Narrative Directions: In this module you and your partner have learned that levers and pulleys can create a mechanical advantage. Gears are wheels with toothed edges. Two gears with meshed teeth make a simple gear train. Gears are used to change the direction of a force or movement. If the drive gear is turning clockwise, any other gear directly meshed with it will turn counter-clockwise While your partner is completing the test on the computer, you will complete the critical writing activity on a separate page supplied by the instructor. When you have both finished with this activity, trade places. You will now complete the test on the computer and your partner will complete the critical writing activity. Critical Writing: You are on another summer overnight hike in the mountains with your older brother who is home from college. As always, your backpacks contain all the necessary supplies including food, water, a hatchet, a first aid pouch, and sleeping gear. You also packed an extra rope, pulleys, extra tent stake nails, and your parents’ cellular phone. Your brother Neil is ahead of you on the steep trail and suddenly trips on a tree root, losing his footing. He slides about 40 feet down the mountainside to a ledge. He is OK except for a sprained wrist. It is too steep for him to climb up, plus Neil says he can’t hold anything tight in his injured hand. Your first reaction would be to tie a rope around a nearby tree and throw it down to your brother so he can climb back up, but he can’t use one of his hands. 39 By using single or double pulley systems and any other V. 3.0materials that you have, explain step by step how you will create a mechanical advantage to lift Neil back up to the trail and out of danger. Paxton ActionLABS ® MECHANISMS DAY 5 Narrative/Persuasive Pre-Writing to Writing Process Follow this process when writing your narrative or persuasive assignments. Prewriting: Plan your writing by thinking about the topic and your purpose. Are you explaining or arguing a point of view? A narrative piece requires you to describe in order. Persuasive writing requires you to first state your point of view, then tell why you think it is correct and present facts to support your opinion. 1. Identifying – Choose the main elements you wish to write about. There should not be more than three. 2. Drafting – Jot your ideas down in rough form. 3. Revising – Change and improve the rough draft. Get rid of unnecessary parts. Add important material based on your writing goal – to explain or defend. 4. Proofreading – Correct any errors in spelling, punctuation, and clarity. Care should be taken to make the writing communicate clearly. 5. Publishing – After final editing, finish the writing and make it available for others to read. Edit your piece one more time before you rewrite (publish it) for the audience to read. 40 AFTER COMPLETING THE CRITICAL WRITING AND THE PROGRESS TEST, RETURN TO THE PAXTON ActionLABS PROGRAM. V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 6 Day 6: Activity 1/Experiment Sprocket Gears and Chain Drives Purpose: The purpose of this experiment is to understand that sprocket gears and chain drives are basically a gear and a belt. A designer always takes the mechanical advantage of the device into consideration when designing machinery. A device has mechanical advantage when it provides a change in force, distance, or direction. Materials Needed: 1 Mechanisms trainer 1 Chain Various sprocket gears Procedure: STEP 1: Read the following about torque. You are using torque when you use a wrench to loosen or tighten a bolt. You gain more torque by increasing the length of the lever used: the longer the lever, the greater the torque. Torque is determined by multiplying the force (pounds) times the length of the lever arm. FORCE X LENGTH OF LEVER ARM = TORQUE If you double the length of the lever arm, you double the amount of torque, making it much easier to cause rotation. The illustration below shows 2 lever arms: one is 1 foot long, the other is 2 feet long. Imagine that the weight (force) you need to lift is 330 pounds. 41 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 6 Use of the formula can determine how much torque is needed to lift the weight using each lever arm. Using a 1 foot long lever arm: Torque = Force x Length of lever arm Torque = 330 pounds x 1 foot Torque = 330 pound-feet Using a 2 foot long lever arm: Torque = Force x Length of lever arm Torque = 330 pounds x 2 feet Torque = 660 pound-feet You can clearly see that the longer the lever arm, the greater the torque, and the greater the torque, the easier it is to cause rotation. You will be using three sizes of sprocket gears during this experiment, as shown below. The 30-tooth sprocket gear will be mounted on a 50-tooth spur gear to provide a means of interface with the main drive gear. You will record your data in your Journal. 