Aristo Darmstadt Nr. 867U

The Darmstadt style rules have single sided stators, with a reversible slide. The back of the slide contains the log-log scales. Here's the whole rule again, with the slide reversed:

A feature of this rule that I really like is the Pythagorean (P) scale, which computes √(1-x²). This scale is especially useful in conjunction with the Sine (S) scale. When an angle is selected on S, the D scale gives its sine as expected. At the same time, the P scale gives the cosine of the same angle. None of my other rules except the Hughes-Owens 1777 have this useful scale.

Another unusual feature of this rule is the centimetre and inch scales along the rule's edge. Although not intended as a drawing or measurement instrument, these scales can come in handy at times in the workshop.

An interesting aspect of this rule (and other Darmstadt-style rules) is the location of the trig and log-log scales. Most of the rules in my collection have the trig scales (S and T) on the slider, and the log-log scales on the stators. The Darmstadt is opposite.

The following is the description of the 867U (and its 25cm/10in and 50cm/20in siblings, the 967U and 1067U) from Aristo's catalog:

ARISTO Darmstadt

The original scale pattern of the Darmstadt system is in the ARISTO Darmstadt rule extended by the addition of a scale of reciprocals, BI. The Log-log scales, placed with a mantissa scale on the reverse of the slide, are visible over the whole length of the slide, through the transparent rule body, making possible the use of the rule with the slide in its normal position. Non-slip rubber inserts (model 967U) facilitate single handed working, with the rule on the desk top. Pocket model ARISTO Darmstadt 867U/400^g is also available, graduated in the new 400^g system.

If I'm unable to find a replacement 867U, I may attempt to make a new cursor for the one I've got, although I'm not yet sure exactly how I'll go about it.

SPECIFICATIONS Make and Model: Aristo 867U Manufactured: Germany, Year Unknown Overall Dimensions:   15.9cm × 4.6cm × 0.5cm (6.3" × 1.8" × 0.2") Scale Length: 12.5cm (4.9") Construction: All Plastic Scales: cm | K A | B BI CI C | D P S T | inch L LL1 LL2 LL3 Cursor: Plastic with Single Hairline (missing) Date Acquired: 1974 (approximately)

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Last updated Saturday April 12, 2008.	E-mail Stefan
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