Pinewood Derby Wheel Balancer

Balance your small wheels with this simple magnetic bearing fixture
42m
1× print file
0.20 mm
0.40 mm
11.00 g
0
3
0
73
updated February 2, 2025

Description

PDF

Check your local rules to see if balancing can be done, or if there are restrictions on how to balance (such as adding or removing mass).

The fixture will require the following additional hardware:

  • Qty 2 - M5 hex nut
  • 16mm or longer M5 Bolt
  • Qty 2 - 8x3mm magnet
  • Qty 4 - Mounting hardware (#6, M4, or similar)
  • 25mm (approximately) magnetic shaft (HSS works well)

Instructions for assembly and use:

  1. Print the model as-is without supports. I like PLA for this since it is rigid but anything will work just fine.
  2. Affix the model to a flat surface with mounting hardware. You need to do this otherwise the magnetism will pull the model together. The other reason to affix it to a larger surface is to make leveling it easy.
    • I used an aluminum plate and put leveling feet in the corners.
  3. Insert one M5 nut into the provided slot.
  4. Flatten the top of the M5 bolt with your favorite method (a lathe is easy but if you don't have one, chuck it into a drill and spin it onto a belt sander).
  5. Affix a magnet to the M5 bolt head (CA glue, etc) ensuring that it is centered.
  6. Insert a magnet into the slot within the model. It should press fit so there is no need for glue.
  7. Install the M5 bolt and magnet assembly by threading it into the captive nut from the inner part of the model.
  8. Create your balance shaft using 25mm long round stock. I turned 2mm HSS stock down to size by chucking it into a drill and running across it with a file.
  9. Created pointed ends on the balance shaft (lathe or drill/belt sander).
  10. Put one end of the balance shaft on the integrated magnet and adjust the M5 bolt to support the balance shaft.
    • The balance shaft should touch one magnet and NOT touch the other magnet. You want the gap as small as possible. If it is touching both, there will be higher friction and the fixture will not work as well.
    • You can test for the gap by sliding the balance shaft from one magnet to the other and hear/feel it move.
  11. Once you have adjusted the M5 bolt, lock it into place with the second M5 nut.
  12. Level your fixture.
  13. Remove the shaft, install a wheel, and gently spin!
  14. The lightest part of the wheel will be facing up. Apply your favorite mass (clear nail polish, CA, etc) to the hub, or remove from the heaviest part, and repeat the balancing. The wheel will be balanced when it doesn't rotate from any position.

Model origin

The author marked this model as their own original creation.

License