Cylinders and valves – Having gone through a thorough selection process, the order for the fabricated cylinder block was placed with Howco at Irvine in Scotland. Howco is part of a large Japanese owned group specialising in oil exploration equipment but given the cyclical nature of the oil business has a stated plan to diversify. They have first class fabrication facilities and a large CNC machining capability along with in house weld procedure development, heat treatment furnaces and comprehensive non-destructive testing (NDT) resources. Whilst complex, our cylinder block fabrication is quite small by their standards.  After a review by Howco, some minor design changes have been made by combining some fabricated sub assembles into fewer parts to be CNC machined from thicker plate than originally proposed in our design.

Howco wasted no time in starting work on the monobloc, here one of the cylinders is machined – Howco Engineering

Perhaps the most difficult part of the fabrication is the cruciform exhaust ports which take exhaust steam from both ends of all three cylinders to the base of the blast pipe. In order to clear the inside cylinder and the inside steam chest, these have to be curving in two directions at once. This is achieved by making each port of rectangular section from pieces of 25mm thick steel plate which is pre-bent then profiled to the required shapes. The problem here is that if each plate is profiled to the finished shape and then bent using a brake press, because the width of each plate is varying and not symmetrical, the required shape will not be achieved. To overcome this the process is to start with a rectangular plate large enough to accommodate all the curves which, being formed on a constant width piece of metal, will come out as expected. However, once we have a an “S” shaped plate it is not possible to use a CNC flame or plasma profiling machine to produce the final shape – these machines need flat plate.

It is therefore necessary to mark out the finished shape on each plate and use hand operated oxy-acetylene burning equipment to produce an approximation to the finished shape, after which the final shape including weld preparations will be achieved by hand grinding, or where applicable by CNC machining.

The problem that then came to light is that the Standard version of Solidworks which we employ in the design work on the P2 is not able to produce these developed shapes automatically, and from previous experience with the guard irons mounted on the front of the frames and the bogie frame, the only way we could produce the necessary profile was by an old fashioned and time-consuming manual method. As we had at least 16 components requiring this treatment, an approach was made to Solid Solutions, the Solidworks UK distributor we use, who said that this could be achieved with the Premium version which is several thousand pounds extra.

As luck would have it, Martin Shepherd, whom we retained initially to turn the valve gear models into manufacturing drawings, has a Premium version of Solidworks which has the additional “Flatten” button. The resultant 2D developed surface is then transferred to a drawing at 1:1 scale which is plotted on paper, the shape accurately cut round with scissors and laid out on the bent plate to enable it to be marked out for flame cutting

To check that this was actually producing the shapes required, two of them have been 3D printed at one third scale (the largest that could be accommodated on the Director of P2 Engineering’s 3D printer) and the one-third scale cut-out developed shape offered up the models to check that they would produce the required shape – they do!

¹/₃ scale cylinder exhaust passage component with paper developed profile overlaid – A1SLT

¹/₃ scale cylinder exhaust passage component with paper developed profile – A1SLT

Martin Shepherd has produced almost all the 2D manufacturing drawings for the valve gear and has now turned his attention to lubrication including oil coolers for the cam boxes and pumped lubrication of the 12 valve spindles. Martin has made further progress with the one third size 3D printed cam box being produced by Warwick University Manufacturing Group (WMG). This is nearing completion following a visit to DLW by Martin who with assistance from Daniela and David Elliott has made the various pieces of plain shaft from steel which would have been difficult to make accurately by 3D printing but is easily sawn and turned from bright bar.

Further progress has been made in tying down the precise specifications and obtaining quotes for the various cardan shafts required for the drives from the return crank gear boxes to the cam boxes and the reverser drive from the cab to the cam boxes.

Pony Truck – The pony truck main frame has been returned from the manufacturer following final machining.  The side control spring components are having the final machining processes completed at DLW following sending out for coded welding.

Pony truck side control components – Daniela Filová

The spherical side bearers (bronze) and the side bearer cups (steel) have been CNC (Computer Numerical Control) machined to an excellent standard by local company Springfield NE Ltd of Chilton.

