⭕ Rim Distance Bench: step-by-step build

Two unequal wheels share one shaft: equal turns, unequal rim travel.

Two wheels finish every turn together, yet the larger rim traces a longer path. This original coaxial comparison separates angular rotation from distance around a circle. A rigid pinned bridge and two shaft retainers support gentle hand turning; spacers and caps keep both wheels seated. Inspired by Brick Experiment Channel’s spinning-wheel demonstration, not its powered speed rig.

  • Level 2 of 5 (easy)
  • About 15 minutes
  • 9 steps, 23 parts
  • Powered by: Hand-crank
  • Series: Starter Builds

What you will learn

  • Axles & Wheels: A wheel on an axle turns dragging into rolling.
  • Axles: An axle is a cross-shaped rod — anything on it turns together.
  • Bushes & Spacers: Bushes stop things sliding off an axle.
  • Frames: A frame is a ready-made strong rectangle.
  • Pins: Grippy or Smooth: Pins join beams together — some hold tight, some let things swing.

Build these first

  • Tiny Roller🚗 Tiny Roller: Your very first rolling car — only 13 pieces! (level 1 of 5, about 5 minutes, 6 steps)

Parts you need

  • 1 × Open frame 5×11
  • 4 × Axle 3
  • 8 × Bush
  • 2 × Black pin (grippy)
  • 1 × Beam 5
  • 1 × Axle 8
  • 4 × Half bush
  • 1 × Yellow-hub wheel
  • 1 × Thin-tyre wheel

Steps

  1. Lay the 5×11 frame flat. Use its four corners for feet and the middle holes of its long sides for a rigid bearing bridge.
  2. Pass a 3-module axle through this corner. Hold it while fitting a full bush underneath as a foot, and another above as a retainer. Repeat at all four corners; rest all four feet on a level table.
  3. Pass a 3-module axle through this corner. Hold it while fitting a full bush underneath as a foot, and another above as a retainer. Repeat at all four corners; rest all four feet on a level table.
  4. Pass a 3-module axle through this corner. Hold it while fitting a full bush underneath as a foot, and another above as a retainer. Repeat at all four corners; rest all four feet on a level table.
  5. Pass a 3-module axle through this corner. Hold it while fitting a full bush underneath as a foot, and another above as a retainer. Repeat at all four corners; rest all four feet on a level table.
  6. Push two black friction pins upward into the middle holes of the long sides. Press the two ends of a flat 5-hole beam onto them. These separated connections prevent the bearing bridge swinging.
  7. Pass an 8-module axle vertically through the centre round hole. Hold it while fitting a half bush immediately below the beam and another immediately above. These retain the shaft in both directions; leave it free to turn.
  8. Slide the yellow-hub wheel down onto the upper spacer. Add a half bush directly above its hub. Its nominal diameter is 43.2 mm; the tyre clears the bridge.
  9. Slide the thin-tyre wheel onto the middle half bush, then add a final half bush above it. Its model diameter is 30.4 mm. Both cross-shaped hubs grip the same axle; the spacer separates their tyres.

Play time

Hold the frame level. Mark both rims; turn gently through one revolution and compare their circumferences. Stop if loose or rubbing. No motors or speed trials.

Real-world inspiration

Cheap the Lego Wheel Spins ALMOST TOO FAST — Brick Experiment Channel — https://www.youtube.com/watch?v=Xp935wmosuY