20th c. Ahrend steel tape model 7427

The 20th c. Ahrend steel tape model 7427.
Figure 1: The 20th c. Ahrend steel tape model 7427.
This steel tape was donated by a former colleague to my collection in 2003. The tape is signed Ahrend, a Dutch office supply house founded in 1896, and is very - but not quite - similar to the other Ahrend tape in my collection.

The tape is made of steel and wound on a steel reel (see figure 1). The difference with the Ahrend No 7421 tape in my collection is its width; this tape is 20mm wide whereas the other is 28mm in width. (see figure 9) Both are 20 metres in length and divided by brass rivets every centimetre, every fifth of which has an additional brass washer (see figure 5).

Every meter small oval brass plates are attached on both sides of the tape, showing identical figures running from 1 to 19, indicating the metres (see figure 5). Every five metres a square copper plate indicates the whole five metres (see figure 6).

Handle showing the signature and type number 'Ahrend No 7427'.
Figure 2: Handle showing the signature and type number 'Ahrend No 7427'.
The handles bear the signature and model number "Ahrend No 7427" (see figure 2) on one side and 'NIET VOOR HANDELSDOELEINDEN' (not for trade purposes) on the other (see figure 3). They are made of brass and have grooves to fit the ground pins that would be used to stake out and measure a trajectory (see figure 4).

The form of the handles indicate that they were made before 19521 and are different on both sides, this in contrast to the 20th c. Tibaut steel tape in the collection (see figure 4). As can be seen here steel tapes and chains quite often had the grooves on the inside at one end of the tape or chain and at the outside at the other end. Normally the groove on the outside was used by the man ahead of the tape, while the man at the rear of the tape would use the handle with the groove on the inside.

The main reason for having the grooves on different sides of the handle is to reduce observation errors due to differences in pin thickness. The groove in the handle would have the same diameter as the pins used with it, but when the diameter of the pins is wrong a tape or chain with grooves at the same side of the handle would produce errors (i.e. each section being measured slightly too short or too long).2 This is thus prevented by having the grooves on one side of the handle at one end and the other side at the other end.

Handle showing 'NIET VOOR HANDELSDOELEINDEN' (not for trade purposes)
Figure 3: Handle showing 'NIET VOOR HANDELSDOELEINDEN' (not for trade purposes)
Steel tapes tend to break easily when not carefully used and this particular example has several repaired sections. Although special sets were available to repair steel tapes, as can be seen at the Tibaut Desimpelaere steel tape, this tape has been repaired by hard soldering the ends together (see figure 5).

Using a steel tape
A set of 11 or 6 pins would have been used with the tape to count the sections. The fore man would have all pins at the start of the measurement, pushing one in the ground every whole length of the tape. The rear man would pick up the pins as they went on. As soon as the fore man had no pins left, both men came together to exchange pins and they knew that another section of 10 or 5 tape lengths had been measured.3

Steel tapes started to be used around the 1840's. Initially they were made of short sections riveted together as there was no method yet to harden and temper continuous strips of steel.4

In 1842 Chesterman, the firm the imperial survey chain came from, made his first steel tapes that consisted of five foot sections.4 In 1853 steel tapes were three times as expensive as chains than half a century later,5,6 which may be an indication for growing demand for the tape during this period. They were preferred above chains as the latter could not be easily calibrated, while chains had to be laid out carefully so that they were fully stretched. For this reason one was not allowed to use chains for accurate measurements in the second half of the 19th century.7 They have been in continual use until at least the 1960's as they could still be purchased from Chesterman in 1962.8

Notes

[1]: With thanks to Otto van Poelje who kindly supplied copies of catalogues by Ahrend from 1922 and 1952. The 1922 catalogue shows the same handles as on the tapes in my collection, whereas they have changed to more oval shaped ones in the 1952 catalogue.
Ahrend, Prijscourant No 31, N.V.WED.J. Ahrend & Zoon's Industrie- en Handelsvereeniging, (Amsterdam, 's Gravenhage, Hilversum, Parijs, 1922), p.135.
Ahrend, Ahrend's Technische Prijscourant, (Amsterdam, Eindhoven, 's Gravenhage, Groningen, Hilversum, Rotterdam, Djakarta, 1952), p.84.
[2]: J.W.L. Habraken, Landmeten en Waterpassen, Handleiding voor het Technisch Onderwijs. Tekst., (Batavia-Centrum, 1940), p.13.
[3]: J.A. Muller, A. Scheffer, Landmeten en Waterpassen, Leerboek ten dienste van het Middelbaar Technische Onderwijs en voor zelfstudie., (Haarlem, Antwerpen, Djakarta, 1954), p.101.
[4]: Chesterman, James Chesterman and Company Limited, Bow Works, Ecclesall Road, Sheffield II, England, Manufacturers since 1821 of Measuring Tapes, Rules, Gauges, Engineer's Tools, Catalogue No. 103, July, 1962, (Sheffield, 1962), p.iii.
[5]: Lerebours et Secretan, Catalogue et Prix des Instruments d'optique, de physique, de chimie, de mathématiques, d'astronomie et de marine, qui se trouvent ou s'exécutant dans les magasins et ateliers de Lerebours et Secretan. Opticiens de S.M. l'Empereur, de l'Observatoire et de la Marine..., (Paris, 1853), p.173.
[6]: Secretan, Extrait - Catalogue Secretan - Géodésie ... Measures de Longueur ... des Angles ... Nivellement ... Mathématiques. G. Secretan, Ingénieur Opticien. 13 Place du Pont-Neuf, Quai de l'Horloge, 41. Place Dauphine, 28. Paris, (Paris, 190x), pp.3-5.
[7]: Jordan W., Handbuch der vermessungskunde, Erster Band. Methoden der Kleinsten Quadrate und Niedere Geodäsie, (Stuttgart, 1877), p.152.
[8]: Chesterman, James Chesterman and Company Limited..., pp.B1,B3.

If you have any questions and/or remarks please let me know.

One handle has the groove on the inside, the other on the outside.
Figure 4: One handle has the groove on the inside, the other on the outside.
 
A section showing the various rivets and a whole metre plate. At the right one of the welds.
Figure 5: A section showing the various rivets and a whole metre plate. At the right one of the welds.

One of the copper plates indicating the whole five metres sections.
Figure 6: One of the copper plates indicating the whole five metres sections.
 
The frame has a straight section to allow space for one of the handles.
Figure 7: The frame has a straight section to allow space for one of the handles.

The tape came with its original (or at least period) bolt and wingnut.
Figure 8: The tape came with its original (or at least period) bolt and wingnut.
 
The difference in width with the 7421 tape (below) is clearly visible.
Figure 9: The difference in width with the 7421 tape (below) is clearly visible.

Surveyor's crosses Geodetic Sextants Theodolites Total Stations Levels Standards Tools Firms
1953 Wild K2 Alidade 19th c. measuring rod 19th c. Lerebours chain 20th c. Chesterman chain 20th c. Tibaut steel tape 20th c. Ahrend steel tape 20th c. Ahrend steel tape 1980s DOSbouw clinometer