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Platform Scale: Four Knife-Edge Hinges and Two Levers to a Steelyard (Fairbanks, 1831)

작성자

Mark

2. 11월 2026

Platform Scale: Four Knife-Edge Hinges and Two Levers to a Steelyard (Fairbanks, 1831)

A scale for wagons and carts, reading the same wherever the load stands. Erastus and Thaddeus Fairbanks of St. Johnsbury, Vermont, patented it in 1831. A plank platform nine by twelve feet rests on four knife-edge hinges, one at each corner, and two levers gather the load from all four onto one rod. The rod pulls on an ordinary steelyard, which then reads only a tenth or a twentieth of the load. Result: a platform scale reading ten times (or twenty times) what the steelyard shows, the same wherever the load stands on the platform. Source: E. & T. Fairbanks, US Patent No. 118 (1837), restating their patent of 13 June 1831. Unknown: the material and sizes of the hinges, knife-edges, fulcra and levers. Picture: patent drawing.

고급

1 week

안내

Build the frame

Lay two timber bed-sills, about 10 inches square and 16 feet long, parallel and about 7 feet apart. Bolt two end timbers, 8 by 14 inches and 12 feet long, across them near their ends. Just inside the end timbers, lay the two rockers, 8 inches square and 9 feet long, with their tops flush with the end timbers. Ours: carriage bolts.

이 단계의 재료:

각재6 2 sills, 2 end timbers, 2 rockers

둥근머리 볼트1 세트

필요한 도구:

두 사람용 동가리톱

오거

망치

Fit the four knife-edge hinges

Bolt a hinge firmly under each end of each rocker, one at every corner of the machine. Each hinge carries two knife-edges. One rests on a fulcrum standing on the bed-sill; the other reaches out to carry the platform. Set every knife-edge parallel to the others: knife-edges at an angle cramp and bind. Not given: the material and size of the hinges, knife-edges and fulcra.

이 단계의 재료:

알 수 없는 재료1 4 hinges, 8 knife-edges, 4 fulcra

둥근머리 볼트1 세트

필요한 도구:

오거

알 수 없는 치수

Join the levers

Run a horizontal lever from each rocker. The longer lever reaches across nearly to the opposite rocker. The shorter one ends at a point equally far from the axes of both, and hangs there from the longer lever by a chain, rod or stirrup, so the two act as one. From the end of the longer lever a rod rises straight up to a steelyard hung from a fixed support. With the two knife-edges of each hinge 6 inches apart and the rod hung 60 inches from the lever's axis, the load is ten times the steelyard reading; at 120 inches it is twenty times. Not given: the lever material. Ours: an iron chain and a wrought iron rod.

이 단계의 재료:

알 수 없는 재료1 2 levers

쇠사슬1 lever link

연철 환봉1 rod to the steelyard

대저울1 개

필요한 도구:

알 수 없는 치수

Lay the platform

Lay two timbers, short enough to pass freely between the rockers, parallel over the bed-sills. Spike stout planks 9 feet long across them, making a platform of about 9 by 12 feet. Under these timbers fasten iron plates that rest on the inner knife-edges of the hinges. Ours: nails as the spikes.

이 단계의 재료:

각재2 platform timbers