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The Skinners’ School
Royal Tunbridge Wells Kent TN4 9PG
www.skinners‐school.co.uk
STEM MAGLEV PROJECT
A Transrapid train in China
A Report for The Skinners’ School SSAT STEM Pathfinder Project 2008‐2009
by David Mahon
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Introduction to maglev principles
Follow the link for information on maglev trains and wind turbines: maglev\about maglev.docx
The Maglev club
A STEM club was set up to produce a model that can be used to explain maglev principles. Real
scale models of maglev railways cost many hundreds of thousands of pounds due to the
complexity of the electronics and electromagnets so our model had to be simple. The project
also had to be reproducible by other schools. At first we did not know what the best approach
was so we followed various threads hoping one would lead to a working model. As we have an
electronics department, one group aimed to make a device that could make a magnet hover,
with an electromagnet and an electronic control system. Others investigated ambitious patterns
of permanent magnets.
The final model was of a train track. The track and train had rows of permanent magnets. The
levitation was achieved with magnetic repulsion. The train was constrained so it did not derail.
Although this meant there was a physical contact, we found out that a pure maglev system with
permanent magnets only was impossible. The propulsion was achieved with a fan. A 6V cell or
photovoltaic cells linked to a motor and propeller.
MAGLEV TRAIN PROJECT TIMELINE – the following timeline details the
steps, successes and problems when attempting such an ambitious project. Pupils from Years 11‐13 were involved in all phases of the project.
Summary Most of the investigative work was carried out after school on Mondays
At first, many avenues were investigated
Later, there were 2 threads of investigation i.e. a guided track and an electronic control system that would suspend a magnet below the electromagnet
The guided track was successfully made
The electronic control system was successfully made but the project as a whole was not made to work in the time available
Red text indicates when materials were bought
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Lunch time meeting 21 Oct 08:
Maglev floated. Interested group consisted of year 11 to year 13 students.
Agreed times for Maglev Club: Monday after school for Years 12 & 13, Tuesday or Thursday lunchtime for Year 11.
Magnadur magnets bought from catalogue, Gaffer tape from B&Q
Monday after school 3 Nov 08:
Aim: to produce an unguided fully levitating railway.
Lots of avenues considered i.e. electronic control system, guided railway, diamagnetism, superconductors
Played around with magnadurs, used rulers and gaffer tape. Tried to make model of maglev with permanent magnets only. No success. Let down by lack of useful materials. Precision is everything here.
Tuesday lunchtime 3 Nov 08
Aim: to produce a guided maglev railway i.e. using magnetic repulsion to keep the train up but with physical guides to keep the magnets aligned
Time spent playing around with magnets. Need a good idea for the guide.
Various cuts of MDF, screws and brackets bought from B&Q Monday afterschool 10 Nov 08
Decided on three avenues of investigation hoping at least one would work - Group 1 (Year 13): using vertical plank to produce frictionless permanent magnet
maglev - Group 2 (Year 12): making an electronic system powering an electromagnet - Group 3 (Year 12): investigating another permanent maglev with vertical sides
A Year 12 pupil (group 3) with track before magnets were placed at bottom and sides. Electronic components ordered from catalogue
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Thursday lunchtime 13 Nov 08
Year 11 found a Perspex guide in the physics prep room
Magnets stuck onto base of Perspex. Problem: they all keep lifting up and moving around.
Monday afterschool 17 Nov 08
DM found a good circuit on the internet. The electronics group getting stuck in to wiring in circuits into breadboards, testing as they go
Other two groups having trouble with stability, no matter what they do
Year 13 pupils making permanent magnet maglev based on a vertical plank with magnets on top and sides
Thursday lunchtime 20 Nov 08
Year 11 group progressing with clear Perspex maglev.
To stop magnets moving around and to make it easy to move magnets to another model a great idea was to tape them to a wooden ruler (same thickness)
Quickly made a working model
Monday afterschool 24 Nov 08
Permanent model made and presented to all groups
It did not work even though it had neat, well positioned stabilizers on the sides.
