Engineering Update - March 2022

As the regulations surrounding Covid have relaxed work on The Unknown Warrior has started to return to a more normal pace. Staffing levels at the PRCLT workshops have returned to pre-Covid levels, allowing more work to be undertaken. Added to this the overhaul of 6233 Duchess of Sutherland has been completed and the locomotive has returned to service hauling trains on the national network, both on its planned commitments and standing in successfully for another locomotive.

Kevin West and Colin Hall discuss progress alongside 5551 during one of our monthly meetings. Photo by Andy Collinson

The last edition of the Warrior did not carry a normal Engineering Update, as it contained the Project Reset presentation that was given at our AGM in November. I will try to cover the major events and progress from August 2021 in the report. 

The PRCLT engineers have returned to more regular work on 5551 allowing the delivery of the full assessment of the chassis to progress. Our engineering team have continued monthly meetings at West Shed to keep track of current work and forward plan the work program.


The main activity on the chassis since last August has involved checking the main frame assembly and the of components mounted on it. This work was deemed necessary following the removal of the outside cylinders for some welding work.

Once the cylinders had been removed it showed the frame plates still had ‘mill scale’ on the surface. This ‘mill scale’ is formed during the manufacturing process while the hot material is rolled to the required thickness. A skin forms on the surface which can be rough and flaky. This scale must be removed to provide a flat, clean surface for any component to mount against.

Chassis being prepared for removal of the Inside Cylinder. Photo by Andy Collinson

With ‘mill scale’ found on the frame mounting surfaces for the outside cylinders and the bogie mounting stretcher, which was removed at the same time, this led us to question the condition under other parts fitted to the frames. A sample Spring Hanger Bracket and a Horn Guide were removed and showed up problems with both the frame surface condition and issues around the fixing holes. The correct fitting condition will give full surface contact between the two parts over the whole contact area. Conditions found have included what appears to be mill scale, plus burrs around the fixing holes that have been formed when the holes have been drilled and reamed. The burrs may be only small but they are strong enough to hold the mating part off the surface of the frame plate. This allows moisture and debris to get into the resultant gap and cause corrosion. Also, if left while the locomotive is working, the burr could be fretted away resulting in the fitted part becoming loose requiring the loco being taken out of service for repairs.

A close up of one of the Frame holes showing the burrs and the rough surface condition of the frame surface. Photo by Kevin West

A view showing the condition of the Frame plate following removal of one of the Spring Hanger Brackets. The silver shows where there has been good contact between the parts. The black areas is where dirt has found its way into the small gap and an area of surface corrosion can be seen under the centre hole. Photo by Kevin West

These burrs should have been removed before the parts were finally fitted, but it appears this has not happened in numerous places over the frame assembly. The only correct course of action is to check everything that had been fitted to the complete assembly. So far, between the frames the Inside Cylinder and all Stretchers back to the Leading Driving Axle, along with all the Horn Guides, Spring Hangers and Brake Hangers have been removed and rectification work is underway. 

Chassis prepared for repairs, Feb 2022. Photo by Kevin West

The Motion Girders and Mounting Brackets have been removed from the outside of the frames for similar work. Once the holes have been de-burred, the frames will be shot blasted back to bare metal to produce the clean flat surface required before everything is refitted. New fixings are required as we have no documentation for those originally fitted.

Outside of Frames prepared for repairs, Feb 2022. Photo by Kevin West

The rear end is being left to maintain alignment of the chassis. Once the front end has been completed attention will switch to the rear end. At the front end of the locomotive it has been found that the Front Buffer Beam and the mounting brackets have been drilled incorrectly which has resulted in the frames being slightly out of alignment. As we have no documentation for the mounting brackets these will be replaced along with a new Buffer Beam as it is cheaper and easier to replace than repair.

Front Beam. Photo by Kevin West

The chassis has been placed on a set of rail mounted trucks to allow it to be moved around the workshop and outside for the shot blasting.

5551 in the West Shed, Dec 2021. Photo by Andy Collinson

The workshop has become very crowded with parts of 5551 removed for the current work. We are to provide another container for storage of parts and material which will clear space in the workshop to aid the next phase of the work.

Various chassis parts from 5551 in the West Shed, Feb 2022. Photo by Kevin West

Following the scanning of some documents from the early years of the project, examination of invoices showed that some welding work had been undertaken on the Frame Plates. If done properly the weld should be almost invisible. Unfortunately, these welds have been found to be been poorly executed, with voids instead of solid material. The decision to check all the chassis mountings has proved to be necessary as these poor welds were previously hidden behind mounted parts. Also, there is no surviving documentation to cover this work. Rectification will involve removing the existing weld back to virgin material before the weld is replaced to the required standard, with all the supporting method statements and documentation.

Poor welded repair on Frame Plate, Feb 2022. Photo by Kevin West


Machining of other fittings continues as time allows.

‘New’ Lathe

PRCLT have made an important addition to the workshop machinery at West Shed, with our help. In January 2022 they acquired a Dean Smith & Grace type 25 lathe along with a large selection of tooling and attachments. This will enable a wide range of components for 5551 to be worked on in-house, with economic and project control benefits. As a minimum, these will include piston heads and rods, valve heads and rods, rear cylinder covers, motion bushes, reversing shaft ejector ring, rear cylinder covers and multiple non-ferrous castings.

