We are pleased to announce that we have approached five engineering companies to manufacture the complex fabricated cylinder block with responses to our Request for Quotation for Construction expected before the end of March 2021. In addition, and as part of the continued application of modern techniques in the design and development of the improved class P2, The A1 Steam Locomotive Trust has commissioned Frewer & Co Engineers Ltd of Dorking, Surrey to undertake a Computational Fluid Dynamics analysis of the inlet and exhaust steam passages of the cylinder block.

Despite the impact of COVID-19, progress on the construction of our new Gresley class P2 ‘Mikado’ continues to move forward rapidly. The engine has reached the condition where it is recognisably a P2 and the structurally complete tender tank and tender wheelsets are now at Darlington Locomotive Works. Construction and assembly work continues on all fronts, including boiler, wheelsets, tender frames, heavy motion, pipework and electricals. Design work for the extensively modified and improved cylinder block is nearly complete, with the focus now turned to adaptation of the Lentz rotary cam poppet valve gear to further improve the original design.

P2 Cylinder Block – Request for Quotation for Construction

The redesign of the cylinder block is one of the four principal areas of redesign identified by the project team before the launch of the project to build an improved Gresley class P2 in 2013:

• Develop improved pony truck and frame design using VAMPIRE modelling data to confirm ride characteristics - completed
• Investigate and confirm valve gear to be fitted - choices were improved Lentz/Franklin, Walschaerts or British Caprotti; Lentz/Franklin was the final choice
• Investigate and reduce risk of crank axle failure apparent in original design - completed
• Investigate and confirm design and method of construction of cylinders (cast versus fabrication) including Computational Fluid Dynamics (CFD) study.

As part of the redesign process, our team led by David Elliott, Director of P2 Engineering, took into consideration the following issues:

• The cylinders on the original Gresley class P2 were two inches wider overall than the Peppercorn class A1 cylinders
• Modern track on Network Rail has reduced clearance between track and station platforms
• Consequently, No. 2007 Prince of Wales must be no wider than No. 60163 Tornado to retain route clearance
• Using a 250psi boiler on No. 2007 Prince of Wales as fitted to No. 60163 Tornado, in place of the 220psi boiler fitted to the original class P2s, permits reduction in cylinder diameter to 19¾in to maintain tractive effort
• Use of fabricated steel instead of cast iron will enable No. 2007 Prince of Wales’ cylinders to be no wider than those on No. 60163 Tornado
• Elimination of unsatisfactory features of original design.

Upon the completion of the redesign work and the conversion of the design from a single monoblock casting of all three cylinders weighing around 5½ tons to a fabricated steel structure, David Elliott used a 3D printer to construct a 1/8 scale model of the new cylinder block to assist the selected manufacturer in its assembly.

Following initial dialog with eight engineering companies, the Trust has issued a formal Request for Quotation (RFQ) to five organisations with all replies expected before the end of March 2021. All of the five companies have been issued with a 3D drawing of the modified cylinder block along with a Detailed Scope and Specification Document and associated manufacturing drawings.

Graeme Bunker-James, Commercial Director, A1SLT, commented, “When considering the award of this key contract our decision-making criteria will focus on potential suppliers demonstrating previous experience of projects of this scale and complexity, their ability to manufacture to the specified tolerances & surface finishes, their capacity to deliver the project within the required timescales, the value for money of the proposal and the long term financial stability of the business. Along with the valve gear, the placing of the order for the cylinder block in April 2021 will be the last major hurdle to overcome in the construction of No. 2007 Prince of Wales.”

Fluid Dynamics

As part of the continued application of modern techniques in the design and development of the improved class P2, The A1 Steam Locomotive Trust has commissioned Frewer & Co Engineers Ltd of Dorking, Surrey to undertake a Computational Fluid Dynamics analysis of the inlet and exhaust steam passages of the cylinder block to ensure that these were both optimised and free and an avoidable throttling.

Frewer Engineering took the Trust’s computer model of the cylinder assembly and converted this into a model of the steam passages. To reduce the computing time the model was split in half, taking advantage of the symmetry of the port designs. This left only the rear steam passages to be analysed.

Each inlet and exhaust valve has been simulated individually with the start and end conditions of the models for steam pressure, temperature and flow rate provided based on the performance of No. 60163 Tornado. The results of this analysis have confirmed that the design of the modified fabricated cylinder block is as efficient as it can be given the design restrictions. The study has confirmed that the highest-pressure drop is through the small cross-sectional area of the valves themselves.

Several areas have been identified where minor modifications can be made to further improve the flow which will now be subject to a design review to determine the impact of adopting them.

Ben McDonald, Group Director of Engineering, A1SLT, commented, “The commissioning of Frewer Engineering to undertake a Computational Fluid Dynamics analysis of the inlet and exhaust steam passages of the cylinder block is part of the continued application of modern techniques in the design and development of our improved class P2, completing the work of Sir Nigel Gresley from the 1930s.”

An enhanced CAD drawing from Frewer & Co. Engineers

A further superb rendering by Frewers.

Fundraising

Our fundraising is also moving forward well. The monthly ‘P2 for the price of a pint of beer a week’ Covenant scheme has already attracted over 940 Covenantors. The Cylinder Club was founded in October 2017 to fund the initial redesign and manufacture of the cylinder block with an initial target of raising £100,000 plus Gift Aid from 100 supporters each donating £1,000 in up to eight payments of £125 by standing order. In March 2018 we were delighted to announce that thanks to the generosity of our supporters this initial target had been achieved. Once the overall cost of the new cylinder block has been determined the Trust will decide which new funding campaigns to put in place.

Mark Allatt, Trustee, A1SLT, commented, “We are delighted with the support the project to build Britain’s most powerful steam locomotive has received since its launch seven years ago. With over £3.4m spent and more than £3.8m donated to-date of the estimated £5m, we remain on-track for completion within three years. However, to maintain this progress we need to raise £700,000 per year and we are still seeking to recruit additional ‘P2 for the price of a pint of beer a week’ regular donors or covenantors. Once the cost of manufacture of the new cylinder block has been determined we will put in place an appropriate fundraising campaign.”