Design

Right hand valve gear

Livio Dante Porta

On hearing of the project in October 1991, the Argentinian locomotive engineer Livio Dante Porta contacted the trust, hailing the project as the start of a "renaissance of steam technology". In 1992, he submitted A proposal for the Tornado project. In it, he proposed to the trust several design improvements that could be made to Tornado that, while preserving the outer form, would make Tornado a second-generation steam locomotive.

Since the trust was not creating a replica of a Peppercorn A1, but the next in class, the proposals were duly considered. However, the trust decided it could only adopt some of the proposals, and improved Tornado remains strictly a first-generation locomotive. The trust felt there were too many risks in adopting all of the untried proposals, and in Porta's own words, it would have taken 20,000 test miles to iron out his improvements, something the Trust probably could not finance. The expense of testing the heavily modified preserved Duke of Gloucester was also cited as a factor.

Ironically, in 2003, it had been decided to make Tornado oil-fired, for cost and operational reasons, following earlier dual-fuelled coal-and-oil-fired proposals in 1998, when boiler design commenced. This was later abandoned in favour of the original design of coal firing, due to the large increase in global fuel prices, and to save the certification costs of this design difference.

Draughting

Tender body, 2007 (no large image available)

Rough engineering dimensions for Tornado were obtained from measuring Blue Peter at the National Railway Museum (NRM). Due to there being no general arrangement drawing of a Peppercorn A1, one from an A2 was used.

Many of the drawings originally used at Doncaster Works for the A1 Peppercorn class had been preserved at the NRM, and a team of volunteers spent three days collating these in the autumn of 1991. The original drawings were India ink drawings on linen; these had to be scanned into a Computer Aided Design (CAD) software program, as the microfilm NRM copies were not suitable for manufacturing purposes, and direct dyeline copies could not be made. About 95 per cent of the original drawings were found, with 1,100 scanned by 1993, and a further 140 in 2001. A few poor-quality originals required re-drawing.

Updated specifications were required to be drawn up to account for out of date material specifications, and drawing notes whose original meaning could not be determined. Other design details were also obtained through interviews with Arthur Peppercorn's former assistant, J.F. Harrison.

Changes from original

Cab electrics

The design was modified where necessary to better suit modern manufacturing techniques, and to fit in with the modern high speed railway, while retaining the greater part of the original design. As an evolution of the Peppercorn A1 class, Tornado would also incorporate improvements that would have been made to the class had steam continued, such as correction of the rough riding faults of the original 49 Peppercorn A1s.

The following design changes were made for cost or operational reasons:

  • All welded boiler (i.e. not riveted)
  • Steel firebox (not copper)
  • One piece frames
  • Roller bearings
  • Improved front bogie
  • Improved steam circuit
  • Altered tender coal/water balance (more water)
  • Overall weight reduction

Additionally, to meet with current safety and operation standards, Tornado includes:

  • Up-rated electrical supplies
  • Primary air (not steam) brakes
  • LED cluster based head-tail lamps
  • Vacuum brakes (for heritage railway stock)
  • 1 inch (2.5 cm) reduction in overall height (for overhead line equipment (OLE) regulations)
  • Automatic Warning System (AWS),
  • Train Protection & Warning System (TPWS).
  • Data recorder
  • European Rail Traffic Management System (ERTMS) compatible GSM-Railway (GSM-R) cab radio

With advances in manufacturing, as opposed to the original Peppercorn A1, which had two piece frames riveted together, Tornado's 48-foot-6-inch (14.8 m) long steel plates were electronically cut from one piece of steel. These are probably the most accurate steam locomotive frames ever produced.

Cartazzi axle

Despite their higher costs, roller bearings were used owing to the reliability they had demonstrated after a trial of some of the original Peppercorn A1s. This caused an unforeseen problem in 2003 since the modifications made to the tender in the original fitting of roller bearings as an experiment to some Peppercorn A1s had not been properly drawn for the Cartazzi axle of the trailing wheels.

