Musgrave's ''non-dead-centre'' engine was a

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 car ...

of unusual design, intended to solve the problem of stopping on dead centre. It was designed in 1887 to serve as a

marine engine An inboard motor is a marine propulsion system for boats. As opposed to an outboard motor, where an engine is mounted outside the hull of the craft, an inboard motor is an engine enclosed within the hull of the boat, usually connected to a prop ...

. It used a pair of linked cylinders to prevent the engine from stopping in a position where no turning force can be applied. At least one engine is known to survive.

Dead centres

The ' dead centre' of a

piston engine A reciprocating engine, more often known as a piston engine, is a heat engine that uses one or more Reciprocating motion, reciprocating pistons to convert high temperature and high pressure into a Circular motion, rotating motion. This article ...

with cranks is when the piston is at the ''exact'' top or bottom of the stroke and so the piston cannot exert any torque on the

crankshaft A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...

. If a

steam engine A steam engine is a heat engine that performs Work (physics), mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a Cylinder (locomotive), cyl ...

stops on dead centre, it will be unable to restart from that position. Several solutions to this have been applied. One of the simplest is to try not to stop in this position, the crudest to apply a strong arm with a crowbar to turn the engine over a little. Small steam

barring engine A barring engine (also called barring motor) is a small engine that forms part of the installation of a large engine, and is used to turn the main engine to a favourable position from which it can be started. If the main engine has stopped close ...

s were also used to move the engine away from dead centre before starting. If the engine has multiple cylinders, most geometries for these are arranged so that all cylinders are never at dead centre together and so one may always be used for starting. Musgrave's solution was more complex: using two cylinders, additional

connecting rod A connecting rod, also called a 'con rod', is the part of a reciprocating engine, piston engine which connects the piston to the crankshaft. Together with the crank (mechanism), crank, the connecting rod converts the reciprocating motion of the p ...

linkages, and

geometry Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...

to avoid the problem. Dead centre is rarely a problem for internal combustion engines, as these usually require cranking over to provide cylinder compression and so do not attempt to self-start from stationary. Some large stationary diesel engines, where these used a compressed air starting mechanism, have suffered from the problem of dead centres and so used a small manual barring gear.

Geometry

In appearance, the engine resembles a '

parallel twin A straight-twin engine, also known as an inline-twin, vertical-twin, inline-2, or parallel-twin, is a two-cylinder piston engine whose cylinders are arranged in a line along a common crankshaft. Straight-twin engines are primarily used in motor ...

' with two vertical cylinders and a single crankshaft between them, but set perpendicular to the line of the cylinders and sharing a single crankpin. A parallel twin with this many cylinders would be self-starting from dead centre anyway (assuming the usual crankshaft with cranks at 90°). The geometry in operation is more like that of a vee-twin engine. The two cylinders work together, but with one leading the other by approx. 30°. The difference in this case is that the cylinders are no longer directly in line with the crankshaft and so use the connecting rod as a form of

bellcrank A bellcrank is a type of crank that changes motion through an angle. The angle can range from 0 to 360 degrees, but 90-degree and 180-degree bellcranks are most common. The name comes from its first use, changing the vertical pull on a rope to ...

. If one cylinder is at dead centre, the other will be away from it by the amount of this angle. A vee-twin would offer all the advantages of the Musgrave engine, but would only need two simple connecting rods. The cylinders would no longer be parallel, but that is far from impractical to manufacture, as demonstrated by the even earlier diagonal engine.

Connecting rod

The two cylinders are connected to the single crankpin through a complex

of four separate links, and a rigid mounting point to the frame and cylinders. The main connecting rod is a large triangular frame, driven by both cylinders and driving the crankpin. Owing to the

phase difference In physics and mathematics, the phase (symbol φ or ϕ) of a wave or other periodic function F of some real variable t (such as time) is an angle-like quantity representing the fraction of the cycle covered up to t. It is expressed in such a s ...

between the cylinders, this frame tilts back and forth as the engine rotates and so the cylinder

crosshead In mechanical engineering, a crosshead is a mechanical joint used as part of the slider-crank linkages of long stroke reciprocating engines (either internal combustion or steam) and reciprocating compressors to eliminate sideways force on the ...

s drive it through two short connecting rods, allowing for some movement side-to-side. A large rocking lever attached to the engine's frame holds the connecting rod roughly central. On the Bolton engine, this lever is extended past the frame and used to drive the condenser air pump.

Similarities to the Ross yoke

A similar mechanism appears to have been invented independently, much later on. This is the Ross yoke, invented by

Andy Ross Andrew Bryant Ross is an American musician. He has been the guitarist, keyboardist and vocalist for the rock band OK Go since 2005. He is also behind a solo project, Secret Dakota Ring, which released albums in 2004 and 2008. Ross is also co-f ...

for use with

Stirling engine A Stirling engine is a heat engine that is operated by the cyclic expansion and contraction of air or other gas (the ''working fluid'') by exposing it to different temperatures, resulting in a net conversion of heat energy to mechanical Work (ph ...

s. A pair of parallel cylinders, one for the piston (driving), one containing the (driven) displacer, are connecting so that they drive back and forth with a suitable phase shift between them.

History

Marine engines

The design of the engine originated with W.Y. Fleming and P.Ferguson, marine engineers of

Glasgow Glasgow is the Cities of Scotland, most populous city in Scotland, located on the banks of the River Clyde in Strathclyde, west central Scotland. It is the List of cities in the United Kingdom, third-most-populous city in the United Kingdom ...

