Propeller-driven Racing Cars
Louise's car, 'The Maximum Ride'
Class: Year 10
Teacher: Steve Pearce
School: Takapuna Grammar School
Category: Teaching Activity focusing on evaluation/modification
This teaching snapshot demonstrates how student enthusiasm over a 'fun' activity extended to their Technological Practice. During this section of their unit students focussed on outcome development and evaluation from the Technological Practice strand of the curriculum. Their work also incorporated ideas from the Technological Knowledge strand, Technological Modelling , as they tested their prototypes and made modifications to ensure their fitness for purpose.
Multi-materials Technology teacher Steve Pearce had taught a popular Year 10 unit in which students developed jet-propelled racing cars, using fizzy drink bottles pressurised with water. They raced their cars in the corridor, and then each student evaluated how well their car had performed and what changes would be required to improve it. The move into a new Technology building made the testing and racing more difficult, and Steve considered dropping the unit – he wouldn't miss the mess and tomfoolery involved in mixing water and (mostly) boys. However, the unit had been so successful that he decided to adapt it so that students could work on basically the same skills to develop a propeller-driven racing car.
The three Year 10 classes (of which about 10% are girls) were timetabled so that they all worked on the one-term Racing Cars unit at the same time. Steve taught two of the classes and first-year teacher Demelza Cusens the third.
The students designed their own cars but were given precise parameters for size – essential because the vacuum-former , which they would use to construct the body, only takes plastic in specific sizes. Steve showed his students a prototype car, and then they began developing their own versions. The students did profile drawings in which they showed the bottom line, chassis line, frame line, propeller, and motor, they then sketched the front elevation and a pan view of their model. Steve says that this was really easy and a good example to students of how to actually make the cars – they could see from their drawings what was and wasn't required, for example, a full width body wasn't needed as it only needed to be wide enough for the rubber motor to go through. In the construction phase, the students made a wooden chassis first, then a duplicate chassis on which they built the body, in stages. They also made the wheels and bearings (the commercial propeller was the only component given to them). The students vacuum-formed their cars, added guides and loops, and then were ready to race.
While racing the cars might appear to be the pinnacle of the unit for students, Steve says they actually gained the most enjoyment from racing them once and then making improvements. "It was a continual evaluation/improvement process. Some changed the size of the wheels, others used more rubber bands – they did all sorts of things."
Brae's modifications
An example of student modification is shown in the photo. Brae analysed the performance of his car and adjusted different features, testing the car after each change to evaluate how it performed post-modification. During this process he:
- made smaller rear wheels to lower the centre of gravity;
- drilled holes in the wooden chassis and wheels, to make the car lighter;
- inserted metal loops for the guide string, to assist the straight running of the car;
- used a range of rubber band sizes to test speed/duration combinations; and
- moulded a clear body shell – this allowed a visual check of the rubber motor windings to ascertain the optimum number of turns.
About 70 racing cars were tested on racing day. Steve says, "it was really good and a lot of fun, and you'd get kids really excited about what they'd done."
He was pleased with the success of the adapted unit and will use it again, saying it was better than the previous one because it provided more of a challenge and students had to be more focussed. He comments that student enjoyment was marked by the fact that he only had two cars left to show future students because the rest were taken home.
"It was a wonderful, empowering course because it was individual, everyone made their own thing. While we set it up, they made everything and had to think about how they made it. Students weren't given any help unless it was a particularly difficult problem, then we'd give them some direction and leave them to work out their own way and introduce their own design patterns."
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