Engineering up-date - July 2018

Locomotive Frame Assembly

Work continues on the construction of The Unknown Warrior at number of locations.

The Unknown Warrior at Llangollen. Photo – Kevin West

Following the report in the last Warrior we have seen work re-started at Llangollen Railway Engineering, but not at the speed we had hoped. At least progress is being made.

We continue to work with Llangollen Engineering to establish a work schedule for the completion of the locomotive chassis.

Locomotive Chassis

Work has restarted on the locomotive chassis over the last few weeks and parts continue to arrive at Llangollen for fitting in the future.

The Exhaust Blast Pipe and Cap following painting. Photo – Kevin West

The Clothing Bands around the Cylinder Relief Valve Mountings are being trimmed before the mounting holes are drilled and tapped into the cylinder castings.

A selection of Clothing Bands below the RH Cylinder. Photo – Kevin West

Dan offers up a Band following trimming to check for fit. Photo – Kevin West

The Sand Pipes from the Sandboxes down to the guns by the Driving Wheels have all been formed to shape, fitted to the chassis and painted.

The Sand Pipes after fitting to the chassis. Photos – Kevin West

The Splashers over the trailing Bogie Wheel have been fitted to the Locomotive frame and the underside of the Lower Slidebar.

Bogie Splasher in position. Photo – Kevin West

The inside of the cab has received the first coat of the correct red below waist height. David Hughes is now experimenting on how to obtain the correct scrumbled (wood grain) effect for the cream section above.

Cab interior with the Drain Cock Operating Lever prominent. Photo – Kevin West

The drivers and fireman’s seat bases and pivots have been delivered and painted.

Design for the Injector Water Cock operating Levers and Brackets has been completed and these will be cast in the near future. The Coal Slacking Cock is also under way.

The Inside Front Cylinder Cover is being prepared for fitting.

Inside Front Cylinder Cover. Photo – Kevin West

Pistons, Valves and Motion

Work presently being undertaken includes refurbishment of the legacy motion obtained for use on The Unknown Warrior. This includes replacement of the bushes where required.

One of the Outside Combination Levers showing the original, worn bushes and Oil Rings. Photo – Kevin West

After refurbishment with replacement bushes and Oil Rings. Photo – Kevin West

The new Inside Combination Lever was made to the design and details on an original North British Locomotive Company drawing for the Royal Scot class. Most of the motion parts are identical on the Royal Scot, Patriot and Jubilee classes. Once the new part was delivered to Llangollen and compared to the existing legacy parts obtained for the Unknown Warrior from Jubilee’s, a number of modifications that must have been made in the locomotive’s lift time became apparent. These primarily concerned the lubrication arrangements of the bronze bushes.  The original design has just a plain bronze bush pressed into the steel rod.

New Inside Combination Lever as made to original 1927 design. Photo – Kevin West

The legacy parts showed a later design, where the rods are counter bored around the bush and additional bronze Oil Rings are added. These provide additional side thrust bearing area. The new Inside Combination Lever is being modified to incorporate these Oil Rings.

Inside Combination Lever with Oil Rings positioned to show modified design. Photo – Kevin West

An Outside Radius Rod following fitting a new bronze bush to remove wear in the original Rod. Photo – Kevin West.

The inside Big End is being prepared for final fitting to the Crank Axle. The Oil Caps and wells are being finished on the leading end of the Outside Eccentric Rods.

Inside Big End and Outside Eccentric Rods. The large Coupling Rod at the rear is from GWR 2-8-0 No 3802. Photo – Kevin West

A selection of motion parts in the machine shop at Llangollen, including the Inside Radius Rod in the center. Photo – Kevin West

The Outside Radius Rods have had the Lifting Arm Slots checked and measured which will allow drawings to be produced for the Die Blocks.

On the Connecting Rods, the Little and Big End Bushes are being machined and white metaled. The white metal forms the actual bearing surface against the Crank Pins. This soft material is heated until molten and then poured into the bearing bronze. The inside of the bearing bronze is serrated to provide a key for the white metal. Once the white metal has cooled and solidified it is machined to the correct clearance to the Crank Pin. Unfortunately, sometimes during this process, the white metal does not fully adhere to the bronze and ‘pulls away’ as it cools. This happened to one of our bushes and the white metal had to be removed and re-done.  

The replacement Reverser Shaft Castings have been delivered and are now being machined. 

The Intermediate Reverser Shaft Casting. Photo – Kevin West

The Reverser Shaft Castings await machining. Photo – Kevin West

The Cab Reverser Unit is almost complete and ready for assembly. The nut and leadscrew are being machined as this report is written, following delays due to machine breakdowns and staff holidays!

The Return Cranks have been trial fitted to the Crank Pins, which has shown up an issue with the keyways on the Crank Pins. Discussions are now underway with the suppliers, South Devon Railway Engineering regarding work required.  