, in 1887. It was intended for use as a

, and at least 23 were supplied to ship builders requiring compact engines suitable for restricted space in engine rooms.

Stationary engines

John Musgrave & Sons John Musgrave & Sons was a company that manufactured stationary steam engines. It was founded in 1839 by John Musgrave and his son, Joseph, at the Globe Ironworks, in Bolton, historically in Lancashire, England. In 1854 the company supplied a t ...

of the Globe Ironworks,

Bolton Bolton ( , locally ) is a town in Greater Manchester in England. In the foothills of the West Pennine Moors, Bolton is between Manchester, Blackburn, Wigan, Bury, Greater Manchester, Bury and Salford. It is surrounded by several towns and vill ...

was a mill engine builder, supplying the local cotton mills. He licensed the design in 1892, then patented further improvements to it in 1893. Musgrave built up to 50 of these engines, the largest offering 1,500 ihp with quadruple expansion working. Ten of these quadruple expansion, four cylinder engines were built, the remainder mostly being two-cylinder

compound engine A compound engine is an engine that has more than one stage for recovering energy from the same working fluid, with the exhaust from the first stage passing through the second stage, and in some cases then on to another subsequent stage or even s ...

s, as the

Park Street Mill A park is an area of natural, semi-natural or planted space set aside for human enjoyment and recreation or for the protection of wildlife or natural habitats. Urban parks are green spaces set aside for recreation inside towns and cities. N ...

engine. The larger engines used

Corliss valve Corliss is both a surname and a given name. People Given name * Corliss Lamont (1902–1995), American philosopher, political activist, and philanthropist * C. C. Moseley (1894–1974), American aviator and aviation businessman * Corliss Palmer ...

s. (illustration shown in Hills, Power from Steam) The non-dead-centre mechanism also evened-out power as the crank rotated, making it suitable for driving dynamos for electricity generation. The engine also had relative high speed for its day, making it possible to drive dynamos directly. A 500 hp Corliss valve engine was installed for electricity generation in

Southport Southport is a seaside resort, seaside town in the Metropolitan Borough of Sefton in Merseyside, England. It lies on the West Lancashire Coastal Plain, West Lancashire coastal plain and the east coast of the Irish Sea, approximately north of ...

. A poster in the

Science Museum A science museum is a museum devoted primarily to science. Older science museums tended to concentrate on static displays of objects related to natural history, paleontology, geology, Industry (manufacturing), industry and Outline of industrial ...

advertises engines to "Fleming, Ferguson, & Dixon's patent". These are twin-cylinder compound engines with a single semi-rotary valve per cylinder (as for

) and are offered in a range from 8 to 250 ihp and with speeds from 160 to 250 rpm. Their working pressure is not specified, but the same poster also offers

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 t ...

s of up to 200

psi Psi, PSI or Ψ may refer to: Alphabetic letters * Psi (Greek) (Ψ or ψ), the twenty-third letter of the Greek alphabet * Psi (Cyrillic), letter of the early Cyrillic alphabet, adopted from Greek Arts and entertainment * "Psi" as an abbreviat ...

. All of these engines are of robust construction, with large

cast iron Cast iron is a class of iron–carbon alloys with a carbon content of more than 2% and silicon content around 1–3%. Its usefulness derives from its relatively low melting temperature. The alloying elements determine the form in which its car ...

frames that have the cylinders

cast Cast may refer to: Music * Cast (band), an English alternative rock band * Cast (Mexican band), a progressive Mexican rock band * The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis * ''Cast'', a 2012 album by Trespassers William ...

integrally with them. The

engine is made from two large castings bolted together along a central plane and with the steam passages

core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (laboratory), a highly specialized shared research resource * Core (manufacturing), used in casting and molding * Core (optical fiber ...

d directly into the castings. The

s are of the slipper pattern. This design has asymmetric bearing surfaces and so supports the forces better when the engine rotating in one direction than the other. They are commonly found on stationary engines that do not need to be reversed. However, in the Musgrave design, the two slideways face each other and so one of them will always be working "in reverse" to usual practice.

Patents

* Fleming & FergusonHills, Power from Steam, ch.13 ref.27 ** 1887 ** 1889 ** 1890 ** 1891 *Musgrave & Dixon ** Improvements in Triple Expansion Engines, (1893).

Surviving examples

Park Street Mill

Only one Musgrave non-dead-centre engine is known to survive, now preserved at the

Bolton Steam Museum Bolton Steam Museum is a museum in Bolton, Greater Manchester, England, which houses a variety of preserved steam engines. Based in the cotton store of the former Atlas Mill in Mornington Road, it is owned and run by the Northern Mill Engi ...

as part of the Northern Mill Engine Society collection. On steam days these engines (or at least some) may be seen in action. The collection also includes two other engines built by Musgrave's, which are not non-dead-centre engines but much smaller

Models

Science Museum, London The Science Museum is a major museum on Exhibition Road in South Kensington, London. It was founded in 1857 and is one of the city's major tourist attractions, attracting 3.3 million visitors annually in 2019. Like other publicly funded ...

: A small model of a twin-cylinder compound engine is on display. *

Model Engineer magazine A model is an informative representation of an object, person, or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin , . Models can be divided int ...

: In 2009 the ''Model Engineer'' serialized the construction of a Musgrave engine, from castings supplied by the German firm of Lothar Matrian.

References

{{reflist, colwidth=30em Stationary steam engines