The tender was redesigned internally, removing the water scoop, increasing the water capacity from 5,000 to 6,000 gallons, and reducing coal capacity from 9 to 7.5 tons.

A 1-inch (25 mm) reduction in height from the original 13-foot-1-inch (4.0 m) height was required by the Network Rail OLE regulations, and was achieved by a redesign of the dome and safety valve mountings on the boiler, and by reprofiling of the cab roof and chimney.

Testing was planned to occur with a lipped chimney, and on receipt of the first full livery, Tornado would be fitted with an authentic rimless chimney, described as the original non-capped version. The fluted chimney intended for Apple Green running was still not fitted at the time of the green livery launch on 13 December, due to it still being machined at the manufacturer. It was completed and fitted in time for the inaugural main line passenger run. The locomotive chimney would also be fitted with a spark arrestor. The locomotive number on the smokebox door may be moved higher up as was "once the norm" (requiring the moving of the lamp-bracket). Moving the number plate above the smokebox door hand-rail was confirmed as being intended at the time of Tornado's unveiling at the NRM. Tornado would also be fitted with a chime whistle from an A4 class locomotive.

Tender

Tornado shunts at the GCR, showing the Tender design, 4 October 2008

In 1991, a preference for a 'Doncaster pattern' riveted tender was expressed, as per the Doncaster-built Peppercorn A1s. The redundant tender of the Flying Scotsman was acquired, although later returned unused, allowing Tornado to remain a completely originally manufactured locomotive.

By 2002, it was agreed that a flush sided (all welded) boiler and tender was appropriate for a Darlington built Peppercorn A1, and making construction and maintenance easier. In 2003 the need for a second tender for Tornado was discounted. The tender features spoked wheels as per at least three historical LNER Peppercorn A1s.

Boiler

Consideration of the boiler began in late 1998. No standard gauge boiler had been built in Britain since the 1960s, at least not for such a large engine. It was required to be based on the original LNER Diagram 118 design, but meet modern safety standards. Design changes included the cheaper modern day fabrication method of a welded rather than a riveted firebox and boiler tube, and use of steel rather than copper for the firebox, and the height reduction for OLE regulations.

While the manufacturing facilities still existed in Britain to manufacture such a large component, due to the design differences from the originals, the Trust required a supplier with the specific experience of designing, building and certification of steam engine boilers to modern day safety regulations, as required by the European Union's Pressure Equipment Directive

Meiningen Steam Locomotive Works, 2005

In early 2002, the Deutsche Bahn Meiningen Steam Locomotive Works in the former East Germany was identified as a supplier. They possessed the required knowledge as mainline steam operation had continued in East Germany until the mid-1980s, and 70% of its work still involved steam, and they still possessed the powerful plate roller machines. The trust did not have funding to place the order until January 2005.

On 16 July 2006 the boiler arrived by sea and was unloaded at Darlington with a 200 ton crane, having taken just nine months to build. The fitting of the 21 ton firebox and boiler unit to the wheeled locomotive frame was said to have been a perfect fit, requiring no grinding at all, a tribute to the accuracy of the design and construction by the Meiningen works. The fitting was not without incident though, as the extra weight caused some compaction of the track bed, meaning that assistance was required to move the locomotive back into the works, being winched, towed by a forklift truck and pushed with Land Rovers.

Motion and wheelset

The motion components cost 150,000: 50,000 to forge (taking three years to complete) and 100,000 to machine. The first mainline steam locomotive wheelset manufacture in Britain since 1960 took 5 years, involved 9 suppliers and cost 100,000, even with generous sponsorship. The wheels were so smooth, that the complete locomotive could easily be pushed out of the works by human power alone, as seen when moving the locomotive outside in preparation for the first steam powered moves. If the locomotive was suspended, the entire wheel and motion arrangement could be turned by hand.