Pony truck spherical side bearer – David Elliott

A trial fit of a side bearer cup on the pony truck – David Elliott

The pony truck set up for measurement with bearer cups trial fitted – David Elliott

Machined pony truck spring planks – David Elliott

We are pleased to announce that both machined outside connecting rods have now been delivered to Darlington Locomotive Works only seven years after the launch of the project. The fundraising campaign to raise an initial target of £210,000 needed to pay for the manufacture of the heavy motion has also made good progress, with £178,000 plus Gift Aid already pledged by 178 supporters.  In May 2018 the Trust placed a £181,000 order with Stephenson (Engineering) Ltd of Atherton, Manchester for the heavy motion. The order included the forging, machining and heat treatment of the nine heavy motion rods – intermediate coupling rod LH/RH, trailing coupling rod LH/RH, leading coupling rod LH/RH, outside connecting rod LH/RH and the inside connecting rod assembly (including strap, gluts and strap nuts and washers) – and the combined piston and rod.

Two connecting rods and six coupling rods – enough for a ‘Mikado’! – A1SLT

David Elliott, Director of P2 Engineering, The A1 Steam Locomotive Trust, commented, “The delivery of the outside connecting rods for Prince of Wales is a major step forward for the project, especially given the limitations of working during the COVID-19 pandemic. The machining of each rod by Stephenson (Engineering) Ltd takes around 100 hours. The next few months will see the completion of all of the heavy motion and the trial fitting of the coupling rods to the engine – creating the first tender-engine standard gauge ‘Mikado’ in the UK since 1945.”

Mark Allatt, Trustee, The A1 Steam Locomotive Trust, added, “We are delighted with the support the project to build Britain’s most powerful steam locomotive has received since its launch over seven years ago. With over £3.4m spent and almost £4m donated to-date of the estimated £5m required, 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 members of The Motion Club in order to complete the funding for the heavy motion as well as additional ‘P2 for the price of a pint of beer a week’ regular donors or covenantors.”

You can join The Motion Club here.

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 examine the impact of the Coanda effect on the new locomotive.  Following the successful partnership with Frewer & Co Engineers Ltd announced in March 2021 where Frewer undertook the Computational Fluid Dynamics (CFD) analysis of the cylinder block steam passageways, a further project has been commenced.

The second of the original Gresley class P2s No. 2002 Earl Marischal, was completed at Doncaster Works five months after No. 2001 Cock o ’the North in October 1934. Unlike No. 2001, which was equipped with Lentz-type rotary-cam actuated poppet valve-gear supplied by the Associated Locomotive Equipment Company, No. 2002 was fitted with Walschaerts valve gear as used on the Gresley class A1 and A3 ‘Pacifics’. As a consequence, No. 2002 was documented as suffering from issues with exhaust steam obscuring the view of the driver. This problem was initially addressed by fitting additional smoke deflectors to No. 2002 and was finally resolved with the fitment of a Gresley class A4-style streamlined front-end to the class P2s. The final four Gresley class P2s, No. 2003 – No. 2006, were fitted with the streamlined front-end from new in 1936, No. 2002 in 1936 and No. 2001 in 1938 when also rebuilt with Walschaerts valve gear.

In order to ensure that No. 2007 does not suffer from the same problem with the original Gresley class P2 boiler casing design, a CFD study of the influence of the Coanda effect on the exhaust steam over the casing is currently underway.

The Coanda effect is the tendency of a fluid to follow a flat or curved surface. In the case of the class P2, a crosswind travelling over the casing will ‘stick’ to the casing and draw the exhaust steam down over the surface obscuring the Driver’s view of the railway ahead. The study aims to attempt to replicate the documented problem in the simulation environment. If this is achieved, design changes can then be tested to investigate how to prevent this problem occurring with No. 2007 – the intention being to find a means of influencing the air and steam flow that does not change the design outline of the locomotive’s boiler casing.

