The most important skill in learning the Frederick Post Versalog Catalog No. 1460 is understanding the purpose of each scale.
A slide rule does not contain a calculator mechanism. Instead, each scale represents mathematical relationships through logarithmic spacing. Once the purpose of each scale is understood, the movement of the slide and cursor becomes a simple method of arranging these relationships.
The Post Versalog 1460 contains a wide range of scales designed to make engineering and scientific calculations efficient.
Reading a Slide Rule Scale
The markings on a slide rule are not evenly spaced.
On a normal ruler, the distance between 1 and 2 is the same as the distance between 8 and 9. On a logarithmic scale, the spacing represents the logarithm of each number.
This allows multiplication and division to be performed mechanically.
The distance from 1 to 2 represents:
log(2) = 0.3010
The distance from 1 to 3 represents:
log(3) = 0.4771
The physical distances can therefore be added or subtracted to perform calculations.
The D Scale
The D scale is one of the fundamental scales on the Versalog 1460.
It is located on the fixed body of the instrument and is used as a primary reference scale.
The D scale is used for:
- Multiplication.
- Division.
- Reading results from other scales.
- Comparing values.
The D scale represents numbers from 1 to 10 using a logarithmic arrangement.
The C Scale
The C scale is located on the movable slide.
It works together with the D scale for basic calculations.
The relationship between the C and D scales allows multiplication and division by aligning values and reading the result.
Although many modern slide rule instructions begin with the C and D scales, the Post Versalog manual places significant emphasis on efficient use of the CI scale for reducing slide movements.
The CI Scale
The CI scale is the reciprocal scale of the C scale.
The numbers are arranged in the opposite direction.
CI means: C Inverted
The CI scale allows the user to perform calculations involving reciprocals without repeatedly reversing the slide position.
The CI scale is particularly valuable for:
- Division.
- Reciprocal multiplication.
- Long chained calculations.
- Reducing cursor and slide movement.
The Versalog method uses the CI scale because efficient movement is important when performing multiple calculations.
The Relationship Between C, D and CI
The C, D and CI scales work together as a calculation system.
The D scale provides the fixed reference.
The C scale provides normal logarithmic alignment.
The CI scale provides the inverted relationship.
Understanding these three scales is the foundation for becoming efficient with the Versalog 1460.
The A and B Scales
The A and B scales are square scales.
They contain values representing the squares of numbers on the C and D scales.
They are used for:
- Squaring numbers.
- Finding square roots.
- Calculations involving second powers.
For example:
If a number is positioned on the D scale, the corresponding square can be found on the A scale.
The reverse operation provides the square root.
The K Scale
The K scale is the cube scale.
It is used for:
- Cubing numbers.
- Finding cube roots.
- Calculations involving third powers.
The K scale extends the capabilities of the Versalog 1460 beyond basic arithmetic.
The L Scale
The L scale is the linear logarithm scale.
Unlike the other scales, it is evenly spaced because it directly represents logarithmic values.
The L scale is used to find:
- Common logarithms.
- Antilogarithms when combined with other scales.
Trigonometric Scales
The Versalog 1460 includes specialised scales for trigonometric calculations.
These scales allow users to calculate:
- Sine values.
- Tangent values.
- Related angular relationships.
These functions were essential for engineering applications involving geometry, structures and mechanical systems.
Log-Log Scales
The Log-Log scales are among the most powerful features of the Versalog 1460.
They allow calculations involving:
- Exponential relationships.
- Powers with fractional exponents.
- Growth and decay functions.
These scales extend the slide rule beyond ordinary multiplication and division.
Learning the Scales in Order
A recommended learning sequence is:
- D scale.
- C scale.
- CI scale.
- A and B scales.
- K scale.
- Trigonometric scales.
- L scale.
- Log-Log scales.
Mastering the first three scales provides the foundation for almost every calculation performed on the Versalog 1460.
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