42 continued… V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 6 STEP 2: Using ONLY 50-tooth spur gears, set up the trainer as shown below. STEP 3: Lower the safety shield. STEP 4: Turn on the motor switch and observe the two 50-tooth spur gears and the direction of their movement. Record the gears’ directions in your Journal. STEP 5: Stop the motor, lift the safety shield, and remove the 50-tooth spur gear from mounting post #1. Mount the 30tooth sprocket gear attached to the 50-tooth spur gear on mounting post #1. Adjust the gears so they engage. Secure them with the retainer collars. STEP 6: Hang the chain on the sprocket gear as shown below. 43 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 6 STEP 7: Insert the 20-tooth sprocket gear in the lower hanging part of the chain. Make sure the gear’s teeth are nested in the chain links. Let the chain and gear hang free. STEP 8: Lower the safety shield. STEP 9: Turn on the motor switch and observe the direction of rotation of both sprocket gears. Record both gears’ directions in your Journal. STEP 10: Turn off the motor and raise the safety shield. STEP 11: Clear mounting post #3 of all gears. Place two retainer collars on mounting post #3 and loosen post #3 so it can move easily. STEP 12: Place the 20-tooth sprocket gear on mounting post #3, making sure the dot faces out, and secure it with a retainer collar. 3 STEP 13:1Adjust and tighten mounting post #3 so tension is applied to the chain. See below. Mounting Post 44 Caution: Sprockets and chain drives can be dangerous! Keep hands, fingers, and clothing clear of moving gear drives! V. 3.0 STEP 14: Lower the safety shield. Paxton ActionLABS ® MECHANISMS DAY 6 STEP 15: Turn on the motor switch and rotate the 30tooth sprocket gear 10 full revolutions. Count and record the number of revolutions of the 20-tooth sprocket gear in your Journal. STEP 16: Turn off the motor. Replace the 20-tooth sprocket gear with the 10tooth sprocket gear. Use mounting post #4 for the 10-tooth sprocket gear. Lower the safety shield. Turn on the motor. Rotate the 30-tooth sprocket gear 10 full revolutions. Lower the safety shield. Count and record the number of revolutions of the 10tooth sprocket gear in your Journal. STEP 17: Turn off the motor. Disassemble all gear trains and replace all components in their proper locations. STEP 18: Answer the following questions in your Journal. 1) A device has mechanical advantage when it provides a change in what? 2) If a 30-tooth gear is used to drive a 10tooth gear, what is the ratio of the gears? 3) Define a sprocket gear and chain drive. STEP 19: Please clean up your module work area. Conclusion: You have seen the difference between the directional travel of a spur gear and a sprocket gear with a chain drive. We know that greater force and torque can be generated by a sprocket and chain drive system. When operating properly, the chain and sprockets produce reliable movement in many applications. V. 3.0 AFTER COMPLETING THIS ACTIVITY, RETURN 45 46 V. 3.0 Paxton ActionLABS ® MECHANISMS DAY 10 Day 10: Activity 1/Critical Writing – Persuasive Directions: While your partner is completing the test on the computer, you will complete the critical writing activity on a separate page supplied by the instructor. When you have both finished with this activity, trade places. You will now complete the test on the computer and your partner will complete the critical writing activity. Critical Writing: In this module you have learned about the Mighty Five simplest machines which include the inclined plane, the wedge, the screw, the lever, and the wheel. The lever is the simplest machine for increasing force. A pulley is a wheel that transmits power with a rope or cord, and more pulleys increase the mechanical advantage. Gears are used to change the direction of a force or movement. Gears are also used to change the speed of another rotating gear; a larger gear turns a smaller gear at a faster rate. Special gears called sprockets mesh together with chain drives. As you have learned, mechanisms are everywhere in our daily life. Scenario: You are a mountain bike trail guide at the Chipaway summer camp facilities. Your expertise in trail guiding and bike repair have allowed you to take groups on daily rides in the area surrounding the camp. Some of the boys and girls are good riders but others, especially those from the city, have not had as much experience riding bicycles with multiple gears. Before any group rides, you must train all participants to change gears at particular times to accommodate hilly areas. They will also need to know how to continue riding and prevent fatigue on the long trails. 47 Answer this question in 2 paragraphs. How V. 3.0would you prepare the mountain biking group for their ride? Include the comparison of low gears to high gears in relationship Paxton ActionLABS ® MECHANISMS DAY 10 Narrative/Persuasive Pre-Writing to Writing Process Follow this process when writing your narrative or persuasive assignments. Prewriting: Plan your writing by thinking about the topic and your purpose. Are you explaining or arguing a point of view? A narrative piece requires you to describe in order. Persuasive writing requires you to first state your point of view, then tell why you think it is correct and present facts to support your opinion. 