Friday 12 January 2007

Early Locomotive Design

This post is based on a talk given by Jan Ford at the Museum of Science and Industry in Manchester.

In the eighteen twenties, Manchester was already a thriving city with a business class of prosperous, imaginative entrepreneurs. Landlocked, Manchester looked to Liverpool, both for the import of raw materials and for the export of finished products. But communications with Liverpool, by road and canal, were inconvenient and slow.

One of the most successful early railways was the Stockton and Darlington Railway opened in 1825 in the North East of England. Although it was a mineral line and speeds were slow, it proved that steam locomotives offered a practical method of shifting heavy loads on a regular basis. With this inspiration, the Manchester businessmen looked to build a railway line from Manchester to Liverpool. Passenger carrying was envisaged from the start. The promoters’ dream was to travel from Manchester to Liverpool, transact their business and return to Manchester in time for dinner the same day!

There were vested interests who opposed the railway and the first attempt at securing the necessary Act of Parliament failed. Better prepared for the second attempt, the Act was secured. George Stephenson became involved in the project and the route decided upon included gradients (‘inclined planes’) gentle enough to allow the use of steam locomotives on the main part of the route. But the matter was not cut-and-dried. Locomotive design was still in its infancy and the possibility of fixed steam engines with cable haulage was seriously entertained.

A stationary engine could, if required, be large and fed from a generously-proportioned boiler. Permanent arrangements for the supply of water and fuel could be made. In contrast, locomotive engines had to fit the boiler and all the mechanism of the steam engine together with supplies of coal and water on a wheeled carriage which then proceeded to shake itself to pieces whilst breaking the rails upon which it ran. Materials were of generally poor quality and production techniques, such as involved in the casting and boring of cylinders, were still primitive. Essentially, locomotive building was blacksmith’s work.

The Directors of the Liverpool and Manchester Railway decided upon a competition, with a £500 prize to the winner, to find the best steam locomotive design before finally deciding upon the method of traction for their line. In 1929, the Rainhill Trials were held, amid massive public interest. The watching spectators viewed the event like a horse race, but the Directors had a more serious intent, seeking a locomotive which could haul a significant load and prove reliable but was not so heavy as to damage the track. The competitors who made an appearance represented a variety of approaches to the problems.

‘Cycloped’ was an ingenious way of utilising the power of a horse on a railway but it represented a dead-end.

‘Novelty’ was the entrant which caught the eye of the crowd, dashing around at spectacular speeds. The design was derived from the reasonably-successful steam carriage but 'Novelty' was plagued with problems and the design would have been difficult to extend into a larger, more powerful machine.

'Perseverance' was another 'steam carriage' design but here the problems were so severe that she was withdrawn from the competition without running.

There were two contenders from the North East. The Stephensons, father and son, produced ‘Rocket’, the eventual winner. Timothy Hackworth competed with ‘Sans Pareil’. The similarities and differences between these locomotives illustrate the essentials of an effective locomotive design and we’ll study these competitors in greater detail in a later article.

Although ‘Rocket’ won the Rainhill Trials and the Stephensons produced a number of copies for the Liverpool and Manchester in the 1830s, they were rather lightweight machines. The fairly similar ‘Northumbrian’ class quickly followed. But, in very short order, the Stephensons produced the ‘Planet’ which, in its own way, was as revolutionary as ‘Rocket’ had been.

Having put the essentials in place, design evolved in a less spectacular manner. To allow a larger locomotive, an extra pair of wheels was added and the 2-2-2 wheel arrangement of the ‘Patentee’ was copied by a number of manufacturers. For goods engines requiring additional traction, the leading pair of wheels was replaced by a coupled axle, giving an 0-4-2 wheel arrangement. In 1838, when the short-lived partnership of Todd, Kitson and Laird built ‘Lion’ for the Liverpool and Manchester Railway, they produced an 0-4-2 of distinctly Stephenson appearance.

As materials improved, bar or plate frames tended to replace the use of sandwich frames (or simply hanging parts on the boiler itself) but the general layout of locomotives of this period, with horizontal boiler and more-or-less horizontal cylinders inside or outside the framing was retained for the next century.

'Henry'

These notes were written some years ago when I was a regular driver at Birmingham Railway Museum. I believe I was the last person to have the locomotive in steam before the firebox was finally condemned. I'm not aware that the locomotive has been returned to steam (but I may be wrong). At the time, there was a 'Henry Club', championed by Jo Howard, to interest children in steam railways.

