Gear Wheels

Also known as 'cogs' or just 'gears', this is an activity that is both educational and good fun.  It's suitable for a wide range of ages and could be part of a number of different topics (maths, engineering or a particular topic such as bicycles, wheels, etc) or just done for the sake of it as a project all by itself!

This idea was taken from one of an excellent 1970's series of children's educational books (Macdonald Starters - "Wheels").

What you will need:

The main thing you need to make the wheel gears are some round lids (old Darylea or 'La Vache Qui Rit' [Laughing Cow] cheese boxes are ideal) and some corrugated cardboard.  Because we were doing this activity as part of a lessons on windmills, that's why you can see pictures of windmill gears in the background.  You will also need the following: either a piece of wood OR several layers of thick cardboard; a few nails or screws (longer than the depth of the round lids); glue; paper or paint or things to decorate your gears and the background you're going to attach them to (if you feel so inclined).

Step 1 - First cut strips of corrugated cardboard the same depth as the round lids.  Glue these round the edge of the lids.  Make a hole in the top of the lids towards one edge big enough to hold a pencil.  This is easiest done by making a little hole first with something pointy (like the point on a compass for example) and then pushing a pencil through to widen the hole.  If you want to decorate your gears, then cut out round pieces of paper or colour them or whatever.  Remember to re-make the hole, though, if need be.  Here's a decorated and undecorated version:

Step 2 - Now you need to attach your gears to a surface.  Make a hole in the middle of each gear - not too big.  The original book showed the gears nailed to a plank, but if you don't have a spare piece of wood lying around, several layers of cardboard serves just as well.  We used an old cardboard box folded and flattened.  We also used screws rather than nails - a) because that's all we could find but b) because it makes a slightly more secure hold than a nail.  Fix the two gears so they are nestled up tight against one another.  Stick a pencil into the hole of either one and use that as a pencil to 'turn' the gears.  Note what happens - that one turns one way and pushes the other gear to turn the other way.  If the kids don't know 'clockwise' or 'anticlockwise' then this is an excellent exercise to teach them!

This one<<<<<<shows a close up of the screw head and hole for the pencil 'handle'.We used old, saved wrapping paper to decorate these, incidentally!Step 2 (alternate) - Just for those who might really want to do this project but don't have cardboard or wood to hand (or screws or nails), then this was our first attempt (before we thought about the layers of cardboard) involving lumps of blu-tak under the centre of each gear and then a cocktail stick (point snipped off) sticking through the gear centre and into the blu-tak:

You could use clay, perhaps, as a better alternative to blu-tak.  Either way this is quite wobbly and you do have to hold the gears together a bit so it's not ideal.  Even so, the gears do work (though not as smoothly as they could) and the children would get a clear idea of what was happening.  You would not be able to go any further than just these two gears, though, simply because this version is rather unstable.

Step 3 - Now make a smaller gear.  Again, any round lid will do.  Try to find something that is half the size of the ones you've already made if you can, though it's not essential.  We used the sliced off end of an old loo roll, taped a circle of cardboard over one end and that worked well.  If your gear is as small as ours, then it will probably not be feasible to make a pencil hole in it - and after all it will get pushed round by the other gears.  Make a hole in the middle to secure it to your base.

Step 4 - Attach your smaller gear and decorate it.  This is best done with at least one circle (or in our case a pom-pom) or something the children can easily take note of as it turns.  Now get them to turn the middle gear and to see whether the smaller gear goes at the same speed as the other two or not.  Even quite young ones will notice it turns more quickly, and with something to watch go round they should even be able to see that it goes round twice for every one turn of the bigger gear (if you've managed to make your smaller gear half the size).  Older children can learn that this means they have a "gear ratio" of 2:1 and perhaps discuss actually pieces of engineering where such gears might be used in real life (such as on a bicycle, for example).

One last thought/suggestion: if I did this again, I would get them to decorate the cardboard base as well - either glue a sheet of coloured or patterned paper onto it or paint it.