General Information

Serial #

1872-117 (Inv.)

Part Number

1

Total Parts

1

AKA

N/A

Patents

N/A

General Description

WOOD/ BRASS

Dimensions

Note: These reflect the general size for storage and are not necessarily representative of the object's true dimensions.

Length

64.2 cm

Width

33.6 cm

Height

45.1 cm

Thickness

N/A

Weight

N/A

Diameter

N/A

Volume

N/A

Lexicon

Group

Mathematics

Category

Models

Sub-Category

N/A

Manufacturer

AKA

DeLagrange

Country

France

State/Province

Unknown

City

Paris

Context

Country

Unknown

State/Province

Unknown

Period

Unknown

Canada

In 1872 the South Kensington Museum in London UK commissioned Fabre de Lagrange of Paris to make 45 mathematical models for their Education Collection. The Canada Science and Technology Museums Corporation obtaind 28 of them from the Science Museum in 1973 through a deaccession. They still have seventeen models from the original commission.

Function

USED AS VISUAL AID FOR TEACHING DESCRIPTIVE GEOMETRY OF ENGINEERING.

Technical

In this model, the inner drum, of yellow thread, represents this surface. In a skew surface, with a right line director; and its faces, the planes of the two semi-circles, are usually parallel, although the model permits them to be placed obliquely to one another. The horizontal line joining the centres of the two large semi circles is the right line director. The construction for any one of the generating lines is as follows - Draw a plane through the right line director at any selected obliquity. This will give the radii of the outside circles, and the line joining the points at which it cuts the inside semi circles will be a generator of the surface. This line will evidently pass through the director line, because it is in the same plane with it. In stone or brick work, the sides of the voussoirs joints are therefore plane, and the simplicity thus gained is the chief reason for adopting this form of skew arch. It is usual to take the right line director perpendicular to the openings and symmetrical to them, that is to say, passing through the middle point of the parallelogram of the springing plane. When the openings are not parallel the voussoir joints shown by the model are deformed into hyperbolic paraboloids. This deformation is, however, very slight, and in practical work would be avoided altogether by adhering to the principle of drawing a plane through the director line. The opening of the voussoirs is usally determined by dividing the outer semi-circle into equal parts. This form of arch is incovenient when the obliquity and the length of the barrel are excessive, for the generators are not generating lines of the cylinder containing the opening semi circles, but chords of it, and, therefore, at the middle, falling considerably inside it. The arch, therefore, droops in the middle, and this would be ugly and inconvenient if the proportions were excessive.

Area Notes

Unknown

Details

Markings

S/N '1872-117'

Missing

Two legs from underside of top

Finish

RECTANGULAR WOOD BOX BASE 24-1/2" X 12-3/4" X 10-1/2" HIGH/ ON THE COVER AT ONE END IS A 12" DIA. BRASS PLATE SWIVELLED TO A BRASS FRAME/ MOUNTED ON THE FRAME 11-1/4" APART, ARE 2 BRASS HALF-RINGS SWIVELLED TO THE TOP BAR BY THE MIDDLE OF THEIR FLAT SIDE. RINGS ARE 10" DIA./ THERE ARE 2 ARCS FOR THREADS TO RUN BETWEEN THE 2 HALF-RINGS, THEN DROP INTO THE BOX THROUGH A SLOT IN THE FLAT BRASS PLATE/ FLAT PLATE HAS A HANDLE TO ROTATE IT; GOOD, FEW THREADS BROKEN/

Decoration

N/A