Drivers, Wind Your Rubber Bands! Paint Stick Propeller Racers!
Intro: Drivers, Wind Your Rubber Bands! Paint Stick Propeller Racers!
Let's build some inexpensive propeller-driven STEM racers using a paint stick, and reusable or low-cost materials that even Newton would be proud of!
STEP 1: Gathering Your Parts
For the paint sticks, I went to the local hardware store and was given a couple of dozen for free. The wheels can be sourced in a number of ways. For my prototype, I used pinewood derby car wheels. They roll really nice and are solid and handle uneven or textured surfaces the best. However, they're also a bit pricey I settled on toy car wheels that I purchased in bulk online. I bought a couple hundred for twelve dollars. I'm sorry, I can't recall who I ordered them from. It's been over a year ago. Another possible source is a thrift shop in the toy section. You can also use soda bottle caps. that have been drilled to accept an axle. The propeller assembly I ordered from a STEM education site. The balsa was purchased from a hobbies and crafts chain and cut to length as described in the following steps.
STEP 2: Let's Start Building!
I began using a razor saw and cutting my axles made from the 3/8 x 3/8 balsa stock at 2 inches in length. When making several kits I used a scroll saw. You can vary the length of the axles depending on if you prefer a short or wider wheelbase. Just keep in mind that the wider the wheelbase, the more stable your vehicle. Mark the width of your paint stick onto your axles and mark the axle centerline on the paint stick at the location you have chosen to place them. Next glue the axels in place using hot glue. and set aside.
For the propeller mount. I cut the 1/4 x 1 balsa stock at 3 1/2 inches long to ensure I had good clearance for the propeller. Using a crafting stick I cut (with scissors) to fit at the top of the 1/4 x 1 balsa. Mark out the length of the desired mount and cut and attach to the main mount. The craft sticks were perfect for these propeller mounts. You needn't glue them since they have a pretty tight fit. However, if you would prefer the added security, go ahead and glue them. Add the entire assembly to the chassis, sans propeller, and set aside.
We discovered that the tension from the rubber band would pull the main mount from the paint stick, or the craft stick from the upright. If you do use hot glue, I suggest that you reinforce these parts with fillets and use the glue in liberal amounts and allow plenty of time for it to cool and set. Otherwise, if you are planning to stretch this project out over time, I would use quality wood glue. Parts separation will not be an issue and this will be useful if you decide to add a second rubber band to increase your power.
We are almost there. Predrill a location at the front of the racer where you will add your eye screw. This will make it easier to attach it. As you are turning the screw, add a drop of cyanoacrylate to ensure that the screw does not pull free from the tension of the rubber band.
STEP 3: Get Rolling
As you allow your glue to set, you can begin prepping your wheels. For the prototype, I used a pin vise to drill the hubs of my wheels. I used a drill press when I drilled hubs for 16 racers. That's a lot of wheels. Select a drill bit that will provide enough diameter for your nail to go through and allow the wheel to spin freely. If you're using chromed finishing nails you can skip using the steel wool, or sanding film to polish the nail. Otherwise, you'll want to polish the nail. Just before racing, give each hub a dose of powdered graphite; this cut the friction on the hub and squeeze a bit more speed out of your racer. Predrill each axle and gently tap the wheels and hubs onto the axles. You're about ready to race! All that is left is attaching your propeller and rubber band!
STEP 4: Customize and Let's Go Racing!
You can customize your racer any way you like. Perhaps add a fairing to the front to make it a bit more aerodynamic, or as with my prototype, I added images of Dick Dastardly and Muttly from Whacky Racers. The triaxle seemed like something he would drive, or even paint them! This project is suitable for kiddos ages 7 and up. The little, littles, may require some extra help. This is also a fantastic project for discussing Newton's Laws of Motion. However you decide to incorporate them, the kids will have a great time racing them. Just be prepared for all of the trash talk in the pits before each heat.