Stop the Train! Magnetic Brakes for a Maglev Train
AbstractDid you know that you can use magnets to build a train that floats above its tracks? In this project, you will also use magnets to make the train stop, preventing it from crashing into the end of the track. Will adding more magnets help the train stop sooner?
Measure how the number of magnet "brakes" changes the stopping distance for a train sliding down a hill.
Does a train without wheels sound crazy? How could a train possibly move along the tracks without wheels? Trains that hover just above the tracks are actually possible due to magnetic levitation, or maglev for short. These trains use powerful magnets to stay in the air. Magnets generate a magnetic field. This magnetic field can push or pull on other nearby magnets, or generate a force. Whether the magnets push or pull depends on the direction in which the magnetic poles are facing (see the Electricity, Magnetism, & Electromagnetism Tutorial to learn more).
In the case of a maglev train, the magnets are placed such that this magnetic force is used to push against the train's weight. Weight is the force that pulls an object down toward Earth because of gravity. If the magnetic force is strong enough, it can overcome the train's weight and push it up into the air! Figure 1 shows a diagram of the forces acting on the maglev train that you will build in this project.
Figure 1. A cross-sectional diagram of the maglev train. The train has two magnets on the bottom of it. These magnets push against two magnets that form the tracks. If the force from the magnets is strong enough, the train will float in the air above the tracks.
In this project, you will build a maglev train with an added challenge, making the train stop when it reaches the end of the track. You will tilt the track at an angle so the train can slide down a hill. You will put a magnet on the end of the train, and build a magnetic "stopper" to prevent the train from sliding off the end of the track without crashing. Will adding more magnets to the stopper help the train stop earlier? Try this project to find out!
Terms and Concepts
- Magnetic levitation
- Magnetic field
- Magnetic poles
- What is a magnet?
- What are some different kinds of magnets?
- What are magnetic poles?
- When does a magnet push (repel) or pull (attract) on another magnet?
- How does magnetic force change with distance? In other words, if you increase the distance between magnets, will they attract (or repel) each other more, or less?
- Science Buddies. (2015, March 14). Electricity, Magnetism, & Electromagnetism Tutorial. Retrieved March 4, 2016.
- Rader, A. (n.d.). Electricity & Magnetism: Magnets. Physics4kids.com. Retrieved March 4, 2016.
- Bosnor, K. (n.d.). How Maglev Trains Work. HowStuffWorks. Retrieved March 4, 2016.
For help creating graphs, try this website:
- National Center for Education Statistics, (n.d.). Create a Graph. Retrieved June 25, 2020.
Materials and Equipment
Note: the dimensions listed here match the materials shown in the Procedure. You can use parts with different dimensions, but will need to adjust some of the spacing for your train accordingly (see Figures 3 and 4 in procedure). The materials for this project are available online or at a hardware store.
- Magnetic tape, 1/2" wide, cut into two 24" pieces and two 5" pieces. Note: You will need monopolar magnetic tape for this project, which means that each side of the tape has only one polarity (N or S). Many magnetic tapes that you can buy online are bipolar or multipolar, which means that they consist of many strips of alternating N and S poles. If you buy a bipolar or multipolar tape, you can repolarize it to make it work in this project. Follow the instructions in step 7 of the FAQ section to repolarize the magnetic tape before you start with this project.
- 90° plastic angle pieces (2), 24" long and 3/4" wide. Available online or at a hardware store.
- Wood block, 5"×3/4"×1-1/2" (note: a piece of wood listed as 1"×2" at a hardware store has actual dimensions of 3/4"×1-1/2")
- Flat piece of wood or corrugated cardboard, at least 24" long and 3" wide
- Rectangular magnets (5), approximately 1"×3/4"×3/16". See Figure 8 in procedure for size relative to wood block.
- Clear tape
- Clear double-sided tape
- Double-sided foam tape
- Several books
- Lab notebook
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Building Your Train
This video and the following written instructions will show you how to assemble your train. Attention to detail and patience are needed for this project. After building, you will need to make adjustments to get it working perfectly. The train floats above the tracks well once everything is lined up carefully. See the FAQ if you have trouble getting your train to work.
- Before you start building your train, check to make sure you have the right magnetic tape. If you have monopolar magnetic tape, the strips of tape should repel each other. You can go ahead and use the monopolar tape as is. If the strips of your magnetic tape attract each other, the tape might be bipolar or multipolar. In that case, you will have to repolarize your tape first. Follow the instructions in step 7 of the FAQ section for this project to repolarize your magnetic tape. Once you are done, your magnetic strips should repel each other.
- Peel the paper backing off the two short magnetic strips and attach them to one side of the wooden block, as shown in Figure 2. The edges of the strips should line up with the edge of the block. This block will be your train car. Note: if the magnetic strips are not sticky enough to stick to the wood on their own, use clear double-sided tape.
Figure 2. Magnetic strips attached to the wooden block.
- Cut a piece of wood or cardboard at least 24" long by 3" wide. This will serve as the base for your train track.
