KEVOS® MAKEOS · Manufacturing
Forging Hammer Efficiency by the Heim Lead Cylinder Test (Work per Blow and Efficiency)
If I let my forging or drop hammer strike a pure lead cylinder and measure how much it was shortened, how much work does each blow do, how much useful power does the hammer deliver at its blow rate, and how efficient is it against the power it takes?
Work done by one blow of a forging hammer from the Heim test the handbook describes: a pure lead cylinder 1.5 times as high as its diameter is struck, and the work follows from its diameter and the relative reduction in height by the empirical formula Work = 36.75 D³ [8.85 A + 13.12 (A² + A⁴)] foot-pounds (D in inches). The tool converts your millimetre measurements, gives the work per blow in joules and foot-pounds, the useful power at the blows per minute, and the efficiency against the power supplied to the hammer.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Lead cylinder | ||
| Diameter of the lead cylinder | mm | Diameter of the pure lead test cylinder; the handbook’s Table 5 gives the size used for each falling weight of hammer. |
| Height of the cylinder before the blow | mm | Original height of the cylinder; the method uses cylinders 1.5 times as high as their diameter. |
| Height of the cylinder after the blow | mm | Height of the cylinder after one blow of the hammer. |
| Hammer | ||
| Blows per minute | blows/min | Blows per minute with the hammer running continuously (steam hammers must be tested running, not on a single blow). |
| Power supplied to the hammer while running | kW | Power supplied to the hammer while it runs at that rate, measured at the motor or from the steam or air supply. |
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.
Lead cylinder
What this means: Diameter of the lead cylinder
- What it is
- Diameter of the pure lead cylinder used for the test blow.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The work per blow grows with the cube of the diameter.
- Get it right
- Choose the size the handbook’s Table 5 gives for the falling weight of the hammer, and measure it before the blow.
What this means: Height of the cylinder before the blow
- What it is
- Height of the lead cylinder before the blow, 1.5 times its diameter.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 75 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- With the height after the blow sets the reduction A.
- Get it right
- Face both ends square and measure on the axis.
What this means: Height of the cylinder after the blow
- What it is
- Height of the lead cylinder after one blow of the hammer.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 48 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger reduction in height means more work per blow.
- Get it right
- Measure on the axis once the cylinder has cooled to room temperature.
Hammer
What this means: Blows per minute
- What it is
- Blows per minute with the hammer running continuously.
- Units and format
- Enter a number in blows/min: blows/min. The form accepts 0.000001 blows/min to 2000 blows/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 180 blows/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Useful power grows in direct proportion.
- Get it right
- Count blows over a full minute; steam hammers must be tested running, not on a single blow.
What this means: Power supplied to the hammer while running
- What it is
- Power supplied to the hammer while it runs at that blow rate.
- Units and format
- Enter a number in kW: kilowatts. The form accepts 0.000001 kW to 100000 kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 7.68 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Only moves the efficiency.
- Get it right
- Measure the motor input power or the steam or air power over the same period.
Method and formulas
- A = (H − H₁) ÷ H, the reduction in height as a fraction of the original height.
- B = 8.85 A + 13.12 (A² + A⁴), the bracketed factor of the Heim formula (tabulated by the handbook as Table 6 for A = 0.10 to 0.60).
- Work per blow = 36.75 D³ B foot-pounds with D in inches (D = mm ÷ 25.4); 1 ft·lb = 1.3558 J.
- Useful power = work per blow × blows per minute ÷ 60.
- Efficiency = useful power ÷ power supplied.
- Example: a 50 mm lead cylinder shortened from 75 to 48 mm (A = 0.36) shows 1,940.9 J per blow; at 180 blows per minute that is 5.8228 kW, 75.818 % of the 7.68 kW supplied.
Limitations
- The formula is empirical (Heim), found with pure lead cylinders 1.5 times as high as their diameter; other proportions or impure lead change the result.
- Table 6 covers A from 0.10 to 0.60; outside that range the formula is extrapolated.
- The test measures the work done on the lead in one blow; it does not give the force of the blow or the energy absorbed by the anvil and foundation.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Test whether a forging hammer still delivers the energy it should
- Compare hammers by the useful work each delivers
- Find the efficiency of a hammer from the power it draws
Who it is for
- Forge supervisors
- Maintenance engineers
- Plant engineers
What you get
- Relative reduction in height A
- Factor B = 8.85 A + 13.12 (A² + A⁴)
- Work per blow in foot-pounds and joules
- Useful power at the blow rate
- Efficiency against the power supplied
Interpreting the result
- Pick the lead cylinder size for the hammer’s falling weight so the reduction falls inside the tabulated range.
- A fall in efficiency over time points to losses in the drive, guides, valves or packing; repeat the test under the same conditions to compare.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3234–3236. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These KEVOS® Library readings explain the method this tool uses, with worked examples.
Useful alongside · KEVOS® original book
Screw presses, fly presses and drop hammers
In Power Presses by the Numbers
What it covers: Energy machines and the principle of work: Hodgson's copying press and fly press restated in SI, force against stopping distance, drop hammers, and a slip in a 1903 worked example.
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