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Section of track the ‘train’
Unstable Year 13 pupils investigating instability
Monday afterschool 1 Dec 08
Demonstrated why a permanent magnet only maglev is impossible. According to Earnshaw’s theorem there will always be instability.
The group then switched emphasis to guided tracks. It was decided that while the Perspex track looked good, a central guide was the way forward. This was because the Perspex was a one off and not having sides would be a neater solution. The Perspex one also jammed up occasionally.
Electronics group continued manufacturing circuits and investigate making an electromagnet from a transformer coil.
Monday afterschool 8 Dec 08
Electronics group developed the duty cycle circuit with success, observing the correct waveforms on the oscilloscope.
Recycled electromagnet (from obsolete physics equipment) up and running. Can tolerate 5Amps
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Perspex guided model made by Year 11. Note the floating train
Monday afterschool 15 Dec 08
Year 13 testing a track with a guide made of plastic metre rules. These could be bent to make a corner. An oval track would allow continuous travel.
Year 13 made a simple train with ‘keels’ made of MDF. These wobbled too much – another solution needed
Simple MDF train. Vertical guides fit into space between two plastic metre rules to stop it derailing
Year 13 manufactured and successfully built a hall circuit (detecting magnetic field strength)
Pupils scavenge fans from an old 486 computer for a potential propulsion system
Investigation into what combination of electromagnet + battery works the best for a linear motor
Monday1 afterschool Jan 09
Test track completed over the Christmas break. Half had plastic rulers as a guide, the other half had two wooden planks with a gap. The latter looked better and was easier
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to make well. The plastic ruler method would be vital if we had time to make a curved track.
Simple train made over the break. It had a keel to fit into the guide, covered with Teflon at the ends to reduce friction.
Upside down train showing keel The train levitating above the track.
Note the two styles of track on view
The train glided nicely. It was decided to build a 2 metre long track.
The keel only touched the guide at the ends – the group got thinking of a way to have two thin keels at each end. This could also allow curved travel.
The linear motor would be too difficult so this idea was dropped.
Thursday lunchtime Jan 09
Some year 11s investigated propulsion. The fan from the 486 was not powerful enough. The motor was connected to a propeller rescued from an obsolete piece of equipment. The fan worked but was not enough to drive the train along. Must reduce friction!
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A year 11 pupil investigating the fan propulsion system
Thursday lunchtime Jan 09
Further investigation of the fan mounted on the train. A mains supply made it go really fast but burned the motor out! We need a portable power supply anyway.
Year 11s burning out motors to achieve the maglev speed record! More magnadur magnets bought from catalogue Monday afterschool Feb 09
2 metre track over the weekend.
Using available materials, a new keel system was devised using a thick bolt with Teflon wrapped around. Time was spent tweaking it so it could run smoothly.
The electronics group managed to complete the other systems. After some trouble shooting the whole electronic control system worked! I.e. the power of the magnet
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was switched on/off a thousand times a second in response to a nearby magnet. A major achievement!
The whole electronic system. This was shown to work using an oscilloscope
Sixth formers tweaking the keels on the new train. Note the new track in the background, the old train/track in the foreground.
Monday afterschool Feb 09
Large 6V cell placed on train made it ground out so the keels were trimmed.
The motor was taped to the top of the cell
The propeller was better at pulling than pushing
It was decided that mounting the motor on a tower would be an improvement. This was made with some 18mm MDF and metal brackets.
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To reduce friction, sellotape was applied to the guide rails, wiped with WD‐40
Using the large 6V cell, decent accelerations were produced
The electronics team put the whole circuit onto a single large breadboard. They continued this in their study periods.
The final design for the train. The tower stops the airflow from interfering with cells or PVs mounted on the top of the train
Monday afterschool March 09
The track was not working very well. There was too much friction. The session was spent troubleshooting to find the source of the mystery friction.
The friction was from a combination of including a raised grain on the wooden planks, a knot that popped out slightly, crinkled sellotape, flared Teflon, grounding out and wobble of the keels caused by too much ‘abuse’. The plank of wood on which the rails were fixed to was very warped.