- Using one of the long plastic angle pieces as a straightedge, draw five lines lengthwise on your base as shown in Figure 3.
- Draw a center line down the middle of the base.
- Draw one line 5 mm to each side of the centerline.
- Draw one line 20 mm to each side of the centerline.
Figure 3. Dimensions for lines you will draw on your base.
- Attach the long magnetic strips and plastic angle pieces to your base, as shown in Figures 4 and 5. Pay close attention to the spacing, it is important for getting your train to work properly.
- Peel the paper backing off the long magnetic strips. Carefully place them on the base so their inside edges line up with the lines 5 mm from your centerline, so the strips are 10 mm apart. Note: if the magnetic strips are not sticky enough to stick to the base on their own, use clear double-sided tape. Make sure you press down firmly so they stick in place.
- Use double-sided tape to attach the plastic angle pieces to the base so their inside edges line up with the lines 20 mm from your centerline, so they are 40 mm apart.
Two plastic angle pieces are placed parallel to each other on a cardboard sheet with a 40 millimeter gap between them. Two magnetic strips are also placed in parallel between the plastic pieces and should have a gap of 10 millimeters.
Figure 4. Cross-sectional view of the spacing for the magnet strips and plastic angle pieces.
Figure 5. Picture of a completed track.
- Place your train on the track with the magnetic strips facing down. It should hover parallel to the tracks as shown in Figure 6, and you should be able to slide it back and forth without getting stuck. If your train does not hover as shown in Figure 6, see the FAQ for troubleshooting information.
Figure 6. Train hovering parallel to the tracks.
- Build a magnetic "stopper" on one end of your track, as shown in Figure 7.
- Cut a small rectangular piece of cardboard, about 7 cm by 5 cm.
- Use tape to attach the piece of cardboard at a right angle to one end of your track.
- Use double-sided foam tape to attach a rectangular magnet to the cardboard. Make sure the magnet is at the same height as the wooden block of the train when it is floating above the track, and is centered between the two plastic pieces.
Figure 7. A magnetic stopper at one end of the track.
- Use double-sided foam tape to attach one rectangular magnet to each end of your train, as shown in Figure 8. The magnets are heavy, so you need one on each side to keep the train balanced.
- Important: Test the magnets to see which side repels the magnet that is attached to the stopper. Make sure this side of the magnet is facing outward when you tape it to the train. Otherwise your braking system will not work, and your train will be attracted to the stopper instead of pushed away from it!
Figure 8. Magnets attached to both ends of the train.
- Elevate one end of your train track using several books, as shown in Figure 9. The exact height of one end of the track does not matter for this experiment (see the Variations section for an idea about how to measure the effect of this height).
Figure 9. Maglev train track placed on an incline using some textbooks.
Collecting Your Data
- Practice using your maglev train's stopper. Gently place the train about halfway up the track and let it slide down toward the stopper. The train should come to a stop before it touches the stopper. There are a couple problems you could run into, so do not worry if you need to adjust a few things before your stopper works nicely:
- If your train jumps off the tracks, it might be going too fast. Try starting it farther down the ramp, or decreasing the angle of the ramp.
- If your train gets stuck before it gets close to the stopper, there might be too much friction between the train and the plastic angle pieces. Try moving the plastic pieces apart slightly, or increasing the angle of the track so the train slides faster.
- The magnets on your stopper and the train might not be well-aligned. This can also cause the train to jump off the tracks, and the sides of the magnets to snap together instead of staying spaced apart. If necessary, adjust the height of the magnet on your stopper.
- Once you have your track adjusted so the stopper is working well, leave it in place. Use a pen or pencil to mark the approximate starting place on the track that works well.
- Now that you have seen how the stopper works, what do you think will happen when you add more magnets to the stopper?
- Create a data table, like Table 1, in your lab notebook.
|Distance Between Magnets|
|Number of Magnets||Trial 1||Trial 2||Trial 3||Average|
- Let the train slide down the track and come to a stop.
- Measure the distance between the stopper magnet and the magnet on the front of the train, as shown in Figure 10, and record it in your lab notebook. This counts as one trial.
Figure 10. Measure the distance between the two magnets, shown with the red arrow.
- Repeat steps 4–5 two more times, for a total of three trials.
- Now, add a second magnet to your stopper, as shown in Figure 11. It should snap into place directly on top of the first magnet (if the magnets are pushing away from each other, flip the new magnet around).
Figure 11. Second magnet added to the stopper.
- Repeat steps 4–6 with two stopping magnets stacked on top of each other. Make sure you record all of your results in your data table.
- Add a third magnet to the stopper and repeat steps 4–6.
- Add a fourth magnet to the stopper and repeat steps 4–6.
- For each number of magnets, calculate an average for your three trials and enter it in your data table. For example, say that for one magnet you measured distances of 18, 22, and 20 mm. The average is (18+22+20)÷3=20. Ask an adult if you need help calculating an average.
- Create a graph with the distance between magnets on the vertical axis and the number of magnets on the horizontal axis. See the Create a Graph website if you need help creating a graph.