1. Identifying – Choose the main elements you wish to write about. There should not be more than three. 2. Drafting – Jot your ideas down in rough form. 3. Revising – Change and improve the rough draft. Get rid of unnecessary parts. Add important material based on your writing goal – to explain or defend. 4. Proofreading – Correct any errors in spelling, punctuation, and clarity. Care should be taken to make the writing communicate clearly. 5. Publishing – After final editing, finish the writing and make it available for others to read. Edit your piece one more time before you rewrite (publish it) for the audience to read. AFTER COMPLETING THE CRITICAL WRITING AND THE POST TEST, FINISH YOUR DESIGN BRIEF 48 V. 3.0 Paxton ActionLABS ® MECHANISMS Spur Gear Identification Chart This chart has been provided for ease of identification of spur gears supplied with the mechanisms trainer. To identify a spur gear, lay the actual gear over the gear outline. All spur gears with the exception of the 20 tooth spur gear have the gear tooth count imprinted on the face of the gear as shown in the illustration V. to 3.0 the right. 49 50 V. 3.0 Paxton ActionLABS ® MECHANISMS Design Brief #1 Introduction For the past one thousand years, inventors have been attempting to develop machines that, once set in motion, would continue to move indefinitely. Any machine that could accomplish this feat would be called a perpetual motion machine. Although a perpetual motion machine is a great concept, the restrictions of the atmosphere on Earth (gravity, etc.) have, thus far, made the accomplishment of this task impossible. The National Mechanical Power Society is sponsoring a contest that requires participants to create a perpetual motion machine. Because of the mechanical skills that you and your partner have exhibited lately, your instructor has asked you to develop a model of a perpetual motion machine for entry into this contest. Your Task Create a perpetual motion machine! The device must be designed to stay in motion for as long as possible after being initially started. Some materials will be provided, but you are not limited by these alone. If you have ideas for additional materials, please discuss these with your instructor prior to using them. The contest rules state that a design must also label each type of simple machine used in your contest submission. Materials You and your partner may use the following materials or additional materials to solve this problem: Mechanisms module, computer, and associated materials and equipment; 1 - Set plastic gears; 1 - Pine board 3/4" x 7-1/4" x 15-7/8"; 2 - Plastic pulleys; 1 - Standard sheet poster board (instructor provided); 1 - Set miscellaneous bolts/screws Craft sticks Historical Research As your design begins the process of uncovering information that will ultimately lead to the solution of this design brief, you will need to explore early inventors like DaVinci, artists like Piranesi and of course, books, and CD-ROM’s. All mechanisms necessary to solve this design brief have been used by designers and engineers for centuries and should be easy to identify in science and technology books. Investigate the Internet, libraries, books, industry, as well as conducting interviews with scientists, inventors and engineers. Answer the following questions to get your team on the right track: DB1 1. What are some of the advantages and limitations in using levers, spur gears, pulleys, incline planes, sprockets, and screws to V. 3.0 design the mechanism? 2. How are simple machines used in real mechanisms? Paxton ActionLABS ® MECHANISMS Parameters After completing your design and building the prototype, your team should be prepared to demonstrate the machine and illustrate the way it could be used to demonstrate scientific concepts. You should also be prepared to demonstrate and explain how you developed different simple machines to accomplish the most dramatic and exciting mechanical performance. Include a labeled design with your completed project. After the final prototype test, a report for the machine must be developed that includes the following information: 1. A drawing of the completed machine; 2. A chart labeling each simple machine used in the design; 3. A successful mechanical device must be submitted with the report that meets the contest criteria: a. Powered only through the mechanical components included in the machine; b. Moves by itself after being initially set in motion; and, c. Uses various simple machines to operate. 