Invisible Sword Construction and Testing

Jul 15, 2024

Invisible Sword Presentation

Introduction

  • Observation: Saw a picture of an invisible sword.
  • Goal: Build an invisible, destructible, and sharp sword.
  • Problem-solving: Figure out the method to create and then test its sharpness and durability.

Material Selection

  • Rejected Material: Glass
    • Pros: Transparent and can be sharp using a diamond stone.
    • Cons: Breaks too easily.
  • Chosen Material: Polycarbonate
    • Pros: 10 times more impact resistant than steel by weight, used for riot shields, armored vehicles, safety glasses.
    • Test: Hit with a big sledgehammer.
      • Result: Panel remained intact, only had one scratch.

Sword Construction

  1. Preparation: Panel and Shape
    • Material: 2m x 0.5m, 12mm thick polycarbonate panel.
    • Method: Use tape to outline katana shape, jigsaw to cut smaller perimeter around the sword.
  2. Cutting Shape: Band saw to cut actual katana shape.
    • Note: Model was too big initially, but polycarbonate's lightweight nature mitigated this issue.
  3. Fine Detailing: Fixing details using a belt grinder.
    • Test weight: Found to be balanced and manageable.

Achieving Invisibility

  • Method: Remove the protective film.
    • Challenges: Indoor lights weakened the effect.
    • Solution: Smoothing out the blade and spine to reduce reflection and make it more transparent.
  • Bevel Creation: Using a caliper, pencil, and belt grinder to create symmetrical bevels on both sides.
    • Challenges: First-time grinding, took 1 hour for the initial side.
  • Polishing: Sander with eight different pads, progressing from coarse to fine.
    • Final Polish: Removing micro-scratches and achieving transparency.
  • Issue: Variable thickness creates distortion.
    • Fix: Create a shorter bevel to minimize distortion.

Final Sword Assembly

  • Handle Construction: Polycarbonate pieces glued to create handle.
    • Initially planned to use acrylic block but changed plan to avoid polishing difficulties inside a drilled hole.
    • Effect: Glue created an 'ice-like' aesthetic.

Testing

  1. Soft Targets: Pineapple and watermelon.
    • Outcome: Successfully cut through easily.
  2. Hard Targets: Pumpkin and Wooden Plank
    • Outcome: Sliced pumpkin cleanly, broke wooden plank without damage to the blade.
  3. Extreme Targets: Ballistic Dummy and Brick
    • Outcome: Shattered dummy bone, cracked brick, minor blade damage.

Conclusion & Next Steps

  • Successful Build: Transparent, sharp, and durable katana.
  • Planned Next Build: Insanely powerful slingshot.
  • Future Projects: Open for suggestions from viewers.
  • Extras: Behind-the-scenes and early video access available on Patreon.

Takeaways

  • Polycarbonate proved to be a highly suitable material for the project due to its toughness and flexibility.
  • The key to achieving transparency lies in minimizing bevel-induced distortions and thorough polishing.
  • Handle rigidity can negatively affect polycarbonate's flexibility and lead to breakage under stress.