1:48 Scale
The sector, also known as a proportional compass or military compass, was a major calculating instrument in use from the end of the sixteenth century until the nineteenth century. It is an instrument consisting of two rulers of equal length which are joined by a hinge. more...
 Home
Beanies
Construction Toys & Kits
Creative Toys/ Activities
Diecast & Vehicles
Educational Toys
Electronic Pets
Fast Food/ Cereal/ Sweets...
Games
Jigsaws & Puzzles
Model Kits
 Aircraft (Military)
Aircraft (Non-Military)
Boats & Ships
Cars
Character Figures/ Animals
Military
 1:100 Scale & Smaller
1:25 Scale & Larger
1:32 Scale
1:35 Scale
1:48 Scale
1:72 Scale
1:76 Scale
1:87 Scale
Other Military
Monsters
Motorcycles
Other Model Kits
Paints/ Accessories
Rockets
Scenery/ Props/ Buildings
Science Fiction
Space
Superhero
Trucks
Wooden/ Matchstick Kits
Other Toys & Games
Outdoor Toys & Activities
Pre-School/ Young Children
Radio-Controlled
Scalextric & Slot Car
Soft Toys/ Stuffed Animals
Steam
TV & Film Character Toys
Toy Soldiers
Vintage/ Classic Toys
Wargames & Role-Playing
A number of scales are inscribed upon the instrument which facilitate various mathematical calculations. It was used for solving problems in proportion, trigonometry, multiplication and division, and for various functions, such as squares and cube roots. Its several scales permitted easy and direct solutions of problems in gunnery, surveying and navigation. The sector derives its name from the forth proposition of the sixth book of Euclid, where it is demonstrated that similar triangles have their like sides proportional. It has four parts, two legs with a pivot (the articulation), a quadrant and a clamp (the curved part at the end of the leg) that enables the compass to function as a gunner's quadrant.
History
The sector was invented, essentially simultaneously and independently, by a number of different people just prior to the start of the 17th century. The credit is usually given to either Thomas Hood, a British mathematician, or to the Italian mathematician and astronomer Galileo Galilei. Galileo is certainly the most famous of these two individuals and earlier studies usually attributed its invention to him.
The Scales
The following is a description of the instrument as it was constructed by Galileo, and for which he wrote a popular manual. The terminating values are arbitrary and varied from manufacturer to manufacture.
The Arithmetic Lines
The innermost scale of the instrument are called the Arithmetic Lines from their division in arithmetical progression; that is, by equal additions which proceed out to the number 250. It is a linear scale generated by the function: f(n) = Ln/250, where n is an integer between 1 and 250, inclusive and L is the length at mark 250.
The Geometric Lines
The next scales are called the Geometric Lines and are divided in geometric progression out to 50. The lengths on the geometric lines vary as the square root of the labeled values. If L represents the length at 50, then the generating function is: f(n) = L(n/50)1/2, where n is a positive integer less than or equal to 50.
The Stereometric Lines
The Stereometric Lines are so called because their divisions are according to the ratios of solid bodies, out to 148. One of this scales applications is to calculate: when given one side of any solid body; find the side of another similar one that has a given volume ratio to it. If L is the scale length at 148, then the scale generating function is: f(n) = L(n/148)1/3, where n is a positive integer less than or equal to 148.
Read more at Wikipedia.org
|
Contact