After agreeing the business case, the LMS-Patriot Project has provided loan finance to enable the purchase with a phased repayment agreement.

The new lathe in position in the West Shed. Photo by Andy Collinson

Inside Cylinder following removal – 2nd Feb 2022. Photo by Kevin West


The Inside Cylinder was removed from the chassis in January 2022 to allow access to frame repair works.

Detailed work in preparation for the installation of the Valve Guide Bars into the outer cylinders has been completed and the cylinders have been delivered to the specialist welding company. Whilst the bars are being welded in position some work will also be undertaken on the Exhaust Flange, where the casting was a little short on material. This resulted in the mounting holes being very close to the edge of the flange which is not acceptable.

The Outside Cylinders loaded for transport to the welding specialist. Photo by PRCLT

Driving Wheels

The Driving Wheels have continued to be a large portion of our work effort over the period of this report. The foundry that supplied the original castings has been working cooperatively with us to establish the way forward. Following our first discussions after our June 2021 testing by British Engineering Services, the foundry brought in their own castings experts in the summer to examine the defects and the casting process used from start to finish. Their initial thoughts were that, while the cause of the defects was unclear, repair could be carried out, subject to agreement on the repair methodology, and subject to further metallurgical analysis by their expert involving a sample taken from one of our wheels. We agreed to this analysis being carried out, and at this point decided to involve our certification body and a volunteer metallurgist in a joint technical review. The team met the foundry in October to discuss the technical casting issues, the further analysis needed, and the safety certification requirements. The metallurgical analysis was completed by the foundry’s expert in November and shared with us. This led to the foundry concluding that the defects had arisen during the casting process; and that repair would not be practicable to the standard required. The foundry had previously advised us that they were no longer equipped to cast wheels of the size we need; so a further meeting with the foundry took place in December, leading to constructive settlement terms being agreed

After consideration of the limited options available, we are now in advanced discussions with William Cook Cast Products of Sheffield to provide the new castings. The casting pattern has been dispatched to the foundry and needs a little repair work following 10 years in store. At a recent meeting held at Cook’s plant we were able to view the first two Driving Wheels that have been cast there for Class B17 No. 61673 Spirit of Sandringham. They are excellent castings.

We expect to be in a position to place an order in the next few weeks. Full details will follow in Warrior 53.

Driving Wheel casting for the B17 Spirit of Sandringham at William Cook’s Cast Products. Photo by Kevin West


Work continues on the rework of the bogie as time permits. 

A 12-feed Silvertown Lubricator from 6203. Photo by Kevin West

Lubrication System

Design work has been completed on the 12-feed Silvertown Mechanical Lubricators using the original fitted to 46203 Princess Margret Rose as a pattern. Drawings have been completed for checking by PRCLT and quotations have been received for the patterns and castings.

The Drive Clutch on the Lubricator from 6203. Photo by Kevin West

The Drive Cage on the Lubricator from 6203. The pump units have been removed to allow preparation of drawings. Photo by Kevin West

It is believed several other locomotive groups require the same 12-feed Silvertown Lubricators as fitted to 5551, so we are making enquiries and will possibly produce a small batch of lubricators alongside those for 5551.


Manufacture of our Safety Valves has been completed by Locomotive Maintenance Services of Loughborough.

The Safety Valves. Photo by Andy Collinson


HBSS have completed the installation of the Boiler Slides. Fitting of the Transverse Stays that run across the Firebox above the Inner Firebox is the next task to be undertaken.

A fitted Boiler Slide. Photo by HBSS


Work continues on the Tender Chassis at Leaky Finders as time permits. The chassis has recently been moved into their new workshop.

Tender Tank Design

No progress since last report.

Paperwork, Approvals and Certification

We have scanned all the Engineering invoice documents held in our Stafford office to make them readily available to all of the Engineering team.

The task of collating the paperwork required for approval and certification continues. Amongst the work-streams being undertaken are Risk Assessments for the current and future work streams, compilation of the necessary documentation and paperwork for all components on the locomotive. One area that has been a concern is the provision of material grade confirmation certificates, but recent discussions with a number of parties has indicated that on-site testing at West Shed will be possible which will save on the amount of work required and significantly reduce the cost.

Certification Forms to track progress and eventually sign off as complete individual parts are being developed. We have trialed the first iteration of form and this has shown up some refinements required. We expect these updated forms in the next few weeks, after which we will start another large session of form filling.

Planning for the Future

When 5551 is complete and ready to haul trains on the main line and heritage railways we will need a support crew to look after the locomotive and undertake the daily preparation duties.

Andy Collinson and Kevin West have joined the support crew for 6233 Duchess of Sutherland to both help the locomotive on its workings and also to give us experience of what is involved in running a locomotive out on the national network. At present we are waiting to undertake our PTS (Personal Trackside Safety) examinations which we hope to complete in the next month. Until these are completed we are getting our hands dirty with cleaning duties.

6233 at West Shed . Photo by Andy Collinson

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