Pinewood Derby Car Axle Keepers

thingiverse

When using provided slots in a derby car, the likelihood of encountering a blowout or experiencing an axle come loose is quite high. Many people use glue to hold the axles in place, but I've designed these axle keeps to offer a more secure solution. They function similarly to some off-the-shelf products and utilize five #6 3/8" long screws for added stability. You can purchase a pack of 12 of these screws at your local Home Depot for approximately $1 or so. As an update, I discovered that using #4 1/4" long slotted screws from Menards is also an effective option. These screws are lighter and have a lower chance of splitting the wood, and they don't require pilot holes. To assemble the axle keeps, follow these steps: 1. Position the axle keeper in the center of the slot. 2. Insert the center screw all the way down. 3. Drill small pilot holes for the other screws to prevent the wood from splitting. 4. Start the remaining screws but do not tighten them yet. 5. Press the axles with wheels attached into place, using a credit card to maintain even spacing between the wheel and car body. 6. Tighten the remaining four screws, taking care not to overtighten. The pinewood used in these derby cars is relatively soft and may not hold screws securely. 7. Place the car on a perfectly flat surface and adjust the axles as needed to achieve straight wheels. 8. Push the car across a flat surface to test its rolling performance. If it does not roll straight, repeat steps 7 and 8 until desired results are achieved. To ensure optimal performance, print the templates at 100% scale, keeping in mind that they will still be relatively lightweight. The added weight of the screws should be factored into your build calculations. Before assembling the car, weigh all components, including wheels, axles, weights, and any additional features you plan to add. If you intend to paint the car, allow for some extra weight allowance to compensate for the added weight. A common recommendation is 0.1 oz of paint weight, but if you're planning a more extensive painting process, consider allocating at least 0.3 oz of weight allowance and adding additional weight as needed. As an update from February 6th, I made some adjustments to the axle keeps by narrowing them by 0.4 mm. This modification allows them to fit snugly up to the end of the block, eliminating any potential issues with wheel rotation.