Mechanical Models –
Bringing pictures to life
Level: Year 9
School: St Cuthbert's College
Teacher: Steve Pearce
Steve Pearce from St Cuthbert's College in Auckland has been taking a mechanical models unit for his Year 9 students since 2002. This Teaching Snapshot describes how this successful unit works, the resources required, and the benefits it offers students, including modelling, testing and materials knowledge.
"This unit is about constructing a mechanical model of a chosen subject," explains Steve. "The students create a 200mm tall wooden model that has a handle that can be turned to create a set of movements through a series of cams or a crank mechanism."
Each year Steve chooses a different theme for the students to base their models on. Each theme must have strong potential for the creation of movement in the models, and be of interest to the students. Steve chose the Auckland Zoo as the theme for the 2011 unit.
"We have always used Auckland Zoo as a starting point for our research. Last year we looked at New Zealand's vanishing species, chose a creature that was in plight and produced a poster that advertised what could be done to preserve it. So, we had some existing links to it, and I thought 'Why not do the zoo this year?'."
Preparation
Before the unit began, Steve created a series of rhinoceros models to different outcome levels to demonstrate a clear differentiation between assessment criteria. These models were displayed in the workroom as a sample for the students to refer to throughout the unit.
"Each rhino model comes from the same starting point, with the same crank driven frame and the same picture used to model the parts, but they all fit into four distinct categories that are labelled Not Achieved, Achieved, Merit and Excellence. The girls can look at the models and know the expectation for each grade and what to aim for," says Steve.
As this is a one-term unit Steve also saves time by having plenty of the basic components ready for the students before they begin. "I kit-set all of the frames for them so if they are making a crank model I have a box with all of the parts that they need to make it. So, they all have that same starting point and no one's going to have an initial disaster because they couldn't put a nail in – everything will work fine with the parts supplied."
Student process
When introducing the unit, Steve's first priority is to get the students enthused about its potential. "I try to stress that if they choose a suitable subject they can produce something that is pretty awesome."
The students then research the chosen theme, in this case zoo animals, and create a shortlist of creatures. This is eventually narrowed down until each student has an image of one chosen animal that will inform their design brief.
"They essentially make up their own design brief as to what the model will do. It will state what they intend to model, what they intend to have moving on the model, what mechanisms they will use to make that happen, and the materials they will use in its construction," explains Steve.
The students then draw their designs onto wood using their chosen image as a model. If their design requires holes for joints, these are put in at this time. The designs are then cut out using scroll saws.
The students then begin piecing the models together, a process that Steve describes as "a constant form of testing".
"Even when you put the frame together, you will put a piece of dowel through the drive mechanism and spin the frame to see if it spins true. Then once the mechanism is in you will check that to see it runs smoothly. So, it's a constant evaluation, modification, and re-test process throughout the whole project because every stage has to work before you can move onto the next one."
Resources required
Steve uses a variety of woods for the models so that students can learn their different qualities. However, the materials used in the unit are cheap and easy to source and include pine, MDF, plywood, dowel, wire, and occasionally plastic.
The tools required are also fairly standard for a hard materials room. "I have 12 scroll-saws and that does make the cutting easier. You could do it by hand though it would be quite a drawn out procedure and you would also need vices. So, the scroll-saws take that problem away and allow a class of up to 28 to do this unit."
Steve also has several specialist clamps for holding small pieces of wood so they can be drilled safely. For the drilling, Steve sets up six clearly-labelled drills with a range of standard bit sizes.
"This saves time as the kids don't have to change drill bits all the time – if I change a drill I change the label. So, we have a lot of good systems in place like that to help this unit go smoothly."
Challenges
The biggest challenge for Steve is to makes sure he has set achievable goals at the design stage.
"Sometimes the students want to overcomplicate things and the complexity of movement they want isn't always achievable using our simple mechanisms. So, I talk to all of the girls before they start to make sure they are hitting it about right," says Steve. "We may have to make compromises sometimes, but a total failure is never an option."
Finding the right theme for the unit is also difficult, but Steve feels this is essential to the unit's success.
"You can't say 'make anything you like', that would be awful and the unit would fail. So, you need a focus and boundaries otherwise students get lost in the thinking – if you keep them to one area they are actually more comfortable with that."
Outcomes
Steve is still surprised by the level of originality and ingenuity that some students put into their models each year. Standouts from this unit include an anteater that chases a moving ant with its head, and a beautifully modelled toucan. The skills and knowledge gained from this project have always been a huge incentive for Steve to continue it over the years.
"They learn a lot about materials; which are resilient and which can be carved. They also learn about sequencing, common sense procedures, and systems – something I see as a way to ensure success and safety."
Over the years, the unit has become a favourite among the students. "The students see the previous work displayed and they think it's fabulous, and it's the highlight of the Year 9 year."
What next
Steve never repeats the same theme over two years, so he is currently looking into his next idea. Due to its proven popularity, Steve will continue to focus on living creatures.
"Mythical creatures are something I've thought could be very interesting for the students; there is a huge potential there and a lot that the students could research."
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