Pinewood Derby Car Axle Keepers

thingiverse

When using the provided slots in a derby car, the chances of creating a blowout or having an axle loosen up and fall out is pretty high. I see a lot of people using glue to hold the axles in. So I designed these axle keeps which are similar to some off the shelf products. They use 5 #6 3/8" long screws to hold them in. You can pick a 12 pack of these screws up at your local Home Depot for a $1 or so. (UPDATE: I found some #4 1/4" long slotted screws at Menards for $0.40 for a bag of 8. These grab well, weight less and less chance of splitting the wood and didn't need pilot holes.) You will want to put the axle keeper on before inserting axles to help guide them down the slot. 1. Center the axle keeper on the slot. 2. Put in the center screw all the way. 3. Drill small pilot holes for the other screws (or the wood will split!). 4. Start the other screws but do not tighten. 5. Press in axles with wheels on. Use a credit card for spacing between wheel and car body. 6. Tighten down the other 4 screws. DO NOT OVER TIGHTEN. The pinewood used in these derby cars is pretty soft and is not the best for holding screws. Just get the screw snug. If you do strip one out you can put a drop of super glue on the screw and screw down and let dry. The super glue will act like Loctite and hopefully secure the screw. Try not to super glue anything else in the process. 7. Put the car on a perfectly flat surface. You can tweak / adjust the axles a little bit as needed to get your wheels straight. 8. Push car on flat surface to see if it rolls straight. If not rinse and repeat steps 7 and 8. Print the templates at 100%, they are still pretty light. The screws will add a bit of weight so factor all this in to your build. It's a good idea to weigh the car, axles, wheels weights and anything else you plan to use before assembling. If you are going to paint, leave some cushion for that. I have heard recommendations for 0.1 oz for paint. I would say if you are just doing one light coat or so that is fine. If you are doing a nice paint job with primer, sanding, clear coat, etc., give yourself at least 0.3 oz of room and add a weight on the bottom if needed. UPDATED 2/6/19: I made the axle keepers just 0.4 mm narrower. They fit pretty much up to the end of the block and I was a bit concerned if any of the axle keeper was hanging over it could cause issues with the wheels rotating.