BIZOMAT MAKEOS · Mechanics
Porter Governor Check (Heights, Sleeve Travel, Ball Radius, Centrifugal Force)
Over its control range, how far does this loaded fly-ball governor’s sleeve move, where do the balls run, and what centrifugal force do they carry?
Check of a loaded (Porter) or simple fly-ball governor with equal arms pivoted on the spindle axis: governor height at the working speed and the ends of the control range, sleeve height change and coefficient of speed variation (as the fly-ball governor tool), the ball radius from the arm length and height, and the centrifugal force on each ball at that radius (as the centrifugal force tool), checked against the sleeve travel you need and the largest speed variation you accept.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Mass of one ball | kg | Mass of each fly-ball. |
| Central load (0 = simple governor) | kg | Mass of the central (sleeve) load of a Porter governor; 0 for a simple Watt governor. |
| Governor speed | rpm | Normal running speed of the governor spindle. |
| Minimum speed of the control range | rpm | Lowest speed of the control range. |
| Maximum speed of the control range | rpm | Highest speed of the control range. |
| Arm length (pivot to ball centre) | mm | Length of each arm from its pivot on the axis to the ball centre. |
| Requirements | ||
| Least sleeve travel over the range | mm | Sleeve movement the control linkage needs over the range. |
| Largest coefficient of speed variation | Largest speed variation over mean speed you accept. | |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Mass of one ball
- What it is
- The mass of one of the fly-balls that swing out on the governor arms, weighed or taken from the drawing; both balls are assumed equal.
- Units and format
- Enter a number in kg: kilograms. The form accepts 0.000001 kg to 10000 kg. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 kg as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- With a central load, heavier balls lower the governor height and sleeve travel; the centrifugal force per ball rises with ball mass.
- Get it right
- Enter the mass of a single ball, not the pair, and in kilograms rather than newtons.
What this means: Central load (0 = simple governor)
- What it is
- The mass of the central sleeve load that the balls lift in a Porter (loaded) governor; set it to zero for a simple Watt governor with no central weight.
- Units and format
- Enter a number in kg: kilograms. The form accepts 0 kg to 100000 kg. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 kg as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Height and sleeve travel scale with (c + w) ÷ w, so a heavier central load makes the governor stand taller and move further.
- Get it right
- 0 means a simple governor. Enter the load as a mass in kilograms, including the sleeve itself if it is carried by the arms.
What this means: Governor speed
- What it is
- The normal running speed of the governor spindle, at which the working height, ball radius and centrifugal force are reported.
- Units and format
- Enter a number in rpm: revolutions per minute. The form accepts 0.000001 rpm to 100000 rpm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200 rpm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Governor height falls with the square of speed, so a small speed rise lowers the balls noticeably.
- Get it right
- Use the governor spindle speed; if the governor is driven through gears or belts from the engine, convert the engine speed first.
What this means: Minimum speed of the control range
- What it is
- The lowest spindle speed of the control range, where the balls hang lowest and the governor stands at its greatest height.
- Units and format
- Enter a number in rpm: revolutions per minute. The form accepts 0.000001 rpm to 100000 rpm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 190 rpm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A lower minimum speed raises the height at the bottom of the range, increasing sleeve travel and the coefficient of speed variation.
- Get it right
- It must be below the maximum speed, and the height at this speed must stay shorter than the arm length or the tool rejects the inputs.
What this means: Maximum speed of the control range
- What it is
- The highest spindle speed of the control range, where the balls fly out furthest and the sleeve reaches the top of its travel.
- Units and format
- Enter a number in rpm: revolutions per minute. The form accepts 0.000001 rpm to 100000 rpm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 210 rpm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher maximum widens the speed band: sleeve travel and the coefficient of speed variation both increase.
- Get it right
- Take both range limits from the speed band the controlled machine must hold, not from the governor’s mechanical limits.
What this means: Arm length (pivot to ball centre)
- What it is
- The length of each arm from its pivot on the spindle axis to the centre of the ball it carries, measured on the governor or its drawing.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- It does not change the height or travel; a longer arm puts the balls at a larger radius and raises the centrifugal force.
- Get it right
- Measure to the ball centre, not to its outer surface; the tool assumes the arms pivot on the axis itself.
Requirements
What this means: Least sleeve travel over the range
- What it is
- The least movement of the sleeve between the minimum and maximum speeds that the throttle or control linkage needs to work through its full stroke.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from the linkage geometry: the sleeve movement that moves the valve or rack from one end of its stroke to the other.
What this means: Largest coefficient of speed variation
- What it is
- The largest coefficient of speed variation you accept: the spread of the control range divided by its mean speed, a measure of how tightly the governor holds speed.
- Units and format
- Enter a plain number with no unit. The form accepts 0.001 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.12 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Type it as a fraction, not a percentage: a 5 % speed band is entered as 0.05.
Method and formulas
- Height h = (g ÷ ω²) × (c + w) ÷ w at each speed; sleeve change = h_min − h_max; coefficient of speed variation = (n_max − n_min) ÷ mean (as the fly-ball governor tool).
- Ball radius r = √(L² − h²) for arms pivoted on the axis.
- Centrifugal force on a ball = w ω² r (as the centrifugal force tool).
- Example: at 200 rpm the governor stands 134.14 mm high with the balls at 148.35 mm radius carrying 130.14 N; the sleeve moves 26.962 mm over the range.
Limitations
- Frictionless, symmetric governor with arms pivoted on the axis.
- Steady speeds; hunting and damping are not covered.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a mechanical governor for an engine or turbine
- Choose a central load for the speed range
- Teach governor sensitivity
Who it is for
- Mechanical engineers
- Restoration engineers
- Students
What you get
- Height at speed and over the range
- Sleeve travel and speed variation
- Ball radius and centrifugal force
Interpreting the result
- A heavier central load raises the speed the governor works at without changing its sensitivity.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3453–3455, 187–190. Topic reference; no source tables or recommended settings are reproduced.
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Open the Porter Governor Check (Heights, Sleeve Travel, Ball Radius, Centrifugal Force) calculator