Ben McDonald, Group Director of Engineering, A1SLT, commented, “The commissioning of Frewer to undertake a Computational Fluid Dynamics analysis of the influence of the Coanda effect on the exhaust steam over the casing 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.”

Martha Cooper, Head of Advance Analysis Division, Frewer, added, “We are very excited to be contributing to this project, and it is a unique opportunity to demonstrate how modern analysis tools and capabilities can be applied to a classic design, inspiring the next generation of engineers. We have found it really interesting to work closely with A1SLT and appreciate the expertise and attention to detail, both in Gresley’s original and in the modern improvements to the design.”

Funds raised to build new Gresley class P2 No. 2007 Prince of Wales reached £3.9m

We are thrilled to announce that all six machined coupling rods have now been delivered to Darlington Locomotive Works only seven years after the launch of the P2 project. The fundraising campaign to raise an initial target of £210,000 needed to pay for the manufacture of the heavy motion has also made good progress, with £178,000 plus Gift Aid already pledged by 178 supporters.

Despite the impact of COVID-19, progress on the construction of the 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 continue on all fronts, including boiler, wheelsets, tender frames, heavy motion, pipework and electricals. Design work for the extensively modified and improved cylinder block is complete, with the focus now turned to adaptation of the Lentz rotary cam poppet valve gear to further improve the original design.

The final pair of machined (trailing) coupling rods at DLW – A1SLT

The work involved in manufacturing the motion includes:

• Redesign of coupling and connecting rods to use modern material as pre-war nickel chrome steel alloy proved prone to fracture
• Incorporation of late-pattern BR-type continuous white metal lined crank pin bearing bushes
• Use of the late-A1 design of inside connecting rod which overcame the tendency for the original design of inside connecting rods on LNER ‘Pacifics’ to big-end failure
• Open die forging of six coupling rods, two outside connecting rods and the inside connecting rod and strap
• CNC machining of all rods
• Manufacture of oil box lids, coupling rod knuckle pins, nuts & washers and bearing bush keys
• Casting of leaded gunmetal and phosphor bronze castings of crank pin bearing bushes
• Machining and white metalling of bearing bushes
• Fitting oil box tops
• Assembly of bearing bushes to rods
• Polishing rods.

In May 2018 the Trust placed a £181,000 order with Stephenson (Engineering) Ltd of Atherton, Manchester for the heavy motion. The order included the forging, machining and heat treatment of the nine heavy motion rods – intermediate coupling rod LH/RH, trailing coupling rod LH/RH, leading coupling rod LH/RH, outside connecting rod LH/RH and the inside connecting rod assembly (including strap, gluts and strap nuts and washers) – and the combined piston and rod.

Progress to-date on the heavy motion includes:

• Six coupling rods: all six coupling rods have now been delivered to DLW; the intermediate coupling rods (between second and third coupled wheelsets) have been fettled, polished to a fine finish and fitted with white metal lined bronze bushes; the leading coupling rods (between first and second coupled wheelset) have also been fettled and polished to a fine finish; the trailing coupling rods (between third and fourth coupled wheelset) have both been delivered to DLW, both have had the tapered gradient pin holes lapped, one has been fettled and the other is being fettled
• Two outside connecting rods: both have been forged and heat treated; machining is underway with delivery to DLW expected by the end of May 2021
• Inside connecting rod and strap: the inside connecting rod has been forged, heat treated and is now ready for machining; the strap has been forged, to be followed by heat treatment and machining with delivery to DLW expected at the end of July 2021
• Bronze white metal lined rod bushes: the first four bushes (for the intermediate coupling rods) were delivered to DLW from Locomotive Maintenance Services Ltd (LMS) of Loughborough in January 2021; LMS has the materials for the final four with an order expected to be placed over the next week
• Gradient pins: the drawings are being finalised and will be made inhouse by apprentice machinist Ed Laxton

In April 2018, we launched a new appeal to raise the funds to manufacture the motion for No. 2007 Prince of Wales. The Motion Club was established with the aim of raising £210,000 from 175 supporters each donating £1,000 (plus Gift Aid) to the project in up to eight payments of £125 by standing order. The appeal started well and in just seven weeks it had already reached over a quarter of its target. Within three months, we had recruited over 140 members, with around £170,000 pledged, including Gift Aid.  To find out more and to join The Motion Club follow this link.