Completed electronic circuitry. Control system tested successfully.
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Year 12 pupils testing the system with magnets and an oscilloscope.
Although the control system works, the electromagnet (on retort stand) wasn’t working properly, probably due to the high switching speed.
Contiboard and gaffer tape bought from B&Q
Monday afterschool March 09
A new and improved track was made. The rails were sanded after removing knots and screwed to the Contiboard. The sellotape was reapplied carefully. The main body of the train was recut.
The train now accelerated well! A real result.
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May 09
On a sunny afternoon, Photo Voltaic cells (PVs) were investigated for a power source. 3 flexible PVs connected in parallel made the train accelerate nicely if the PVs were angled towards the sun.
PV setup
A solar powered maglev train!
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For the full step by step guide for the maglev model…..
How to build a maglev train model
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How to build a maglev train model
Contents
Page 15 Overview 16 Making the track 19 Making the train 21 Trouble shooting 22 Propulsion systems 22 Battery powered fan 23 Solar powered fan 24 Costings
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Overview
Proper levitation is only achieved with an arrangement of electromagnets driven by
electronic control systems (although levitation can be achieved in the lab with
superconductors or diamagnetic materials). Although it would seem that a complex
arrangement of permanent magnets can produce levitation, this is in fact impossible
(Google ‘Earnshaw’s Theorem’). A compromise is therefore used i.e. rows of permanent
magnets to provide vertical repulsion and a guide rail to stop the ‘train’ from ‘derailing’
These notes will show you how to construct the track, train, and propulsion system. The
track will be straight as a curved track would be much harder to manufacture.
The magnets will be bought from a science equipment supplier but much of the other
materials can be sourced from the DT department in your school, recycled from obsolete
equipment or bought cheaply from a hardware retailer.
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Making the Track
Materials for a 2 metre track:
A plank to mount the rails on. I used Contiboard. This does not have a grain so is less likely to
warp compared to wood. It is a good idea to check it is not warped before you buy it though.
2 smaller wooden planks. 18x44mm were used for this project as this was a convenient size at
B&Q. The width is not critical (wider would have been better) but they need a decent
thickness or else you will have problems guiding the train down the track. Make sure they are
straight when you buy them!
4 old metre rules to mount the magnets on
Large roll of Gaffer tape
80 x 50mm magnadur magnets. These are about 50p each from a science catalogue.
Screws. These will depend on the materials but I used 4 x 30mm to secure the 2 planks and
4x19mm to secure the metre rules
Saw, cordless drill/screwdriver
Screws wood on top, Conti underneath The materials required
(magnet rails already assembled)
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Method
1. Sand the inside faces of the 2 wooden planks. Wipe the dust off. Carefully cover with a continuous piece of sellotape, making sure all of the air bubbles are ironed out. This will reduce the friction.
2. Decide on a gap size for the guide. I used 13mm. The plank will be 6.5mm from the centre. Mark out a straight line for the plank – this is important else it will not end up being straight.
3. Put marks every 20cm. Drill a pilot hole then countersink so you will lose the screw head.
4. Screw the plank down, making sure the edge of the wood is exactly on the line.
5. If the train is ready, it may be a convenient time to coat the sellotape with WD‐40, although this can be done later.
6. Get some spacers too maintain a constant plank separation. 13mm tokens from a child’s game were used here! Anything will do as long as the gap is constant.
7. Push the second plank onto the spacers and screw down.
Conti board
Sellotape
Countersunk pilot hole
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Coating inside rail with WD‐40 planks nicely screwed down Mounting the magnets. The magnadurs have poles on their flat faces. These could be glued onto the wood but it would then be difficult to recover then e.g. if the wood warped or if they were needed for a motor practical. It is a good idea therefore to tape them to metre rules so the complete magnetic rails could be removed easily. This saved lots of time.
8. Gaffer tape is strong and conveniently 50mm wide. Fix each magnet with 10cm of tape, then wrap another 10cm across each magnet join followed by a final 1m length to make it look neat. To save time on mistakes, check each magnet is the same way around as the others. Note: if this is stored in the sun it will start to wrinkle!
