This is really just a chassis to get students inquiring into wheels and axles. There are so many ways for them to modify this design to personalise it to make it into a finished car--or for them to build multiple versions to try to measure the impact that each component has on performance (i.e. changing the diameter of the wheels.)
Last year, I did a similar project with wooden cars (click here for that Instructable) but this one is even simpler. Now the students can do everything themselves. I have been using this with students as young as grade 1 and up to grade 4 and it has been going very well.
Step 1: Step 1: What Do We Need?
For this project, we need some cardboard, barbecue skewers and a straw. We use a hot glue gun to fasten it together. Since I am working with younger kids, I use low temperature glue guns (~100℃ instead of ~200℃)
If you are cutting the circles and squares by hand, you will need a good pair of scissors (and probably something to trace).
For cutting the barbecue skewers, we use wire cutters. It's a little easier and safer than using scissors since it's unlikely to twist.
Once we cut the skewer to length, we use the pencil sharpener to sharpen the end so it's easier to poke through the cardboard. You could just as easily use a pencil but I think it's good to demonstrate to students that we can use tools in different ways.
Step 2: Step 1 (contd.): a Die Cutter Can Make Things Easier
I have a ton of equipment in our makerspace, including 3D printers, a CNC, laser engraver etc. But the thing that gets the most use by far is the die cutter. This thing makes my life so much easier and allows students to do so much more of the work for themselves. We can cut fabric, cardboard, plastic and wood with it. And yes, kids can use scissors too, especially for the squares. But sometimes, it's really great to have a huge supply of circles in different sizes, ready to go. Even very young students can use it on their own and they can concentrate on construction instead of having to meticulously measure each and every piece... I get custom dies done (for things like cams and gears) for under a $100. For this project, we used dies with different sized circles and squares.
Step 3: Step 2: the Body
Now it's time to start building!
Mine started with a couple of 3" squares. Students were given a chance to examine the structure of the cardboard. We peeled some open so they could see the flutes inside. They realised that you can make it stronger if you glue two squares together with the flutes perpendicular to one another. I showed them how the same thing is done with wood grain when they make plywood.
Step 4: Step 3: Axle Sleeves
Run a line of hot glue along one edge of the square and attach a straw so itis flush with the edge. Cut the excess so that it runs edge to edge.
Do the same on the other side. The skewers will go through these sleeves to become the axles.
Step 5: Step 4: the Wheels
The students noticed that its difficult to find the centre of a circle, but easy to find the centre of a square. Since we had squares to match the diameters of each of our circles, this was easy. We chose our wheel size, found a matching square and drew lines from corner to corner. Then we poked a hole through the centre with one of the skewers. Then, we laid that overtop of each of the circles to make a mark in the centres of those.
To make things easier, small twist drills can be handy for piercing the centres. We use these a lot for these sorts of projects. I get them at the dollar store.
The next step is to layer a couple of these together with some hot glue to make them a bit stronger. Once again, we turned the layers perpendicular to one another for some added rigidity.
Then we poked a skewer through the centre and glued it in place.
Step 6: Step 5: Putting the Axles in Place
The next step is to slide the skewer through the straw and cut it off, leaving enough room for the wheel, but not so much that it will slide back and forth.
We used wire cutters to cut the skewers. I found them to be easier and safer than scissors for this job. We used the pencil sharpener to sharpen the newly cut end so that it could be easily poked through the other wheel.
Step 7: Step 6: All Set!
Use hot glue to fasten the last wheel on (it's best to put the glue on the outside so it doesn't interfere with the wheel's rotation) and trim off the excess from the barbecue skewer and you are done!
Now, you can dress it up any way that you like.
Recently, we have been running this as a co-curricular activity with grade 4 students and they have been having a ball. Teams have had plenty of opportunity to build and test multiple iterations of their cars to try to work out the best combination to get theirs to go faster or travel further. Some kids just wanted to make the silliest cars they could, so there are also ones with really long axles that slide back and forth and off-centre axles where the cars wobble up and down.
First, they built their own ramps from a long roll of corrugated cardboard. It was interesting to see them experimenting in different ways but the cars often slid off the edge.
We found an old pine derby track that I inherited that has been great for testing. They are getting more systematic with their modifications--building several versions of the same car, where they make incremental changes to each one so they can compare. The one in the picture above with the box on top allowed them to add one gram of weight at a time until they found the sweet spot. It was able to make it all the way to the end of the ramp.
I hope you find this Instructable helpful. Please let me know what you think!