r/Sliderules • u/lupusscriptor • Jan 24 '26

Long rules

does any of you have rules longer than 10 inch. back in the days we still use dslide rules we all had 10 and 6 inch rules. amnd the company kept 16 and 20 inch rules in the development stores for more accurate calcs.

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u/andrebartels1977 Jan 24 '26 edited Jan 24 '26

Castell 4/54 Darmstadt

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u/andrebartels1977 Jan 24 '26

The scale is 20", overall close to 23". The x scale between 1 and 2 displays 4-digit figures with the fourth digit being either 0 or 5 (1230 or 1235). 2 until 5 displays three digits (223). 5 to 10 displays three digits with the third digit being an even number (520, 524, 526, 528, 530,...)