Mark Allatt, Trustee, The A1 Steam Locomotive Trust, commented, “We are delighted with the support the project to build Britain’s most powerful steam locomotive has received since its launch over seven years ago. With over £3.4m spent and around £3.9m donated to-date of the estimated £5m required, 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 members of The Motion Club in order to complete the funding for the heavy motion as well as additional ‘P2 for the price of a pint of beer a week’ regular donors or covenantors.”

David Elliott, Director of P2 Engineering, The A1 Steam Locomotive Trust, added, “The delivery of the final pair of coupling rods for Prince of Wales is a major step forward for the project, especially given the limitations of working during the COVID-19 pandemic. The machining of each rod by Stephenson (Engineering) takes around 100 hours. The next few months will see the completion of all of the heavy motion and the trial fitting of the coupling rods to the engine – creating the first tender-engine standard gauge ‘Mikado’ in the UK since 1945.”

Further progress is being made a I D Howitt Ltd at Crofton, Wakefield with the tender frames. All the hornblocks have had their manganese steel liners finish machined and are now permanently mounted on the frames. Good progress has been made with details of the brake and hand brake linkage.

The tender hornguides being set up at Crofton. – Leigh Taylor

The hornguides finish-fitted. – Leigh Taylor

Tender brake stay and bearing details. – Ian Howitt Engineering

Meiningen continues to make good progress with both the boiler for Prince of Wales and the spare for both engines (all photos by DB Meiningen unless stated).

 

The outer firebox is welded to the boiler barrel.

The firebox tubeplate is tried for size.

The inner firebox welded up.

A view of the firebox combustion chamber with the tubeplate welded in place.

The boiler shell in Meiningen’s X-ray room for weld checking.

A detailed image of some of the welded seams in the firebox.

An example of the X-ray output from this process.

A series of photos showing the machining of the boiler supports from solid steel.

Locomotive Maintenance Services at Loughborough were given the job of applying the bronze coating on the regulator cross shafts where they pass through the glands in the stuffing boxes. However, the first time they did this a number of gas bubbles formed in the bronze layer. Eventually after considerable experimentation with combinations of material, TIG welder and shielding, gas pressure has been achieved and the cross shafts are back at DLW enabling Ed Laxton to complete the machining of the stuffing boxes for the two new boilers.

The machined regulator stuffing box. – Leigh Taylor

 

The regulator cross shaft. – Daniela Filová

Since 2019’s announcement of the placing of a £1m order for two new Diagram 118 boilers from DB Meiningen (DBM) significant progress has been made on both boilers and assembly of the first boiler is nearing completion.  So far, The Boiler Club has received pledges of £450,000 (excluding Gift Aid) from 225 supporters – 75% of the 300 needed!

We are delighted to announce that our online donations system is now live on the P2 website for signing up as a P2 Covenantor, joining any of the P2 clubs and contributing to The P2 Support Coach Appeal. Please use this link to sign up to the Boiler Club online – help us reach our 300 members target!

Locomotive frames – With the engine’s frames erected, all the major frame stays, brackets, horn blocks, axle boxes & buffers have been cast and fitted using around 1,000 driven bolts.  With the tender tank undercoating complete it has been possible to remove the wheelsets from under the engine frames. This has permitted fitting of the remaining driven bolts and cold turned rivets in the outside motion brackets and the spring hangers.

