What makes your car engine work? You might be surprised to know that it’s all done with a series of controlled, contained, explosions.

Gail’s enlisted some help to explain. Martin and Brian have some tricks up their sleeves involving gunpowder.

Here’s some. Doesn’t look like much, does it? A small pile of the stuff on lump of rock. Gunpowder is interesting stuff, because as well as being a good fuel, it also supplies its own source of oxygen. All you need to make it burn is…

…a little heat. If you saw the show, however, you’ll know that this little explosion was all smoke and flame, but very little noise. There certainly wasn’t a loud ‘bang!’ That’s because the explosion wasn’t contained.

Here’s a second gunpowder explosion. The gunpowder has been put inside this small mortar, a type of cannon. So it’s surrounded by the mortar barrel and by…

…the cannonball.

This time there’s a more satisfying bang, and the gunpowder fires the cannonball into the old dock behind the Glasgow Science Centre.

But what, you might wonder, has all this to do with internal combustion engines – car engines? Well, inside a car engine are cylinders. Have a look on the model:

Each cylinder works a bit like the mortar cannon – a mixture of fuel (petrol or diesel, or sometimes liquified petroleum gas) and air takes the place of the gunpowder. Rather than firing a cannonball, the exploding mix of fuel and air shoves a piston down the cylinder.

Here, you can see one of the pistons being pushed down by Gail’s finger.

In a car engine, pushing one piston down turns a crankshaft that, ultimately, turns the car’s wheels, driving it forward. It also pushes up another piston, ready for the cycle to repeat.

So, how does an internal combustion engine work? It’s not at all unlike one of these cannons.