Faber-Castell 111/38 Stadia 360°

October 17, 2010

The Faber-Castell 111/38 Stadia 360° desktop surveyor’s rule seems to be extremely rare. My searches of the Internet have brought up a few examples of the 111/38 Stadia 400^g, but almost none of the 360° version. My father found this one in an antique shop, in nearly mint condtion, complete with its case. Thanks Dad!

The 111/38 is a full-sized rule, with scales on only one side of the stator, but both sides of the slide. The front contains L, A, B, CI, C, D, P, S, and T scales (the P scale computes 1-x², which is also the cosine of the angle on S) These scales are all self-documenting, with the scale name at the left end of the scale, and its mathematical formula at the right end. A noticeable ommission is the K scale. Perhaps surveyors don’t have much need to compute cubes or cube roots.

Along the upper edge of the rule is a 10-inch measuring scale, subdivided to 1/32 of an inch. The combination of an inch scale and angles measured in degrees leads me to believe that this rule was manufactured for the North American market.

Being the 360° model of the rule, the angles on the S and T scales are expressed in degrees. The subdivisions are in decimal degrees, as opposed to the minutes and seconds found on some slide rules.

The back of the slide appears to have five scales, but there are actually only three:

• The 1−cos² scale is double length, covering 1.85° to 5.75° in one range and 5.7° to 20° in the second.
• Similarly, the 1¾-length sin·cos scale has two ranges, covering 0.5° to 6° and 5° to 40°. For an angle α, this is used to compute sin α  times cos α.
• Finally, there is a ¼-length cos² scale, covering the range of 5° to 40°.

These special scales, used in surveying calculations, can be used in two ways:

1. With the slide installed so the front (B, CI, and C) is showing, the desired angle on the scale of interest can be slid under the hairlines found on the back of the rule in the stator cut-outs. The result can then be read on the C scale above the index of the D scale.
2. With the slide reversed (surveying scales showing) and the slide’s index marks aligned with the index of D, the cursor can be moved to the desired angle on the scale of interest and the result read on the D scale.

The back of the rule shows four diagrams illustrating various surveying situations and the formulae involved. There is also a table of values to be used in conjunction with these formulae.

Specifications
Make and Model:	Faber-Castell 111/38 Stadia 360°
Manufactured:	Germany
Overall Dimensions:	30cm × 5cm × 0.65cm (12″ × 2″ × 0.25″)
Scale Length:	25cm (9.8″)
Construction:	All Plastic
Scales:	L A | B CI C | D P S ST | 1−cos2 sin·cos cos2 |
Cursor:	Plastic with One Hairline
Date Acquired:	October 2010

The plastic display and carrying case is in very good condition. I suspect it spent a lot of time in a drawer, but had never been in the field. The felt pads that keep the rule away from the case are still clean and white.

Unfortunately, there was no instruction manual for this rule, and I haven’t found one online anywhere either. It was fairly straightforward to figure out how to use it, but I’m curious about the sorts of surveying computations that it was designed for.

Update 2011-Jan-01: My father wrote to Faber-Castell in Germany, where Ms. Stefanie Bauer took the time to photocopy the manual in their archives and mail it to us. I haven’t yet had the time to read through all of it (reading German requires a bit of concentration on my part), but here’s an excerpt about the sin·cos scale:

The manual covers both the 360° and 400^g versions of the 111/38 rule, as well as the 4/38 and 67/38b rules. Thanks again Dad, and danke schön Ms. Bauer!

                    

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