We now have the profiles for the “shelf” under the back of the cab and Ian Matthews has started making some special tooling to facilitate hot bending of the 20mm thick plate to form the flanges on each end which mate with the outer Cartazzi frame plates. Normally, shaping like this is carried out cold using a brake press forming a series of small bends, however, the radius required in this case is equal to the thickness of the material necessitating the bending to be undertaken at red heat. In this condition the metal, which is 20mm thick,  will be sufficiently pliable to be bent using form tools in our 30ton press. As it is important that the finished article is a good fit between the outer frames, doing the work in house as opposed to by a plate bending firm will enable subtle adjustments to be made to ensure a tight and parallel fit.

The “shelf” bending jig – Leigh Taylor

When fitted to the frames, the shelf will complete the frame structure and enable Ian to start fitting the electrical trunking under the cab which is relatively complex as the 3D CAD view shows.

3D CAD view of the trunking on the shelf. – Alan Parkin

Tender – Steady progress with the tender frames continues at Ian Howitt’s works at Crofton. The initial machining of the hornblocks has been completed, the hornblocks dispatched to NVES in Darlington for welding on manganese steel liners (NVES, thanks to our activities over the years, maintain a welding procedure for welding manganese steel to cast or mild steel), and are now back at Crofton for final machining. Many details for the brake linkage and hand brake mechanism have been made including the brake cross stay and brake cross shaft.

Tender hornguides with manganese steel liners welded in place. – Daniela Filová

The hornguides being set up on the tender frames. – Ian Howitt Engineering

Alan Parkin has now produced several manufacturing drawings for the approximately 140 individual components which are required to fabricate the cylinder block. At the same time David Elliott is building up the scale 3D printed model to determine the best construction sequence to ensure that all seams can be fully welded. The intention was to issue a “request for expressions of interest” to a number of fabricators during December. The target is for an almost full set of manufacturing drawings at the end of January to enable shortlisted companies to quote for the whole job.

The latest cylinder CADs and the assembled scale model of the cylinder block. – David Elliott

In parallel with discussions are at an advanced stage with a specialist company in CFD (computational fluid dynamics) to model the steam flow through the cylinder block to ensure that we do not have avoidable pressure reducing features to enable us to optimize the detail of the design – there is little scope for significant redesign of the block as the steam and exhaust passages are already as large as practical within the tight limits of the envelope of the block, however some gains may be possible through increasing radii on the inner corner of bends etc.

It is expected that this work will lead on to a more extensive model to analyse steam flow from the regulator to the blast pipe which will assist in fine tuning the profiles of the cams and the diameter of the blast pipe tops.

A further use of CFD will be look at smoke lifting. The original P2 No. 2001 Cock o’ the North did not have smoke lifting issues as even at low powers, as students of the history of the P2s will be aware, but the second engine, No. 2002 Earl Marischal (as first built with Walschaerts valve gear and the same smoke box and smoke lifting plates as No. 2001), immediately suffered from drifting smoke affecting the driver’s view resulting in early fitment of large and rather ugly smoke deflectors. The main difference is that piston valves open and close the exhaust valves gradually, with very little cross section for gas flow at the start and end of each event resulting in the exhaust appearing to “leak” from the chimney encouraging it to stick to the boiler top, which with the cross winds and the Coanda effect draws the exhaust down on the leeward side of the boiler. By contrast, poppet valves open and close to full area quickly resulting in sharper edged exhaust beats. Whilst not a problem on No. 2001, with all the computer modelling to optimize efficiency and power, there is a risk that the “squareness” of 2007’s exhaust beats may end up less sharp. If a smoke lifting problem is identified it is anticipated that with 80+ years of aerodynamic development since No. 2002 appeared, some relatively unobtrusive aerodynamic fences or strakes could be applied to solve the problem.

A short-term lack of Solidworks drafting capability has been identified and steps are in hand to recruit addition resources to cover this to expedite production of the detailed drawings for the valve gear. Low risk items such as reversing gear, return crank gear boxes and cardan shafts, and casting and machining valve covers can then be put into manufacture. In parallel it is intended to prototype a cam/follower/tappet/valve assembly and subject it to some fatigue testing before committing to a full set.

