INSTRUCTIONS
How to operate the Eckel Dial -O-Matic Engineers - or the Engineers Log Log Slide Rule.
You now possess one of the most simple slide rules to operate. The same simplicity of operation extends to the Engineers Log Log Slide Rule as in the Engineers.
With a little practice you will come to appreciate the many novel advantages of your circular slide rule.
The following instructions for the Eckel Dial-O-Matic Engineers or Engineers Log Log Slide Rule are straight forward, concise and simple. They comprise the essential suggestions to operate either the Eckel Engineers or the Engineers Log Log Slide Rule. At the outset it is assumed that the operator is familiar with exponential theory, and that he is able to read the conventional slide rule scales and is also familiar with the powers of ten method for setting the decimal point.
For special techniques for handling special problems and short cuts preparatory to
slide rule evaluations, we refer you to the many existing texts on slide rule theory and
practice. Suffice it to say, however, that the Dial-O-Matic feature embodied in the Eckel
circular slide rule construction obviates the necessity for the operator to pay attention
to the addition and subtraction of mantissas in multiplication and division, as is
the case with conventional straight and circular slide rules. The answer
never goes off the rotor scale.
The Dial-O-Matic features place the Eckel form of circular slide rule considerably in advance of all existing types - straight or circular.
The advanced features of this present new Eckel slide rule empels its use by every operator who requires a slide rule in his every day work, for special or general use.
OPERATIONAL RULES TO EVALUATE ON THE ENGINEERS SLIDE RULE
| Rule 1 | Locate the first factor on the rotor, and all subsequent factors on the stator. | |
| Rule 2 | For multiplication always use the D scale. For division always use the DI scale. There are no exceptions. | |
| The procedure with angles follows as outlined in "Operational Rules & Steps" only angle numbers replace ordinary numbers. A (D) scale on the back enables one to obtain the anti-functions of the trigonometric and hyperbolic angles without the necessity of turning the rule over. | ||
| Rule 3 | Disregard scale directions and cursor movement direction. Always set cursor hairline over corresponding numerical values of factors on proper scales -either side of the rule. | |
| Rule 4 | Always unlock cursor if there is a subsequent factor to be entered. Don't unlock if you are ready to read the answer. | |
| Rule 5 | The answer is always read on the rotor (C) scale or Log Log scale under the hairline - preferably in the index position | |
| Rule 6 | Square and cube root factors are located on the appropriate scale and in the logarithmic cycle regions on the stator, after which lock cursor to rotor and pull cursor hairline to 0 index on stator. | |
| NOTE: If root is in the denominator - rationalize. | ||
| EXAMPLE: To evaluate a b /c | ||
| Step 1 | Set the cursor hairline to the (a) factor on the rotor.Lock cursor to rotor and pull cursor hairline to the D index on the stator - unlock cursor. | |
| Step 2 | Set the cursor hairline to the (b) factor on the D scale of the stator,
lock cursor to rotor and pull locked cursor to rotor - either direction to the D scale
index. The answer thus far is under the cursor hairline on the C scale of the rotor. |
|
| Step 3 | Unlock cursor and set cursor hairline to the (c) factor on the DI scale of the stator. | |
THAT'S ALL |
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| Subsequent factors are handled in the same way after indexing the
cursor hairline to the stator 0 scale index N to Log N or Number to Mantissa Scale |
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| Rule 7 | Set the cursor hairline to any number (n) on the stator D scale - read the log (n) (mantissa) on the stator (L) scale under the cursor hairline or visa-versa. | |
TRIGONOMETRIC AND HYPERBOLIC ANGLES
Trigonometric and Hyperbolic angles (expressed decimally) are located on the back. After setting to angle, lock cursor to rotor, turn role over and pull cursor hairline either direction to index. Subsequent factors can be entered on the front or hack (indiscriminately). The final answer is always read on the C scale of the rotor under cursor hairline.
The unique feature here is that you simply set to numbers on the front or to angles on the back of the stator - lock cursor to rotor and pull to D scale index on the front - that is all - don't worry about, cursor direction or scale direction - front or back.
OPERATIONAL RULES TO EVALUATE ON THE ENGINEERS LOG LOG SLIDE ROLE
(THE FOUR CASES)
Case 1. aN
2. (a-1)N
3. a 1/N
4. (a-1) 1/N
NOTE: a-N is adjacently below aN. This yields a 50 inch reciprocal scale for reading reciprocals directly. Get used to using it for straight reciprocal work.
| Step 1 | Locate (a) on the rotor, lock cursor to rotor and pull cursor hairline to
index. Unlock cursor and locate N on the D scale, or 1/N on the 01 scale on the stator. Lock cursor to rotor and read answer following these very simple roles. |
| Case: | aN D scale |
If cursor hairline falls in Positive angle. Log Log answer is read on same scale. If cursor hairline falls in Negative angle. Log Log answer is read on scale one step below. |
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| Case: | (a-1) 1/N | If cursor hairline falls in Negative angle Log Log answer is read on same scale If cursor hairline falls in Positive angle Log Log answer is read on scale one step above. |
NOTE: When N is greater than 10, re-express the quantity either
(a10) m/10 or as (a n/m) m for instance.
a21.3
The foregoing is applicable to the form cases of exponential evaluations.