4. The winner will be the design with the best examples of machine usage in order to create a machine that stays in motion for the longest period of time! Evaluation Research team solutions will be evaluated according to the following criteria: • Completed Prototype: Did the design team develop a creative project that met all of the design criteria? • Research Report: Did the design team prepare and submit a research report that meets all of the design parameters listed in the "Parameters‖ section? • Historical Research: Did the design team provide adequate responses to each of the questions outlined in the "Historical Research" section? • Time: Teams will receive points for every complete minute that the machine operates (moves), once it is set in motion. DB2 V. 3.0 Paxton ActionLABS ® MECHANISMS Design Brief #2 Introduction The National Rube Goldberg Invention Convention, sponsored by the American Council of Cool Science Toys, is next month and preparation must begin immediately. Although you and your partner have a great deal of expertise in the use of mechanisms and are gifted in the development of simple machines, that does not pay the bills! If you can develop the best science toy, you will make a great deal of money. The most successful design will be massproduced for an educational science toy for 5th graders. The convention requires that the toy be designed to spark the interest of fifth grade students and pique their interest in the physical sciences. The theme of the convention is "The Big Bang Theory" and the toy should be related to that concept. Your Task Create a device that is powered through the potential energy contained in a large marble. The device should be designed to begin movement as the marble is rolled and continues by itself through five distinct mechanical moves using various simple machines to finally pop a balloon. Some materials will be provided, but you are not limited by these alone. The contest rules state that the final design of the toy must include a label that identifies each type of simple machine used in your contest submission. Materials Mechanisms module, computer, and associated materials and equipment; 1 - Set plastic gears; 1 - Pine board 3/4" x 7-1/4" x 16"; 2 - Plastic pulleys; 1 - Standard sheet poster board (instructor provided); 1 - Set miscellaneous bolts/screws 1 - Marble Craft sticks Historical Research As your design begins the process of uncovering information that will ultimately lead to the solution of this design brief, you will need to explore early inventors like DaVinci, artists like Piranesi and of course, the drawings of Rube Goldberg, for whom the contest has been named. Examine books/CD-ROM’s written by David MaCauley. All mechanisms necessary to solve this design brief have been used by designers and engineers for centuries and should be easy to identify in science and technology books. Investigate the Internet, libraries, books, industry, as well as conducting interviews with scientists, inventors and engineers. Answer the following questions to get your team on the right track: 1. What are some of the advantages and limitations in using levers, spur gears, DB3 pulleys, incline planes, sprockets, and screws to V. 3.0 design the toy? 2. How are simple machines used in real mechanisms? Paxton ActionLABS ® MECHANISMS Parameters After completing your design and building the prototype, your team should be prepared to demonstrate the toy and illustrate the way it could be used to demonstrate scientific concepts. You should also be prepared to demonstrate and explain how you developed different simple machines to accomplish the most dramatic and exciting mechanical performance. Include a labeled design with your completed project. After the final prototype test, a report for the toy must be developed that includes the following information: 1. A drawing of the completed machine; 2. A chart labeling each simple machine used in the design; 3. A successful mechanical device must be submitted with the report that meets the contest criteria: a. Powered only through the potential/kinetic energy of a marble; b. Rolls by itself through five distinct mechanical moves; and, c. Uses various simple machines to finally pop a balloon. 4. The winner will be the design with the best examples of machine usage in order to create the most exciting changes of direction, speed, and drama resulting in the surprise balloon burst! Evaluation Research team solutions will be evaluated according to the following criteria: • Completed Prototype: Did the design team develop a creative project that met all of the design criteria? • Research Report: Did the design team prepare and submit a research report that meets all of the design parameters listed in the "Parameters‖ section? • Historical Research: Did the design team provide adequate responses to each of the questions outlined in the "Historical Research" section? ® V. 3.0 Copyright © 2006 Paxton/Patterson LLC - All Rights Reserved. DB4 All printed and electronic materials in Paxton ActionLABS Learning System are copyright protected including but limited to student guidebooks, graphics, tests, rubrics, videos, and instructor and student orientations.
