- 6 hours
Parental supervision required
Try out these kits, they're cracking!
As seen in the TV show. Cedric Lynch's concept made the DC motor even more powerful. This kit shows you how it all works.
Let’s get technical: The electrical power is sent to a coil via the brushes; the coil becomes magnetic and moves around to be nearer the magnet. As it does this, the brushes move on to the next contact and energise the next coil. Genius.Instructions below
If the motor stops (or stalls) it could short-circuit the battery. Make sure you turn off the power or the wires will get hot hot hot!Download kit Instructions and extra parts to make your kit look great! PrintPrint these instructions and get making!
First, let’s get to know some of the main parts.
The part of an electric motor that spins, including the wire coils and contacts.
Where two pieces of metal touch and transfer power.
A series of contacts arranged on the armature to form a series of switches
A pair of contacts fixed to the stationary part of the motor that form a circuit with the commutator.
The fixed part of the motor that holds the magnets in position.
1 Cut out armature disk and glue ink-side-down in the centre of the CD protector. Use PVA glue. Leave to dry.
2 Drill small holes in disk’s outer edge where indicated. Don’t press hard. Let the drill do the work or the plastic might crack.
3 Hot-glue the plastic side of the CD so that when squished it covers the red and blue rings. Press a piece of tin foil onto it using scrap pieces of wood so you don't burn yourself (heat travels through aluminium foil really fast). Leave to cool.
4 Peel paper pattern off CD. Glue ink-side-up this time, over the foil. Use PVA glue so you can remove it later.
5 Glue dry? Good. Now using a craft knife cut around the blue and red rings. Cut through the foil too. Then cut the vertical lines.
6 Peel the paper off again. Scrape away any leftover glue.
7 Go back over the cuts to make sure they’ve gone through the foil. You're trying to electrically isolate each piece of foil. If you’ve got a multimeter, use it to check for continuity between each pair. You might need to cut each one again and remove a thin piece of foil between each contact. This is painstaking, but get it wrong and the motor won't work.
8 Drill the smallest hole you can on the edge of each contact, and in the plastic beside it. Use the paper pattern as a guide.
9 Wind a screw into each of the outer holes, all poking through to point towards the commutator (the foil contacts you've just made). Hot-glue each one in place from the back.
10 Take about 2 metres of copper wire, leave 10cm on one end and wind the rest around one of the screws – all 16 need to be wound the same way – in the same direction too. Leave 20cm on the end of the wire. Hot-glue the top to hold it all in place.
11 This bit is really important! Fold a piece of sandpaper in half and scrape the insulation off the end of each wire – this bit has to be done well (test with a multimeter if you can). Check continuity between the two ends, and try moving the probes up and down the wire to make sure all the insulation has been removed.
12 Take the shorter piece of wire and loop it through the hole in the nearest outer ring. Loop it around several times between the two holes to sew it onto the foil. Hot-glue the back to hold it in place.
13 Take the second (longer) piece of wire, and run it down the back of the disk to the holes in the blue ring. Loop it through as before. Trim off excess.
14 Repeat for all the other screw posts.
15 Drill a hole dead-centre of the bottle top and CD cake spindle.
16 Cut down the spindle so the base is smaller and hot-glue it to the CD. Make sure the base is the opposite side to the foil commutator.
17 Hot-glue the bottle cap in place. Push a straight kebab skewer through the centre to form the axle.
18 Test-spin the whole thing in your fingers. It should spin with very little wobble!
19 If you have a multimeter do a final circuitry test. There should be a continuous circuit between each segment on the inner ring and its neighbour on the outer ring. Touch the probes lightly against pairs of foil to test this. If any of them aren't working, investigate and fix. Try bending the wire down with the probe so it makes a better contact.
21 Cut out the leftover printed parts and stick them onto some stiff balsa sheets.
22 Cut the parts to the shapes shown. Cut away the grey areas of the paper but not the wood.
23 Drill holes in parts 2 and 4. These will be shored up with a plastic bush later.
24 Test-fit the base (1) and two walls (2, 4). Face both printed sides to the front of the engine.
25 Assemble the armature shaft in this order: part 2, 9, 8, armature, 8, 9, 4. If everything lines up nicely, dismantle it all and hot-glue the two bushes (9) into place.
26 Reassemble as before, but glue the base together this time. Try to get the walls as upright as you can. Make sure armature spins freely.
27 Add the magnets. Put a magnet either side of the wall. This way you can move them about later to fine-tune.
28 Glue 2 x part 5 together back-to-back. Do the same with 2 x part 6. Glue the two brush supports back-to-back on the base as shown.
30 Straighten a paper clip. Using pliers put a tiny loop in one end, and a bigger loop in the other. Solder a normal electrical wire onto the big loop.
31 Glue the big loop to part 7 as shown.
32 Test-fit the brush into position on the lower brush support. Use pliers to bend/twist the paper clip until it neatly touches the contact at the bottom of the wheel.
33 Hold it in place with blu-tac. Adjust it so that it gently touches the wheel. Test spin the wheel – the contacts should stay touching without snagging on the wires or causing too much friction. The armature rotates anti-clockwise only.
34 Repeat for the other brush. The second brush sits on the higher support, and touches the bottom contact of the inner ring.
35 Grab that multimeter! Test continuity between the two wires coming from the brushes as you spin the wheel. It should be connected most of the time the wheel spins.
36 Solder the switch to one of the brush wires.
37 Solder the other terminal to another wire. Don't make the final connection yet. We need to check which way round the battery should go. This particular design of motor only works well in one direction.
Adjust the magnets to sit on the dotted line on the walls.
Test-spin the armature and make sure the brushes are touching gently – not snagging.
Attach a 9V battery to a battery holder. Check the switch is off and twist the wires together with the ones from the brushes/switch as shown.
Turn the switch on and give the disk a gentle spin. If it doesn’t spin well the wires are back to front. Switch off, untwist and reconnect.
If it starts spinning all by itself, well done! Try adjusting the magnets to make it run better.
Try adjusting the brushes so they touch more gently. The lower the force, the less the friction and your motor will waste less power overcoming it. Too little force and they won’t touch the commutator enough for it to work. It’s a balancing act!
Try spinning the motor artificially fast with your fingers. Does it sustain a faster speed?
You'll probably find you burn through batteries pretty quickly. If performance suddenly drops you know where to look!
Experiment with other battery voltages too. Does a 1.5V AA battery run the motor? What about a 7.2V remote-control car battery?
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