Chain Drum
Description
A surveyor's chain drum made up of a thin metal band or tape wound on a metal holder. There is a winding handle on one side and a leather strap on the opposite side, the two sides of the holder being held together using a screw and wing nut. There is a plastic label stuck on both sides which reads " DANGER / BEWARE OF / POWER LINES. "
A chain man (surveyor's assistant) would hold onto this chain drum while the surveyor held the end of the steel band which he placed in a “link stick” for measuring against the side of the theodolite or underneath it by means of plumb bob string. The band could be thrown across creeks to the surveyor on the other side for measuring the distance from bank to bank, for example. The number stamped on the side of the drum was recorded with the Lands and Survey department as it needed to be checked periodically for accuracy - bands could stretch and break, particularly as they became brittle with age.
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Public comments
It’s a surveying chain drum which superseded the Gunter's chain. Gunter’s Chain being 100 links long x 0.201168 = 20.12 metres, the standard width of a New Zealand road, boundary to boundary. The terminology “chain” as in the 100 links of the Gunter's chain carried through to this chain drum. The chain-man being the surveyors assistant held onto this chain drum while the surveyor held onto the end of the steel band which he placed in a “link stick” for measuring against the side of the theodolite or under by means of plumb bob string. The end of this band is broken which had an eyelet and leather strip attached which was held in place by one of the 2 brackets on the side of the chain drum. The band could be carefully gathered in number 8 loops and thrown across creeks to the surveyor on the other side for measuring bank to bank etc. The number stamped on the side of the drum was recorded with the Lands and Survey department as it needed to be checked for accuracy periodically as the bands can stretch and always broke, more so if they became brittle with age. Mended with brass sleeves and solder. If they broke in the field they can be joined temporarily with electrical wire joiners with the insolation cut off so they did not catch on foliage etc.
- Darryn posted 2 years ago.