3D Printing is not rocket science, but this lesson is!
This lesson idea was developed by our community members Ralph McNeill & Avril Stringer at 3D Print Works.

You can download the chassis and wheels for a rocket car race used in seminars given by 3DPrintworks to teachers of science,craft and design. It was originally shown as an example of how 3D Printers could be used in the classroom, to design 3D Printed parts, and also how these parts could be used to further demonstrate science and explain how rockets work, and show the concepts of thrust, mass, acceleration etc. Also it is a fun way to learn.

The lesson can be run in a 1 hour time scale, uses parts which can be printed i.e. chassis and wheels, all the other parts can be bought from local stores, and the pumps from a bicycle supplier. The idea is that a group spits into 2s or 3s and is each given a kit to build a rocket car which they race against the other teams, the list of parts is below.

The main design considerations are how many pin holes do you make at the rear of the bottle and where they are placed, also on a team level how to manage stopping air leaking out during pumping up and before launch, also who will steer, remember you only have 10 fingers! The rules are basic and can be made up as you wish, but a basic formulae is that its a time trial up and down a straight track about 15 metres long, you could just make it one way, but the turn around means more fun and organisation needed, it is possible with the correct number of holes to run for 15 metres with out more pumping up which is allowed (if you decide) steering may also be allowed with a stick, and the timing starts from when you start pumping. and stops after the finish line is crossed.

Each team picks a name for their team at the beginning of the lesson, this is timed also at 1 min.

The list of parts required for each team are:

  • 1 x 2 litre plastic bottle
  • 2 x chassis (it takes the average printer 3 hours to print these)
  • 4 x wheels (it takes about 2 hours to print these)
  • 2 x axles 2.3mm diameter 120mm long (welding wire, or metal coat hangers)
    rubber bands (to hold chassis on)
  • Car tyre valve (from amazon or your local tyre fitting company)
  • Drill a hole in the bottle cap approx. 8mm diameter, use pliers to pull the valve through.
  • 1 x bicycle pump the one in the picture works best but foot pumps also work, a pressure gauge is desirable, especially if you want to do experiment and look at thrust in the physics lab.
  • 1 x pin (either a board pin)
  • 1 x steering stick 500mm long (wood cane or plastic rod)

You will need 1 set of parts per 2 or 3 students so for a group of 30 students you need 15 kits at least plus spares to cover the inevitable breakages.
After the race and when everyone is sat down the science can be discussed and the concepts of thrust, mass and acceleration teased out, also pressure and flow can be explored, and who knows even a first prize and booby prize may be given. Its a simple fun demonstration, but has real science behind it, as well as a design element, I can see the design department could encourage a better chassis, perhaps aerodynamics, or the effect of different sized wheels, the possibilities are many.

In The Classroom

This works best as a small group activity, each group will need a rocket car kit which has been prepared in advance. This includes a set of 3D Printed chassis and wheels. Once the kits have been prepared, they can be used time and time again and only require a new plastic drink bottle each time.

Alternatively this can be extended into a mini-project. 1 single rocket car can be made for demonstration purposes and teams can then be tasked with designing their own chassis and/or wheels using suitable CAD software and 3D Printing them prior to assembling their rocket car. This allows students to investigate the effects of different size and/or thickness of wheels, different wheel surface textures (grips) etc.

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