Henry is a classical-design four-coupled industrial saddle tank locomotive produced in 1901 but very similar in design to locomotives produced half a century later.

Boiler: Parallel boiler with round-topped, flush firebox. Conventional dome with 2-port slide-valve regulator. Firebox provided with a single row of firebars. Ashpan provided with a single, trailing damper, operated by a lever moving vertically on the left side of the firebox. Round firehole with split firedoors sliding horizontally. Ramsbottom safety valve (twin branch with single coil spring and relieving lever extending into cab) on top of firebox outside cab together with steam manifold. An auxiliary steam manifold is provided inside the cab on top of the firebox. Built-up smokebox with hinged, dished smokebox door, secured by a dart and tightened by a wheel. Cast chimney. Feed water introduced on vertical centre line of boiler, midway along length, on both left and right sides at clack valves provided with integral shut-off cocks. The clacks are supplied from two injectors with integral water cocks, bolted onto the underside of the saddle towards the rear of the tank, one on each side of the boiler. The water cocks are operated from the cab by horizontal levers which pull to open, push to shut off. Steam to the injectors is supplied by two cocks on the manifold operated from handles inside the cab. The overflow from each injector is taken downwards through the footframing.

Coal and water: Two coal bunkers are provided, one on either side of the firebox. Water is provided in a saddle tank, extending from the front of the smokebox to the rear of the boiler, but not covering the firebox. The dome and chimney pierce the tank, which has a lift-off lid for filling at the firebox end.

Steam distribution: The main steam pipe runs from the regulator valve in the dome to the smokebox, where it branches into two steam pipes passing to the valve chests. The two valve chests are mounted vertically between the frames adjacent to the two cylinders mounted outside the frames. Steam distribution is by slide valves operated from Stephenson's Link motion. The driving axle is provided with four eccentrics, forward and reverse for each cylinder. The end of each forward eccentric rod is connected to the top of the associated curved, slotted expansion link, the reverse eccentric rod to the bottom of the link. Each valve rod is operated from a die block sliding in the curved slot of the associated expansion link. Each link is suspended from the transverse weigh shaft by two lifting links. The weigh shaft is operated from the reversing lever on the right hand side of the cab via the reversing rod. Notches in the reversing quadrant allow the reversing rod to be set to Full Forward, Expansive Forward, Mid-gear, Expansive Back, Full Back. Drain cocks are provided for the front and back of each cylinder and for each valve chest. All six cocks are operated via a mechanical linkage from a vertical lever alongside the reversing quadrant (lift for cocks open).

Each cylinder drives a crosshead guided by two slide bars. The slide bars are attached to the cylinder casting at the front and a plate motion bracket at the rear. The crosshead drives the crankpin on the driving axle via the gudgeon pin and connecting rod. Each big end is provided with two semi-circular bearing brasses, adjusted by a gib and cotter. Two coupling rods distribute power to the leading axle.

Braking: Henry is provided with a single steam brake cylinder with relief valve mounted under the rear left of the cab with the piston rod operting horizontally, fore and aft, onto the transverse brake shaft. Two sets of brake rigging connect the brake shaft to the bottom of four brake hangers provided with cast brake blocks. A coil spring is provided at the front of the locomotive on the centreline to pull off the brakes. The steam brake is controlled by a rotary brake valve on the auxiliary steam manifold (fountain) in the cab. When the valve is open, live steam is supplied to the brake cylinder, proportional to valve opening. Closing the valve vents the brake cylinder to atmosphere via a pipe passing upwards through the cab roof.

To allow the locomotive to work passenger trains, a vacuum ejector has been provided above the foot framing on the right hand side of the smokebox. This is controlled from a live steam cock on the right hand side of the cab. The steam cock should not be opened too far as, otherwise, turbulence within the ejector will render it less effective at creating vacuum. The ejector exhausts a system of 2" piping connected to standard flexible vacuum hoses on the front and rear buffer beams. A driver's application valve and vacuum relief valve is provided on the right-hand side of the

Lubrication: Each axlebox has an integral oil reservoir cast on top, accessed by lifting a sheet steel cover plate. Three tail trimmings feed oil from each reservoir to the two hornguides and the journal.