Elliot Steam Indicator's

Could anyone tell me anything about Darke's Patent High Speed Indicator, manufactured in 1870 by Elliot Bros of London eg were they used for measuring horsepower ?

Elliot Bros. were among the first producers of steam engine indicators for "high speed" engines. The indicator you mention was no doubt an extension of their newly developed "steam engine indicator" expertise and an attempt to compete in what by the 1870's was likely becoming a "crowded" market.

Developed in response to the American invention of the high speed engine by Charles T. Porter, the high speed steam engine indicator was the invention of an American college professor named Charles Richards, who was a friend, advisor and later colleague of Porter.

In 1863, Charles Porter exhibited his high speed engine at an "Engineering Fair" in England. (America being at the time in the midst of a Civil War) The engine was praised by the English press for it's technical merits but was privately derided for it's high speed and lack of a steam condenser, which was considered "standard" and essential by the English steam engineering practice of the time. During this exhibition, Porter met Richards who was showing his indicator invention as well.

The two hit it off immediately and together later improved and patented the indicator for better application to Porter's high speed steam engines.

An English instrument maker, Elliot Bros. were the first contractor and "patent licensees" to make the "Richards Indicator" which they continued as a successful product line for at least a generation afterwards. Many Elliot/Richards indicators were imported into the United States as the quicker adoption of the high speed steam engine in this country furthered the need for high speed adapted indicators as well.

Elliot held a technical market advantage for many years afterwards until Crosby, Ashcroft and other American instrument makers developed their own line of high speed adapted indicators.

To read further the development of the high speed steam engine and the indicators get, ENGINEERING REMINISCENCES written by Charles T. Porter. The book was reprinted by Lindsay Publications in 1985 and is still available (http://www.lindsaybks.com/) An enjoyable technical but rather disheartening read (at least for this engineer) that showed "politics" and "favoritism" goes before good engineering practice.

If you're into indicators, another technical book on indicators that is not reprinted is A TREATISE ON THE RICHARDS STEAM-ENGINE INDICATOR,WITH DIRECTIONS FOR ITS USE, also written by Porter. See www.abebooks.com for a used book search service that has this rather pricey reference.

Hope this helps, Joe "Yankee Mechanic" (Licensed professional engineer, 1st class operating steam engineer.)