Desk scales : C E W Bean

Places
Accession Number REL39686
Collection type Heraldry
Object type Heraldry
Physical description Brass, Velveteen, Wood
Maker Unknown
Date made Unknown
Conflict Period 1930-1939
Period 1950-1959
Period 1960-1969
Second World War, 1939-1945
Period 1920-1929
Period 1940-1949
Description

Set of desk scales for weighing correspondence. The brass Roberval balance scales are mounted on a wooden base which has three round, velveteen lined recesses to house the 8 weights. The weights are 8 ounces, 4 ounces, 2 ounces, 1 ounce, 1/2 ounce, 1/4 ounce, 15 grams and 4 grams. The scales have two rectangular plates and one is impressed with 'POSTAL RATES/ FOR/ LETTERS/ NOT EXCEEDING 4 0Z 1D/ 6 .. 1 1/2/ 8 .. 2/ 10 .. 2 1/2/ 12 .. 3/ 14 .. 3 1/2/ 16 .. 4/ BOOKS 2 OZ - 1/2 D'. The horizontal arm of the scale is impressed with 'WARRANTED ACCURATE'.

History / Summary

The Roberval Balance is a weighing scale presented to the French Academy of Sciences by the French mathematician Gilles Personne de Roberval in 1669.

In this scale, two identical horizontal beams are attached, one directly above the other, to a vertical column, which is attached to a stable base. On each side, both horizontal beams are attached to a vertical beam. The six attachment points are pivots. Two horizontal plates, suitable for placing objects to be weighed, are fixed to the top of the two vertical beams. An arrow on the lower horizontal beam (and perpendicular to it) and a mark on the vertical column may be added to aid in leveling the scale.

The object to be weighed is placed on one plate, and calibrated masses are added to and subtracted from the other plate until level is reached. The mass of the object is equal to the mass of the calibrated masses - regardless of where on the plates items are placed. Since the vertical beams are always exactly vertical, the masses can only practically exert wholly downwards force (vertical vectors with no horizontal vectors).