3D CAD view of poppet exhaust valve. – David Elliott

Cylinder drain cocks – Considerable progress has been made (mainly by Ian Matthews) in installing Alan Parkin’s cylinder drain cock design onto the frames. The design is closely based on that on Tornado to eliminate the use of Bowden cables (as used on the original P2s).

Cylinder drain cock actuating linkages. – Ian Matthews

With the system design largely complete the Electrical System Specification has been updated to reflect all the new design elements.  A start has been made on writing the section on standards compliance, which involves a clause-by-clause assessment of relevant standards.  Many standards have been replaced since we designed the A1 so this represents a lot of new work.  We are also using the electrical system to pilot the Trust’s updated approach to risk assessment.  This is based on the new railway Common Safety Method for Risk Evaluation and Assessment (CSM-RA).  A first draft Hazard Log has been produced.  This describes potential safety hazards associated with the electrical system and lists causes, consequences and safety measures for each hazard.  A Risk Ranking is then allocated to each one and, where appropriate, additional mitigations are put in place.  The updated draft documents are currently under review by Graham Nicholas, the Trust’s Professional Head of Engineering.

Some of the structured electrical trunking and junction boxes. – Daniela Filová

Starting the turbogen on the A1 involves a manual process of warming through the turbine to expel water before running it up off-line and connecting the power supplies once it is operating at full speed.  DB Meiningen offers a control box which contains a circuit that uses the alternator tachometer output to determine when the turbine is up to speed before automatically connecting it to the batteries using relays.  However, this system is designed for direct battery connection.  The A1 system connects the turbogen via DC-DC converters, which is incompatible with the Meiningen circuit, so we have not used it on our engine.

As we are moving to a two turbogen solution for the P2 we are taking the opportunity to design our own start-up circuit, so the crew do not need to manually start and bring each turbogen online.  A prototype tachometer circuit has been designed and bench tested.  This will be used to drive a relay which will connect the turbogen to the loads once it is running above a pre-determined speed.  The next step will be to test this on the A1 when it is next in steam to confirm the optimum speed for switching.  The circuits will then be incorporated into the Turbogen Control Box system, which has already been designed.

The prototype tachometer set-up. – Rob Morland

Work on the new combined head/tail/marker lamp luminaire continues.  We have received the first driver PCBs back from Stevenage Circuits and Alan Green has built and tested an initial batch for use in finalising the design.  Roger Millington, Alan and Rob are now working together to ensure that the lamp performance when displaying each of the three aspects is optimised.

The initial delivery of driver PCBs for testing. – Rob Morland

For the rear of the tender we are planning to use two original Stones marker lamp housings to display the marker and tail aspects, as on the A1.  Provision will be made for fitting and connecting the new P2 headlamps to display the head aspect when running tender-first on the main line.  Alan Green has updated the A1 marker/tail driver circuit design to include modern driver components (the original design is now 12 years old!).  This will be compatible with the A1 lamps, so we will have replacement PCBs for those when they reach the end of their useful life.

We were delighted during the build of Tornado when supporters came forward and offered us original Stones housings that allowed us to fully fit the engine.  We now have a requirement for a further two housings for the P2.  We would be pleased to receive any offers of housings that will allow us to meet this requirement.  They need to be the same design as on Tornado and ideally have a clear lens.  Please get in touch if you have one that you would like to see fitted to the P2!

A Stones marker lamp of the type required for No. 2007. – David Elliott

Work on the electrical conduit system for the tender is currently paused, awaiting the next phase of work on the East Coast Digital Project, which we expect to include installation of the European Train Control System (ETCS) on Tornado.  As mentioned in TCC 58 we are taking the opportunity to incorporate several of the P2 electrical system design improvements into the design for Tornado, especially around the arrangements that permit cab removal.  Once this is agreed we will import the A1 design back into the P2 and complete the conduit work.

The A1 Steam Locomotive Trust has announced a new £40,000 appeal – The Turbogen Club – to fund the first of the two turbo-generators required to power the modern electrical system necessary for No. 2007 Prince of Wales to operate on the Network Rail main line.  To find out more and to join the club follow this link.