- How does the distance between magnets change as you add more magnets to the stopper? Is this what you expected based on your background reading about magnets?
For troubleshooting tips, please read our FAQ: Stop the Train! Magnetic Brakes for a Maglev Train.
Ask an Expert
- In this project, you used a stack of books to elevate one side of the track. Can you measure what happens when you create a steeper ramp? For this test, you would keep the number of magnets in your stopper constant and change the angle of your ramp. You can choose to measure the angle of the ramp with a protractor, or use the height at the far end of the track as an indicator of the "steepness" of the track.
- In this project, you started the train at the same position on the track each time. Does changing the train's starting position on the ramp affect your results? Keep the number of magnets and the track angle constant, but change the train's starting position as your independent variable. What happens?
- For a more advanced project, you can use a camera to film the train as it slides down the ramp. Take a close-up video as the train gets close to the stopper. Does the train get close to the stopper, then bounce back? Or does it gradually coast to a stop? Can you graph the distance to the stopper over time? Can you measure the closest distance between the two magnets and their final resting distance by analyzing the video? Tracker is a free program for analyzing video that makes it easy to measure distances.
Frequently Asked Questions (FAQ)
Figure 12. The plastic angle pieces on this track are too far apart, allowing the wooden block to tip over.
- First, make sure you have the right magnetic tape. The magnetic tape for this science project needs to be monopolar, which means that each side of the magnetic tape has only one polarity (N or S). Many magnetic tapes that you can buy online are bipolar or multipolar. This means they consist of many magnetic strips that alternate in polarity, as shown in Figure 13. These magnetic tapes will attract each other. If you happen to use a bipolar or multipolar magnetic tape, you can repolarize it. Follow the instructions in step 7 (below) to do that.
Figure 13. Magnetic tape can be multipolar (left), bipolar (middle), or monopolar (right).
- The magnetic strips on your track might be too close together, like in Figure 14. As shown in Figure 4 of the procedure, the strips should be 10 mm apart. If they are too close together, then they will not be aligned with the magnetic strips on the train car, and this can result in the car being attracted to the tracks instead of repelled. If this happens, move the magnetic strips on your track farther apart.
Figure 14. The magnetic strips on this track are too close together, resulting in the train being attracted to the track instead of repelled.
- Your plastic angle pieces might be too far apart, like in Figure 15. This gives the train car too much room to shift side to side, and it can be pulled down to the tracks instead of repelled. As shown in Figure 4 of the procedure, the inside edges of the plastic angle pieces should be 40 mm apart. This gives the wooden block enough space to slide back and forth without getting stuck, but prevents it from moving side-to-side. If this happens, move the plastic angle pieces on your track closer together.
Figure 15. The plastic angle pieces on this track are too far apart, allowing the train car to shift sideways and be attracted to the track instead of repelled.
- The final and least likely possibility is that the polarization (which way the north and south poles face) of one set of your magnetic strips has been reversed, meaning the non-adhesive sides of the strips are attracted to each other instead of repelled. If the magnetic strips are touching each other and their edges are aligned like in Figure 16, you will need to repolarize two of your strips as described in the following steps. Only do this after you have tried steps 1 and 2 to make sure your spacing is correct.
Figure 16. These magnetic strips are attracted to each other instead of repelled, so the train sits flat on the tracks with the strips aligned.
- You can use a compass to check the polarity of the magnetic strips. Hold the compass up to one of the magnetic strips on your train car as shown in Figure 17. Pay close attention to whether the red tip of the compass needle points towards or away from the magnetic strip.
Figure 17. The red tip of the compass needle points towards the magnetic strip in this image (your result may be the opposite). Ignore the N/S/E/W markings on the compass, you only need to look at the needle.
- Do the same thing for one of the magnetic strips on your train track.
- If your results are the same for both strips (the red needle tip points towards both of them, or points away from both of them), then your strips are polarized correctly and should repel each other. Go back to steps 1 and 2 to check the alignment of your track.
- If your results are different for both strips (the red needle tip points towards one of the strips, but away from the other one), then you need to re-polarize one set of your strips. Proceed to step 7.
You can use a small neodymium magnet to re-polarize the magnetic strips by rubbing it against them, as shown in Figure 18. To do this:
- Check again whether the magnetic strips on your train car attract or repel the red tip of the compass needle.
- Find the end of the neodymium magnet that attracts the same end of the compass needle as the magnetic strip on the train car.
- Slowly rub this end of the magnet along the entire magnetic strip, going back and forth several times to cover its entire width (the neodymium magnet is narrower than the strip).
- Do this for both magnetic strips on your train car.
- Place your train car on the track and see if it hovers instead of touching the track. If not, you may need to keep rubbing the same end of the neodymium magnet along the car's strips to increase their strength (do not re-check the strips with the compass each time, or you will continue to reverse their polarization).
- If you still cannot get your maglev train to work properly, contact us at email@example.com for support.
Figure 18. Rub the neodymium magnet along the magnetic strip to repolarize it.
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