de Prony brake dynamometers at a tractor contest in 1910. Schematic of a de Prony brake. The de Prony Brake is a simple device invented by Gaspard de Prony to measure the torque produced by an engine. The term  brake horsepower  is one measurement of power derived from this method of measuring torque. (Power is calculated by multiplying torque by rotational speed .).
Typically tree trunks are thought of as being in various shades of brown. They can have many different colours to them, however.Grey is a common colour in tree trunks, as is green when they're younger. Specific species of trees usually have specific bark colour at specific times of year so you should look up the trees you're interested in if you need more information.ypically tree trunks are thought of as being in various shades of brown. They can have many different colours to them, however.
Poplar is a closed-grain hardwood that has many uses. Poplar is a type of wood that is commonly used to make furniture, wood toys, moldings and paneling.ecause of this, there may be some confusion as to why poplar wood is considered a âhardwood.â Since the yellow poplar is a deciduous tree â meaning that the tree sheds its leaves annually â the wood from the yellow poplar is considered to be a hardwood rather than the âsoftwoodsâ that evergreen trees produce.