9. Carefully drill countersunk pilot holes in the metre rules, making sure they will not coincide with the screws below.
10. Screw down the magnet strips. The magnets should be on the outside. It is important to leave a gap of 2‐3 mm between the edge of the rule and the gap else the tape will foul the keels of the train.
The railway is now complete. Now for the train!
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Making the Train
Materials:
MDF: 112x300x6m. To save buying a big sheet it may be worth seeing what off cuts are
available in the DT department.
Magnadur magnets
Gaffer tape
60 cm of wooden rule
2 keels (see text) e.g. Teflon, bolt, nut washer.
1. Cut the main body. A good length is 30cm i.e. 6 magnets long. The magnets will be taped up to
the edge of the board so the width has to be such that the train magnets lie exactly above the track magnets. In the one below the dimensions were 112x300x6mm
2. Fix magnets to wooden rules e.g. 30cm lengths cut from an old metre rule. Tape them on as before. The neat underside will be the same polarity as the top of the track for repulsion.
Magnets fitted. Note the ‘keel’. The bolt, giving the keel rigidity
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3. Fix keels. This will stop the train from ‘derailing’ i.e. will keep the magnets perfectly aligned with the track. The keel could be continuous but one thin one each end is better. The form of these really depends on the materials available and will require some experimentation. Shiny plastic coated with WD‐40 may be sufficient.
The one above comprised of Teflon sheet wrapped around a bolt. Drill a hole through the centreline of the main body and fix the top with a washer and nut. The hole needs to be exactly on the centreline or the magnets will not be aligned properly. That will probably be enough to keep it rigid if it fits the hole snugly. Then fix the Teflon. Curl a rectangle around the bolt and pinch the ends. Mark where a bolt is needed, nearer the edge is better. Force pointed scissors etc through mark to make hole then insert a small bolt, securing with a small nut. Push onto the big bolt and tighten the small nut so the Teflon does not fall off.
The completed train
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Trouble shooting The train should now levitate nicely above the track. If built well it should not lurch to one side. When it is going well it will glide nicely with only a small push. Here are some tips.
Apply WD‐40 to keels and sides of the guide rails on the track.
Make sure the grain has not come out on the guide rails. Sand down if necessary.
Knots may rise up above the surface of the guide rails. Remove or sand down.
The sellotape may have buckled up over time, possibly due to the above. Reapply if necessary.
The magnets may not be aligned, possibly due to off centre drill holes in the main body. Get them right first time or remake the main body!
The keel may be too long. This will cause it to ground out, especially when the load increases e.g. from a battery. Trim carefully in increments until it is OK.
The keel may wobble, especially if the drill hole was too big. A washer/bolt below may be the answer.
The small bolts holding the Teflon to the bolt may be grinding out on the track. If so cut the top off the Teflon to move them up.
The gap in the guide may be variable. Careful construction will prevent this!
The keel may be too wide (will get stuck) or too narrow (will flap about). It should have a tiny amount of play at all times, ideally around 1mm. To achieve this packing out or using a smaller diameter bolt may be the solution.
You will hopefully now have a train that can glide nicely when given a small push.
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The Propulsion System A really neat propulsion system would involve some kind of linear motor, like on real maglev systems. A d.c. linear motor would require some electronic expertise as Hall devices and op amps would be required along with a push pull amplifier and electromagnet. This would be time consuming, even if you know what to do. The method below is far simpler.
Battery Powered Fan
Materials
Propeller
A 3V or 6V d.c. motor. Most physics departments will have these, otherwise order from a
science or electronic supplier (e.g. Rapid)
Wire, crocodile clips
Angle brackets, screws
Gaffer tape
Large 6V cell (battery)
Soldering iron
1. Strip the ends of 25cm of insulated wire. Solder one end to the motor, fix the other end to a
crocodile clip.
2. A simple and inexpensive plastic propeller can be bought from a model shop. Push onto the motor. If you have a selection of motors, now is a good time to test them to see which is best.
