A semi-portable engine is a form of

stationary steam engine Stationary steam engines are fixed steam engines used for pumping or driving mills and factories, and for power generation. They are distinct from locomotive engines used on railways, traction engines for heavy steam haulage on roads, steam c ...

. They were built in a factory as a single unit including the

boiler A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, centr ...

, so that they could be rapidly installed on site and brought into service. Although the earliest examples can be dated to

Richard Trevithick Richard Trevithick (13 April 1771 – 22 April 1833) was a British inventor and mining engineer. The son of a mining captain, and born in the mining heartland of Cornwall, Trevithick was immersed in mining and engineering from an early age. He ...

in around 1800, the type is best known as the products of Robey & Co. of Lincoln who patented their design in 1873. The distinctive Robey design was an undertype with one or two cylinders mounted beneath a

locomotive boiler A fire-tube boiler is a type of boiler in which hot gases pass from a fire through one or more tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating t ...

. The cylinders were mounted beneath the

smokebox A smokebox is one of the major basic parts of a steam locomotive exhaust system. Smoke and hot gases pass from the firebox through tubes where they pass heat to the surrounding water in the boiler. The smoke then enters the smokebox, and is ...

and a transverse crankshaft ran crossways beneath the boiler, just ahead of the firebox. The frame of these engines was a large

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...

box casting that formed a single piece foundation for both the engine and boiler. Owing to the small height available with this pre-fabricated foundation, the semi-portable engine had no large

flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, assu ...

, as was standard practice for stationary engines. The need for a more even power delivery, without the smoothing effect of a flywheel, encouraged the use of twin cylinder engines, even though a larger single cylinder would be cheaper and equally powerful. Where a flywheel was supplied, this was smaller than usual and would still require a pit digging in which to site it. During factory testing, the engine bed would have to be raised on timber baulks to provide this extra height. A typical large stationary engine of this time used a number of

lancashire boiler A shell or flued boiler is an early and relatively simple form of boiler used to make steam, usually for the purpose of driving a steam engine. The design marked a transitional stage in boiler development, between the early haystack boilers and ...

s, set in brickwork surrounds. These took a considerable time to build their masonry, let alone install the equipment. The vertical cross-tube boilers used for small portable machinery such as

steam crane A steam crane is a crane powered by a steam engine. It may be fixed or mobile and, if mobile, it may run on rail tracks, caterpillar tracks, road wheels, or be mounted on a barge. It usually has a vertical boiler placed at the back so that ...

s had much less steam generation capacity and could only run at full power intermittently. Locomotive boilers though, as used here, had greater capacity and could provide a mechanical plant that could run continuously for long periods. Robey also built some examples, around 1886, with launch-type boilers. Marshall undertype steam engine, Fengate Farm - geograph

Marshall undertype steam engine, Fengate Farm - geograph

Where engines were to be shipped overseas, the ancillary equipment, spare parts etc. were packed into riveted iron sheet boxes. On installation, these boxes could be re-used as water tanks.

Applications

Many of these semi-portable engines were used for large civil engineering and mining projects, driving

water pump A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they ...

air compressor An air compressor is a pneumatic device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). By one of several methods, an air compressor forces ...

s, drilling and piling machinery. Some specialised engines were also built with drums for

winding An electromagnetic coil is an electrical conductor such as a wire in the shape of a coil (spiral or helix). Electromagnetic coils are used in electrical engineering, in applications where electric currents interact with magnetic fields, in de ...

in mine shafts, especially when exploratory shafts were being sunk. If a mine was successful and went into production, a full

engine house __NOTOC__ An engine house is a building or other structure that holds one or more engines. It is often practical to bring engines together for common maintenance, as when train locomotives are brought together. Types of engine houses include: * m ...

could be built later.

References

{{Reflist Stationary steam engines

Applications

See also

References