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.
Most oak tree leaves sport a deep green hue during the summer months, but transform into red and brown colors for the fall. 1  The oak tree is one of the most colorful fall trees, which is another reason they are popular in many types of landscaping today.ehold the breadth of the oak family. There are approximately 600 individual species listed in the Quercus (Oak) genus--most are trees, though a few are shrubs. Some are deciduous, some evergreen, some semi-evergreen.