LH Driving Wheel and Return Crank. Photo – Kevin West

LH Crank Pin. Photo – Kevin West

Castings for the bronze Piston Rod Glands have been delivered and are away for machining. Drawings for the Cast Iron gland packings, springs, covers and squab boxes have been completed and quotes obtained for casting and machining.


Construction of the boiler for the Unknown Warrior continues to make good progress at Heritage Boiler Steam Services.

Work had progressed on the Outer Firebox with both the Doorplate and Throatplate trial fitted to the Wrapper and the rivet holes drilled in both. The Wrapper has had all the Stay hole positions marked and pilot drilled, nearly 1000 of them! The Foundation Ring rivet holes have been drilled as well.

The next stage has seen the Doorplate riveted to the Wrapper.

The Outer Firebox Wrapper showing the Doorplate riveted in position. Photo – Kevin West

The next big development was the trial fitting of the Inner Firebox and Foundation Ring into the Outer Wrapper and Doorplate.

The front view of the Firebox showing the Inner Firebox and Foundation Ring in position. Photo – Kevin West

Close up view showing the Inner Firebox in position. Photo – Kevin West

A view of the of the Firebox Crown  showing the stay holes drilled in each plate. The Crown stays will be fitted in these holes to support the 2 plates against the boiler pressure. Photo – Kevin West

A view showing the Outer Throateplate in position. The Inner Firebox can be seen inside. Photo – Heritage Boiler Steam Services

All the major components of the Firebox and barrel outside the Heritage Boiler Steam Services workshop at the Midland Railway Centre. Photo – Kevin West

Heritage Boiler Steam Services are now in the process of moving from the West Shed to their own premises in the North West. This will be closer to the staff’s homes and also a larger workshop to allow greater flexibility for the boiler work.

The next major milestone will see the locomotive chassis and the Boiler components come together in the autumn to establish all the alignments and allow the barrel to be fitted to the Firebox. This work will be undertaken in private due to the nature of the heavy lifting and precision required, but it is expected that an event for members will be held to enable viewing of the locomotive with the boiler temporarily fitted. Details of the location and date will be given to members once known.

Brake System and Lubrication System

Work continues on installing the lubrication system pipework. Work has been concentrated around the Inside Cylinder and on installing the pipe runs from the Oil Boxes.

Some of the pipe runs on the RH side of the locomotive during installation. Photo – Kevin West

Neat pipe runs to the bulkhead on the rear of the Inside Cylinder. Photo – Kevin West

An area that is not normally seen, as it is behind a cover. The lubrication pipes for the Inside Cylinder Valve Chest. This is a continuation of the pipe runs shown in the previous picture. Photo – Kevin West

We have recently contracted completion of the Lubrication system to Nigel Day. Nigel is a highly respected steam engineer and has recently overseen the complete rebuilding of the locomotive River Esk at the Ravenglass & Eskdale Railway. The locomotive was extensively damaged in a major fire in the railway’s workshop in which only a few original parts survived for re-use. 

All parts for the Locomotive Brake Cylinder are now at Llangollen ready for final assembly. Once this has been undertaken the Cylinder can be mounted under the Drag Box.

Brake Cylinder Piston ready for assembly into the Body. Photo – Kevin West

Refurbishment of the original 9” Tender Brake Cylinder from 8F 48518 continues at Harco Engineering.


Drain Cock Gear, Cylinder Relief Valves & Sanding Gear

The replacement casing castings for the Cylinder Relief Valves have been delivered and are being machined. Once complete they will be delivered to the Valve company in Gloucester for assembly and testing, before delivery of the completed valves to Llangollen for fitting to the Cylinders.

Replacement Relief Valve Casings on the right, alongside a pair of Piston Rod Gland castings. The pattern for the 3 Drain Cock bodies we require is the red piece to the right. Photo – Kevin West

Relief Valve Casings and Piston Rod Gland castings. The rectangular Cast Iron part at the top centre is a bogie centre casting for a 15” gauge Bassett-Lowke pacific! Photo – Kevin West

Once this is complete the remaining Drain Cock Operating Gear can be assembled and tested.


We are waiting to take delivery of the Steam Heating Valves from Tyseley before the mounting brackets can be designed and manufactured.

Work is in progress to source the many other fitting that are required to finish the locomotive.


Work had continued with holes being countersunk in readiness for riveting the chassis. A sequence is being worked to determine in which order parts are attached to make sure tools can be accessed to undertake the work.

Tender Outside Frames with newly countersunk holes. Photo – Kevin West

Discussions continue with various parties regarding riveting the chassis and completion to a rolling chassis.

We are also in detailed discussions with a number of possible suppliers of the new Tender Tank.

Future Work Planning

Areas of existing design work include, Boiler Cladding Sheets, Cab Footplate structure and Tender Tank.

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