3. Fix to main body. At first it can simply
be taped to the 6V cell but it helps if the motor is mounted on a tower when different arrangements are being considered. This can be improvised from any old piece of wood e.g. 120x30x18mm MDF. It is best fixed with some brackets and screws. Play around with the battery and tower to get the train balanced.
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Solar Powered Fan
This is a nice solution as it makes students think about sustainable ways of creating electricity and also ways minimising power loses (due to friction). PVs do not produce much current so connect a few in parallel and try it on a sunny summer’s day.
Materials
Track and train as before minus battery
2, 3 or 4 PVs
The PVs used here are double flexible ones from www.pluggingintothesun.org.uk @ £22 each Note: there are loads of other ideas for schools. The solar model cars are really good. Method
Connect 3 PVs in parallel (Google ‘parallel circuit’ if you are not sure)
Put the 3 PVs on the train so they are angled into the sun
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Costings
Track: £ Contiboard B&Q 3.90 Magnets for 2m track: Philip Harris 80x50p 40.00 Screws B&Q 4.44 2 guide planks B&Q 2x1.60 3.20 Gaffer tape B&Q 3.98 Train 6mm MDF sheet B&Q 6.48 6V “lantern battery” rapid 1.85 3V high power motor rapid 0.54 Propeller model shop 1.25 Magnets for 30 cm train: Philip Harris 12x0.5 6.00 Metal brackets 3.49 Screws B&Q 1.25 3flexible PVs The Rapid/Philip Harris items may incur p&p charges
For short videos of the working systems follow these links:
maglev1.AVI
maglev2.AVI
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Evaluation
The maglev track is a very good topic for a STEM club for the following reasons:
Magnetic levitation is an interesting subject which grabs pupils attention
The basic design is quite simple making appropriate for GCSE students or above.
The limiting factor is the practical skills of the students rather than academic knowledge.
The main activities involve drilling, screwing, measuring and sticking.
With the materials and plans available, a group will be able to rapidly build a model with
minimal equipment
There are many ways to make improvements
A large model is produced, appropriate for open day etc
The costs are relatively low. The bulk of the money is for magnets which a physics
department could use afterwards if the no longer needed.
Notes:
1. A good group size is about 6 students.
2. The model could be made in 10 hours, depending on how focused and accurate the
students were. With a willing group, a whole school year could be used improving on the
design.
3. It does require some teacher input to keep it going as some students are keen to get on
and make a lot of errors, especially in screwing the pieces together. Leaving it all to the
students will not work. As they cannot operate tools well, they will not progress very well
and may lose interest. With some teacher guidance they will have the confidence to
design and manufacture components accurately.
4. Breaking the team up into proper roles is a good idea so club members have ownership
over parts of the model.
5. Investigating other avenues at the same time by another group is good to create a buzz
of ideas. See next section
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Other avenues for a maglev club
Adaptations to track idea
Design better guides to reduce friction.
Design and make a lightweight body for the train to make it more train like.
Curved track. Could be done with plastic rulers held in place by brackets. Firstly, different
arcs of curvature can be investigated to see what works. Minimising friction will be
important, so will redesigning the keels.
Linear motor to propel train along track with magnets. Would be fiddly to make but
would be really neat if it worked. Some electronic would be necessary. There are some
ideas from the following link: simple linear motor.doc
Diamagnetism
Some materials are diamagnetic i.e. will always repel magnets. Diamagnetism can be
used to capture a permanent magnet in a field to levitate it. The following link is to a
document found on the internet: diamagnetic levitation.docx
Electromagnet levitation
Real maglev systems use electromagnets with a control system. They change magnetic
strength with proximity to a magnet to maintain a separation.
A sixth form group of electronic students tried to make a ‘simple’ levitator. The control
system worked but there was a problem with the transistor, possibly because it was
switching the large electromagnet on and off at 1000Hz. They ran out of time but it
would be an exceptional demonstration piece if it worked. Should only be undertaken if
op‐amps and 555 timers are well understood.
For a detailed step by step guide on how to make an electromagnetic levitator follow this
link: electromagnet levitation.docx
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