Nitro engine

A nitro engine generally refers to an engine powered with a fuel that contains some portion (usually between 10% and 40%) of nitromethane mixed with methanol. Nitromethane is a highly combustible substance that is generally only used in very specifically designed engines, and is primarily used almost entirely by itself in certain high-performance classes of automotive drag racing.

The term "nitro" has only come into use in the last few years to describe these engines, and has its origins in marketing hype in the model car market. For the fifty or so years prior to this term since the engines were first developed, they were simply referred to as "glow engines", but the term "nitro" has more impact in ad copy. These engines are actually fueled by methanol, but the fuel is often doped with nitromethane as a performance additive. The ignition system consists of a glow plug - hence the proper term "glow" engine - which has a coil of platinum containing wire alloy, usually platinum-iridium. The glow plug is heated with electric current for starting, after which power is disconnected and the combination of residual heat and catalytic action of the platinum alloy with methanol ignites the fuel mixture.

Pencil sharpener

A pencil sharpener (also referred to in Ireland as a parer or topper) is a device for sharpening a pencil's writing point by shaving away its worn surface. Pencil sharpeners may be operated manually or by an electric motor

History

Before the development of dedicated pencil sharpeners, a pencil was sharpened by whittling it with a knife. Pencil sharpeners made this task much easier and gave a more uniform result. Some specialized types of pencils, such as carpenter's pencils are still usually sharpened with a knife, due to their flat shape, though since the 2000s a fixed-blade device with a rotatable collar has become available.

French mathematician Bernard Lassimonne applied for the first patent (French patent #2444) on pencil sharpeners in 1828, but it was not until 1847 that the pencil sharpener in its recognisable modern form was invented by fellow Frenchman Thierry des Estivaux. The first American pencil sharpener was patented by Walter K. Foster of Bangor, Maine in 1855. Electric pencil sharpeners for offices have been made since at least 1917.