English pewter English pewter While the term pewter covers a range of tin-based alloys, the term English pewter has come to represent a strictly-controlled alloy, specified by BSEN611-1 and British Standard 5140, consisting mainly of tin (ideally 92%), with the balance made up of antimony and copper. Significantly, it is free of lead and nickel. Although the exact percentages vary between manufacturers, a typical standard for present-day pewter is approximately 91% tin, 7.5% antimony and 1.5% copper. By the 15th century, the Worshipful Company of Pewterers controlled pewter constituents in England. This company originally had two grades of pewter, but in the
Blade element momentum theory We can derive an expression for formula_52 in a similar manner. This allows us to understand what is going on with the rotor and the fluid. Equations of this sort are then solved by iterative techniques. Blade element momentum theory Blade element momentum theory is a theory that combines both blade element theory and momentum theory. It is used to calculate the local forces on a propeller or wind-turbine blade. Blade element theory is combined with momentum theory to alleviate some of the difficulties in calculating the induced velocities at the rotor. This article emphasizes application of BEM to ground-based