Structures

The structure is what holds the entire kart together and transmits the weight of the driver down to the wheels. This section will help you make a light, strong kart.

Forces
Newton's 2nd Law tells us that the force needed to accelerate or decelerate (slow) the kart can be worked out by multiplying its mass and its acceleration:

Force = mass x acceleration

This means that you need more force to accelerate karts with large masses quickly.

So how can we reduce the mass and make a fast kart?

Materials
The karts will be made from steel. Steel is an alloy (a mixture) of iron and carbon, and is the metal from which most bikes and cars are made. Steel is very cheap and strong, but also very dense.

A litre bottle of water has a mass of one kilogram, but a litre of steel has a mass of eight kilograms.

To make a kart that is easy to accelerate the design must try to make the best use out of each steel beam added to it to keep its mass as small as possible.

Joining the frame together
The frame will mostly be fixed together using a process called welding.

To weld two pieces of steel together, the steel is heated and melted, so that the liquid metal from both parts can run together. If this is done carefully then a strong joint is formed when it cools and solidifies.

Design
There are many ways of solving the actual kart design problem, but here are a few tips and tricks to help you:

Try to avoid four-sided shapes (quadrilaterals):

The pictures above show four steel bars joined at their corners. You could use this shape as the chassis (main structure) of the kart, with the wheels at each joint. The problem is, it doesn't require much force for the shape on the left to be deformed into the one on the right.

Try to include three-sided shapes (triangles):

If you look at many engineering structures and you'll notice that they're made up of triangles. A bicycle is a good example.

In the picture (left), three steel bars are joined together at their corners. This time, the force cannot push the triangle out of shape until one of the bars breaks. Triangles are very strong shapes.

Can you see how to make two triangles out of the four-sided shape above? This would make it a lot stronger and prevent it from being deformed.

Conclusion
To make a fast kart, we want it to have as little mass as possible, yet still strong enough to hold the driver and be able to last until the end of the race. This means we need to use materials wisely. Triangles are a good way to make a light, strong structure.