Spudguns: Potato Cannon Guide

Original Article ↗ Hacker News Discussion ↗

Design, Performance & Tuning

  • Many recall starting with simple “tube + hairspray + lighter” builds, then learning that chamber/barrel ratios and proper air–fuel mix dramatically improve range and consistency.
  • Advanced designs mentioned: propane systems with mixing fans, taser or piezo ignition, coaxial piston launchers, golf-ball and ice-slug cannons, and valve systems (e.g. piston-based) that dump pressure very quickly.
  • Users note impressive performance: potatoes crossing several football fields, denting 1/4" steel, punching holes in sheet metal, walls, play structures, and even a car door.

Fuels, Propellants & Alternatives

  • Common fuels: hairspray, starting fluid, isopropyl alcohol, MAPP gas, propane, acetylene, and even hydrogen from MRE heaters.
  • Some experiment with pure oxygen or oxy-fuel mixes; others warn this can transition from deflagration to detonation and effectively create a bomb.
  • Several prefer pneumatic (compressed air) launchers for controllable, gauge-measurable pressure.

Safety, Materials & Failure Modes

  • Strong emphasis on PSI ratings and not exceeding pressure or using non–pressure-rated PVC.
  • Multiple stories of catastrophic failures: PVC shattering, oil-drum rupture, dry ice bomb experiments, and near-miss or serious injuries (e.g., facial cuts, orbital fracture, potential blindness).
  • Schedule 80 PVC or metal pipe is often recommended; ABS is seen as safer than shattering PVC. Outdoor exposure and impacts can weaken pipe.
  • Disagreement over whether combustion pressures are “only ~30–40 psi” versus much higher; citations and videos are referenced on both sides.

Legality & Regulation

  • Legal status varies by country and even city. Some jurisdictions treat combustion guns as firearms or “destructive devices,” while air-powered launchers may be exempt.
  • In denser European countries, bans are defended as pragmatic due to noise, risk, and limited open space; others see it as excessive sensitivity to weapons.

Culture, Learning & Anecdotes

  • Many describe spudguns as formative for physics and engineering interest, including science projects on barrel length, internal ballistics, and data-logging “fake potatoes” with accelerometers.
  • Thread is filled with nostalgic and often hair-raising stories: evading angry drivers, accidental hits on houses and cars, near-military incidents, and police confiscations.
  • Some argue risks outweigh fun; others advocate careful design, remote firing, open spaces, and protective gear rather than abandonment.