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Governor

Made of

Iron Brass Steel

Brief description

A governor, or speed limiter, is a device used to measure and regulate the speed of a machine, such as an engine. A classic example is the centrifugal governor, also known as the Watt or fly-ball governor on a reciprocating steam engine, which uses the effect of centrifugal force on rotating weights driven by the machine output shaft to regulate its speed by altering the input flow of steam.

Use / Function

  • Primary Use: To maintain a constant engine speed regardless of the load (e.g., in a generator or mill).
  • Secondary Uses: To prevent an engine from overspeeding and destroying itself (safety).

Operating principle

The governor senses the speed of the engine and adjusts the fuel or steam supply accordingly (negative feedback loop).

  1. Centrifugal Force: As the engine spins faster, weights on the governor spin faster and fly outward due to centrifugal force.
  2. Mechanical Linkage: The outward movement of the weights lifts a sleeve or lever.
  3. Valve Control: This lever is connected to the steam throttle valve or fuel injection pump.
  4. Feedback: If the engine speeds up, the valve closes slightly (reducing power). If it slows down (load increases), the valve opens (increasing power).

How to create it

Simple Fly-Ball Governor

  1. Spindle: A vertical shaft driven by the engine (via a belt or gears).
  2. Arms: Two or more arms pivoted at the top of the spindle.
  3. Weights (Fly-balls): Heavy metal balls (usually Iron or Brass) attached to the ends of the arms.
  4. Sleeve: A collar that slides up and down the spindle, connected to the arms by links.
  5. Linkage: A system of rods and levers connecting the sleeve to the engine’s throttle valve.

Materials needed

  • Weights: Heavy metal (Iron, Brass, Lead).
  • Spindle/Arms: Steel or Iron.
  • Springs: (Optional) To oppose the centrifugal force for better control.

Variants and improvements

  • Watt Governor: The original gravity-loaded type. Simple but has “droop” (speed decreases slightly as load increases).
  • Porter Governor: Adds a central weight to increase sensitivity.
  • Spring-loaded Governor: Uses a spring instead of gravity; works in any orientation and is faster acting.
  • Isochronous Governor: Maintains exact speed regardless of load (no droop), but is harder to stabilize (hunting).

Limits and risks

  • Hunting: If the governor is too sensitive or has too much friction/lag, the engine speed will oscillate (surge up and down) indefinitely.
  • Deadband: Friction can cause the governor to not respond to small speed changes.
  • Failure: If the drive belt breaks, the governor stops spinning, the valve opens wide, and the engine runs away (destroys itself).