Counterweights on a Steelyard and Why a Wall Settles Away From Its Batter
Effort varying with position along a rod, and the sinking of masonry on its foundations
The upper studies treat a sliding weight m on a rod, which gives the counterweight n a different effort at every position (h versus a), and a cord b c whose felt load from X changes with where it is tied on the shaft (very great at i, much less at q). A lower passage turns to masonry: because a wall rests on its foundations, the more heavily loaded part sinks more, and since the wall's batter (scarpa) carries only the outer skin of stone, the wall b c settles more than the batter a b, so the wall must shorten by the width of one stone. The diagrams show a graduated steelyard, a cord-and-shaft arrangement, columns of numbers, and a wall with a battered face.
On this page
A sliding weight gives the counterweight a different effort at each position
The weight m gives the counterweight n as many varied efforts as there are places it is moved to along its rod, for n plainly feels a different effort when the weight is at h than when it is at a. The note fanne sperientia calls for testing this by experiment.
Cord tension changes with its tie-point on the shaft
The load the cord b c feels from X varies with where the cord is tied on the shaft: tied at i, the weight X appears very great to the cord; tied at q, the weight X diminishes greatly. The adjacent column of numbers (40, 20, 10, 5...) tabulates this fall-off.
A wall settles more than its battered face
Because the wall rests on its foundations, the part of the foundation bearing more weight sinks more, and the less-loaded part sinks less. The batter (scarpa) carries only the skin of the wall, one stone wide; so the wall b c does not settle together with the batter a b, and, sinking more, the wall must shorten by the width of one stone.