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

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 cars , agricultural engines used for ploughing or...

 of unusual design, intended to solve the problem of stopping on dead centre

Dead centre

In a reciprocating engine, the dead centre is the position of a piston in which it is farthest from, or nearest to, the crankshaft. The former is known as top dead centre while the latter is known as bottom dead centre ....

.

Dead centres

The "dead centre

Dead centre

In a reciprocating engine, the dead centre is the position of a piston in which it is farthest from, or nearest to, the crankshaft. The former is known as top dead centre while the latter is known as bottom dead centre ....

" of a piston engine with cranks

Crank (mechanism)

A crank is an arm attached at right angles to a rotating shaft by which reciprocating motion is imparted to or received from the shaft. It is used to change circular into reciprocating motion, or reciprocating into circular motion. The arm may be a bent portion of the shaft, or a separate arm...

 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

Crankshaft

The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

. If a large stationary engine

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 cars , agricultural engines used for ploughing or...

 stops on dead centre, it will be unable to re-start 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

Barring engine

A barring engine is a small engine, usually a steam engine, that forms part of the installation of a large stationary steam engine. It is used to avoid the problem of the main engine stopping on its dead centre and so being unable to re-start....

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

Connecting rod

In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts linear motion into rotating motion....

 linkages, and geometry

Geometry

Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....

 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" 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. 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 connecting rod

Connecting rod

In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts linear motion into rotating motion....

 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 between the cylinders, this frame tilts back and forth as the engine rotates and so the cylinder crossheads 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 for use with Stirling engine

Stirling engine

A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....

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.

Marine engines

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

Glasgow

Glasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...

, in 1887. It was intended for use as a marine engine

Marine steam engine

A marine steam engine is a reciprocating steam engine that is used to power a ship or boat. Steam turbines and diesel engines largely replaced reciprocating steam engines in marine applications during the 20th century, so this article describes the more common types of marine steam engine in use...

, but it is unclear if they were ever used as such.

Stationary engines

John Musgrave & Sons

John Musgrave & Sons

John Musgrave & Sons was a company that manufactured stationary steam engines. It was based at The Globe Ironworks, Bolton, Greater Manchester in England...

 of the Globe Ironworks, Bolton

Bolton

Bolton is a town in Greater Manchester, in the North West of England. Close to the West Pennine Moors, it is north west of the city of Manchester. Bolton is surrounded by several smaller towns and villages which together form the Metropolitan Borough of Bolton, of which Bolton is the...

 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

IHP

IHP is a three letter acronym that can stand for:*International Hydrological Programme*Indicated horsepower*Innovations for High Performance Microelectronics, a German institute and part of the Gottfried Wilhelm Leibniz Scientific Community...

 with quadruple expansion working. Ten of these quadruple expansion, four cylinder engines were built, the remainder mostly being two-cylinder compound engines, as the Park Street Mill engine. The larger engines used Corliss valve

Corliss Steam Engine

A Corliss steam engine is a steam engine, fitted with rotary valves and with variable valve timing patented in 1849, invented by and named after the American engineer George Henry Corliss in Providence, Rhode Island....

s.

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

Southport is a seaside town in the Metropolitan Borough of Sefton in Merseyside, England. During the 2001 census Southport was recorded as having a population of 90,336, making it the eleventh most populous settlement in North West England...

.

A poster in the Science Museum

Science museum

A science museum or a science centre 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 and industrial machinery, etc. Modern trends in museology have broadened the range of...

 advertises engines to "Fleming, Ferguson, & Dixon's patent". These are twin-cylinder compound engines with a single semi-rotary valve per cylinder (as for Park Street Mill) and are offered in a range from 8 to 250 ihp

IHP

IHP is a three letter acronym that can stand for:*International Hydrological Programme*Indicated horsepower*Innovations for High Performance Microelectronics, a German institute and part of the Gottfried Wilhelm Leibniz Scientific Community...

 and with speeds from 160 to 250 rpm. Their working pressure is not specified, but the same poster also offers Lancashire boilers of up to 200 psi

Pounds per square inch

The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...

.

All of these engines are of robust construction, with large cast iron

Cast iron

Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

 frames that have the cylinders cast integrally with them. The Park Street Mill engine is made from two large castings bolted together along a central plane and with the steam passages cored directly into the castings.

The crossheads 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 & Ferguson
  • 1887
  • 1889
  • 1890
  • 1891
• Musgrave & Dixon
  • 1893

Park Street Mill

Only one Musgrave non-dead-centre engine is known to survive, now preserved at the Bolton Steam Museum 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 (not non-dead-centre): much smaller barring engine

Barring engine

A barring engine is a small engine, usually a steam engine, that forms part of the installation of a large stationary steam engine. It is used to avoid the problem of the main engine stopping on its dead centre and so being unable to re-start....

s.

Photo galleries of this engine may be seen on the NMES web site or a video of it in action.. There are also images on Flickr.

Models

• Science Museum, London

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

• Model Engineer magazine
  Model Engineer magazine
  Model Engineer Magazine was first published to support the hobby of model engineering in 1898 by Percival Marshall, who was to remain its editor for over 50 years. It has been published by My Hobby Store since 2008. The magazine addressed the emergence of a new hobby — the construction of models ...
  
  

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