Keufell & Esser N 4102 Surveyor's

The N 4102 Surveyor's Duplex was produced by K&E since 1915 until 1949. As well as the other K&E rules of that time, it was fabricated with Mahogany wood covered with white celluloid where scales were engraved, and hold with brass braces. Cursor in the first models was frameless, and by the second half of the 1930's was equiped by the traditional wireframed. With an initial cost of $18.00 USD (About $532 USD in 2022), it was designed to tackle some of the difficult astronomical calculations requiered during surveying. As stated in the 1915 product catalog:

The fact that all astronomical data essential to surveying, such as azimuth, time, latitude, etc. can be ascertained by means of the usual type of Transit with vertical but without solar attachment, while generally known, is rather seldom utilized in this country. The main reason for this surprising condition is the difficulty of computing, in the field of spherical trigonometry, the resultso of the observations.

The new K&E Surveyor's Rlide Rule enterely eliminates this difficulty by reducing the hitherto complicated calculations to more machanical oprations, thereby rendering the method of field astronomy with the regular Engineering's Transit extremely simple and practical.

The scales on the N 4102 are: Front: Vert 1/2 sin2a (55' - 4o 37'), A, B, CI, C, D, Vert 1/2 sin2a - HOR cos2a. Back: D, sin d (folded), cos l & h, C, tan (5o 44' - 45o), tan I, Az (double). The precision achieved in the N 4102 for the trigonometric calculations is of 1 minute of arc.

Besides the regular A, B, CI, C and D scales for general calculations, the N 4102 has the next specialized scales:

  • sin d: folded scale (at 5o 44' ), from 2o 22' - 24o 44' , used for declination.

  • cos l and h, inverted scale, from 0o to 84o 15', for latitude and altitude

  • tan I , inverted scale, from 20o 50' to 75o

  • Az, Azimuth double scale or scale of natural cosines, for reading azimuth or cosine bearings, from 0o to 60o (inverted upper scale), and from 50o to 100o (lower scale)

  • HOR 1/2 cos2a, inverted scale, from 0o to 45o , to calculate horizontal distance

  • VERT 1/2 sin2a, splitted scale, one portion from 29.9' to 5o 45', and the second portion from 5o 45' to 40o , to calculate vertic;al distance

According with the serial number engraved on the specimen in this collection (598512), and the correlation done by Ed Chamberlain, this rule was fabricated around 1935, and was sold for $24 USD (about $522 in 2020 USD)

I have not found a copy of the User Manual for the N 4102, but I have include here an excellent explanatory article about this rule

KE-SurveyorsN4102-Oarticle.pdf

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